post: Add convenience procedures for post author, tags, and title.

Author, tags and title metadata are commonly used,

* haunt/post.scm (post-author, post-tags, post-title): New procedures.
* tests/post.scm ("post-author, author metadata", "post-tags, tags
metadata", "post-title, title metadata", "post-author, no metadata",
"post-tags, no metadata", "post-title, no metadata"): New tests.
* doc/haunt.texi (Posts): Docs for new procedures.

3 files changed, 59 insertions, 2 deletions

diff --git a/doc/haunt.texi b/doc/haunt.texi
index 23f45d8..3deba4c 100644
--- a/doc/haunt.texi
+++ b/doc/haunt.texi
@@ -530,6 +530,21 @@ specified.
 Sort @var{posts}, a list of posts, in reverse chronological order.
 @end deffn
 
+@deffn {Scheme Procedure} post-author @var{post}
+Return the author of @var{post}, or @code{#f} if no author is
+specified.
+@end deffn
+
+@deffn {Scheme Procedure} post-tags @var{post}
+Return list of tags for @var{post}, or the empty list if no tags are
+specified.
+@end deffn
+
+@deffn {Scheme Procedure} post-title @var{post}
+Return the title of @var{post}, or @code{#f} if no title is
+specified.
+@end deffn
+
 @deffn {Scheme Procedure} posts/group-by-tag @var{posts}
 Create an association list of tags mapped to the posts in the list
 @var{posts} that used them.
diff --git a/haunt/post.scm b/haunt/post.scm
index ebe2689..d15efd2 100644
--- a/haunt/post.scm
+++ b/haunt/post.scm
@@ -40,6 +40,9 @@
             post-slug
             %default-date
             post-date
+            post-author
+            post-tags
+            post-title
             posts/reverse-chronological
             posts/group-by-tag
 
@@ -73,7 +76,7 @@
   (or (post-ref post 'slug)
       (string-join (map (lambda (s)
                           (string-filter char-set:slug s))
-                        (string-split (string-downcase (post-ref post 'title))
+                        (string-split (string-downcase (post-title post))
                                       char-set:whitespace))
                    "-")))
 
@@ -94,6 +97,19 @@ specified."
         (lambda (a b)
           (time>? (post-time a) (post-time b)))))
 
+(define (post-author post)
+  "Return the author of POST, or #f if no author is specified."
+  (post-ref post 'author))
+
+(define (post-tags post)
+  "Return list of tags for POST, or the empty list if no tags are
+specified."
+  (or (post-ref post 'tags) '()))
+
+(define (post-title post)
+  "Return the title of POST, or #f if no title is specified."
+  (post-ref post 'title))
+
 (define (posts/group-by-tag posts)
   "Return an alist of tags mapped to the posts that used them."
   (let ((table (make-hash-table)))
@@ -103,7 +119,7 @@ specified."
                               (if current
                                   (hash-set! table tag (cons post current))
                                   (hash-set! table tag (list post)))))
-                          (or (post-ref post 'tags) '())))
+                          (post-tags post)))
               posts)
     (hash-fold alist-cons '() table)))
 
diff --git a/tests/post.scm b/tests/post.scm
index db1a82c..d01ed84 100644
--- a/tests/post.scm
+++ b/tests/post.scm
@@ -53,6 +53,32 @@
       (list newest middle oldest)
       (posts/reverse-chronological (list oldest newest middle))))
 
+  (let ((example-post (make-post "foo.skr"
+                        '((author . "Eva Luator")
+                          (tags "foo" "bar" "baz")
+                          (title . "Hello, world!"))
+                        '())))
+    (test-equal "post-author, author metadata"
+      "Eva Luator"
+      (post-author example-post))
+    (test-equal "post-tags, tags metadata"
+      '("foo" "bar" "baz")
+      (post-tags example-post))
+    (test-equal "post-title, title metadata"
+      "Hello, world!"
+      (post-title example-post)))
+
+  (let ((no-metadata-post (make-post "foo.skr" '() '())))
+    (test-equal "post-author, no metadata"
+      #f
+      (post-author no-metadata-post))
+    (test-equal "post-tags, no metadata"
+      '()
+      (post-tags no-metadata-post))
+    (test-equal "post-title, no metadata"
+      #f
+      (post-title no-metadata-post)))
+
   (let ((foo-post (make-post "foo.skr" '((tags "foo")) '()))
         (another-foo-post (make-post "another-foo.skr" '((tags "foo")) '()))
         (bar-post (make-post "bar.skr" '((tags "bar")) '())))