;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2021 Sarah Morgensen <iskarian@mgsn.dev>
;;;
;;; 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 hash)
  #:use-module (gcrypt hash)
  #:use-module (guix serialization)
  #:use-module (srfi srfi-1)
  #:use-module (srfi srfi-11)
  #:export (vcs-file?
            file-hash*))

(define (vcs-file? file stat)
  "Returns true if FILE is a version control system file."
  (case (stat:type stat)
    ((directory)
     (member (basename file) '(".bzr" ".git" ".hg" ".svn" "CVS")))
    ((regular)
     ;; Git sub-modules have a '.git' file that is a regular text file.
     (string=? (basename file) ".git"))
    (else
     #f)))

(define* (file-hash* file #:key
                     (algorithm (hash-algorithm sha256))
                     (recursive? #t)
                     (select? (negate vcs-file?)))
  "Compute the hash of FILE with ALGORITHM.  If RECURSIVE? is true, recurse
into subdirectories of FILE, computing the combined hash of all files for
which (SELECT?  FILE STAT) returns true."
  (if recursive?
      (let-values (((port get-hash)
                    (open-hash-port algorithm)))
        (write-file file port #:select? select?)
        (force-output port)
        (get-hash))
      (file-hash algorithm file)))