;; This file is part of eris-cl.
;; Copyright (C) 2022 Piotr Szarmański

;; eris-cl is free software: you can redistribute it and/or modify it under the
;; terms of the GNU Lesser General Public License as published by the Free
;; Software Foundation, either version 3 of the License, or (at your option) any
;; later version.

;; eris-cl 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
;; eris-cl. If not, see <https://www.gnu.org/licenses/>.

(in-package :eris)

(defclass hash-backend (encoding-backend decoding-backend)
  ((table :type hash-table)))

(defmethod shared-initialize :after ((hash-backend hash-backend) slot-names
                                     &rest initargs
                                     &key &allow-other-keys)
  
  (declare (ignore initargs slot-names))
  (let ((hash-table (make-hash-table :test #'equalp)))
    (with-slots (table output-function fetch-function) hash-backend
      (setf table hash-table
            fetch-function (lambda (reference)
                             (declare (type octet-vector reference))
                             (copy-seq (gethash reference hash-table)))
            output-function (lambda (block reference)
                              (declare (type octet-vector block reference))
                              (setf (gethash reference hash-table)
                                    (copy-seq block))
                              block)))))

(defmethod fetch-data (read-capability (backend hash-backend) &key &allow-other-keys)
  (declare (type read-capability read-capability))
  (with-slots (fetch-function) backend
    (eris-decode read-capability fetch-function :cache-capacity nil)))

(defmethod store-data (input (backend hash-backend) &key (secret null-secret) (block-size 1kib) &allow-other-keys)
  (declare (type octet-vector secret))
  (with-slots (output-function) backend
    (eris-encode input
                 block-size
                 output-function
                 :hash-output nil
                 :secret secret)))