;; -*- lexical-binding: t -*-

(require 'ennum-html)
(require 'ennum-image)
(require 'ox)
(require 'seq)
(require 'loadhist)
(require 'map)
(require 'memoize)
(require 'simple-httpd)

(defgroup ennum nil
  "Org-mode static blog generator."
  :group 'applications)

(defconst ennum-version "0.1.0"
  "Ennum version string.")

(defcustom ennum-blog nil
  "Property list specifying ennum publish settings.

Valid properties are described below.

`:working-directory'

Absolute path to directory containing the blog source code. All
paths (`:posts-directory', `:images-directory',
`:static-directory', `:videos-directory' `:other-files-directory',
`:output-directory', `:store', etc.) are interpreted relative to
this path.

`:output-directory'

Path to output directory. All output paths (`:atom-feed-file',
`:tag-directory', etc.) are interpreted relative to
`:output-directory'.

`:posts-directory'

Source directory with blog posts to publish. All posts in this
directory are exported. If the post contains source blocks that
need to be tangled, the tangled files are written to a
`:static-directory' relative to `:output-directory'.

`:images-directory'

Source directory containing images that are linked to. Images
contained in this directory that are also linked to from a post
using the \"image\" link type, or are a poster of a linked to
video file are published.

`:static-directory'

Source directory containing linked static files. Static files
that are linked to from a post using the \"static\" link type are
published. Static files not linked to from any post are not
published.

`:videos-directory'

Source directory containing video files that are linked to. Video
files that are linked to from a post using the \"video\" link
type are published. Video files not linked to from any post are
not published.

`:other-files-directory'

Source directory containing other files to publish. org files in
this directory are exported. Other files are copied verbatim. The
directory structure in this directory is mirrored in the output
directory.

`:tag-directory'

Output directory to which to write per-tag post
listings. Defaults to \"tag\".

`:atom-feed-file'

Path to the Atom feed file. Defaults to \"blog.atom\".

`:atom-feed-number-of-posts'

Number of most recent posts to include in the Atom feed. Defaults
to 12.

`:blog-title'

Title of the blog.

`:blog-subtitle'

Subtitle of the blog.

`:blog-scheme'

Scheme of blog URI. Usually, one of \"http\" or
\"https\". Defaults to \"https\".

`:blog-domain'

Domain the blog will be published on. For example,
\"example.com\".

`:blog-license'

Text declaring the license the blog is published under. For
example, \"All content is licensed under a Creative Commons
Attribution-ShareAlike 4.0 International License.\"

`:image-width'

Width to downsize images to. Defaults to 640 pixels.

`:image-link-width'

Width of images linked to from downsized images. Defaults to 1024
pixels.

`:image-thumbnail-width'

Width of thumbnail images in post listings. Defaults to 320
pixels.

`:locale-alist'

Association list mapping languages to locales. Defaults
to ((\"en\" . \"C\")).

`:required-metadata'

List of post metadata properties that are required. If any post
does not have the listed metadata properties, an error is
raised. Defaults to (:title :date).

`:store'

Path to the ennum store. The store is a temporary directory used
to cache various versions of built artifacts. It is always safe
to delete. If the store path is relative, it is interpreted
relative to `:working-directory'. Defaults to \".ennum\"."
  :group 'ennum)

(defvar ennum-track-features
  '(ennum ennum-html ennum-image ob-tangle org ox ox-html)
  "List of features to track on expression evaluation.")

(defvar ennum-feature-hash
  nil
  "List of hashes tracking current state of features.")

(defmacro ennum-with-file-contents (file &rest body)
  "Create a temporary buffer, insert contents of FILE into that
buffer and evaluate BODY. The value returned is the value of the
last form in BODY."
  (declare (indent defun))
  `(with-temp-buffer
     (insert-file-contents ,file)
     ,@body))

(defmacro ennum-with-current-directory (directory &rest body)
  "Change to DIRECTORY, evaluate BODY and restore the current
working directory. The value returned is the value of the last
form in BODY."
  (declare (indent defun))
  (let ((current-directory-symbol (make-symbol "current-directory")))
    `(let ((,current-directory-symbol default-directory))
       (unwind-protect (progn (cd ,directory) ,@body)
         (cd ,current-directory-symbol)))))

(defmacro ennum-with-temporary-directory (temporary-directory &rest body)
  "Create temporary directory, evaluate BODY with the absolute
path of that directory assigned to TEMPORARY-DIRECTORY and
finally delete the temporary directory. The value returned is the
value of the last form in BODY."
  (declare (indent defun))
  `(let ((,temporary-directory (make-temp-file "ennum" t)))
     (unwind-protect
         (progn ,@body)
       (delete-directory ,temporary-directory t))))

;; TODO: Should the store have an absolute path to deal with directory
;; changes? Yes, since we ask for an absolute working directory, we
;; should.
(defun ennum-intern (filename)
  (let* ((store-item
          (expand-file-name (ennum-file-hash filename)
                            (ennum-setting :store)))
         (interned-path (expand-file-name (file-name-nondirectory filename)
                                          store-item)))
    (unless (file-exists-p store-item)
      (message "Interning %s in %s" filename store-item)
      (ennum-copy filename interned-path t)
      (ennum--set-file-modes-recursively store-item #o555 #o444 #o555))
    interned-path))

(defun ennum--hash ()
  "Return SHA256 hash of buffer contents encoded using
filename-safe base64 encoding. See RFC 4648§5. Briefly, this is a
variant of base64 encoding where characters + and / are replaced
respectively by - and _, and the pad character = is optional."
  (replace-regexp-in-string
   (rx (any ?+ ?/ ?=))
   (lambda (str)
     (pcase str
       ("+" "-")
       ("/" "_")
       ("=" "")))
   (base64-encode-string
    (secure-hash 'sha256 (current-buffer) nil nil t))))

(defun ennum-file-hash (file)
  (ennum--file-hash file (file-attribute-modification-time
                          (file-attributes file))))

(defmemoize ennum--file-hash (file _last-modified)
  (with-temp-buffer
    ;; TODO: Use ennum-with-file-contents
    (set-buffer-multibyte nil)
    (insert-file-contents-literally file)
    (insert file)
    (ennum--hash)))

(defun ennum--feature-environment (feature)
  "Return hash of the current state of FEATURE.

The returned hash is the hash of the file providing FEATURE, and
the current state of all its variables."
  (pcase (feature-symbols feature)
    (`(,file . ,entries)
     (with-temp-buffer
       ;; Print hash of file.
       (print (ennum-file-hash file) (current-buffer))
       ;; Print variables and their values.
       (dolist (variable entries)
         (print (if (and (atom variable)
                         (boundp variable)
                         ;; Exclude `ennum-feature-hash' since it
                         ;; is meant to be changed on each run.
                         (not (eq variable 'ennum-feature-hash)))
                    (cons variable (symbol-value variable))
                  variable)
                (current-buffer)))
       (ennum--hash)))))

(defun ennum--set-file-modes-recursively (directory directory-mode file-mode executable-file-mode)
  (chmod directory directory-mode)
  (dolist (file (ennum-directory-files directory t t))
    (chmod file
           (cond
            ((file-directory-p file) directory-mode)
            ((file-executable-p file) executable-file-mode)
            (t file-mode)))))

(defmacro ennum-exp (&rest body)
  `(ennum-eval (lambda () ,@body)))

(defun ennum-eval (closure)
  (let ((output
         (expand-file-name
          (with-temp-buffer
            (let ((print-length nil)
                  (print-level nil))
              (print ennum-feature-hash (current-buffer))
              (print closure (current-buffer)))
            (ennum--hash))
          (ennum-setting :store))))
    ;; Create store if it doesn't exist
    (ennum-mkdir-p (ennum-setting :store))
    ;; Create store item if it doesn't already exist
    (unless (file-exists-p output)
      (message "Building %s" output)
      (ennum-with-temporary-directory temporary-directory
        (ennum-with-current-directory temporary-directory
          (funcall closure))
        (rename-file temporary-directory output))
      (ennum--set-file-modes-recursively output #o555 #o444 #o555))
    output))

(defun ennum-store-item-union (items)
  "Return a store item that is the union of ITEMS."
  (ennum-exp
   (dolist (item items)
     (dolist (destination (reverse (ennum-directory-files item nil t)))
       ;; TODO: Print warning about overwriting files?
       (let ((source (expand-file-name destination item)))
         (unless (file-exists-p destination)
           (if (file-directory-p source)
               (make-directory destination)
             (copy-file source destination t))))))))

(defmacro ennum-make-functional-setter (name copier accessor)
  `(defun ,name (object new-value)
     (let ((object-copy (,copier object)))
       (setf (,accessor object-copy) new-value)
       object-copy)))

(cl-defstruct (ennum-post (:constructor ennum-make-post)
                          (:copier ennum-copy-post))
  filename slug author date language links tangle
  summary tags thumbnail title translation-group translations)

(ennum-make-functional-setter
 ennum-post-set-translations ennum-copy-post ennum-post-translations)

(ennum-make-functional-setter
 ennum-post-set-links ennum-copy-post ennum-post-links)

(cl-defstruct (ennum-link (:constructor ennum-make-link)
                          (:copier nil))
  type path)

(cl-defstruct (ennum-post-link (:constructor ennum-make-post-link)
                                (:copier ennum-copy-post-link)
                                (:include ennum-link (type 'post)))
  target-title)

(ennum-make-functional-setter
 ennum-post-link-set-target-title ennum-copy-post-link ennum-post-link-target-title)

(cl-defstruct (ennum-video-link (:constructor ennum-make-video-link)
                                (:copier nil)
                                (:include ennum-link (type 'video)))
  poster)

(defun ennum-posts (posts-directory)
  (sort (seq-mapcat
         ;; Set translations slot of post objects.
         (pcase-lambda (`(,_ . ,posts))
           (let ((translations
                  (seq-map (lambda (post)
                             (cons (ennum-post-language post)
                                   (ennum-post-slug post)))
                           posts)))
             (seq-map (lambda (post)
                        (ennum-post-set-translations
                         post
                         (seq-remove (pcase-lambda (`(,_ . ,slug))
                                       (string= (ennum-post-slug post) slug))
                                     translations)))
                      posts)))
         (let ((posts
                ;; Read posts from org files.
                (ennum--filter-map
                 (lambda (file)
                   (when (string= (file-name-extension file) "org")
                     (ennum-read-post file)))
                 (ennum-directory-files posts-directory))))
           ;; Group posts by translation group.
           (seq-group-by
            'ennum-post-translation-group
            ;; Set target title slot of post links.
            (seq-map
             (lambda (post)
               (ennum-post-set-links
                post
                (seq-map (lambda (link)
                           (if (and (ennum-post-link-p link)
                                    (eq (ennum-post-link-target-title link) 'required))
                               (ennum-post-link-set-target-title
                                link
                                (seq-some (lambda (post)
                                            (when (string= (ennum-post-slug post)
                                                           (ennum-link-path link))
                                              (ennum-post-title post)))
                                          posts))
                             link))
                         (ennum-post-links post))))
             posts))))
        'ennum-later-post-p))

(defun ennum-later-post-p (post1 post2)
  (time-less-p (ennum-post-date post2)
               (ennum-post-date post1)))

(defun ennum-read-post (filename)
  (ennum--read-post
   filename (file-attribute-modification-time
             (file-attributes filename))))

(defmemoize ennum--read-post (filename _last-modified)
  (ennum-with-file-contents filename
    (let ((metadata (org-export-get-environment 'ennum-html))
          (export (apply-partially 'org-export-with-backend 'ennum-html)))
      (dolist (key (ennum-setting :required-metadata))
        (unless (plist-member metadata key)
          (user-error "Metadata %s not specified" key)))
      (let* ((tree (org-element-parse-buffer))
             (links (org-element-map tree 'link
                      (lambda (link)
                        (let ((link-type (org-element-property :type link))
                              (path (org-element-property :path link)))
                          (pcase link-type
                            ("post"
                             (ennum-make-post-link
                              :path path
                              :target-title (if (org-element-contents link)
                                                'not-required 'required)))
                            ("video"
                             (ennum-make-video-link
                              :path path
                              :poster (ennum-video-poster path)))
                            (_ (ennum-make-link
                                :type (intern link-type)
                                :path path))))))))
        (ennum-make-post
         :filename filename
         :slug (file-name-base filename)
         :author (seq-first (plist-get metadata :author))
         :date (org-timestamp-to-time (seq-first (plist-get metadata :date)))
         :language (plist-get metadata :language)
         :links links
         ;; TODO: Deal with cases when the :tangle parameter is "yes"
         :tangle (seq-uniq
                  (org-element-map tree 'src-block
                    (lambda (src-block)
                      (pcase (org-babel-get-src-block-info nil src-block)
                        (`(,_ ,_ ,arguments ,_ ,_ ,_ ,_)
                         (let ((tangle-output-file (map-elt arguments :tangle)))
                           (pcase tangle-output-file
                             ("no" nil)
                             (_ tangle-output-file))))))))
         :summary (when-let (summary (plist-get metadata :summary))
                    (funcall export (seq-first summary)))
         :tags (plist-get metadata :filetags)
         :thumbnail (or (plist-get metadata :thumbnail)
                        (seq-some (lambda (link)
                                    (let ((path (ennum-link-path link)))
                                      (pcase (ennum-link-type link)
                                        ('image path)
                                        ('video (ennum-video-poster path)))))
                                  links))
         :title (funcall export (seq-first (plist-get metadata :title)))
         :translation-group (or (plist-get metadata :translation-group)
                                (file-name-base filename)))))))

(defun ennum-directory-files (&optional directory full include-directories)
  "Return recursively the list of all files under DIRECTORY. Files are
returned in depth first order.

If DIRECTORY is nil, the current working directory is assumed. If
FULL is non-nil, absolute file names are returned. Else, the file
names are relative to the current directory. If
INCLUDE-DIRECTORIES is non-nil, include directories in the
output."
  (let* ((directory (or directory default-directory))
         (files (directory-files-recursively
                 directory (rx anything) include-directories)))
    (if full
        files
      (seq-map (apply-partially 'string-remove-prefix
                                ;; Expand directory in case it is a
                                ;; relative path.
                                (file-name-as-directory (expand-file-name directory)))
               files))))

(defun ennum--org-output-filename (filename)
  (concat (file-name-sans-extension filename) ".html"))

(defun ennum-export-post (post interned-org-file &optional output-html-file body-only)
  "Export INTERNED-ORG-FILE of POST to OUTPUT-HTML-FILE using the
ennum-html backend. INTERNED-ORG-FILE must be an org file
interned into the ennum store.

When optional argument BODY-ONLY is non-nil, only return body
code, without surrounding template. See `org-export-as'.

When optional argument OUTPUT-HTML-FILE is nil, return exported
result as a string."
  (let ((system-time-locale (map-elt (ennum-setting :locale-alist)
                                     (ennum-post-language post)))
        (ext-plist (list :ennum-post post)))
    (ennum-with-file-contents interned-org-file
      (cond
       (output-html-file
        (ennum-mkdir-p (file-name-directory output-html-file))
        (org-export-to-file 'ennum-html output-html-file nil nil nil body-only ext-plist))
       (t (org-export-as 'ennum-html nil nil body-only ext-plist))))))

(defun ennum-publish-post (post)
  (let ((interned-org-file (ennum-intern (ennum-post-filename post))))
    (append
     (list
      (ennum-exp
       (ennum-export-post post
                          interned-org-file
                          (ennum--org-output-filename (ennum-post-filename post)))))
     (when (ennum-post-tangle post)
       (list
        (ennum-exp
         ;; TODO: Handle tangle outputs that are nested
         ;; into directories, and when each tangle output
         ;; is nested into a different directory.
         (let* ((post-file-copy
                 (expand-file-name
                  (file-name-nondirectory interned-org-file)
                  (ennum-setting :static-directory))))
           (ennum-copy interned-org-file post-file-copy)
           (org-babel-tangle-file post-file-copy)
           (delete-file post-file-copy)))))
     (seq-mapcat 'ennum-publish-link (ennum-post-links post)))))

(defun ennum-publish-generic (other-files-directory file)
  (let ((interned-file (ennum-intern
                        (ennum--file-join other-files-directory
                                          file))))
    (ennum-exp
     (let ((output-file
            (pcase (file-name-extension file)
              ("org" (ennum--org-output-filename file))
              (_ file))))
       (pcase (file-name-extension interned-file)
         ("org"
          (when (file-name-directory output-file)
            (ennum-mkdir-p (file-name-directory output-file)))
          (ennum-with-file-contents interned-file
            (org-export-to-file 'html output-file)))
         (_ (ennum-copy interned-file output-file)))))))

(defun ennum-video-poster (video)
  (or (seq-some (lambda (file)
                  (and (string= (file-name-base file)
                                (file-name-base video))
                       (file-name-nondirectory file)))
                (ennum-directory-files (ennum-setting :images-directory)))
      (user-error "Poster for %s not found" video)))

(defun ennum-add-tongue-suffix (filename tongue)
  (pcase tongue
    ("en" filename)
    (_ (format "%s.%s%s"
               (file-name-sans-extension filename)
               tongue
               (file-name-extension filename t)))))

(defun ennum-index-filename (filename-prefix tongue &optional extension page-number)
  (let ((extension (if extension (concat "." extension) "")))
    (ennum-add-tongue-suffix
     (if page-number
         (format "%s-%s%s" filename-prefix page-number extension)
       (concat filename-prefix extension))
     tongue)))

(defun ennum-publish-index-page (filename-prefix title last-page posts page-number tongue output-file)
  (ennum-exp
   (let ((system-time-locale
          (map-elt (ennum-setting :locale-alist) tongue)))
     (when (file-name-directory output-file)
       (ennum-mkdir-p (file-name-directory output-file)))
     (with-temp-buffer
       (insert (format "#+TITLE: %s\n" title))
       (insert (format "#+LANGUAGE: %s\n" tongue))
       (insert "#+OPTIONS: num:nil toc:nil\n\n")
       (dolist (post posts)
         (insert (format "* [[post:%s][%s]]\n"
                         (ennum-post-slug post)
                         (ennum-post-title post)))
         (insert (format-time-string "/%b %e, %Y/\n\n" (ennum-post-date post)))
         (when-let ((thumbnail (ennum-post-thumbnail post)))
           (insert (format "[[thumbnail:%s]]\n\n" thumbnail)))
         (when-let ((summary (ennum-post-summary post)))
           (insert summary)
           (insert "\n\n"))
         (when-let ((tags (ennum-post-tags post)))
           (insert "Tags: ")
           (insert
            (string-join
             (seq-map (lambda (tag)
                        (format "[[tag:%s][%s]]" (ennum-add-tongue-suffix tag tongue) tag))
                      tags)
             ", "))
           (insert "\n\n")))
       (unless (= page-number 1)
         (insert (format "[[./%s][Newer posts]]\n\n"
                         (ennum-index-filename (file-name-nondirectory filename-prefix)
                                               tongue nil (1- page-number)))))
       (unless last-page
         (insert (format "[[./%s][Older posts]]\n"
                         (ennum-index-filename (file-name-nondirectory filename-prefix)
                                               tongue nil (1+ page-number)))))
       (org-export-to-file 'html output-file)))))

(defun ennum-publish-index-home (first-index-page-output filename-prefix tongue)
  (ennum-exp
   (ennum-copy (ennum--file-join first-index-page-output
                                 (ennum-index-filename filename-prefix tongue "html" 1))
               (ennum-add-tongue-suffix (format "%s.html" filename-prefix) tongue))))

(defun ennum-publish-index (filename-prefix title posts-per-page tongue posts)
  (let* ((number-of-pages (ceiling (length posts) posts-per-page))
         (page-numbers (number-sequence 1 number-of-pages))
         (output-files (seq-map (apply-partially
                                 'ennum-index-filename filename-prefix tongue "html")
                                page-numbers))
         (outputs (seq-mapn (lambda (post page-number output-file)
                              (ennum-publish-index-page
                               filename-prefix title
                               (= page-number number-of-pages)
                               post page-number tongue output-file))
                            (seq-partition posts posts-per-page)
                            page-numbers
                            output-files)))
    (cons (ennum-publish-index-home (seq-first outputs) filename-prefix tongue)
          outputs)))

(defun ennum--absolute-uri (path)
  (format "%s://%s/%s"
          (ennum-setting :blog-scheme)
          (ennum-setting :blog-domain)
          path))

(defun ennum--atom-date (date)
  (format-time-string "%Y-%m-%dT%H:%M:%SZ" date))

(defun ennum-publish-feed (feed-file title rights posts)
  (let ((interned-post-files
         (seq-map (lambda (post)
                    (ennum-intern (ennum-post-filename post)))
                  posts)))
    (ennum-exp
     (message "Writing %s" feed-file)
     ;; TODO: Create ennu-mkdir-p-for-file
     (when (file-name-directory feed-file)
       (ennum-mkdir-p (file-name-directory feed-file)))
     (with-temp-file feed-file
       (insert
        (xmlgen
         `(feed :xmlns "http://www.w3.org/2005/Atom"
                (id ,(ennum--absolute-uri ""))
                (title ,title)
                (updated ,(ennum--atom-date (ennum-post-date (seq-first posts))))
                (link :rel "self" :href ,(ennum--absolute-uri feed-file))
                (generator
                 ,(format "Emacs %d.%d Org-mode %s ennum %s"
                          emacs-major-version emacs-minor-version (org-version) ennum-version))
                (rights ,rights)
                ,@(seq-mapn (lambda (post interned-post-file)
                              (ennum--feed-entry post interned-post-file))
                            posts interned-post-files))))))))

(defun ennum--feed-entry (post interned-post-file)
  (let ((link (ennum--absolute-uri (ennum--org-output-filename
                                    (ennum-post-filename post)))))
    `(entry (id ,link)
            (title :xml:lang ,(ennum-post-language post) ,(ennum-post-title post))
            (updated ,(ennum--atom-date (ennum-post-date post)))
            ,@(when org-export-with-author
                `((author
                   (name ,(ennum-post-author post))
                   (email ,user-mail-address))))
            (content :type "html" :xml:lang ,(ennum-post-language post)
                     ,(ennum-export-post post interned-post-file nil t))
            (link :rel "alternate" :href ,link)
            ,@(seq-map (lambda (tag) `(category :term ,tag))
                       (ennum-post-tags post)))))

(defun ennum-setting (property)
  (pcase property
    ((or :blog-domain :blog-license :blog-title
         :images-directory :output-directory :posts-directory
         :static-directory :videos-directory :working-directory)
     (or (plist-get ennum-blog property)
         (user-error "Property %s not defined" property)))
    ((or :atom-feed-number-of-posts :atom-feed-file
         :blog-scheme :index-posts-per-page
         :image-width :image-link-width
         :locale-alist :other-files-directory
         :store :tag-directory :image-thumbnail-width
         :required-metadata)
     (plist-get (org-combine-plists
                 (list :atom-feed-number-of-posts 12
                       :atom-feed-file "blog.atom"
                       :blog-scheme "https"
                       :image-width 640
                       :image-link-width 1024
                       :index-posts-per-page 12
                       :locale-alist '(("en" . "C"))
                       :store ".ennum"
                       :tag-directory "tag"
                       :image-thumbnail-width 320
                       :required-metadata (list :title :date))
                 ennum-blog)
                property))
    (_ (error "Unknown property %s" property))))

(defun ennum-image-output-filename (image width)
  (format "%s-%spx.%s"
          (file-name-sans-extension image)
          width (file-name-extension image)))

(defun ennum--file-join (&rest components)
  (string-join
   (seq-map (lambda (component)
              (string-remove-suffix "/" (file-name-as-directory component)))
            components)
   "/"))

(defun ennum-publish-image (image width)
  (let ((interned-image (ennum-intern image)))
    (ennum-exp
     (message "Resizing %s to width %s" image width)
     (ennum-mkdir-p (ennum-setting :images-directory))
     (ennum-image-optimize-image
      (ennum-image-resize-image
       interned-image
       (ennum--file-join
        (ennum-setting :images-directory)
        (ennum-image-output-filename
         (file-name-nondirectory interned-image) width))
       width)))))

(defun ennum-publish-copy (file)
  (let ((interned-file (ennum-intern file)))
    (ennum-exp (ennum-copy interned-file file))))

(defun newest-file (files)
  (pcase files
    (`(,head . ,tail)
     (seq-reduce (lambda (file1 file2)
                   (if (file-newer-than-file-p file1 file2)
                       file1 file2))
                 tail head))))

(defun ennum-mkdir-p (directory)
  (make-directory directory t))

(defun ennum-copy (source destination &optional quiet)
  "Copy file or directory from SOURCE to DESTINATION.

Overwrite if DESTINATION already exists. Create any parent
directories required.

If SOURCE is a file and DESTINATION is a directory, copy SOURCE
to a like-named file under DESTINATION. For DESTINATION to be
recognized as a directory, it should end in a slash. See
`file-name-as-directory'."
  (unless quiet
    (message "Copying %s to %s" source destination))
  (if (file-directory-p source)
      (copy-directory source destination)
    (when (file-name-directory destination)
      (ennum-mkdir-p (file-name-directory destination)))
    (copy-file source destination t)))

(defun ennum--filter-map (function sequence)
  (seq-filter 'identity (seq-map function sequence)))

(defun ennum-publish-link (link)
  (pcase (ennum-link-type link)
    ('image
     (seq-map (lambda (width)
                (ennum-publish-image
                 (ennum--file-join (ennum-setting :images-directory)
                                   (ennum-link-path link))
                 width))
              (list (ennum-setting :image-width)
                    (ennum-setting :image-link-width))))
    ('static
     (list
      (ennum-publish-copy
       (ennum--file-join (ennum-setting :static-directory)
                         (ennum-link-path link)))))
    ('video
     (seq-map 'ennum-publish-copy
              (list
               (ennum--file-join (ennum-setting :videos-directory)
                                 (ennum-link-path link))
               (ennum--file-join (ennum-setting :images-directory)
                                 (ennum-video-link-poster link)))))))

(defun ennum-assoc-delete (key alist)
  "Delete KEY from ALIST.

Delete all occurrences of KEY in ALIST. This function is purely
functional. ALIST is not mutated."
  (seq-remove (pcase-lambda (`(,entry-key . ,_))
                (equal entry-key key))
              alist))

(defun ennum-assoc-set (key value alist)
  "Associate KEY with VALUE in ALIST.

This function is purely functional. ALIST is not mutated. Keys
are compared using `equal'."
  (cl-acons key value (ennum-assoc-delete key alist)))

(defun ennum-assoc-prepend (key value alist)
  "Prepend VALUE to that associated with KEY in ALIST.

This function is purely funcion. ALIST is not mutated."
  (ennum-assoc-set key
                   (cons value (map-elt alist key))
                   alist))

(defun ennum-many-to-many-group-by (function sequence)
  "Apply FUNCTION to each element of SEQUENCE.
Separate the elements of SEQUENCE into an alist using the results
as keys. Keys are compared using `equal'."
  (seq-reduce (lambda (result element)
                (seq-reduce (lambda (result key)
                              (ennum-assoc-prepend key element result))
                            (funcall function element)
                            result))
              (seq-reverse sequence)
              nil))

(defun ennum-publish ()
  (interactive)
  ;; Recompute feature hash.
  (setq ennum-feature-hash
        (seq-map 'ennum--feature-environment ennum-track-features))
  (ennum-with-current-directory (ennum-setting :working-directory)
    (let* ((blog-title (ennum-setting :blog-title))
           (posts (ennum-posts (ennum-setting :posts-directory)))
           (posts-per-page (ennum-setting :index-posts-per-page))
           (other-files-directory (ennum-setting :other-files-directory))
           (result
            (ennum-store-item-union
             (append
              ;; Publish posts
              (seq-mapcat 'ennum-publish-post posts)
              ;; Publish feed
              (list (ennum-publish-feed (ennum-setting :atom-feed-file)
                                        blog-title
                                        (ennum-setting :blog-license)
                                        (seq-take posts (ennum-setting :atom-feed-number-of-posts))))
              ;; Publish indices
              (seq-mapcat
               (pcase-lambda (`(,tongue . ,posts))
                 (ennum-publish-index "index" blog-title posts-per-page tongue posts))
               (seq-group-by 'ennum-post-language posts))
              ;; Publish tag indices
              (seq-mapcat
               (pcase-lambda (`(,tag . ,posts))
                 (seq-mapcat
                  (pcase-lambda (`(,tongue . ,posts))
                    (ennum-publish-index
                     (ennum--file-join (ennum-setting :tag-directory) tag)
                     tag posts-per-page tongue posts))
                  (seq-group-by 'ennum-post-language posts)))
               (ennum-many-to-many-group-by 'ennum-post-tags posts))
              ;; Publish thumbnails
              (seq-map (lambda (image)
                         (ennum-publish-image
                          (ennum--file-join (ennum-setting :images-directory) image)
                          (ennum-setting :image-thumbnail-width)))
                       (ennum--filter-map 'ennum-post-thumbnail posts))
              ;; Publish other files
              (seq-map (apply-partially 'ennum-publish-generic other-files-directory)
                       (ennum-with-current-directory (ennum-setting :other-files-directory)
                         (ennum-directory-files)))))))
      ;; Replace old output directory
      (when (file-exists-p (ennum-setting :output-directory))
        (ennum--set-file-modes-recursively (ennum-setting :output-directory) #o755 #o644 #o755)
        (delete-directory (ennum-setting :output-directory) t))
      (copy-directory result (ennum-setting :output-directory))
      (message "Ennum published to %s" (expand-file-name (ennum-setting :output-directory))))))

;;; Server
;;;
;;; Test HTTP server to serve the blog locally

;; TODO: Why can't simple-httpd itself handle the unhexing?
(defun ennum-server-start ()
  (interactive)
  (setq httpd-root (expand-file-name (ennum-setting :output-directory)
                                     (ennum-setting :working-directory)))
  (defun httpd/ (proc uri-path _query request)
    (let* ((uri-path (httpd-unhex uri-path))
           (file-path (httpd-gen-path uri-path)))
      (cond
       ;; If a HTML file other than index.html was requested, reject
       ;; that request.
       ((and (not (string= (file-name-nondirectory file-path) "index.html"))
             (string= (file-name-extension file-path) "html"))
        (httpd-error proc 404))
       ;; If the requested file was found, serve it.
       ((= (httpd-status file-path) 200)
        (httpd-serve-root proc httpd-root uri-path request))
       ;; Perhaps, this is a post or other HTML file that is being
       ;; requested. Try serving a file with a .html extension
       ;; appended.
       (t (httpd-serve-root proc httpd-root (concat uri-path ".html") request)))))
  (httpd-start)
  (message "Ennum web server listening at http://localhost:%d" httpd-port))

(defun ennum-server-stop ()
  (interactive)
  (httpd-stop)
  (message "Ennum web server stopped"))

(provide 'ennum)