;; This file is part of eris-cl.
;; Copyright (C) 2023 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-sqlite)

(defclass sqlite-backend (encoding-backend decoding-backend)
  ((db :initarg :db :type (or string pathname)
       :documentation
       "Pathname to the SQLITE database. After initialization, contains a
DBI:CONNECTION object.")))

(defmethod initialize-instance
    :after ((sqlite-backend sqlite-backend) &rest initargs &key (db nil db-p) &allow-other-keys)
  (declare (ignore initargs))

  (when (or (null db-p) (null (pathname-directory db)))
    (error 'eris::directory-error :message "Incorrectly specified directory."))

  (with-slots ((output-function output-function)
               (fetch-function fetch-function)
               (db-slot db)) sqlite-backend

    ;; This means that we never close the connection. Might potentially be a
    ;; memory leak issue if it's backed up by a foreign memory allocation.
    (setf db-slot (dbi:connect-cached :sqlite3 :database-name db))

    ;; ensure table exists
    (dbi:do-sql db-slot
      "CREATE TABLE IF NOT EXISTS eris_block (
              block_id INTEGER PRIMARY KEY,
              ref BLOB UNIQUE,
              block BLOB
);")

    ;; ensure index exists

    (dbi:do-sql db-slot
      "CREATE INDEX IF NOT EXISTS eris_block_index ON eris_block (ref);")
    
    (setf fetch-function
          (lambda (reference)
            ;; This is slow. Much worse than a proper hash-table. Not sure how
            ;; to improve on this besides indexing. The spec suggests that
            ;; foreign keys should be used to reference blocks but I don't see
            ;; how it could be implemented here.

            (cadr
             (dbi:fetch
              (dbi:execute
               (dbi:prepare
                db-slot
                "SELECT block FROM eris_block WHERE (ref = ?)")
               (list reference)))))
          output-function
          (lambda (block reference)
            (dbi:do-sql db-slot
              "INSERT OR IGNORE INTO eris_block (ref,block) VALUES (?,?)"
              (list reference block))
            block))))

;; Use transactions for block insertion.
(defmethod store-data (input (backend sqlite-backend) &key (secret null-secret) &allow-other-keys)
  (dbi:with-transaction (slot-value backend 'db)
    (call-next-method)))