From 161752ee1943dbb25060a1488086da1a00aeaadb Mon Sep 17 00:00:00 2001
From: Yuchen Pei <id@ypei.org>
Date: Mon, 10 Jul 2023 13:12:18 +1000
Subject: Implement wiki-fetch-prefer-local

---
 wiki-engine.el | 46 +++++++++++++++++++++++++++++++++++++---------
 wiki-utils.el  |  4 ++--
 2 files changed, 39 insertions(+), 11 deletions(-)

diff --git a/wiki-engine.el b/wiki-engine.el
index b82b9aa..fb48994 100644
--- a/wiki-engine.el
+++ b/wiki-engine.el
@@ -37,15 +37,20 @@ The site name is passed as a symbol WIKI-SITE."
   (let ((wiki-site-info (alist-get wiki-site wiki-sites)))
     (cl-assert (eq (plist-get wiki-site-info :engine) 'mediawiki))
     (when (string-empty-p title) (setq title "Main Page"))
-    (wiki-fetch-url
-     (format "%s%s?action=raw"
-             (plist-get wiki-site-info :base-url)
-             title)
-     (lambda ()
-       (wiki-mode)
-       (setq-local wiki-site wiki-site)
-       )
-     )))
+    (unless (and wiki-fetch-prefer-local
+                 (wiki-local-find-file
+                  title
+                  (wiki-locate-dir wiki-site)))
+      (wiki-fetch-url
+       (format "%s%s?action=raw"
+               (plist-get wiki-site-info :base-url)
+               title)
+       (wiki-locate-dir wiki-site)
+       (lambda ()
+         (wiki-mode)
+         (setq-local wiki-site wiki-site)
+         )
+       ))))
 
 (defun wiki-engine-oddmuse-fetch (wiki-site title)
   (let ((wiki-site-info (alist-get wiki-site wiki-sites)))
@@ -54,6 +59,7 @@ The site name is passed as a symbol WIKI-SITE."
      (format "%s?action=download;id=%s"
              (plist-get wiki-site-info :base-url)
              title)
+     (wiki-locate-dir wiki-site)
      (lambda ()
        (wiki-mode)
        (setq-local wiki-site wiki-site)
@@ -67,12 +73,34 @@ The site name is passed as a symbol WIKI-SITE."
      (format "%s%s?action=raw"
              (plist-get wiki-site-info :base-url)
              title)
+     (wiki-locate-dir wiki-site)
      (lambda ()
        (wiki-mode)
        (setq-local wiki-site wiki-site)
        )
      title)))
 
+(defun wiki-locate-dir (wiki-site)
+  "Locate the directory for a WIKI-SITE."
+  (expand-file-name (format "%s" wiki-site) wiki-local-dir))
+
+(defun wiki-local-find-file (title &optional dir create-if-not-exists
+                                   extension)
+  "Find local TITLE in DIR.
+
+Returns the file-name if success, and nil otherwise. If
+CREATE-IF-NOT-EXISTS is non-nil, creates the file is not found.
+DIR defaults to `default-directory'."
+  (unless dir (setq dir default-directory))
+  (let ((file-name (expand-file-name
+                    (if extension
+                        (file-name-extension title extension)
+                      title)
+                    dir)))
+    (when (or (file-exists-p file-name) create-if-not-exists)
+      (find-file file-name)
+      file-name)))
+
 (defun wiki-engine-fetcher (wiki-site-info)
   (intern (format "wiki-engine-%s-fetch"
                   (plist-get wiki-site-info :engine))))
diff --git a/wiki-utils.el b/wiki-utils.el
index 5b66075..c2500a4 100644
--- a/wiki-utils.el
+++ b/wiki-utils.el
@@ -34,14 +34,14 @@
   "If non-nil, visit the local file if exists when instructed for
 fetching.")
 
-(defun wiki-fetch-url (url &optional callback title)
+(defun wiki-fetch-url (url dir &optional callback title)
   "Fetch URL asynchronously.
 
 Then calls CALLBACK which is a closure taking no argument."
   (interactive "sURL: ")
   (let ((file-name (expand-file-name
                     (or title (wiki-make-file-name-from-url url))
-                    wiki-download-dir))
+                    dir))
         (cb (lambda (status file-name)
               (wiki-fetch-url-save-and-switch status file-name)
               (when callback (funcall callback)))))
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