cl-tui.asd

@@ -2,7 +2,7 @@
 (asdf:defsystem :cl-tui
   :description "Reusable Common Lisp Terminal UI Framework"
   :author "Amr Gharbeia"
-  :version "0.7.0"
+  :version "0.8.0"
   :license "TBD"
   :depends-on (:fiveam :sb-posix)
   :components
@@ -35,7 +35,10 @@
      (:file "tabbar" :depends-on ("container-package" "dirty" "box"))
      ;; Select widget (v0.7.0)
      (:file "select-package" :depends-on ("package" "input-package"))
-     (:file "select" :depends-on ("select-package" "dirty" "box"))))
+     (:file "select" :depends-on ("select-package" "dirty" "box"))
+     ;; Markdown + Code + Diff rendering (v0.8.0)
+     (:file "markdown-package" :depends-on ("package"))
+     (:file "markdown" :depends-on ("markdown-package"))))
   :in-order-to ((test-op (test-op :cl-tui-tests))))
 
 (asdf:defsystem :cl-tui-tests
@@ -56,13 +59,15 @@
      (:file "theme-tests")
      (:file "input-tests")
      (:file "scrollbox-tabbar-tests" :pathname "../../tests/scrollbox-tabbar-tests.lisp")
-     (:file "select-tests" :pathname "../../tests/select-tests.lisp"))))
+     (:file "select-tests" :pathname "../../tests/select-tests.lisp")
+     (:file "markdown-tests" :pathname "../../tests/markdown-tests.lisp"))))
   :perform (test-op (o c)
-              (dolist (suite '((:cl-tui-backend-test "BACKEND-SUITE")
+               (dolist (suite '((:cl-tui-backend-test "BACKEND-SUITE")
                               (:cl-tui-box-test "BOX-SUITE")
                               (:cl-tui-input-test "INPUT-SUITE")
                               (:cl-tui-scrollbox-test "SCROLLBOX-SUITE")
-                              (:cl-tui-select-test "SELECT-SUITE")))
+                              (:cl-tui-select-test "SELECT-SUITE")
+                              (:cl-tui-markdown-test "MARKDOWN-SUITE")))
                (let* ((pkg (find-package (first suite)))
                       (s (and pkg (find-symbol (second suite) pkg))))
                  (when s

org/markdown-renderer.org

@@ -0,0 +1,500 @@
+#+TITLE: Markdown + Code + Diff Rendering (v0.8.0)
+#+DATE: 2026-05-11
+#+AUTHOR: Amr Gharbeia / Hermes
+
+* Overview
+
+This module provides rendering of Markdown text, syntax-highlighted code
+blocks, and unified diffs in the terminal. It completes the rendering
+pipeline so that [[file:render.org][the render tree]] can handle rich formatted
+content.
+
+The Markdown renderer is /not/ a general-purpose MD-to-HTML converter.
+It targets TUI output: node types that have clear terminal analogues
+(headings → bold/bright, code blocks → monochrome block, bold → ANSI
+bold, etc.). Edge cases that matter for a terminal (long lines, escape
+sequences inside code, mixed formatting) are handled explicitly.
+
+** Design decisions
+
+1. /Two-phase parse/: block-level first (lines), then inline (characters
+   within each block). This matches how terminals render — block layout
+   first, style within.
+2. /Syntax highlighting by keyword set/: not a full lexer. A lookup
+   table of language → (keywords, types, builtins) sets. Catches ~90%
+   of highlighting cases without pulling in a parser. Fails safe
+   (unmatched tokens render as plain text).
+3. /Diff lines are self-describing/: a diff block starts with ─── or
+   +++, each line has a ± prefix. We don't re-parse patch semantics;
+   we just color by prefix. This makes the renderer tolerant of
+   malformed diffs.
+4. /No recursive descent parser/: a simple state machine over lines for
+   block-level, and a character cursor for inline. Keeps the code
+   short and avoids parser-generator dependencies.
+
+* Code structure
+
+** Node types
+
+We represent the parsed document as a tree of plists. Each node has at
+least a `:type` key. Block-level nodes carry a `:children` list of
+inline nodes. This keeps the data structure simple — no class hierarchy,
+no generic dispatch — while being easy to traverse for rendering.
+
+Node types:
+
+| Block-level      | Inline             |
+|------------------+--------------------|
+| `:heading`       | `:text`            |
+| `:paragraph`     | `:bold`            |
+| `:code-block`    | `:italic`          |
+| `:blockquote`    | `:inline-code`     |
+| `:list-item`     | `:link`            |
+| `:ordered-item`  |                    |
+| `:thematic-break`|                    |
+| `:diff-block`    |                    |
+
+--- per-function: markdown-node-make
+
+~make-md-node~ is a convenience constructor for node plists.
+It ensures `:children` defaults to NIL (not an empty list) so
+renderers can check `(if children ...)` without testing `(when
+children ...)` vs `(if (null children) ...)`.
+
+#+BEGIN_SRC lisp :tangle no
+(defun make-md-node (type &key children properties)
+  "Create a markdown node plist.
+TYPE is a keyword like :heading or :bold.
+CHILDREN is a list of inline node plists (or NIL).
+PROPERTIES is a plist of node-specific extra keys (e.g. :level for headings)."
+  (let ((node (list :type type)))
+    (when children
+      (setf (getf node :children) children))
+    (when properties
+      (setf (getf node :properties) properties))
+    node))
+#+END_SRC
+
+--- per-function: markdown-node-p
+
+~md-node-p~ checks whether something is a markdown node plist.
+We just look for a :type key. This is used in tests and as
+a guard in recursive renderers.
+
+#+BEGIN_SRC lisp :tangle no
+(defun md-node-p (thing)
+  "Return T if THING is a markdown node (has a :type key)."
+  (and (listp thing) (getf thing :type)))
+#+END_SRC
+
+--- per-function: markdown-node-text
+
+~md-node-text~ extracts the plain text from a node tree by
+concatenating all :text children recursively, discarding markup.
+This is useful for things like heading anchors, tooltip strings,
+or search indexing.
+
+#+BEGIN_SRC lisp :tangle no
+(defun md-node-text (node)
+  "Recursively extract plain text from a markdown node tree."
+  (let ((type (getf node :type)))
+    (cond ((eql type :text)
+           (or (getf node :content) ""))
+          ((eql type :link)
+           (concatenate 'string
+                        (md-node-text (first (getf node :children)))
+                        (format nil " (~a)" (or (getf node :url) ""))))
+          ((getf node :children)
+           (apply #'concatenate 'string
+                  (mapcar #'md-node-text (getf node :children))))
+          (t ""))))
+#+END_SRC
+
+** Block-level parser
+
+The block parser operates line-by-line with a simple state machine.
+Each line is classified by its prefix characters, then accumulated
+into a node.
+
+Rules:
+- Lines starting with `#` → heading (count hashes for level)
+- Lines starting with `>` → blockquote (continuation lines merge)
+- Lines starting with `-`, `*`, or `+` → list-item
+- Lines starting with 1-3 digits followed by `.` → ordered-item
+- Lines starting with `` ``` `` → code-block (language on opening line)
+- Lines starting with `---` or `***` → thematic-break
+- Lines starting with `--- ` or `+++ ` → diff-block
+- Empty lines → paragraph boundary
+- Everything else → paragraph (continuation lines merge until blank)
+
+--- per-function: classify-line
+
+~classify-line~ returns a keyword and a data value for a trimmed
+line of text. The state machine uses this to decide what kind of
+block to create or continue.
+
+The function must handle prefix stripping (e.g. remove `# ` after
+counting hashes) and edge cases like `#` inside a code block (which
+we don't classify at all — the code block state machine handles that).
+
+One trap: a line like `#not-a-heading` (no space after hash) is NOT
+a heading in CommonMark. We check for space/tab after the hashes.
+
+Another trap: `* item` in a list vs `**bold**` inline. At the
+block-parser level we only look at /line-start/ `* ` (star + space)
+for list items. A line starting with `** text` could be either a
+nested list item or bold text in a paragraph — we conservatively
+treat it as a list-item (the inline parser will handle ** inside
+paragraphs normally).
+
+#+BEGIN_SRC lisp :tangle no
+(defun classify-line (line)
+  "Classify a trimmed LINE, returning (type . data).
+TYPE is a keyword; DATA is language for code-blocks, level for headings, etc."
+  (cond
+    ;; Empty line
+    ((string= line "") (cons :blank nil))
+    ;; Thematic break: --- or *** (3+ chars, all same, optional whitespace)
+    ((and (>= (length line) 3)
+          (every (lambda (c) (or (char= c (char line 0))
+                                 (char= c #\Space)
+                                 (char= c #\Tab)))
+                 line)
+          (find (char line 0) "-*"))
+     (cons :thematic-break nil))
+    ;; Heading: #+, with space after hashes
+    ((and (char= (char line 0) #\#)
+          (let ((count 0))
+            (loop for c across line
+                  while (char= c #\#)
+                  do (incf count))
+            (and (<= 1 count 6)
+                 (or (>= (length line) (1+ count))
+                     (member (char line count) '(#\Space #\Tab))))))
+     (let* ((hash-count (loop for c across line while (char= c #\#) count c))
+            (content (string-trim (list #\Space #\Tab)
+                                  (subseq line hash-count))))
+       (cons :heading (cons hash-count content))))
+    ;; Blockquote: >
+    ((and (>= (length line) 1) (char= (char line 0) #\>))
+     (let ((content (string-trim (list #\Space #\Tab)
+                                 (subseq line 1))))
+       (cons :blockquote content)))
+    ;; Unordered list: -, *, +
+    ((and (>= (length line) 2)
+          (find (char line 0) "-*+")
+          (char= (char line 1) #\Space))
+     (cons :list-item (string-trim (list #\Space #\Tab) (subseq line 2))))
+    ;; Ordered list: N. or N)
+    ((and (>= (length line) 3)
+          (digit-char-p (char line 0))
+          (loop for c across line
+                while (digit-char-p c)
+                finally (return (find c '(#\. #\) #\Space)))))
+     (let ((dot-pos (position-if (lambda (c) (find c ". )")) line)))
+       (if (and dot-pos (find (char line dot-pos) ". )"))
+           (cons :ordered-item (string-trim (list #\Space #\Tab)
+                                            (subseq line (1+ dot-pos))))
+           (cons :paragraph line))))
+    ;; Diff: --- file or +++ file
+    ((and (>= (length line) 4)
+          (find (char line 0) "-+")
+          (char= (char line 1) (char line 0))
+          (char= (char line 2) (char line 0))
+          (char= (char line 3) #\Space))
+     (cons :diff-header line))
+    ;; Diff: line content with +/- prefix
+    ((and (>= (length line) 1)
+          (find (char line 0) "-+")
+          (not (and (>= (length line) 3)
+                    (char= (char line 1) (char line 0))
+                    (char= (char line 2) (char line 0)))))
+     (cons :diff-line (cons (char line 0) (subseq line 1))))
+    ;; Fenced code block start: ``` or ~~~
+    ((and (>= (length line) 3)
+          (find (char line 0) "`~")
+          (every (lambda (c) (char= c (char line 0)))
+                 (subseq line 0 (min 6 (length line))))
+          (let ((rest (string-trim (list #\Space #\Tab) (subseq line (min 6 (length line))))))
+            (cons :code-start rest))))
+    ;; Default: paragraph content
+    (t (cons :paragraph line))))
+#+END_SRC
+
+--- per-function: parse-blocks
+
+~parse-blocks~ is the main block-level parser. It takes a string
+(possibly multi-line) and returns a list of markdown node plists.
+
+The algorithm:
+1. Split into lines
+2. Classify each line
+3. Accumulate lines of the same type into groups
+4. Convert each group into a node
+
+State transitions:
+- `:paragraph` accumulates until blank line or different block type
+- `:blockquote` accumulates until blank line
+- `:list-item` and `:ordered-item` accumulate until blank line
+- `:code-start` flips to code-block mode; accumulates until matching
+  fence closer or end of input
+- `:diff-header` starts a diff block; diff lines accumulate until
+  blank line or non-diff line
+
+Edge case: a paragraph followed by a list item should stay as
+separate blocks (not merge). The blank-line check handles this
+because the paragraph only continues for non-blank, non-list lines.
+
+#+BEGIN_SRC lisp :tangle no
+(defun parse-blocks (text)
+  "Parse TEXT (a string) into a list of block-level markdown node plists.
+Returns (nodes . unconsumed-lines) for recursive callers."
+  (let ((lines (split-string-into-lines text))
+        (nodes nil)
+        (i 0))
+    (loop while (< i (length lines))
+          do (let* ((line (string-trim (list #\return) (aref lines i)))
+                    (classification (classify-line line)))
+               (case (car classification)
+                 (:blank (incf i))
+                 (:thematic-break
+                  (push (make-md-node :thematic-break) nodes)
+                  (incf i))
+                 (:paragraph
+                  (multiple-value-bind (node consumed)
+                      (parse-paragraph lines i)
+                    (push node nodes)
+                    (setf i consumed)))
+                 (:heading
+                  (let* ((level-and-content (cdr classification))
+                         (level (car level-and-content))
+                         (content (cdr level-and-content)))
+                    (push (make-md-node :heading
+                                        :properties (list :level level)
+                                        :children (parse-inline content))
+                          nodes)
+                    (incf i)))
+                 (:blockquote
+                  (multiple-value-bind (node consumed)
+                      (parse-blockquote lines i)
+                    (push node nodes)
+                    (setf i consumed)))
+                 (:list-item
+                  (multiple-value-bind (node consumed)
+                      (parse-list lines i :unordered)
+                    (push node nodes)
+                    (setf i consumed)))
+                 (:ordered-item
+                  (multiple-value-bind (node consumed)
+                      (parse-list lines i :ordered)
+                    (push node nodes)
+                    (setf i consumed)))
+                 (:code-start
+                  (multiple-value-bind (node consumed)
+                      (parse-code-block lines i (cdr classification))
+                    (push node nodes)
+                    (setf i consumed)))
+                 (:diff-header
+                  (multiple-value-bind (node consumed)
+                      (parse-diff-block lines i)
+                    (push node nodes)
+                    (setf i consumed)))
+                 (t (incf i)))))
+    ;; Return in reading order
+    (nreverse nodes)))
+#+END_SRC
+
+--- per-function: split-string-into-lines
+
+~split-string-into-lines~ is a utility rather than relying on
+~cl-ppcre~ (which we don't depend on). It splits on #\Newline
+and handles the edge case of trailing newlines (doesn't produce
+an extra empty line at the end).
+
+#+BEGIN_SRC lisp :tangle no
+(defun split-string-into-lines (string)
+  "Split STRING into a vector of lines (no trailing newline).
+Handles \\n, \\r\\n, and trailing newlines properly."
+  (let ((result nil)
+        (start 0))
+    (flet ((add-line (end)
+             (push (subseq string start end) result)))
+      (loop for i from 0 below (length string)
+            do (let ((c (char string i)))
+                 (cond ((char= c #\Newline)
+                        (add-line i)
+                        (setf start (1+ i)))
+                       ((and (char= c #\Return)
+                             (< (1+ i) (length string))
+                             (char= (char string (1+ i)) #\Newline))
+                        (add-line i)
+                        (setf start (+ i 2))
+                        (incf i)))))
+      (when (< start (length string))
+        (add-line (length string)))
+      (coerce (nreverse result) 'vector))))
+#+END_SRC
+
+--- per-function: parse-paragraph
+
+~parse-paragraph~ collects one or more contiguous paragraph lines
+until a blank line or a different block type. It joins them with
+spaces (for hard-wrapped prose) and returns a :paragraph node
+with inline-parsed children.
+
+Continuation lines in paragraphs are joined with a single space
+(not a newline). This is correct for Markdown's soft-wrap
+convention where a newline in source = space in output. To force
+a hard break, CommonMark uses two trailing spaces — we skip that
+for now since it's rare in TUI contexts.
+
+#+BEGIN_SRC lisp :tangle no
+(defun parse-paragraph (lines start)
+  "Parse contiguous paragraph lines from LINES starting at START.
+Returns (node . consumed-index)."
+  (let ((text-parts nil)
+        (i start))
+    (loop while (< i (length lines))
+          do (let* ((raw-line (aref lines i))
+                    (line (string-trim (list #\return) raw-line))
+                    (class (classify-line line)))
+               (case (car class)
+                 ((:paragraph)
+                  (push (cdr class) text-parts)
+                  (incf i))
+                 (:blank (incf i) (loop-finish))
+                 (t (loop-finish)))))
+    (let ((text (with-output-to-string (s)
+                  (loop for part in (nreverse text-parts)
+                        for first = t then nil
+                        do (unless first (write-char #\Space s))
+                        (princ part s)))))
+      (cons (make-md-node :paragraph
+                          :children (parse-inline text))
+            i))))
+#+END_SRC
+
+--- per-function: parse-blockquote
+
+~parse-blockquote~ collects contiguous `>` lines, strips the `>`
+prefix, joins them, and wraps in a :blockquote node. Nested
+blockquotes (`> >`) are not supported in this version — a `>` at
+the start of the content is treated as literal text.
+
+#+BEGIN_SRC lisp :tangle no
+(defun parse-blockquote (lines start)
+  "Parse contiguous blockquote lines from LINES starting at START.
+Returns (node . consumed-index)."
+  (let ((text-parts nil)
+        (i start))
+    (loop while (< i (length lines))
+          do (let* ((raw-line (aref lines i))
+                    (line (string-trim (list #\return) raw-line))
+                    (class (classify-line line)))
+               (case (car class)
+                 (:blockquote
+                  (push (cdr class) text-parts)
+                  (incf i))
+                 (:blank (incf i) (loop-finish))
+                 (t (loop-finish)))))
+    (let ((text (with-output-to-string (s)
+                  (loop for part in (nreverse text-parts)
+                        for first = t then nil
+                        do (unless first (write-char #\Space s))
+                        (princ part s)))))
+      (cons (make-md-node :blockquote
+                          :children (parse-inline text))
+            i))))
+#+END_SRC
+
+--- per-function: parse-list
+
+~parse-list~ collects contiguous list items (same type) and returns
+a list of nodes. Each line starting with a list marker becomes one
+list-item node. Nested lists are not supported (lines starting with
+two spaces + marker would be the next level — we skip that for v1).
+
+The TYPE parameter is either `:unordered` or `:ordered` — though
+we return each item labeled by its actual marker type since we
+already classified each line.
+
+#+BEGIN_SRC lisp :tangle no
+(defun parse-list (lines start type)
+  "Parse contiguous list items from LINES starting at START.
+TYPE is :unordered or :ordered.
+Returns (node . consumed-index) where node is a :list-item or :ordered-item."
+  (declare (ignore type))
+  (let ((items nil)
+        (i start))
+    ;; Collect all contiguous list items into ITEMS
+    (loop while (< i (length lines))
+          do (let* ((raw-line (aref lines i))
+                    (line (string-trim (list #\return) raw-line))
+                    (class (classify-line line)))
+               (case (car class)
+                 ((:list-item :ordered-item)
+                  (push (cons (car class) (cdr class)) items)
+                  (incf i))
+                 (:blank
+                  ;; One blank line between items is OK; two ends the list
+                  (if (and (< (1+ i) (length lines))
+                           (let ((next-class (classify-line
+                                              (string-trim
+                                               (list #\return)
+                                               (aref lines (1+ i))))))
+                             (member (car next-class)
+                                     '(:list-item :ordered-item))))
+                      (progn
+                        (push (cons :blank-sep nil) items)
+                        (incf i))
+                      (progn (incf i) (loop-finish))))
+                 (t (loop-finish)))))
+    ;; Convert each item to a node
+    (let ((nodes nil))
+      (dolist (item (nreverse items))
+        (let ((type (car item))
+              (content (cdr item)))
+          (when (and content (not (string= content "")))
+            (push (make-md-node type
+                                :children (parse-inline content))
+                  nodes))))
+      (cons (nreverse nodes) i))))
+#+END_SRC
+
+--- per-function: parse-code-block
+
+~parse-code-block~ reads from the line after the opening fence to
+the closing fence (or end of input). It returns a :code-block node
+with the language (or NIL) and the raw text as the :content. No
+inline parsing is done inside code blocks — everything is literal.
+
+Matching fence: if opened with `` ``` ``, close with `` ``` ``.
+If opened with `~~~`, close with `~~~`. The closing fence must have
+at least as many backticks/tildes as the opening fence (CommonMark
+rule). We use the simpler version: same character, same count.
+
+#+BEGIN_SRC lisp :tangle no
+(defun parse-code-block (lines start lang)
+  "Parse a fenced code block from LINES starting at START.
+LANG is the language string (or empty string) from the opening fence.
+Returns (node . consumed-index)."
+  (let ((code-lines nil)
+        (i (1+ start))
+        (fence-char (char (aref lines start) 0))
+        (fence-len (loop for c across (aref lines start)
+                         while (char= c (char (aref lines start) 0))
+                         count c))
+        (found-close nil))
+    (loop while (< i (length lines))
+          do (let* ((raw-line (aref lines i))
+                    (line (string-trim (list #\return) raw-line)))
+               ;; Check for closing fence
+               (when (and (>= (length line) fence-len)
+                          (every (lambda (c) (char= c fence-char))
+                                 (subseq line 0 fence-len))
+                          (or (= (length line) fence-len)
+                              (every (lambda (c) (find c " \t"))
+                                     (subseq line fence-len))))
+                 (setf found-close t)
+                 (incf i)
+                 (loop-finish))

src/components/markdown-package.lisp

@@ -0,0 +1,65 @@
+;;; markdown-package.lisp — Package definition for cl-tui.markdown
+
+(defpackage :cl-tui.markdown
+  (:use :cl :fiveam)
+  (:export
+   ;; Data structures
+   #:make-md-node
+   #:md-node-p
+   #:md-node-text
+   ;; Parsing
+   #:parse-blocks
+   #:parse-inline
+   ;; Highlighting
+   #:*syntax-highlighters*
+   #:highlight-code
+   ;; Diff
+   #:classify-diff-line
+   ;; Rendering
+   #:render-md
+   #:render-md-node
+   #:render-markdown
+   #:render-inline
+   ;; Styles
+   #:apply-style
+   #:apply-styles
+   ;; Tests (exported test symbols for ASDF integration)
+   #:heading-parsing
+   #:heading-levels
+   #:heading-with-inline-formatting
+   #:paragraph-parsing
+   #:paragraph-multi-line
+   #:bold-parsing
+   #:italic-parsing
+   #:bold-italic-combined
+   #:inline-code-parsing
+   #:link-parsing
+   #:code-block-parsing
+   #:code-block-unknown-language
+   #:blockquote-parsing
+   #:list-item-parsing
+   #:ordered-list-parsing
+   #:thematic-break-parsing
+   #:highlight-lisp-keyword
+   #:highlight-lisp-builtin
+   #:highlight-unknown-language
+   #:highlight-comment
+   #:classify-diff-added
+   #:classify-diff-removed
+   #:classify-diff-hunk
+   #:classify-diff-context
+   #:render-heading-output
+   #:render-paragraph-output
+   #:render-thematic-break-output
+   #:render-code-block-output
+   #:render-diff-block-output
+   #:markdown-integration
+   #:render-markdown-string
+   ;; Internal (for testability)
+   #:classify-line
+   #:split-string-into-lines
+   #:find-closing-marker
+   #:string-prefix-p
+   #:tokenize-line
+   #:apply-highlight-token
+   #:apply-highlight-style))

src/components/markdown.lisp

@@ -0,0 +1,681 @@
+;;; markdown.lisp — Markdown + Code + Diff rendering for cl-tui
+
+(in-package :cl-tui.markdown)
+
+;; ─── Node constructors ────────────────────────────────────────────────────────
+
+(defun make-md-node (type &key children properties content url)
+  (let ((node (list :type type)))
+    (when children (setf (getf node :children) children))
+    (when properties (setf (getf node :properties) properties))
+    (when content (setf (getf node :content) content))
+    (when url (setf (getf node :url) url))
+    node))
+
+(defun md-node-p (thing)
+  (and (listp thing) (getf thing :type)))
+
+(defun md-node-text (node)
+  (let ((type (getf node :type)))
+    (cond ((eql type :text) (or (getf node :content) ""))
+          ((eql type :link)
+           (concatenate 'string
+                        (md-node-text (first (getf node :children)))
+                        (format nil " (~a)" (or (getf node :url) ""))))
+          ((eql type :inline-code) (or (getf node :content) ""))
+          ((getf node :children)
+           (apply #'concatenate 'string
+                  (mapcar #'md-node-text (getf node :children))))
+          (t ""))))
+
+;; ─── Block-level parser ───────────────────────────────────────────────────────
+
+(defun split-string-into-lines (string)
+  (let ((result nil) (start 0))
+    (flet ((add-line (end) (push (subseq string start end) result)))
+      (loop for i from 0 below (length string)
+            do (let ((c (char string i)))
+                 (cond ((char= c #\Newline) (add-line i) (setf start (1+ i)))
+                       ((and (char= c #\Return) (< (1+ i) (length string))
+                             (char= (char string (1+ i)) #\Newline))
+                        (add-line i) (setf start (+ i 2)) (incf i)))))
+      (when (< start (length string)) (add-line (length string)))
+      (coerce (nreverse result) 'vector))))
+
+(defun classify-line (line)
+  (cond
+    ((string= line "") (cons :blank nil))
+    ((and (>= (length line) 3)
+          (let ((c0 (char line 0)))
+            (and (find c0 "-*")
+                 (every (lambda (c) (or (char= c c0) (char= c #\Space) (char= c #\Tab)))
+                        line))))
+     (cons :thematic-break nil))
+    ((and (char= (char line 0) #\#)
+          (let ((count 0))
+            (loop for c across line while (char= c #\#) do (incf count))
+            (and (<= 1 count 6)
+                 (or (>= (length line) (1+ count))
+                     (member (char line count) '(#\Space #\Tab))))))
+     (let* ((hash-count (loop for c across line while (char= c #\#) count c))
+            (content (string-trim (list #\Space #\Tab) (subseq line hash-count))))
+       (cons :heading (cons hash-count content))))
+    ((char= (char line 0) #\>)
+     (cons :blockquote (string-trim (list #\Space #\Tab) (subseq line 1))))
+    ((and (>= (length line) 2) (find (char line 0) "-*+")
+          (char= (char line 1) #\Space))
+     (cons :list-item (string-trim (list #\Space #\Tab) (subseq line 2))))
+    ((and (>= (length line) 3) (digit-char-p (char line 0))
+          (loop for c across line while (digit-char-p c)
+                finally (return (find c ". )"))))
+     (let ((dot-pos (position-if (lambda (c) (find c ". )")) line)))
+       (if (and dot-pos (find (char line dot-pos) ". )"))
+           (cons :ordered-item (string-trim (list #\Space #\Tab)
+                                            (subseq line (1+ dot-pos))))
+           (cons :paragraph line))))
+    ((and (>= (length line) 4) (find (char line 0) "-+")
+          (char= (char line 1) (char line 0))
+          (char= (char line 2) (char line 0))
+          (char= (char line 3) #\Space))
+     (cons :diff-header line))
+    ((and (>= (length line) 1) (find (char line 0) "-+")
+          (not (and (>= (length line) 3)
+                    (char= (char line 1) (char line 0))
+                    (char= (char line 2) (char line 0)))))
+     (cons :diff-line (cons (char line 0) (subseq line 1))))
+    ((and (>= (length line) 3) (find (char line 0) "`~")
+          (let ((fence-len (loop for c across line
+                                 while (char= c (char line 0)) count c)))
+            (and (>= fence-len 3)
+                 (let ((rest (string-trim (list #\Space #\Tab)
+                                         (subseq line fence-len))))
+                   (cons :code-start rest))))))
+    (t (cons :paragraph line))))
+
+(defun find-closing-marker (text start marker)
+  (let ((marker-len (length marker)) (len (length text)))
+    (loop for j from start to (- len marker-len)
+          do (when (and (char= (char text j) (char marker 0))
+                        (string= marker (subseq text j (+ j marker-len)))
+                        (or (= j 0) (not (char= (char text (1- j)) #\\))))
+               (return j))
+          finally (return nil))))
+
+(defun parse-paragraph (lines start)
+  (let ((text-parts nil) (i start))
+    (loop while (< i (length lines))
+          do (let* ((raw-line (aref lines i))
+                    (line (string-trim (list #\return) raw-line))
+                    (class (classify-line line)))
+               (case (car class)
+                 ((:paragraph) (push (cdr class) text-parts) (incf i))
+                 (:blank (incf i) (loop-finish))
+                 (t (loop-finish)))))
+    (values (make-md-node :paragraph :children
+                          (parse-inline
+                           (with-output-to-string (s)
+                             (loop for part in (nreverse text-parts)
+                                   for first = t then nil
+                                   do (unless first (write-char #\Space s))
+                                   (princ part s)))))
+            i)))
+
+(defun parse-blockquote (lines start)
+  (let ((text-parts nil) (i start))
+    (loop while (< i (length lines))
+          do (let* ((raw-line (aref lines i))
+                    (line (string-trim (list #\return) raw-line))
+                    (class (classify-line line)))
+               (case (car class)
+                 (:blockquote (push (cdr class) text-parts) (incf i))
+                 (:blank (incf i) (loop-finish))
+                 (t (loop-finish)))))
+    (values (make-md-node :blockquote :children
+                          (parse-inline
+                           (with-output-to-string (s)
+                             (loop for part in (nreverse text-parts)
+                                   for first = t then nil
+                                   do (unless first (write-char #\Space s))
+                                   (princ part s)))))
+            i)))
+
+(defun parse-list (lines start)
+  (declare (ignore start))
+  (let ((items nil) (i start))
+    (loop while (< i (length lines))
+          do (let* ((raw-line (aref lines i))
+                    (line (string-trim (list #\return) raw-line))
+                    (class (classify-line line)))
+           (case (car class)
+                 ((:list-item :ordered-item)
+                  (push (cons (car class) (cdr class)) items) (incf i))
+                 (:blank
+                  (if (and (< (1+ i) (length lines))
+                           (let ((nc (classify-line
+                                      (string-trim (list #\return)
+                                                   (aref lines (1+ i))))))
+                             (member (car nc) '(:list-item :ordered-item))))
+                      (progn (push (cons :blank-sep nil) items) (incf i))
+                      (progn (incf i) (loop-finish))))
+                 (t (loop-finish)))))
+    (let ((nodes nil))
+      (dolist (item (nreverse items))
+        (let ((type (car item)) (content (cdr item)))
+          (when (and content (not (string= content "")))
+            (push (make-md-node type :children (parse-inline content)) nodes))))
+      (values (nreverse nodes) i))))
+
+(defun parse-code-block (lines start lang)
+  (let ((code-lines nil)
+        (i (1+ start))
+        (fence-char (char (aref lines start) 0))
+        (fence-len (loop for c across (aref lines start)
+                         while (char= c (char (aref lines start) 0)) count c)))
+    (loop while (< i (length lines))
+          do (let* ((raw-line (aref lines i))
+                    (line (string-trim (list #\return) raw-line)))
+               (when (and (>= (length line) fence-len)
+                          (every (lambda (c) (char= c fence-char))
+                                 (subseq line 0 fence-len))
+                          (or (= (length line) fence-len)
+                              (every (lambda (c) (find c " \t"))
+                                     (subseq line fence-len))))
+                 (incf i) (loop-finish))
+               (push line code-lines)
+               (incf i)))
+    (values (make-md-node :code-block
+                          :properties (list :language (and lang (not (string= lang "")) lang))
+                          :content
+                          (with-output-to-string (s)
+                            (loop for cl in (nreverse code-lines)
+                                  for first = t then nil
+                                  do (unless first (terpri s)) (princ cl s))))
+            i)))
+
+(defun parse-diff-block (lines start)
+  (let ((diff-lines nil) (i start))
+    (loop while (< i (length lines))
+          do (let* ((raw-line (aref lines i))
+                    (line (string-trim (list #\return) raw-line))
+                    (class (classify-line line)))
+               (case (car class)
+                 ((:diff-header :diff-line) (push line diff-lines) (incf i))
+                 (:blank (incf i) (loop-finish))
+                 (t (loop-finish)))))
+    (let ((lines-list (nreverse diff-lines)))
+      (values (make-md-node :diff-block
+                            :content
+                            (with-output-to-string (s)
+                              (loop for dl in lines-list
+                                    for first = t then nil
+                                    do (unless first (terpri s)) (princ dl s)))
+                            :properties (list :lines lines-list))
+              i))))
+
+(defun parse-blocks (text)
+  (let ((lines (split-string-into-lines text)) (nodes nil) (i 0))
+    (loop while (< i (length lines))
+          do (let* ((line (string-trim (list #\return) (aref lines i)))
+                    (classification (classify-line line)))
+               (case (car classification)
+                 (:blank (incf i))
+                 (:thematic-break (push (make-md-node :thematic-break) nodes) (incf i))
+                 (:paragraph
+                  (multiple-value-bind (node consumed) (parse-paragraph lines i)
+                    (push node nodes) (setf i consumed)))
+                 (:heading
+                  (let* ((level+content (cdr classification))
+                         (level (car level+content))
+                         (content (cdr level+content)))
+                    (push (make-md-node :heading :properties (list :level level)
+                                        :children (parse-inline content)) nodes)
+                    (incf i)))
+                 (:blockquote
+                  (multiple-value-bind (node consumed) (parse-blockquote lines i)
+                    (push node nodes) (setf i consumed)))
+                 (:list-item
+                  (multiple-value-bind (node consumed) (parse-list lines i)
+                    (dolist (n node) (push n nodes)) (setf i consumed)))
+                 (:ordered-item
+                  (multiple-value-bind (node consumed) (parse-list lines i)
+                    (dolist (n node) (push n nodes)) (setf i consumed)))
+                 (:code-start
+                  (multiple-value-bind (node consumed)
+                      (parse-code-block lines i (cdr classification))
+                    (push node nodes) (setf i consumed)))
+                 (:diff-header
+                  (multiple-value-bind (node consumed) (parse-diff-block lines i)
+                    (push node nodes) (setf i consumed)))
+                 (t (incf i)))))
+    (nreverse nodes)))
+
+;; ─── Inline parser ────────────────────────────────────────────────────────────
+
+(defun parse-inline (text)
+  (unless (and text (> (length text) 0)) (return-from parse-inline nil))
+  (let ((nodes nil) (i 0) (len (length text)))
+    (loop while (< i len)
+          do (let ((c (char text i)))
+               (case c
+                 (#\*
+                  (multiple-value-bind (node consumed) (parse-star-emphasis text i len)
+                    (if node (progn (push node nodes) (setf i consumed))
+                        (progn (push (make-md-node :text :content (string c)) nodes) (incf i)))))
+                 (#\_
+                  (multiple-value-bind (node consumed) (parse-underscore-emphasis text i len)
+                    (if node (progn (push node nodes) (setf i consumed))
+                        (progn (push (make-md-node :text :content (string c)) nodes) (incf i)))))
+                 (#\`
+                  (multiple-value-bind (node consumed) (parse-inline-code text i len)
+                    (if node (progn (push node nodes) (setf i consumed))
+                        (progn (push (make-md-node :text :content (string c)) nodes) (incf i)))))
+                 (#\[
+                  (multiple-value-bind (node consumed) (parse-link text i len)
+                    (if node (progn (push node nodes) (setf i consumed))
+                        (progn (push (make-md-node :text :content (string c)) nodes) (incf i)))))
+                 (t (let ((start i))
+                      (incf i)
+                      (loop while (< i len)
+                            do (let ((nc (char text i)))
+                                 (if (find nc "*_`[") (loop-finish)
+                                     (progn
+                                       (when (and (< (1+ i) len)
+                                                  (find nc "*_")
+                                                  (char= nc (char text (1+ i))))
+                                         (loop-finish))
+                                       (incf i)))))
+                      (push (make-md-node :text :content (subseq text start i)) nodes))))))
+    (nreverse nodes)))
+
+(defun parse-star-emphasis (text i len)
+  (when (>= i len) (return-from parse-star-emphasis (values nil i)))
+  (if (and (< (1+ i) len) (char= (char text (1+ i)) #\*))
+      (let ((close (find-closing-marker text (+ i 2) "**")))
+        (if close
+            (values (make-md-node :bold :children (parse-inline (subseq text (+ i 2) close)))
+                    (+ close 2))
+            (values nil i)))
+      (let ((close (find-closing-marker text (1+ i) "*")))
+        (if close
+            (values (make-md-node :italic :children (parse-inline (subseq text (1+ i) close)))
+                    (1+ close))
+            (values nil i)))))
+
+(defun parse-underscore-emphasis (text i len)
+  (when (>= i len) (return-from parse-underscore-emphasis (values nil i)))
+  (when (and (> i 0) (not (find (char text (1- i)) " \t\n\r")))
+    (return-from parse-underscore-emphasis (values nil i)))
+  (if (and (< (1+ i) len) (char= (char text (1+ i)) #\_))
+      (let ((close (find-closing-marker text (+ i 2) "__")))
+        (if close
+            (values (make-md-node :bold :children (parse-inline (subseq text (+ i 2) close)))
+                    (+ close 2))
+            (values nil i)))
+      (let ((close (find-closing-marker text (1+ i) "_")))
+        (if (and close
+                 (or (>= (1+ close) len)
+                     (find (char text (1+ close)) " \t\n\r.,;:!?")))
+            (values (make-md-node :italic :children (parse-inline (subseq text (1+ i) close)))
+                    (1+ close))
+            (values nil i)))))
+
+(defun parse-inline-code (text i len)
+  (when (or (>= i len) (not (char= (char text i) #\`)))
+    (return-from parse-inline-code (values nil i)))
+  (let ((bt-count (loop for j from i below (min len (+ i 3))
+                        while (char= (char text j) #\`) count j)))
+    (let ((close (find-closing-marker text (+ i bt-count)
+                                      (make-string bt-count :initial-element #\`))))
+      (if close
+          (values (make-md-node :inline-code
+                                :content (subseq text (+ i bt-count) close))
+                  (+ close bt-count))
+          (values nil i)))))
+
+(defun parse-link (text i len)
+  (when (or (>= i len) (not (char= (char text i) #\[)))
+    (return-from parse-link (values nil i)))
+  (let ((close-bracket (find-closing-marker text (1+ i) "]")))
+    (unless close-bracket (return-from parse-link (values nil i)))
+    (when (or (>= (1+ close-bracket) len)
+              (not (char= (char text (1+ close-bracket)) #\()))
+      (return-from parse-link (values nil i)))
+    (let ((close-paren (find-closing-marker text (+ close-bracket 2) ")")))
+      (unless close-paren (return-from parse-link (values nil i)))
+      (values (make-md-node :link
+                            :children (parse-inline (subseq text (1+ i) close-bracket))
+                            :url (subseq text (+ close-bracket 2) close-paren))
+              (1+ close-paren)))))
+
+;; ─── Syntax highlighting ──────────────────────────────────────────────────────
+
+(defun get-highlighter (lang)
+  (cdr (assoc lang
+              '(("lisp"    . (:comment (";" "#|" ";;") :string ("\"")
+                             :keyword ("defun" "defmacro" "defmethod" "defgeneric"
+                                       "defvar" "defparameter" "defconstant" "defstruct"
+                                       "defclass" "deftype" "define-condition"
+                                       "let" "let*" "flet" "labels" "macrolet"
+                                       "if" "when" "unless" "cond" "case" "ecase" "typecase"
+                                       "loop" "do" "dolist" "dotimes" "tagbody" "go"
+                                       "block" "return" "return-from"
+                                       "progn" "prog1" "prog2"
+                                       "lambda" "function" "quote"
+                                       "setf" "setq" "push" "pop" "incf" "decf"
+                                       "in-package" "defpackage" "export" "import"
+                                       "handler-case" "handler-bind" "ignore-errors"
+                                       "multiple-value-bind" "multiple-value-call"
+                                       "destructuring-bind"
+                                       "declare" "the" "values"
+                                       "and" "or" "not" "null"
+                                       "car" "cdr" "first" "rest" "second"
+                                       "cons" "list" "append" "nconc"
+                                       "mapcar" "mapc" "reduce"
+                                       "find" "position" "count" "subseq"
+                                       "format" "princ" "print" "write" "read"
+                                       "load" "compile" "eval"
+                                       "make-instance" "slot-value"
+                                       "type-of" "class-of")
+                             :builtin ("t" "nil"
+                                       "*standard-output*" "*standard-input*"
+                                       "*error-output*" "*debug-io*"
+                                       "*package*" "*print-circle*")))
+
+                ("common-lisp" . (:comment (";" "#|" ";;") :string ("\"")
+                                 :keyword ("defun" "defmacro" "defmethod" "defgeneric"
+                                           "let" "if" "when" "unless" "cond" "case"
+                                           "loop" "do" "dolist" "dotimes"
+                                           "return" "return-from" "block"
+                                           "lambda" "function" "quote"
+                                           "setf" "setq" "push" "pop" "incf" "decf"
+                                           "handler-case" "handler-bind"
+                                           "declare" "the" "values"
+                                           "defpackage" "in-package" "export" "import"
+                                           "error" "warn" "assert"
+                                           "car" "cdr" "first" "rest"
+                                           "cons" "list" "append" "mapcar" "reduce"
+                                           "format" "princ" "print" "read" "load"
+                                           "make-instance")
+                                 :builtin ("t" "nil")))
+
+                ("python"  . (:comment ("#") :string ("\"" "'" "\"\"\"" "'''")
+                             :keyword ("def" "class" "return" "yield" "import" "from"
+                                       "if" "elif" "else" "for" "while" "in" "not"
+                                       "try" "except" "finally" "raise" "with" "pass"
+                                       "break" "continue" "lambda" "global"
+                                       "assert" "del" "is"
+                                       "self" "cls" "async" "await")
+                             :builtin ("None" "True" "False")))
+
+                ("javascript" . (:comment ("//" "/*") :string ("\"" "'" "`")
+                                :keyword ("function" "class" "const" "let" "var"
+                                          "if" "else" "for" "while" "do" "switch"
+                                          "return" "break" "continue"
+                                          "try" "catch" "finally" "throw"
+                                          "new" "this" "super" "delete" "typeof"
+                                          "import" "export" "from" "default"
+                                          "async" "await" "yield" "of")
+                                :builtin ("true" "false" "null" "undefined" "NaN")))
+
+                ("bash"    . (:comment ("#") :string ("\"" "'")
+                             :keyword ("if" "then" "else" "elif" "fi" "for" "while"
+                                       "done" "case" "esac" "in" "function" "return"
+                                       "export" "local" "unset" "source"
+                                       "echo" "printf" "read" "test" "let" "declare")
+                             :builtin ("true" "false" "cd" "ls" "cat" "grep" "sed"
+                                       "mv" "cp" "rm" "mkdir" "touch" "find" "wc"
+                                       "head" "tail" "date" "sleep" "kill")))
+
+                ("shell"   . (:comment ("#") :string ("\"" "'")
+                             :keyword ("if" "then" "else" "elif" "fi" "for" "while"
+                                       "done" "case" "esac" "in" "function" "return"
+                                       "export" "local" "unset" "source"
+                                       "echo" "printf" "read" "test")
+                             :builtin ("true" "false" "cd" "ls" "grep" "sed"
+                                       "mv" "cp" "rm" "mkdir" "touch" "find"))))
+              :test #'string=)))
+
+(defun tokenize-line (line highlighter)
+  (let ((tokens nil) (i 0) (len (length line))
+        (comment-chars (getf highlighter :comment))
+        (string-chars (getf highlighter :string))
+        (keywords (getf highlighter :keyword))
+        (builtins (getf highlighter :builtin)))
+    (loop while (< i len)
+          do (let ((c (char line i)))
+               (cond
+                 ((find c " \t")
+                  (let ((start i))
+                    (loop while (and (< i len) (find (char line i) " \t")) do (incf i))
+                    (push (cons (subseq line start i) :plain) tokens)))
+                 ((and comment-chars
+                       (some (lambda (cc)
+                               (and (<= (+ i (length cc)) len)
+                                    (string= cc (subseq line i (+ i (length cc))))))
+                             comment-chars))
+                  (push (cons (subseq line i) :comment) tokens) (setf i len))
+                 ((and string-chars (some (lambda (s) (find c s)) string-chars))
+                  (let ((start i))
+                    (incf i)
+                    (let ((triple (and (< i (1- len)) (char= (char line i) c)
+                                       (char= (char line (1+ i)) c))))
+                      (if triple
+                          (progn (incf i 2)
+                                 (loop while (and (< i len)
+                                                 (not (and (char= (char line i) c)
+                                                           (< (1+ i) len)
+                                                           (char= (char line (1+ i)) c)
+                                                           (< (+ i 2) len)
+                                                           (char= (char line (+ i 2)) c))))
+                                       do (incf i))
+                                 (incf i 3))
+                          (progn (loop while (and (< i len) (char/= (char line i) c))
+                                       do (incf i))
+                                 (when (< i len) (incf i)))))
+                    (push (cons (subseq line start i) :string) tokens)))
+                 ((or (digit-char-p c)
+                      (and (find c "+-") (< (1+ i) len) (digit-char-p (char line (1+ i)))))
+                  (let ((start i))
+                    (loop while (and (< i len) (not (find (char line i) " \t()[]{}'\";:#")))
+                          do (incf i))
+                    (let ((token (subseq line start i)))
+                      (if (digit-char-p (char token 0))
+                          (push (cons token :number) tokens)
+                          (push (cons token :plain) tokens)))))
+                 ((or (alpha-char-p c)
+                      (and (find c "-_?!*<>=") (> len 1)))
+                  (let ((start i))
+                    (loop while (and (< i len)
+                                    (or (alphanumericp (char line i))
+                                        (find (char line i) "-_?!*<>=")))
+                          do (incf i))
+                    (let* ((token (subseq line start i))
+                          (down (string-downcase token)))
+                      (cond
+                        ((find down keywords :test #'string=)
+                         (push (cons token :keyword) tokens))
+                        ((find down builtins :test #'string=)
+                         (push (cons token :builtin) tokens))
+                        (t (if (and (< i len) (char= (char line i) #\())
+                               (push (cons token :function) tokens)
+                               (push (cons token :plain) tokens)))))))
+                 (t (push (cons (string c) :plain) tokens) (incf i)))))
+    (nreverse tokens)))
+
+(defun highlight-code (code language)
+  (let ((highlighter (get-highlighter (and language (string-downcase language)))))
+    (unless highlighter (return-from highlight-code (list (cons code :plain))))
+    (let ((tokens nil))
+      (with-input-from-string (stream code)
+        (loop for line = (read-line stream nil nil) while line
+              do (let ((line-tokens (tokenize-line line highlighter)))
+                   (when tokens (push (cons (string #\Newline) :plain) tokens))
+                   (setf tokens (nconc (nreverse line-tokens) tokens)))))
+      (nreverse tokens))))
+
+(defun apply-highlight-token (token category)
+  (let ((code (case category
+                (:keyword "33") (:builtin "36")
+                (:function "34") (:comment "2") (:string "32") (:number "35")
+                (t nil))))
+    (if code (format nil "~c[~am~a~c[0m" #\Escape code token #\Escape) token)))
+
+(defun apply-highlight-style (char-vector)
+  (coerce char-vector 'string))
+
+;; ─── Diff rendering ───────────────────────────────────────────────────────────
+
+(defun string-prefix-p (prefix string)
+  (and (>= (length string) (length prefix))
+       (string= prefix (subseq string 0 (length prefix)))))
+
+(defun classify-diff-line (line)
+  (cond ((string-prefix-p "+++ " line) :file-header)
+        ((string-prefix-p "--- " line) :file-header)
+        ((string-prefix-p "@@" line) :hunk-header)
+        ((string-prefix-p "+" line) :added)
+        ((string-prefix-p "-" line) :removed)
+        (t :context)))
+
+;; ─── Rendering ────────────────────────────────────────────────────────────────
+
+(defun apply-style (style text)
+  (let ((code (cond
+               ((eql style :bold) "1") ((eql style :italic) "3")
+               ((eql style :dim) "2") ((eql style :code) "0")
+               ((eql style :link) "4;36") ((eql style :url) "4;2")
+               ((eql style :underline) "4") ((eql style :strike) "9")
+               ((eql style :black) "30") ((eql style :red) "31")
+               ((eql style :green) "32") ((eql style :yellow) "33")
+               ((eql style :blue) "34") ((eql style :magenta) "35")
+               ((eql style :cyan) "36") ((eql style :white) "37")
+               ((eql style :bright-black) "90") ((eql style :bright-red) "91")
+               ((eql style :bright-green) "92") ((eql style :bright-yellow) "93")
+               ((eql style :bright-blue) "94") ((eql style :bright-magenta) "95")
+               ((eql style :bright-cyan) "96") ((eql style :bright-white) "97")
+               ((string= style "bold") "1") ((string= style "italic") "3")
+               ((string= style "dim") "2") ((string= style "code") "0")
+               ((string= style "link") "4;36") ((string= style "url") "4;2")
+               ((string= style "bright-cyan") "96")
+               ((string= style "bright-yellow") "93")
+               ((string= style "bright-white") "97")
+               ((string= style "bright-red") "91")
+               ((string= style "bright-green") "92")
+               ((string= style "bright-blue") "94")
+               ((string= style "bright-magenta") "95")
+               ((string= style "cyan") "36") ((string= style "yellow") "33")
+               ((string= style "red") "31") ((string= style "green") "32")
+               ((string= style "blue") "34") ((string= style "magenta") "35")
+               ((string= style "white") "37") ((string= style "black") "30")
+               (t nil))))
+    (if code (format nil "~c[~am~a~c[0m" #\Escape code text #\Escape) text)))
+
+(defun render-inline (children)
+  (if (null children) ""
+      (with-output-to-string (s)
+        (dolist (child children)
+          (let ((type (getf child :type)))
+            (case type
+              (:text (princ (or (getf child :content) "") s))
+              (:bold (princ (apply-style :bold (render-inline (getf child :children))) s))
+              (:italic (princ (apply-style :italic (render-inline (getf child :children))) s))
+              (:inline-code (princ (apply-style :code (or (getf child :content) "")) s))
+              (:link (let ((text (render-inline (getf child :children)))
+                           (url (or (getf child :url) "")))
+                       (princ (apply-style :link text) s)
+                       (when (and url (not (string= url "")))
+                         (princ " " s)
+                         (princ (apply-style :url (format nil "(~a)" url)) s))))
+              (t (princ (or (getf child :content) "") s))))))))
+
+(defun render-heading (node)
+  (let* ((level (or (getf (getf node :properties) :level) 1))
+         (prefix (make-string (min level 6) :initial-element #\#))
+         (text (render-inline (getf node :children)))
+         (color (cond ((= level 1) :bright-cyan) ((= level 2) :bright-yellow)
+                      (t :bright-white))))
+    (list (apply-style color (concatenate 'string prefix " " text)))))
+
+(defun render-paragraph (node)
+  (list (render-inline (getf node :children))))
+
+(defun render-blockquote (node)
+  (list (apply-style :dim (concatenate 'string "> " (render-inline (getf node :children))))))
+
+(defun render-code-block (node)
+  (let* ((language (or (getf (getf node :properties) :language) ""))
+         (content (or (getf node :content) ""))
+         (highlighted (unless (or (null language) (string= language ""))
+                        (highlight-code content language)))
+         (lines nil))
+    (when (and language (not (string= language "")))
+      (push (apply-style :dim (format nil "  ~~~~~~ ~a" language)) lines))
+    (if highlighted
+        (let ((cl (make-array 0 :element-type 'character
+                              :fill-pointer 0 :adjustable t))
+              (output nil))
+          (dolist (pair highlighted)
+            (let ((token (car pair)) (category (cdr pair)))
+              (cond ((string= token (string #\Newline))
+                     (push (apply-highlight-style cl) output)
+                     (setf cl (make-array 0 :element-type 'character
+                                          :fill-pointer 0 :adjustable t)))
+                    (t (let ((colored (apply-highlight-token token category)))
+                         (loop for ch across colored
+                               do (vector-push-extend ch cl)))))))
+          (when (> (length cl) 0) (push (apply-highlight-style cl) output))
+          (setf lines (nconc lines (nreverse output))))
+        (with-input-from-string (s content)
+          (loop for line = (read-line s nil nil) while line
+                do (push (apply-style :code line) lines))))
+    (nreverse lines)))
+
+(defun render-diff-block (node)
+  (let* ((lines (getf (getf node :properties) :lines)) (result nil))
+    (dolist (line (or lines
+                      (and (getf node :content)
+                           (let ((l (split-string-into-lines (getf node :content))))
+                             (loop for i from 0 below (length l) collect (aref l i))))))
+      (let* ((class (classify-diff-line line))
+             (color (case class
+                      (:added "32") (:removed "31")
+                      (:hunk-header "36") (:file-header "1;36") (t nil))))
+        (if color
+            (push (format nil "~c[~am~a~c[0m" #\Escape color line #\Escape) result)
+            (push line result))))
+    (nreverse result)))
+
+(defun render-thematic-break (node)
+  (declare (ignore node))
+  (list (apply-style :dim "──────────────────────────────────────────────")))
+
+(defun render-list-item (node)
+  (list (concatenate 'string
+                     (if (eql (getf node :type) :ordered-item) " 1." " * ")
+                     (render-inline (getf node :children)))))
+
+(defun render-md-node (node)
+  (let ((type (getf node :type)))
+    (case type
+      (:heading (render-heading node))
+      (:paragraph (render-paragraph node))
+      (:blockquote (render-blockquote node))
+      (:code-block (render-code-block node))
+      (:diff-block (render-diff-block node))
+      (:thematic-break (render-thematic-break node))
+      (:list-item (render-list-item node))
+      (:ordered-item (render-list-item node))
+      (t (list "")))))
+
+(defun render-md (nodes)
+  (let ((lines nil))
+    (dolist (node nodes) (setf lines (nconc lines (render-md-node node))))
+    lines))
+
+(defun render-markdown (text)
+  (let ((nodes (parse-blocks text)) (parts nil))
+    (dolist (line (render-md nodes)) (push line parts))
+    (with-output-to-string (s)
+      (loop for part in (nreverse parts)
+            for first = t then nil
+            do (unless first (terpri s)) (princ part s)))))

tests/markdown-tests.lisp

@@ -0,0 +1,205 @@
+;;; markdown-tests.lisp — Tests for cl-tui.markdown
+
+(defpackage :cl-tui-markdown-test
+  (:use :cl :cl-tui.markdown :fiveam))
+
+(in-package :cl-tui-markdown-test)
+
+;; Test suite
+(def-suite :cl-tui-markdown-test
+  :description "Markdown parser/renderer tests for cl-tui.markdown")
+
+(in-suite :cl-tui-markdown-test)
+
+;; ─── Parser tests ─────────────────────────────────────────────────────────────
+
+(def-test heading-parsing ()
+  (let* ((result (parse-blocks "# Hello World")) (node (first result)))
+    (is-true (eql :heading (getf node :type)))
+    (is (= 1 (getf (getf node :properties) :level)))))
+
+(def-test heading-levels ()
+  (loop for level from 1 to 6
+        do (let* ((hashes (make-string level :initial-element #\#))
+                  (text (format nil "~a Heading ~d" hashes level))
+                  (result (parse-blocks text))
+                  (node (first result)))
+             (is-true (eql :heading (getf node :type)))
+             (is (= level (getf (getf node :properties) :level))))))
+
+(def-test heading-with-inline-formatting ()
+  (let* ((result (parse-blocks "# Hello **World**"))
+         (node (first result)) (children (getf node :children)))
+    (is-true (eql :heading (getf node :type)))
+    (is (= 2 (length children)))
+    (is-true (eql :text (getf (first children) :type)))
+    (is-true (eql :bold (getf (second children) :type)))))
+
+(def-test paragraph-parsing ()
+  (let* ((result (parse-blocks "This is a paragraph.")) (node (first result)))
+    (is-true (eql :paragraph (getf node :type)))))
+
+(def-test paragraph-multi-line ()
+  (let* ((result (parse-blocks "Line one\nLine two")) (node (first result)))
+    (is-true (eql :paragraph (getf node :type)))))
+
+(def-test bold-parsing ()
+  (let* ((children (parse-inline "hello **world** here"))
+         (bold-node (second children)))
+    (is (= 3 (length children)))
+    (is-true (eql :bold (getf bold-node :type)))))
+
+(def-test italic-parsing ()
+  (let* ((children (parse-inline "hello *world* here"))
+         (italic-node (second children)))
+    (is (= 3 (length children)))
+    (is-true (eql :italic (getf italic-node :type)))))
+
+(def-test bold-italic-combined ()
+  (let ((children (parse-inline "**bold** and *italic*")))
+    (is (= 3 (length children)))
+    (is-true (eql :bold (getf (first children) :type)))
+    (is-true (eql :italic (getf (third children) :type)))))
+
+(def-test inline-code-parsing ()
+  (let* ((children (parse-inline "use `foo` here"))
+         (code-node (second children)))
+    (is (= 3 (length children)))
+    (is-true (eql :inline-code (getf code-node :type)))
+    (is (equal "foo" (getf code-node :content)))))
+
+(def-test link-parsing ()
+  (let* ((children (parse-inline "click [here](https://x.com)"))
+         (link-node (second children)))
+    (is (= 2 (length children)))
+    (is-true (eql :link (getf link-node :type)))
+    (is (equal "https://x.com" (getf link-node :url)))
+    (let ((link-text (getf link-node :children)))
+      (is (= 1 (length link-text)))
+      (is-true (eql :text (getf (first link-text) :type)))
+      (is (equal "here" (getf (first link-text) :content))))))
+
+(def-test code-block-parsing ()
+  (let* ((text (format nil "```lisp~%(defun hello ())~%  (print \"hi\")~%```"))
+         (result (parse-blocks text)) (node (first result)))
+    (is-true (eql :code-block (getf node :type)))
+    (is (equal "lisp" (getf (getf node :properties) :language)))
+    (is-true (search "(defun hello" (getf node :content)))))
+
+(def-test code-block-unknown-language ()
+  (let* ((text (format nil "```~%plain code~%```"))
+         (result (parse-blocks text)) (node (first result)))
+    (is-true (eql :code-block (getf node :type)))
+    (is-false (getf (getf node :properties) :language))))
+
+(def-test blockquote-parsing ()
+  (let* ((result (parse-blocks "> This is a quote")) (node (first result)))
+    (is-true (eql :blockquote (getf node :type)))))
+
+(def-test list-item-parsing ()
+  (let* ((result (parse-blocks "- First item")) (node (first result)))
+    (is-true (eql :list-item (getf node :type)))))
+
+(def-test ordered-list-parsing ()
+  (let* ((result (parse-blocks "1. First item")) (node (first result)))
+    (is-true (eql :ordered-item (getf node :type)))))
+
+(def-test thematic-break-parsing ()
+  (let* ((result (parse-blocks "---")) (node (first result)))
+    (is-true (eql :thematic-break (getf node :type)))))
+
+;; ─── Diff tests ───────────────────────────────────────────────────────────────
+
+(def-test classify-diff-added ()
+  (is (eql :added (classify-diff-line "+this is added"))))
+
+(def-test classify-diff-removed ()
+  (is (eql :removed (classify-diff-line "-this is removed"))))
+
+(def-test classify-diff-hunk ()
+  (is (eql :hunk-header (classify-diff-line "@@ -1,3 +1,4 @@"))))
+
+(def-test classify-diff-context ()
+  (is (eql :context (classify-diff-line " normal context"))))
+
+;; ─── Syntax highlighting tests ────────────────────────────────────────────────
+(def-test highlight-lisp-keyword ()
+  (let ((tokens (highlight-code "(defun hello ()" "lisp")))
+    (is-true (some (lambda (pair) (and (search "defun" (car pair))
+                                       (eql :keyword (cdr pair))))
+                   tokens))))
+
+(def-test highlight-lisp-builtin ()
+  "Test that a Lisp builtin like nil is highlighted as :builtin."
+  (let ((tokens (highlight-code "(if t nil)" "lisp")))
+    (is-true (some (lambda (pair) (and (string= (car pair) "nil")
+                                       (eql :builtin (cdr pair))))
+                   tokens))))
+
+(def-test highlight-unknown-language ()
+  (let ((tokens (highlight-code "hello world" "unknown-xyz")))
+    (every (lambda (pair) (eql :plain (cdr pair))) tokens)))
+
+(def-test highlight-comment ()
+  (let ((tokens (highlight-code "; this is a comment" "lisp")))
+    (is-true (some (lambda (pair) (eql :comment (cdr pair))) tokens))))
+
+;; ─── Render tests ─────────────────────────────────────────────────────────────
+
+(def-test render-heading-output ()
+  (let* ((node (make-md-node :heading :properties (list :level 2)
+                             :children (list (make-md-node :text :content "Test"))))
+         (lines (render-md-node node)))
+    (is (= 1 (length lines)))
+    (is-true (> (length (first lines)) 0))))
+
+(def-test render-paragraph-output ()
+  (let* ((node (make-md-node :paragraph
+                             :children (list (make-md-node :text :content "Hello"))))
+         (lines (render-md-node node)))
+    (is (= 1 (length lines)))
+    (is-true (search "Hello" (first lines)))))
+
+(def-test render-thematic-break-output ()
+  (let* ((node (make-md-node :thematic-break)) (lines (render-md-node node)))
+    (is (= 1 (length lines)))))
+
+(def-test render-code-block-output ()
+  (let* ((node (make-md-node :code-block :content "(print \"hello\")"
+                             :properties (list :language "lisp")))
+         (lines (render-md-node node)))
+    (is-true (> (length lines) 0))))
+
+(def-test render-diff-block-output ()
+  (let* ((node (make-md-node :diff-block :properties
+                             (list :lines
+                                   '("--- a/file" "+++ b/file" "@@ -1 +1 @@"
+                                     "+added" "-removed" " context"))))
+         (lines (render-md-node node)))
+    (is (= 6 (length lines)))
+    (is (search "added" (fourth lines)))
+    (is (search "removed" (fifth lines)))))
+
+;; ─── Integration tests ────────────────────────────────────────────────────────
+
+(def-test markdown-integration ()
+  (let* ((md (format nil "# Title~%~%This is **bold** and `code`.~%~%- Item 1~%- Item 2~%~%> A quote~%~%```lisp~%(defun hello ())~%  (print \"hi\")~%```~%~%---"))
+         (nodes (parse-blocks md)) (lines (render-md nodes)))
+    (is-true (> (length lines) 5))
+    (is-true (search "# Title" (first lines)))))
+
+(def-test render-markdown-string ()
+  (let ((result (render-markdown "**bold** text")))
+    (is-true (stringp result))
+    (is-true (> (length result) 0))))
+
+(def-test md-node-text-simple ()
+  (let ((node (make-md-node :text :content "hello")))
+    (is (equal "hello" (md-node-text node)))))
+
+(def-test md-node-text-nested ()
+  (let ((node (make-md-node :paragraph :children
+                            (list (make-md-node :text :content "hello")
+                                  (make-md-node :bold :children
+                                                (list (make-md-node :text :content "world")))))))
+    (is (equal "helloworld" (md-node-text node)))))