From 0326e6ff2eedbb13882237540ccbcb874536f914 Mon Sep 17 00:00:00 2001
From: Brit Butler <redline6561@gmail.com>
Date: Tue, 21 Aug 2012 21:20:01 -0400
Subject: [PATCH] Add prev/next support.

---
 TODO             |  2 +-
 coleslaw.asd     |  6 +++---
 src/indices.lisp | 13 +++++++------
 src/posts.lisp   | 21 +++++++++++++++------
 4 files changed, 26 insertions(+), 16 deletions(-)

diff --git a/TODO b/TODO
index dbcc304..e43ec24 100644
--- a/TODO
+++ b/TODO
@@ -13,7 +13,7 @@ Plugins? Injection support for HEAD and BODY. What about predicate-based injecti
 How is it served? Hunchentoot, Lighttpd, S3, whomever!
 
 TODO:
-; blockers to use this for redlinernotes: prev/next, rss/atom feed, markdown support
+; blockers to use this for redlinernotes: rss/atom feed, markdown support
 ; after that, focus on injections for code highlighting and latex
 
 ; doc themes and plugins
diff --git a/coleslaw.asd b/coleslaw.asd
index 34e9574..744e0fa 100644
--- a/coleslaw.asd
+++ b/coleslaw.asd
@@ -10,11 +10,11 @@
   :components ((:file "packages")
                (:file "config")
                (:file "git")
-               (:file "coleslaw")
                (:file "themes")
+               (:file "plugins")
+               (:file "coleslaw")
                (:file "posts")
-               (:file "indices")
-               (:file "plugins"))
+               (:file "indices"))
   :in-order-to ((test-op (load-op coleslaw-tests)))
   :perform (test-op :after (op c)
                     (funcall (intern "RUN!" :coleslaw-tests)
diff --git a/src/indices.lisp b/src/indices.lisp
index eef69d4..01bc2e3 100644
--- a/src/indices.lisp
+++ b/src/indices.lisp
@@ -30,7 +30,7 @@
   "Sort POSTS in reverse chronological order."
   (sort posts #'string> :key #'post-date))
 
-(defun write-index (posts filename title)
+(defun write-index (posts filename title &optional prev next)
   "Write out the HTML for POSTS to FILENAME.html."
   (let ((content (loop for post in posts
                     collect (list :url (format nil "~a/posts/~a.html"
@@ -45,18 +45,19 @@
                                 :monthlinks (monthlinks)
                                 :title title
                                 :posts content
-                                ; TODO: Populate prev and next with links.
-                                :prev nil
-                                :next nil)))))
+                                :prev (and prev (format nil "~d.html" prev))
+                                :next (and next (format nil "~d.html" next)))))))
 
 (defun render-by-20 ()
   "Render the indices to view posts in reverse chronological order by 20."
   (flet ((by-20 (posts start)
            (let ((index (* 20 (1- start))))
              (subseq posts index (min (length posts) (+ index 20))))))
-    (let ((posts (by-date (hash-table-value *posts*))))
+    (let ((posts (by-date (hash-table-values *posts*))))
       (loop for i = 1 then (1+ i)
-         do (write-index (by-20 posts i) (format nil "~d.html" i) "Recent Posts")
+         do (write-index (by-20 posts i) (format nil "~d.html" i) "Recent Posts"
+                         (and (plusp (1- i)) (1- i))
+                         (and (< (* i 20) (length posts)) (1+ i)))
          until (> (* i 20) (length posts))))))
 
 (defun render-by-tag ()
diff --git a/src/posts.lisp b/src/posts.lisp
index d3730c2..6ce5c41 100644
--- a/src/posts.lisp
+++ b/src/posts.lisp
@@ -22,10 +22,20 @@
                    (post-slug post))
             (setf (gethash (post-slug post) *posts*) post))))))
 
+(defun post-url (post)
+  "Return the relative URL for a given post."
+  (format nil "posts/~a.html" (post-slug post)))
+
 (defun render-posts ()
   "Iterate through the files in the repo to render+write the posts out to disk."
   (load-posts)
-  (maphash #'write-post *posts*))
+  (loop with posts = (sort (hash-table-values *posts*) #'string< :key #'post-date)
+     for i from 1 upto (length posts)
+     for prev = nil then post
+     for post = (nth (1- i) posts)
+     for next = (nth (1+ i) posts)
+     do (write-post post :prev (and prev (post-url prev))
+                         :next (and next (post-url next)))))
 
 (defgeneric render-content (text format)
   (:documentation "Compile TEXT from the given FORMAT to HTML for display.")
@@ -51,18 +61,17 @@
            (append args (list :content (read-line in nil)
                               :slug (slugify (getf args :title))))))))
 
-(defun write-post (slug post)
+(defun write-post (post &key prev next)
   "Write out the HTML for POST in SLUG.html."
-  (render-page (format nil "posts/~a.html" slug)
+  (render-page (post-url post)
                (funcall (theme-fn "POST")
                         (list :title (post-title post)
                               :tags (post-tags post)
                               :date (post-date post)
                               :content (render-content (post-content post)
                                                        (post-format post))
-                              ; TODO: Populate prev and next with links.
-                              :prev nil
-                              :next nil))))
+                              :prev prev
+                              :next next))))
 
 (defun slug-char-p (char)
   "Determine if CHAR is a valid slug (i.e. URL) character."