From 8d612cb1905ab3d989ab795e08495d9c716fb007 Mon Sep 17 00:00:00 2001
From: Yuchen Pei <id@ypei.org>
Date: Sun, 9 Jul 2023 17:17:41 +1000
Subject: Implement wikilink following

---
 wiki-engine.el | 25 +++++++++++++------------
 wiki-markup.el | 15 ++++++++++++---
 wiki-utils.el  | 18 +++++++++++++-----
 3 files changed, 38 insertions(+), 20 deletions(-)

diff --git a/wiki-engine.el b/wiki-engine.el
index a2fcaef..a9f65d5 100644
--- a/wiki-engine.el
+++ b/wiki-engine.el
@@ -25,22 +25,23 @@
 ;; client to wiki engines, wiki server software.
 
 ;;; Code:
-(require 'wiki-markup)
+(require 'wiki-utils)
 
-(defvar-local wiki-engine-host "https://en.wikipedia.org"
-  "The host of the current wiki engine instance.")
+(defun wiki-make-wikilink-url (title))
 
-(defvar-local wiki-engine-path "/wiki/"
-  "The path to the current wiki engine instance.")
-
-(defun wiki-engine-mediawiki-fetch (title)
-  (interactive "sFetch wiki title: ")
+(defun wiki-engine-mediawiki-fetch (base-url title fetcher)
+  "Fetch a mediawiki entry describing TITLE."
   (wiki-fetch-url
-   (format "%s%s%s?action=raw"
-           wiki-engine-host wiki-engine-path title))
-  (wiki-mode))
-
+   (format "%s%s?action=raw" base-url title)
+   (lambda ()
+     (wiki-mode)
+     (setq-local wiki-fetcher fetcher)
+     )))
 
+(defun wiki-wikipedia-fetch (title)
+  (interactive "sFetch wiki title: ")
+  (wiki-engine-mediawiki-fetch "https://en.wikipedia.org/wiki/" title
+                               'wiki-wikipedia-fetch))
 
 (provide 'wiki-engine)
 ;;; wiki-engine.el ends here
diff --git a/wiki-markup.el b/wiki-markup.el
index 0675c44..4a74974 100644
--- a/wiki-markup.el
+++ b/wiki-markup.el
@@ -68,8 +68,14 @@
 
 (defvar wiki-outline-regexp "=+.*=+\ *$")
 
+(defvar-local wiki-fetcher nil
+  "Buffer-local function to fetch a wiki title")
+(defun wiki-follow-wikilink-action (data)
+  "Button action to follow a wikilink"
+  (funcall wiki-fetcher (alist-get 'title data)))
+
 (defun wiki-outline-level ()
-  (when (looking-at "\\(=+\\).*\\(=+\\)\ *$")
+  (when (looking-at "\\(=+\\).*[^=]\\(=+\\)\\ *$")
     (min (length (match-string 1))
          (length (match-string 2))
          6)))
@@ -83,9 +89,13 @@
             (end (match-end 0))
             (visible-start (or (match-beginning 2) (match-beginning 1)))
             (visible-end (or (match-end 2) (match-end 1)))
+            (title (buffer-substring-no-properties (match-beginning 1)
+                                                   (match-end 1)))
             )
         (put-text-property start visible-start 'invisible t)
-        (put-text-property start end 'font-lock-face 'wiki-link)
+        (make-text-button start end
+                          'action 'wiki-follow-wikilink-action
+                          'button-data `((title . ,title)))
         (put-text-property visible-end end 'invisible t)
         (add-text-properties (1- visible-start) visible-start
                              '(rear-nonsticky (invisible)))
@@ -105,7 +115,6 @@
   (setq-local comment-start "<!--")
   (setq-local comment-end "-->")
 
-  ;; FIXME: this should not be necessary in outline mode
   (setq-local font-lock-defaults
               '(wiki-font-lock-keywords
                 t
diff --git a/wiki-utils.el b/wiki-utils.el
index 80680b7..53b7bd0 100644
--- a/wiki-utils.el
+++ b/wiki-utils.el
@@ -25,14 +25,21 @@
 ;; wiki utility functions.
 
 ;;; Code:
+(require 'url-parse)
+
 (defvar wiki-download-dir "~/Downloads")
 
-(defun wiki-fetch-url (url)
-  "Fetch url and returns the buffer."
+(defun wiki-fetch-url (url &optional callback)
+  "Fetch URL asynchronously.
+
+Then calls CALLBACK which is a closure taking no argument."
   (interactive "sURL: ")
   (let ((file-name (expand-file-name (wiki-make-file-name-from-url url)
-                                     wiki-download-dir)))
-    (url-retrieve url 'wiki-fetch-url-save-and-switch (list file-name)))
+                                     wiki-download-dir))
+        (cb (lambda (status file-name)
+              (wiki-fetch-url-save-and-switch status file-name)
+              (when callback (funcall callback)))))
+    (url-retrieve url cb (list file-name)))
   )
 
 (defun wiki-fetch-url-save-and-switch (status file-name)
@@ -41,7 +48,8 @@
     (write-file file-name)
     (let ((coding-system-for-read 'utf-8))
       (revert-buffer t t))
-    (switch-to-buffer (current-buffer))))
+    (switch-to-buffer (current-buffer))
+    ))
 
 (defun wiki-delete-http-header ()
   (delete-region (point-min) (progn (wiki-skip-http-header) (point))))
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