#!/usr/bin/csi -s

(import
  (chicken file)
  (chicken format)
  (chicken io)
  (chicken pathname)
  (chicken port)
  (chicken process)
  (chicken process-context)
  (chicken string)
  (clojurian syntax)
  ersatz
  lowdown
  scss
  srfi-1  ;; list utils
  srfi-13 ;; string utils
  srfi-14 ;; charsets
  sxml-transforms
  symbol-utils ;; (unspecified-value)
  utf8
  )

;; small utilities ---------------------------------


;; (bail [message [exit-status]])
;; end the program immediately.
;; if a message is provided, print it to the screen.
;; exit-status defaults to 1.
(define (bail #!optional msg (status 1))
  (when msg (print msg))
  (exit status))

;; clojureish "debugging by print statement" tool since i still haven't reached
;; lisp enlightenment
(define ((inspect #!optional label #!rest args) s)
  (display (list label ":" args " => " s) (current-error-port))
  (newline (current-error-port))
  s)

;; decompose a path s into its constituent parts. returns values:
;;
;; root: "/" if it's an absolute path, "" if relative directory-elements: a list
;; of each directory from root, () if none basename: the filename with extension
;; removed like "readme" or ".bashrc" extension: the file extension with the
;; dot, like ".txt" or "" if none relative-root: the relative path from the
;; given path to the root
;;  e.g foo/bar/baz.html -> ../../
;;
;; this is intended to provide default values that make for easier reassembly
;; into filenames.
;;
;; typical use:
;; (->> source-file
;;  (pathparts)
;;  (define-values (root elements basename extension relative-root)))
;;
(define (pathparts s)
  (define-values (dirname basename extension)
    (decompose-pathname s))
  (define-values (origin root directory-elements)
    (decompose-directory (or dirname "")))
  ;; discarding origin because idgaf about windows
  (values (or root "")
          (or directory-elements '())
          basename
          (if extension (string-append "." extension) "")
          (->>
           (or directory-elements '())
           (map (constantly "../"))
           (apply string-append))))

;; like (substring) but doesn't break if start and end are too big/small
(define (substring* s start end)
  (substring s (max start 0) (min end (string-length s))))

;; merge alists a and b. values in b "win"
(define (alist-merge a b)
  (lset-union (lambda (x y) (eq? (car x) (car y))) a b))

;; like alist-ref but works on nested alists by specifying a path (list of keys)
(define (alist-ref-in keys alist #!optional (test eqv?))
  (if (null? (cdr keys))
      (alist-ref (car keys) alist test)
      (alist-ref-in (cdr keys) (alist-ref (car keys) alist test) test)))

;; like alist-update, but works on nested alists by specifying a path (list of
;; keys)
(define (alist-update-in keys value alist #!optional (test eqv?))
  (cond
   ((not alist) #f)
   ((null? (cdr keys))
    (alist-update (car keys) value alist test))
   (else
    (alist-update (car keys)
                  (alist-update-in (cdr keys) value (alist-ref (car keys) alist test) test)
                  alist test))))

(define (unless-equals s1 s2)
  ;; if s1 == s2, then s1, otherwise #f
  (and (equal? s1 s2) s1))

;; auto-apply ids to headings ---------------------------------
(define (slugify inner)
  (->
   inner
   (pre-post-order*
    `((*text* .
       ,(lambda (_ str)
          (if (string? str)
              (->
               str
               (string-downcase)
               (string-translate "/,:;\"[]{}()=+")
               (string-translate " _." "---"))
              str)))
      ,@alist-conv-rules*))
   (flatten)
   ((flip map) ->string)
   (string-intersperse "")
   (substring* 0 40)))

(define (enumerate-tag inner)
  (let ((slug (slugify inner)))
    `((@ (id ,slug))
      ,inner
      (a (@ ((title "Permalink to this section")
             (href "#" ,slug)))))))

;; a relative link to a file within our own repo should get .html added to the
;; target, since we make that filename change when rendering files for the web.
;;
;; thought it might also be good to apply that same treatment to any absolute
;; links into our repo (or other repos on the same forge?) but that gets a bit
;; messy, would need to drag variables holding current site, path, repo name all
;; the way into here
;;
;; if adjust-relative is not false, it is a prefix to be added to relative
;; links, to make the top-level readme link correctly into the site.
(define (adjust-relative-link adjust-relative inner)
  (let* ((linkurl (alist-ref-in '(@ href) inner equal?))
         (linkurl-startswith (cute string-prefix? <> (car linkurl))))
    (if
     (any linkurl-startswith '("#" "mailto:" "gemini:" "http://" "https://"))
     inner
     (alist-update-in '(@ href) (cons adjust-relative (append linkurl '(".html"))) inner equal?))))

(define (sxml-html-rules adjust-relative)
  `(;; assign all headings an id so you can link to them
    (h1        . ,(lambda (t i) (cons t (enumerate-tag i))))
    (h2        . ,(lambda (t i) (cons t (enumerate-tag i))))
    (h3        . ,(lambda (t i) (cons t (enumerate-tag i))))
    (h4        . ,(lambda (t i) (cons t (enumerate-tag i))))
    (h5        . ,(lambda (t i) (cons t (enumerate-tag i))))
    ;; if adjust-relative is true, all relative links should get prefixed with
    ;; the relative-root
    (a         . ,(lambda (t i) (cons t (adjust-relative-link adjust-relative i))))
    ;; this copied from lowdown's html-serialization-rules* because it is for
    ;; some reason not exported, so i can't just import it??
    (*COMMENT* . ,(lambda (_t i) (list #\< "!--" i "--" #\>)))
    ;; ignore any #<unspecified> values in the tree
    (*text*    . ,(lambda (_t i) (if (unspecified? i) "" i)))
    ,@alist-conv-rules*))

;; reading in data from git commands ---------------------------------

(define (in-git-directory?)
  (not (eof-object? (call-with-input-pipe "git rev-parse --git-dir" read-line))))

;; a weird hack to detect whether git considers a blob to be a binary or a text
;; file. works by requesting the numstat diff between it and the empty tree.
;; binary files give not a line count but '-' placeholders.
(define (git-file-is-text? source-file)
  (not (equal?
        "-\t-\t"
        (call-with-input-pipe
         (string-append "git diff 4b825dc642cb6eb9a060e54bf8d69288fbee4904 --numstat HEAD -- " source-file)
         (cute read-line <> 4)))))

(define (git-repository->paths-list)
  (call-with-input-pipe "git ls-tree -r --name-only HEAD" read-lines))

(define (git-file->string source-file)
  (->
   (format "git show HEAD:~a" source-file)
   (call-with-input-pipe read-lines)
   (string-intersperse "\n")))

;; the result of asking git for some configuration; #f if no result.
(define (git-config->string key)
  (let [(result (call-with-input-pipe (string-append "git config " key) read-line))]
    (if (eof-object? result) #f result)))

;; environment always takes precedent over git-config
(define (config key)
  (or
   (get-environment-variable (string-append "REPO2HTML_" (string-upcase key)))
   (git-config->string (string-append "repo2html." (string-downcase key)))))

;; sxml generators for constructed pages ---------------------------------

(define (source->sxml source-file) ;; src/main.scm
  (define-values (_ _ basename extension _)
    (pathparts source-file))
  (define (image-link)
    `(p (img (@ src ,basename ,extension))))
  (define (plaintext)
    `(pre ,(git-file->string source-file)))
  (define (binary)
    '(p "(Binary file)"))
  (case (string->symbol extension)
    ((.md .markdown)
     (handle-exceptions exn
         (begin
           (format (current-error-port) "Error parsing ~a\n" source-file)
           `((p (b "There was an error parsing this file as Markdown."))
             ,(plaintext)))
       (markdown->sxml (git-file->string source-file))))
    ((.jpg .jpeg .png .gif .webp .webm .apng .avif .svgz .ico)
     (image-link))
    ((.svg)
     (list (image-link) (plaintext)))
    ((.gz .pack .idx)
     (binary))
    (else
     (if (git-file-is-text? source-file)
         (plaintext)
         (binary)))))

(define (filelist->sxml source-files-list relative-root)
  `((h1 "Files")
    ((ul
      ,(map
        (lambda (source-file)
          `(li (a (@ (href ,(make-pathname relative-root source-file))) ,source-file)))
        source-files-list)))))

(define (commits->sxml)
  `((h1 "Commits")
    (table
     (tr
      ,@(map (lambda x `(th ,x)) '("Date" "Ref" "Log" "Author")))
     ,(map
       (lambda (line)
         (let-values (((date ref title author) (apply values (string-split line "\t"))))
           `(tr (td ,date) (td ,ref) (td ,title) (td ,author))))
       (call-with-input-pipe "git log --format=format:%as%x09%h%x09%s%x09%aN HEAD" read-lines)))))

(define (contributors->sxml)
  `((h1 "Contributors")
    (table
     (tr (th "Author") (th "Commits"))
     ,(map
       (lambda (line)
         (let-values (((commits author) (apply values (string-split line "\t"))))
           `(tr (td ,author) (td ,commits))))
       (call-with-input-pipe "git shortlog -ns HEAD" read-lines)))))

(define (issueslist->sxml source-files-list)
  `((h1 "Issues")
    ((ul
      ,(filter-map
        (lambda (source-file)
          (and
           (string-prefix? "ISSUES/" source-file)
           `(li (a (@ (href ,source-file))
                   ,(->
                     source-file
                     ((flip format) "git show HEAD:~a")
                     (call-with-input-pipe read-line)
                     (string-trim (string->char-set "# ")))))))
        source-files-list)))))

;; used by ersatz writer
(define (alist->tvals vars)
  (map (lambda (pair)
         `(,(car pair) . ,(sexpr->tvalue (cdr pair)))) vars))

;; this version uses a jinja-style template via ersatz
(define (make-template-writer-ersatz templates-directory #!optional vars)
  (define template (statements-from-file (template-std-env search-path: (list templates-directory)) "default.html"))
  (lambda (output-filename body-sxml #!optional newvars)
    ;; create destination directory if needed
    (if-let (destination-directory (pathname-directory output-filename))
            (create-directory destination-directory #t)
            '())

    (let* (;; vars = global vars + file-specific vars
           (vars (alist-merge vars (or newvars '())))
           (adjust-relative (unless-equals (alist-ref 'relative_root vars) "html/"))
           ;; render the sxml to a html string that we can hand to the template
           (body-html
            (with-output-to-string
              (lambda ()
                (SXML->HTML (pre-post-order* body-sxml (sxml-html-rules adjust-relative))))))
           ;; vars = vars + body k/v pair
           (vars (alist-cons 'content body-html vars)))

      (with-output-to-file output-filename
        (lambda ()
          (display (eval-statements template models: (alist->tvals vars))))))))

;; main program ------------------------------------------------------------------------------

(define (generate-html-files html-repo-path templates-directory)
  ;; git automatically updates this hash when you checkout/pull/etc.
  (let* ((version-ident       "$Id$")
         (source-files-list   (git-repository->paths-list))
         (forge-root          (string-append (string-chomp (or (config "forgeroot") "") "/") "/"))
         (repository-path     (or (config "path")
                                  (and (not (equal? forge-root "/"))
                                       (string-prefix? forge-root html-repo-path)
                                       (string-drop html-repo-path (string-length forge-root)))
                                  (pathname-strip-directory html-repo-path)))
         (template-alist
          `(;; variables provided to template at all times. beware: ersatz
            ;; templates break if you attempt to use a variable with a hyphen.

            ;; the list of all files in the git repo
            (source_files_list      . ,source-files-list)
            ;; the description of the repo, taken from: env, config, cgit-like
            ;; description file
            (repository_description . ,(or (config "description")
                                           (if-let (f (file-exists? "description"))
                                                   (with-input-from-file f read-lines) #f)
                                           ""))
            ;; the name of the repo, which is usually but not necessarily the
            ;; same as its directory name (and last path element of the url)
            (repository_name        . ,(or (config "name")
                                           (-> html-repo-path
                                               (string-chomp ".git")
                                               (pathname-strip-directory))))
            ;; the path from the forge root to the repository
            (repository_path        . ,repository-path)
            ;; the repository_path with the last path element removed
            (repository_path_parent . ,(or (pathname-directory repository-path) ""))
            ;; the repository_path_parent as a list of path components
            (repository_ancestors   . ,(or (string-split (or (pathname-directory repository-path) "") "/") '()))
            ;; the first README file found among these, if any.
            (readme_file            . ,(find (cut member <> source-files-list)
                                             '("README.md" "README" "README.txt")))
            ;; the first LICENSE file found among these, if any.
            (license_file           . ,(find (cut member <> source-files-list)
                                             '("LICENSE.md" "LICENSE" "LICENSE.txt")))
            ;; the string "ISSUES" if any files exist in ISSUES/
            (issues_file            . ,(and (find (cut string-prefix? "ISSUES/" <>) source-files-list) "ISSUES"))
            (repo2html_version      . ,(if (equal? version-ident (list->string '(#\$ #\I #\d #\$)))
                                           ""
                                           (substring* version-ident 5 12)))
            ))
         (write-with-template
          (make-template-writer-ersatz templates-directory template-alist)))
    (define html-path (make-pathname html-repo-path "html"))

    (create-directory html-repo-path #t)
    ;; special files
    (write-with-template (make-pathname html-path "files" "html") (filelist->sxml source-files-list ""))
    (write-with-template (make-pathname html-path "contributors" "html") (contributors->sxml))
    (write-with-template (make-pathname html-path "commits" "html") (commits->sxml))
    ;; htmlified repo contents
    (for-each
     (lambda (source-file)
       (->> source-file
            (pathparts)
            (define-values (root elements basename extension relative-root)))
       (write-with-template
        (make-pathname html-path source-file "html")
        (source->sxml source-file)
        `(;; additional per-page variables provided to template
          (source_file   . ,source-file)
          (root          . ,root)
          (elements      . ,elements)
          (basename      . ,basename)
          (extension     . ,extension)
          (relative_root . ,relative-root)
          ))
       ;; if it's an image, also write it verbatim to output directory
       (case (string->symbol (or (pathname-extension source-file) ""))
         ((jpg jpeg png gif webp webm svg apng avif svgz ico)
          (system (format "git show HEAD:~a > ~a"
                          source-file
                          (make-pathname html-path source-file))))))
     source-files-list)
    ;; if README.md, README, or README.txt exists, regenerate it as index.html.
    ;; otherwise regenerate files.html as index.html.
    (write-with-template
     (make-pathname html-repo-path "index" "html")
     (if-let (readme-file
              (alist-ref 'readme_file template-alist))
             (source->sxml readme-file)
             (filelist->sxml source-files-list "html"))
     ;; TODO: do we need the full set of template variables defined here?
     ;; if so maybe this and the set above should be lifted out somewhere
     `((relative_root . "html/")))

    ;; if the ISSUES directory got created, write out an index file for the
    ;; stuff in there.
    (when (file-exists? (make-pathname html-path "ISSUES"))
      (write-with-template (make-pathname html-path "ISSUES" "html") (issueslist->sxml source-files-list)))))

(define (main #!optional html-repo-path templates-directory)

  (unless html-repo-path
    (bail "please specify a destination directory for html files"))

  (unless (in-git-directory?)
    (bail "woops this isn't a git directory"))

  (unless templates-directory
    (bail "please specify the directory containing the templates.\nnote: built-in sxml templates have been removed."))

  (generate-html-files (string-chomp html-repo-path "/") templates-directory))

(apply main (command-line-arguments))