Follow link in toc: M-x markdown-toc-follow-toc-link-at-point

Related #42

markdown-toc.el

@@ -217,7 +217,7 @@ Return the end position if it exists, nil otherwise."
           markdown-toc-header-toc-end))
 
 (defcustom markdown-toc-indentation-space 4
-  "Let the user decide the indentation level")
+  "Let the user decide the indentation level.")
 
 (defcustom markdown-toc-user-toc-structure-manipulation-fn
   (lambda (toc-structure) toc-structure)
@@ -264,6 +264,8 @@ If called interactively with prefix arg REPLACE-TOC-P, replaces previous TOC."
          markdown-toc--generate-toc
          insert)))
 
+(defalias 'markdown-toc/generate-toc 'markdown-toc-generate-toc)
+
 ;;;###autoload
 (defun markdown-toc-generate-or-refresh-toc ()
   "Generate a TOC for markdown file at current point or refreshes an already generated TOC."
@@ -284,7 +286,44 @@ If called interactively with prefix arg REPLACE-TOC-P, replaces previous TOC."
   (save-excursion
     (markdown-toc--delete-toc t)))
 
-(defalias 'markdown-toc/generate-toc 'markdown-toc-generate-toc)
+(defun markdown-toc--read-title-out-of-link (link)
+  "Extract the link title out of a markdown LINK title.
+This assumes no funky stuff in the markdown link format ` - [<title>](...) `  "
+  (->> link
+       s-trim
+       (s-chop-prefix "- [")
+       (s-split "]")
+       car))
+
+(defun markdown-toc--title-level (link)
+  "Determine the markdown title LINK out of its indentation.
+If misindented or not prefixed by `-`, it's considered not a link
+and returns nil. Otherwise, returns the level number."
+  (when (s-prefix? "-" (-> link s-trim)) ;; if not, it's not a link title
+    (let ((indent (->> link
+                       (s-split "-")
+                       car  ;; first string contains a string with empty spaces
+                       ;; which should be a multiple of
+                       ;; `markdown-toc-indentation-space`
+                       length)))
+      (when (zerop (% indent markdown-toc-indentation-space))
+        (+ 1 (/ indent markdown-toc-indentation-space))))))
+
+;;;###autoload
+(defun markdown-toc-follow-toc-link-at-point ()
+  "On a given toc link, navigate to the current markdown header.
+If the toc is misindented (according to
+markdown-toc-indentation-space`) or if not on a toc link, this
+does nothing.
+"
+  (interactive)
+  (let* ((full-title (buffer-substring-no-properties (point-at-bol) (point-at-eol))))
+    (let ((level (markdown-toc--title-level full-title)))
+      (when level ;; nil if misindented or not on a title
+        (let ((title (markdown-toc--read-title-out-of-link full-title)))
+          (goto-char (point-min))
+          (search-forward-regexp (format "%s %s" (s-repeat level "#") title))))
+      (message "markdown-toc: Not on a link (or misindented), nothing to do"))))
 
 (defun markdown-toc--bug-report ()
   "Compute the bug report for the user to include."

test/markdown-toc-test.el

@@ -716,5 +716,90 @@ System information:
                                                     ((:input '((:message2)) :output :res2))))
                    (markdown-toc-bug-report)))))
 
+(ert-deftest markdown-toc--read-title-out-of-link ()
+  (should (string= "this is the title"
+                   (markdown-toc--read-title-out-of-link "  - [this is the title](#this-is-the-link)   ")))
+  (should (string= "another title"
+                   (markdown-toc--read-title-out-of-link "  - [another title](#this-is-the-link)
+with multiple line
+should not matter "))))
+
+(ert-deftest markdown-toc--title-level ()
+  (should (eq 1
+              (markdown-toc--title-level "- [this is the title](#this-is-the-link)")))
+  (should (eq 4
+              (let ((markdown-toc-indentation-space 4))
+                (markdown-toc--title-level "            - [this is the title](#this-is-the-link)"))))
+  (should (eq 2
+              (let ((markdown-toc-indentation-space 2))
+                (markdown-toc--title-level "  - [another title](#this-is-the-link)
+with multiple line
+should not matter "))))
+  (should (eq 2
+              (let ((markdown-toc-indentation-space 3))
+                (markdown-toc--title-level "   - [another title](#this-is-the-link)
+with multiple line
+should not matter "))))
+  ;; no - as prefix so considered not a title
+  (should-not (markdown-toc--title-level "[this is the title](#this-is-the-link)"))
+  ;; prefixed with a dash but misaligned, title should be indented with a
+  ;; multiple of `markdown-toc-indentation-space` blank spaces
+  (should-not (markdown-toc--title-level " - [title](#this-is-the-link)")))
+
+(ert-deftest markdown-toc-follow-toc-link-at-point()
+  "Follow a correct toc link should follow to the title"
+  (should (string= "## Sources"
+                   (with-temp-buffer
+                     (insert "- [some markdown page title](#some-markdown-page-title)
+- [main title](#main-title)
+    - [Sources](#sources)
+        - [Marmalade (recommended)](#marmalade-recommended)
+
+# main title
+## Sources
+### marmalade
+...
+")
+                     (search-backward "- [Sources]")
+                     (call-interactively 'markdown-toc-follow-toc-link-at-point)
+                     (buffer-substring-no-properties (point-at-bol) (point-at-eol))))))
+
+(ert-deftest markdown-toc-follow-toc-link-at-point-failures()
+  "Follow a misindented toc link should do nothing"
+  (should
+   ;; not move
+   (string= "   - [Sources](#sources)  <- misindented 3 instead of 4 here"
+            (with-temp-buffer
+              (insert "- [some markdown page title](#some-markdown-page-title)
+- [main title](#main-title)
+   - [Sources](#sources)  <- misindented 3 instead of 4 here
+
+# main title
+## Sources
+...
+")
+              (search-backward "- [Sources]")
+              (call-interactively 'markdown-toc-follow-toc-link-at-point)
+              (buffer-substring-no-properties (point-at-bol) (point-at-eol)))))
+
+  (should
+   ;; not move as well because
+   (string= "not a title"
+            (with-temp-buffer
+              (insert "- [some markdown page title](#some-markdown-page-title)
+- [main title](#main-title)
+   - [Sources](#sources)
+        - [Marmalade (recommended)](#marmalade-recommended)
+
+# main title
+## Sources
+### marmalade
+not a title
+...
+")
+              (search-backward "not a title")
+              (call-interactively 'markdown-toc-follow-toc-link-at-point)
+              (buffer-substring-no-properties (point-at-bol) (point-at-eol))))))
+
 (provide 'markdown-toc-tests)
 ;;; markdown-toc-tests.el ends here