break haunt.scm down into smaller (bandali *) modules

[~bandali/bndl.org] / bandali / tags.scm

diff --git a/bandali/tags.scm b/bandali/tags.scm
new file mode 100644 (file)
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--- /dev/null
+++ b/bandali/tags.scm
@@ -0,0 +1,75 @@
+;;; Copyright © 2019 Amin Bandali <bandali@gnu.org>
+;;;
+;;; This program 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.
+;;;
+;;; This program 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 this program. If not, see
+;;; <http://www.gnu.org/licenses/>.
+
+(define-module (bandali tags)
+  #:use-module (bandali prefs)          ; my-*
+  #:use-module (bandali theme)          ; bandali-theme
+  #:use-module (bandali utils)          ; aa
+  #:use-module (haunt builder blog)     ; theme-collection-template
+  #:use-module (haunt html)             ; sxml->html
+  #:use-module (haunt page)             ; make-page
+  #:use-module (haunt post)
+  #:use-module (ice-9 match)            ; match-lambda
+  #:export (tag-uri
+            tag-pages
+            tag-links))
+
+(define* (tag-uri prefix tag #:optional (ext ".html"))
+  "Return a URI relative to the site's root for a page listing entries
+in PREFIX that are tagged with TAG."
+  (string-append "/" prefix "/" tag ext))
+
+(define* (tag-pages #:key
+                    (theme bandali-theme)
+                    (prefix "")
+                    (filter posts/reverse-chronological))
+  "Return a builder procedure that renders a list page for every tag
+used in a post.  All arguments are optional:
+
+PREFIX: The directory in which to write the posts
+FILTER: The procedure called to manipulate the posts list before rendering"
+  (lambda (site posts)
+    (define (tag-list tag posts all-posts)
+      (define (render-list title posts prefix)
+        (let ((body ((theme-collection-template theme)
+                     site title posts prefix all-posts tag)))
+          ((theme-layout theme) site title body)))
+      (make-page (tag-uri my-tag-prefix tag)
+                 (render-list (string-append "Notes tagged ‘" tag "’")
+                              (filter posts)
+                              prefix)
+                 sxml->html))
+    (let ((tag-groups (posts/group-by-tag posts)))
+      (map (match-lambda
+             ((tag . tagged-posts) (tag-list tag tagged-posts posts)))
+           tag-groups))))
+
+(define (tag-links posts)
+  "Generate an alphabetically sorted list of links to tagged posts.
+The link text consists of the tag name and the number of tagged posts
+in parentheses."
+  `(ul (@ (class "tag-list"))
+       ,(map (match-lambda
+               ((tag . posts)
+                `(li
+                  ,(aa (string-append tag
+                                      " ("
+                                      (number->string (length posts))
+                                      ")")
+                       (tag-uri my-tag-prefix tag)))))
+             ;; sort by tag
+             (sort (posts/group-by-tag posts)
+                   (lambda (a b) (string<? (car a) (car b)))))))