builder: Add primitive blog builder.

* haunt/builder/blog.scm: New file.
* Makefile.am (SOURCES): Add it.

Makefile.am

@@ -48,6 +48,7 @@ SOURCES =					\
   haunt/site.scm				\
   haunt/build/html.scm				\
   haunt/builder/atom.scm			\
+  haunt/builder/blog.scm			\
   haunt/ui.scm					\
   haunt/ui/build.scm				\
   haunt/ui/serve.scm				\

haunt/builder/blog.scm

@@ -0,0 +1,81 @@
+;;; Haunt --- Static site generator for GNU Guile
+;;; Copyright © 2015 David Thompson <davet@gnu.org>
+;;;
+;;; This file is part of Haunt.
+;;;
+;;; Haunt is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or
+;;; (at your option) any later version.
+;;;
+;;; Haunt is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+;;; General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with Haunt.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+;;
+;; Page builders
+;;
+;;; Code:
+
+(define-module (haunt builder blog)
+  #:use-module (srfi srfi-19)
+  #:use-module (haunt site)
+  #:use-module (haunt post)
+  #:use-module (haunt page)
+  #:use-module (haunt utils)
+  #:use-module (haunt build html)
+  #:export (blog))
+
+(define (ugly-theme site post)
+  "Render POST on SITE with an unstyled, barebones theme."
+  `((doctype "html")
+    (head
+     (title ,(string-append (post-ref post 'title)
+                            " — "
+                            (site-title site))))
+    (body
+     (h1 ,(post-ref post 'title))
+     (h3 ,(post-ref post 'author))
+     (div ,(post-sxml post)))))
+
+(define* (blog #:key (theme ugly-theme) prefix)
+  "Return a procedure that transforms a list of posts into pages
+decorated by THEME, whose URLs start with PREFIX."
+  (define (make-file-name base-name)
+    (if prefix
+        (string-append prefix "/" base-name)
+        base-name))
+
+  (define (post-uri post)
+    (string-append "/" (or prefix "") (post-slug post) ".html"))
+
+  (define (post->recent-post-entry post)
+    `(li
+      (a (@ (href ,(post-uri post)))
+         ,(post-ref post 'title))))
+
+  (lambda (site posts)
+    (define (post->page post)
+      (let ((base-name (string-append (post-slug post) ".html")))
+        (make-page (make-file-name base-name)
+                   (theme site post)
+                   sxml->html)))
+
+    (define index-page
+      (make-page (make-file-name "index.html")
+                 `((doctype "html")
+                   (head
+                    (title ,(site-title site)))
+                   (body
+                    (h1 ,(site-title site))
+                    (h3 "Recent Posts")
+                    (ul ,@(map post->recent-post-entry
+                               (posts/reverse-chronological posts)))))
+                 sxml->html))
+
+    (cons index-page (map post->page posts))))