;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2019 Ludovic Courtès <ludo@gnu.org>
;;;
;;; 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/>.

(define-module (guix tests git)
  #:use-module (git)
  #:use-module (guix utils)
  #:use-module (guix build utils)
  #:use-module (ice-9 match)
  #:use-module (ice-9 control)
  #:export (git-command
            with-temporary-git-repository
            find-commit))

(define git-command
  (make-parameter "git"))

(define (populate-git-repository directory directives)
  "Initialize a new Git checkout and repository in DIRECTORY and apply
DIRECTIVES.  Each element of DIRECTIVES is an sexp like:

  (add \"foo.txt\" \"hi!\")

Return DIRECTORY on success."

  ;; Note: As of version 0.2.0, Guile-Git lacks the necessary bindings to do
  ;; all this, so resort to the "git" command.
  (define (git command . args)
    (apply invoke (git-command) "-C" directory
           command args))

  (mkdir-p directory)
  (git "init")

  (let loop ((directives directives))
    (match directives
      (()
       directory)
      ((('add file contents) rest ...)
       (let ((file (string-append directory "/" file)))
         (mkdir-p (dirname file))
         (call-with-output-file file
           (lambda (port)
             (display contents port)))
         (git "add" file)
         (loop rest)))
      ((('commit text) rest ...)
       (git "commit" "-m" text)
       (loop rest))
      ((('branch name) rest ...)
       (git "branch" name)
       (loop rest))
      ((('checkout branch) rest ...)
       (git "checkout" branch)
       (loop rest))
      ((('merge branch message) rest ...)
       (git "merge" branch "-m" message)
       (loop rest)))))

(define (call-with-temporary-git-repository directives proc)
  (call-with-temporary-directory
   (lambda (directory)
     (populate-git-repository directory directives)
     (proc directory))))

(define-syntax-rule (with-temporary-git-repository directory
                                                   directives exp ...)
  "Evaluate EXP in a context where DIRECTORY contains a checkout populated as
per DIRECTIVES."
  (call-with-temporary-git-repository directives
                                      (lambda (directory)
                                        exp ...)))

(define (find-commit repository message)
  "Return the commit in REPOSITORY whose message includes MESSAGE, a string."
  (let/ec return
    (fold-commits (lambda (commit _)
                    (and (string-contains (commit-message commit)
                                          message)
                         (return commit)))
                  #f
                  repository)
    (error "commit not found" message)))