#! /usr/bin/env guile
!#

(import (rnrs hashtables)
        (rnrs io ports)
        (srfi srfi-1)
        (srfi srfi-9)
        (srfi srfi-26)
        (srfi srfi-37)
        (srfi srfi-171)
        (ice-9 ftw)
        (ice-9 match)
        (ice-9 popen)
        (ice-9 rdelim))

(define (invoke program . args)
  (unless (zero? (apply system* program args))
    (error "Invocation of program failed" (cons program args))))

(define (call-with-input-pipe proc program . args)
  "Execute PROGRAM ARGS ... in a subprocess with a pipe to it. Call
PROC with an input port to that pipe. Close the pipe once PROC exits,
even if it exits non-locally. Return the value returned by PROC."
  (let ((port #f))
    (dynamic-wind (lambda () (set! port (apply open-pipe* OPEN_READ program args)))
                  (cut proc port)
                  (lambda ()
                    (let ((return-value (status:exit-val (close-pipe port))))
                      (unless (and return-value
                                   (zero? return-value))
                        (error "Invocation of program failed" (cons program args))))))))

(define* (find-files directory #:optional (pred (const #t)))
  "Recursively find all files under DIRECTORY that satisfy PRED."
  (define (do-nothing name stat result)
    result)

  (file-system-fold (const #t)
                    (lambda (name stat result)
                      (if (pred name stat)
                          (cons name result)
                          result))
                    do-nothing
                    do-nothing
                    do-nothing
                    (lambda (name stat errno result)
                      (error (strerror errno) name))
                    '()
                    directory))

(define-record-type <issue>
  (issue file title creator created-date created-relative-date
         assigned keywords open)
  issue?
  (file issue-file)
  (title issue-title)
  (creator issue-creator)
  (created-date issue-created-date)
  (created-relative-date issue-created-relative-date)
  (assigned issue-assigned)
  (keywords issue-keywords)
  (open issue-open))

(define (issues)
  "Return a list of all issues, sorted newest first."
  ;; Get all gemini files except README.gmi and hidden files. Text
  ;; editors tend to create hidden files while editing, and we want to
  ;; avoid them.
  (sort (map (lambda (file)
               (let* ((file-details (file-details file))
                      (creation-details (creation-details file))
                      (all-keywords (hashtable-ref file-details 'keywords '())))
                 (issue file
                        ;; Fallback to filename if title has no alphabetic
                        ;; characters.
                        (let ((title (hashtable-ref file-details 'title "")))
                          (if (string-any char-set:letter title) title file))
                        (assq-ref creation-details 'creator)
                        (assq-ref creation-details 'created-date)
                        (assq-ref creation-details 'created-relative-date)
                        (hashtable-ref file-details 'assigned '())
                        ;; "closed" is a special keyword to indicate
                        ;; the open/closed status of an issue.
                        (delete "closed" all-keywords)
                        (not (member "closed" all-keywords)))))
             (find-files "."
                         (lambda (name _)
                           (and (string-suffix? ".gmi" name)
                                (not (string=? (basename name) "README.gmi"))
                                (not (string-prefix? "." (basename name)))))))
        (lambda (issue1 issue2)
          (> (issue-created-date issue1)
             (issue-created-date issue2)))))

(define (hashtable-append! hashtable key new-values)
  "Append NEW-VALUES to the list of values KEY is associated to in
HASHTABLE. If KEY is not associated to any value in HASHTABLE, assume
it is associated to the empty list."
  (hashtable-update!
   hashtable key (cut append <> new-values) '()))

(define (comma-split str)
  "Split string at commas, trim whitespace from both ends of the split
strings, and return them as a list."
  (map (cut string-trim-both <>)
       (string-split str #\,)))

(define (remove-prefix prefix str)
  "Remove PREFIX from STR."
  (substring str (string-length prefix)))

(define (file-details file)
  "Return a hashtable of details extracted from gemini FILE."
  (let ((result (make-eq-hashtable)))
    (call-with-input-file file
      (lambda (port)
        (port-transduce (tmap (lambda (line)
                                (cond
                                 ;; Lists with the assigned: prefix
                                 ;; specify assignees.
                                 ((string-prefix? "* assigned:" line)
                                  (hashtable-append! result 'assigned
                                                     (comma-split
                                                      (remove-prefix "* assigned:" line))))
                                 ;; Lists with the keywords: prefix
                                 ;; specify keywords.
                                 ((string-prefix? "* keywords:" line)
                                  (hashtable-append! result 'keywords
                                                     (comma-split
                                                      (remove-prefix "* keywords:" line))))
                                 ;; A more fuzzy heuristic to find keywords
                                 ((and (string-prefix? "* " line)
                                       ;; Is every comma-separated
                                       ;; element two words utmost?
                                       (every (lambda (element)
                                                (<= (length
                                                     (string-split element #\space))
                                                    2))
                                              (comma-split (remove-prefix "* " line)))
                                       ;; Does any comma-separated
                                       ;; element contain a potential
                                       ;; keyword?
                                       (any (lambda (element)
                                              (any (lambda (keyword)
                                                     (string-contains element keyword))
                                                   (list "request" "bug" "critical"
                                                         "enhancement" "progress"
                                                         "testing" "later" "documentation"
                                                         "help" "closed")))
                                            (comma-split (remove-prefix "* " line))))
                                  (hashtable-append! result 'keywords
                                                     (comma-split
                                                      (remove-prefix "* " line))))
                                 ;; The first level one heading is the
                                 ;; title.
                                 ((string-prefix? "# " line)
                                  (unless (hashtable-contains? result 'title)
                                    (hashtable-set! result 'title
                                                    (remove-prefix "# " line)))))))
                        (const #t)
                        read-line
                        port)))
    result))

(define (creation-details file)
  "Return an association list of creation details about FILE extracted
from the git repository."
  (call-with-input-pipe
   read
   "git" "log" "--diff-filter=A"
   (string-append "--format=format:("
                  "(creator . \"%an\")"
                  "(created-date . %at)"
                  "(created-relative-date . \"%ar\")"
                  ")")
   "--" file))

(define (git-updated-files transducer start-commit end-commit)
  "Use TRANSDUCER to transduce over the list of files updated between
START-COMMIT and END-COMMIT."
  (call-with-input-pipe
   (lambda (port)
     (port-transduce (compose (tmap (lambda (line)
                                      (match (string-split line #\tab)
                                        ((status file)
                                         (list (match status
                                                 ("A" 'added)
                                                 ("D" 'deleted)
                                                 ("M" 'modified))
                                               file)))))
                              transducer)
                     (const #t) read-line port))
   "git" "diff" "--stat" "--name-status"
   (string-append start-commit ".." end-commit)))

(define rlast
  (case-lambda
    (() #f)
    ((result) result)
    ((result input) input)))

(define (git-first-commit-since since)
  "Return the hash of the first git commit since SINCE, where SINCE is
passed verbatim to the --since argument of `git log'. Return #f if
there is no such commit."
  (call-with-input-pipe
   (lambda (port)
     (port-transduce (tmap identity)
                     rlast
                     read-line
                     port))
   "git" "log" "--format=format:%H" "--since" since))

(define (color code str)
  "Return STR within ANSI escape CODE, thus rendering it in color in a
terminal."
  (format #f "~a[~am~a~a[0m" #\esc code str #\esc))

(define red (cut color 31 <>))
(define green (cut color 32 <>))
(define magenta (cut color 35 <>))
(define blue (cut color 34 <>))
(define cyan (cut color 36 <>))

(define (invalid-option name arg loads)
  (error "Invalid option" name))

(define (invalid-operand arg loads)
  (error "Invalid argument" arg))

(define (gnbug-news . args)
  (let ((args (args-fold args
                         (list (option (list "since") #t #f
                                       (lambda (opt name arg loads)
                                         (acons 'since arg loads))))
                         invalid-option
                         invalid-operand
                         '())))
    (unless (assq 'since args)
      (error "--since argument required"))
    (git-updated-files (tlog (match-lambda*
                               ((_ (status file))
                                (format #t ((case status
                                              ((added) green)
                                              ((deleted) red)
                                              ((modified) magenta))
                                            "~a (~a)~%")
                                        file
                                        (case status
                                          ((added) "new")
                                          ((deleted) "deleted")
                                          ((modified) "updated"))))))
                       (or (git-first-commit-since (assq-ref args 'since))
                           "HEAD")
                       "HEAD")))

(define (gnbug-list . args)
  (let ((args (args-fold args
                         (list (option (list "assigned") #t #f
                                       (lambda (opt name arg loads)
                                         (acons 'assigned arg loads))))
                         invalid-option
                         invalid-operand
                         '())))
    (format #t "~%total ~a~%"
            (list-transduce (compose (tenumerate 1)
                                     (tfilter (match-lambda
                                                ((_ . issue)
                                                 (or (not (assq 'assigned args))
                                                     (member (assq-ref args 'assigned)
                                                             (issue-assigned issue))))))
                                     (tlog (match-lambda*
                                             ((_ (index . issue))
                                              (format #t "~a ~a ~a ~a~a~%"
                                                      (magenta (string-append "#" (number->string index)))
                                                      (issue-created-relative-date issue)
                                                      (cyan (issue-creator issue))
                                                      (issue-title issue)
                                                      (match (issue-assigned issue)
                                                        (() "")
                                                        (assignees
                                                         (magenta (string-append " (assigned: "
                                                                                 (string-join assignees ", ")
                                                                                 ")")))))))))
                            rcount
                            (issues)))))

(define (gnbug-edit issue-number)
  (unless (getenv "EDITOR")
    (error "Please set the EDITOR environment variable to your favorite editor. For example,
export EDITOR=emacsclient"))
  (invoke (getenv "EDITOR")
          (issue-file (list-ref (issues)
                                (1- (string->number issue-number))))))

(define (gnbug-show issue-number)
  (put-string (current-output-port)
              (call-with-input-file (issue-file (list-ref (issues)
                                                          (1- (string->number issue-number))))
                get-string-all)))

(define main
  (match-lambda*
    ((_ command args ...)
     (apply (match command
              ("news" gnbug-news)
              ("list" gnbug-list)
              ("edit" gnbug-edit)
              ("show" gnbug-show))
            args))
    ;; gnbug is an alias for `gnbug list'
    ((_)
     (gnbug-list))))

(apply main (command-line))