#!@GUILE@ \
--no-auto-compile -s
!#

;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2020, 2021, 2022, 2023 Ricardo Wurmus <rekado@elephly.net>
;;; Copyright © 2021 Sarah Morgensen <iskarian@mgsn.dev>
;;; Copyright © 2021 Xinglu Chen <public@yoctocell.xyz>
;;; Copyright © 2022 Maxim Cournoyer <maxim.cournoyer@gmail.com>
;;;
;;; This file is part of GNU Guix.
;;;
;;; GNU Guix 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.
;;;
;;; GNU Guix 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 GNU Guix.  If not, see <http://www.gnu.org/licenses/>.

;;; Commentary:

;; This script stages and commits changes to package definitions.

;;; Code:

(use-modules ((sxml xpath) #:prefix xpath:)
             (srfi srfi-1)
             (srfi srfi-2)
             (srfi srfi-9)
             (srfi srfi-11)
             (srfi srfi-26)
             (ice-9 format)
             (ice-9 popen)
             (ice-9 match)
             (ice-9 rdelim)
             (ice-9 regex)
             (ice-9 textual-ports)
             (guix gexp))

(define* (break-string str #:optional (max-line-length 70))
  "Break the string STR into lines that are no longer than MAX-LINE-LENGTH.
Return a single string."
  (define (restore-line words)
    (string-join (reverse words) " "))
  (if (<= (string-length str) max-line-length)
      str
      (let ((words+lengths (map (lambda (word)
                                  (cons word (string-length word)))
                                (string-tokenize str))))
        (match (fold (match-lambda*
                       (((word . length)
                         (count current lines))
                        (let ((new-count (+ count length 1)))
                          (if (< new-count max-line-length)
                              (list new-count
                                    (cons word current)
                                    lines)
                              (list length
                                    (list word)
                                    (cons (restore-line current) lines))))))
                     '(0 () ())
                     words+lengths)
          ((_ last-words lines)
           (string-join (reverse (cons (restore-line last-words) lines))
                        "\n"))))))

(define* (break-string-with-newlines str #:optional (max-line-length 70))
  "Break the lines of string STR into lines that are no longer than
MAX-LINE-LENGTH. Return a single string."
  (string-join (map (cut break-string <> max-line-length)
                    (string-split str #\newline))
               "\n"))

(define (read-excursion port)
  "Read an expression from PORT and reset the port position before returning
the expression."
  (let ((start (ftell port))
        (result (read port)))
    (seek port start SEEK_SET)
    result))

(define (lines+offsets-with-opening-parens port)
  "Record all line numbers (and their offsets) where an opening parenthesis is
found in column 0.  The resulting list is in reverse order."
  (let loop ((acc '())
             (number 0))
    (let ((line (read-line port)))
      (cond
       ((eof-object? line) acc)
       ((string-prefix? "(" line)
        (loop (cons (cons number                      ;line number
                          (- (ftell port)
                             (string-length line) 1)) ;offset
                    acc)
              (1+ number)))
       (else (loop acc (1+ number)))))))

(define (surrounding-sexp port target-line-no)
  "Return the top-level S-expression surrounding the change at line number
TARGET-LINE-NO in PORT."
  (let* ((line-numbers+offsets
          (lines+offsets-with-opening-parens port))
         (closest-offset
          (or (and=> (list-index (match-lambda
                                   ((line-number . offset)
                                    (< line-number target-line-no)))
                                 line-numbers+offsets)
                     (lambda (index)
                       (match (list-ref line-numbers+offsets index)
                         ((line-number . offset) offset))))
              (error "Could not find surrounding S-expression for line"
                     target-line-no))))
    (seek port closest-offset SEEK_SET)
    (read port)))

;;; Whether the hunk contains a newly added package (definition), a removed
;;; package (removal) or something else (#false).
(define hunk-types '(addition removal #false))

(define-record-type <hunk>
  (make-hunk file-name
             old-line-number
             new-line-number
             diff-lines
             type)
  hunk?
  (file-name       hunk-file-name)
  ;; Line number before the change
  (old-line-number hunk-old-line-number)
  ;; Line number after the change
  (new-line-number hunk-new-line-number)
  ;; The full diff to be used with "git apply --cached"
  (diff-lines hunk-diff-lines)
  ;; Does this hunk add or remove a package?
  (type hunk-type))                     ;one of 'hunk-types'

(define* (hunk->patch hunk #:optional (port (current-output-port)))
  (let ((file-name (hunk-file-name hunk)))
    (format port
            "diff --git a/~a b/~a~%--- a/~a~%+++ b/~a~%~a"
            file-name file-name file-name file-name
            (string-join (hunk-diff-lines hunk) ""))))

(define (diff-info)
  "Read the diff and return a list of <hunk> values."
  (let ((port (open-pipe* OPEN_READ
                          "git" "diff-files"
                          "--no-prefix"
                          ;; Only include one context line to avoid lumping in
                          ;; new definitions with changes to existing
                          ;; definitions.
                          "--unified=1"
                          "--" "gnu")))
    (define (extract-line-number line-tag)
      (abs (string->number
            (car (string-split line-tag #\,)))))
    (define (read-hunk)
      (let loop ((lines '())
                 (type #false))
        (let ((line (read-line port 'concat)))
          (cond
           ((eof-object? line)
            (values (reverse lines) type))
           ((or (string-prefix? "@@ " line)
                (string-prefix? "diff --git" line))
            (unget-string port line)
            (values (reverse lines) type))
           (else
            (loop (cons line lines)
                  (or type
                      (cond
                       ((string-prefix? "+(define" line)
                        'addition)
                       ((string-prefix? "-(define" line)
                        'removal)
                       (else #false)))))))))
    (define info
      (let loop ((acc '())
                 (file-name #f))
        (let ((line (read-line port)))
          (cond
           ((eof-object? line) acc)
           ((string-prefix? "--- " line)
            (match (string-split line #\space)
              ((_ file-name)
               (loop acc file-name))))
           ((string-prefix? "@@ " line)
            (match (string-split line #\space)
              ((_ old-start new-start . _)
               (let-values
                   (((diff-lines type) (read-hunk)))
                 (loop (cons (make-hunk file-name
                                        (extract-line-number old-start)
                                        (extract-line-number new-start)
                                        (cons (string-append line "\n")
                                              diff-lines)
                                        type) acc)
                       file-name)))))
           (else (loop acc file-name))))))
    (close-pipe port)
    info))

(define (lines-to-first-change hunk)
  "Return the number of diff lines until the first change."
  (1- (count (lambda (line)
               ((negate char-set-contains?)
                (char-set #\+ #\-)
                (string-ref line 0)))
             (hunk-diff-lines hunk))))

(define %original-file-cache
  (make-hash-table))

(define (read-original-file file-name)
  "Return the contents of FILE-NAME prior to any changes."
  (let* ((port (open-pipe* OPEN_READ
                           "git" "cat-file" "-p" (string-append
                                                  "HEAD:" file-name)))
         (contents (get-string-all port)))
    (close-pipe port)
    contents))

(define (read-original-file* file-name)
  "Caching variant of READ-ORIGINAL-FILE."
  (or (hashv-ref %original-file-cache file-name)
      (let ((value (read-original-file file-name)))
        (hashv-set! %original-file-cache file-name value)
        value)))

(define (old-sexp hunk)
  "Using the diff information in HUNK return the unmodified S-expression
corresponding to the top-level definition containing the staged changes."
  ;; TODO: We can't seek with a pipe port...
  (call-with-input-string (read-original-file* (hunk-file-name hunk))
    (lambda (port)
      (surrounding-sexp port
                        (+ (lines-to-first-change hunk)
                           (hunk-old-line-number hunk))))))

(define (new-sexp hunk)
  "Using the diff information in HUNK return the modified S-expression
corresponding to the top-level definition containing the staged changes."
  (call-with-input-file (hunk-file-name hunk)
    (lambda (port)
      (surrounding-sexp port
                        (+ (lines-to-first-change hunk)
                           (hunk-new-line-number hunk))))))

(define* (change-commit-message file-name old new #:optional (port (current-output-port)))
  "Print ChangeLog commit message for changes between OLD and NEW."
  (define (get-values expr field)
    (match ((xpath:node-or
             (xpath:sxpath `(*any* *any* package ,field quasiquote *))
             ;; For let binding
             (xpath:sxpath `(*any* *any* (*any*) package ,field quasiquote *)))
            (cons '*TOP* expr))
      (()
       ;; New-style plain lists
       (match ((xpath:node-or
                (xpath:sxpath `(*any* *any* package ,field list *))
                ;; For let binding
                (xpath:sxpath `(*any* *any* (*any*) package ,field list *)))
               (cons '*TOP* expr))
         ((inner) inner)
         (_ '())))
      ;; Old-style labelled inputs
      ((first . rest)
       (map cadadr first))))
  (define (listify items)
    (match items
      ((one) one)
      ((one two)
       (string-append one " and " two))
      ((one two . more)
       (string-append (string-join (drop-right items 1) ", ")
                      ", and " (first (take-right items 1))))))
  (define variable-name
    (second old))
  (define version
    (and=> ((xpath:node-or
             (xpath:sxpath '(*any* *any* package version *any*))
             ;; For let binding
             (xpath:sxpath '(*any* *any* (*any*) package version *any*)))
            (cons '*TOP* new))
           first))
  (format port
          "gnu: ~a: Update to ~a.~%~%* ~a (~a): Update to ~a.~%"
          variable-name version file-name variable-name version)
  (for-each (lambda (field)
              (let ((old-values (get-values old field))
                    (new-values (get-values new field)))
                (or (equal? old-values new-values)
                    (let ((removed (lset-difference equal? old-values new-values))
                          (added (lset-difference equal? new-values old-values)))
                      (format port
                              "[~a]: ~a~%" field
                              (break-string
                               ;; A dependency can be a list of (pkg output).
                               (match (list (map object->string removed)
                                            (map object->string added))
                                 ((() added)
                                  (format #f "Add ~a."
                                          (listify added)))
                                 ((removed ())
                                  (format #f "Remove ~a."
                                          (listify removed)))
                                 ((removed added)
                                  (format #f "Remove ~a; add ~a."
                                          (listify removed)
                                          (listify added))))))))))
            '(inputs propagated-inputs native-inputs)))

(define* (add-commit-message file-name variable-name
                             #:optional (port (current-output-port)))
  "Print ChangeLog commit message for a change to FILE-NAME adding a
definition."
  (format port "gnu: Add ~a.~%~%* ~a (~a): New variable.~%"
          variable-name file-name variable-name))

(define* (remove-commit-message file-name variable-name
                                #:optional (port (current-output-port)))
  "Print ChangeLog commit message for a change to FILE-NAME removing a
definition."
  (format port "gnu: Remove ~a.~%~%* ~a (~a): Delete variable.~%"
          variable-name file-name variable-name))

(define* (custom-commit-message file-name variable-name message changelog
                                #:optional (port (current-output-port)))
  "Print custom commit message for a change to VARIABLE-NAME in FILE-NAME, using
MESSAGE as the commit message and CHANGELOG as the body of the ChangeLog
entry. If CHANGELOG is #f, the commit message is reused. If CHANGELOG already
contains ': ', no colon is inserted between the location and body of the
ChangeLog entry."
  (define (trim msg)
    (string-trim-right (string-trim-both msg) (char-set #\.)))

  (define (changelog-has-location? changelog)
    (->bool (string-match "^[[:graph:]]+:[[:blank:]]" changelog)))

  (let* ((message (trim message))
         (changelog (if changelog (trim changelog) message))
         (message/f (format #f "gnu: ~a: ~a." variable-name message))
         (changelog/f (if (changelog-has-location? changelog)
                          (format #f "* ~a (~a)~a."
                                  file-name variable-name changelog)
                          (format #f "* ~a (~a): ~a."
                                  file-name variable-name changelog))))
    (format port
            "~a~%~%~a~%"
            (break-string-with-newlines message/f 72)
            (break-string-with-newlines changelog/f 72))))

(define (add-copyright-line line)
  "Add the copyright line on LINE to the previous commit."
  (let ((author (match:substring
                 (string-match "^\\+;;; Copyright ©[^[:alpha:]]+(.*)$" line)
                 1)))
    (format
     (current-output-port) "Amend and add copyright line for ~a~%" author)
    (system* "git" "commit" "--amend" "--no-edit")))

(define (group-hunks-by-sexp hunks)
  "Return a list of pairs associating all hunks with the S-expression they are
modifying."
  (fold (lambda (sexp hunk acc)
          (match acc
            (((previous-sexp . hunks) . rest)
             (if (equal? sexp previous-sexp)
                 (cons (cons previous-sexp
                             (cons hunk hunks))
                       rest)
                 (cons (cons sexp (list hunk))
                       acc)))
            (_
             (cons (cons sexp (list hunk))
                   acc))))
        '()
        (map new-sexp hunks)
        hunks))

(define (new+old+hunks hunks)
  (map (match-lambda
         ((new . hunks)
          (cons* new (old-sexp (first hunks)) hunks)))
       (group-hunks-by-sexp hunks)))

(define %delay 1000)

(define (main . args)
  (define* (change-commit-message* file-name old new #:rest rest)
    (let ((changelog #f))
      (match args
        ((or (message changelog) (message))
         (apply custom-commit-message
                file-name (second old) message changelog rest))
        (_
         (apply change-commit-message file-name old new rest)))))

  (read-disable 'positions)
  (match (diff-info)
    (()
     (display "Nothing to be done.\n" (current-error-port)))
    (hunks
     (let-values (((definitions changes) (partition hunk-type hunks)))
       ;; Additions/removals.
       (for-each
        (lambda (hunk)
          (and-let* ((define-line (find (cut string-match "(\\+|-)\\(define" <>)
                                        (hunk-diff-lines hunk)))
                     (variable-name (and=> (string-tokenize define-line)
                                           second))
                     (commit-message-proc (match (hunk-type hunk)
                                            ('addition add-commit-message)
                                            ('removal remove-commit-message))))
            (commit-message-proc (hunk-file-name hunk) variable-name)
            (let ((port (open-pipe* OPEN_WRITE
                                    "git" "apply"
                                    "--cached"
                                    "--unidiff-zero")))
              (hunk->patch hunk port)
              (unless (eqv? 0 (status:exit-val (close-pipe port)))
                (error "Cannot apply")))

            (let ((port (open-pipe* OPEN_WRITE "git" "commit" "-F" "-")))
              (commit-message-proc (hunk-file-name hunk) variable-name port)
              (usleep %delay)
              (unless (eqv? 0 (status:exit-val (close-pipe port)))
                (error "Cannot commit"))))
          (usleep %delay))
        definitions)

       ;; Changes.
       (for-each
        (match-lambda
          ((new old . hunks)
           (for-each (lambda (hunk)
                       (let ((port (open-pipe* OPEN_WRITE
                                               "git" "apply"
                                               "--cached"
                                               "--unidiff-zero")))
                         (hunk->patch hunk port)
                         (unless (eqv? 0 (status:exit-val (close-pipe port)))
                           (error "Cannot apply")))
                       (usleep %delay))
                     hunks)
           (define copyright-line
             (any (lambda (line) (and=> (string-prefix? "+;;; Copyright ©" line)
                                   (const line)))
                  (hunk-diff-lines (first hunks))))
           (cond
            (copyright-line
             (add-copyright-line copyright-line))
            (else
             (let ((port (open-pipe* OPEN_WRITE "git" "commit" "-F" "-")))
               (change-commit-message* (hunk-file-name (first hunks))
                                       old new)
               (change-commit-message* (hunk-file-name (first hunks))
                                       old new
                                       port)
               (usleep %delay)
               (unless (eqv? 0 (status:exit-val (close-pipe port)))
                 (error "Cannot commit")))))))
        (new+old+hunks (match definitions
                         ('() changes) ;reuse
                         (_
                          ;; XXX: we recompute the hunks here because previous
                          ;; insertions lead to offsets.
                          (let-values (((definitions changes)
                                        (partition hunk-type (diff-info))))
                            changes)))))))))

(apply main (cdr (command-line)))