;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2022 pukkamustard <pukkamustard@posteo.net>
;;;
;;; 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 eris fs-store)
  #:use-module (rnrs io ports)
  #:use-module (guix build utils) ; for mkdir-p
  #:use-module (eris utils base32)

  #:export (eris-fs-store-reducer
            eris-fs-store-ref))

;;; Commentary:
;;;
;;; This module provides a file-system based store of ERIS encoded blocks.
;;;
;;; Code:

(define (eris-fs-store-reducer store-directory)
  (case-lambda
    (() (mkdir-p store-directory))

    ((result) result)

    ((_ ref-block)
     (let* ((ref (car ref-block))
	    (b32 (base32-encode ref))
	    (pre (substring b32 0 2))
	    (suf (substring b32 2))
	    (pre-dir (string-append store-directory "/" pre))
	    (path (string-append pre-dir "/" suf))
	    (block (cdr ref-block)))

       (mkdir-p pre-dir)

       (unless (file-exists? path)
	 (call-with-output-file path
	   (lambda (port) (put-bytevector port block))
	   #:binary #t))

       #t))))

(define* (eris-fs-store-ref ref #:key store-directory)
  (let* ((b32 (base32-encode ref))
	 (pre (substring b32 0 2))
	 (suf (substring b32 2))
	 (path (string-append store-directory "/" pre "/" suf)))
    (if (file-exists? path)
	(call-with-input-file path
	  (lambda (port) (get-bytevector-all port))
	  #:binary #t)
	#f)))