/**
 * This file is part of Haketilo.
 *
 * Function: Storage through messages (client side).
 *
 * Copyright (C) 2021 Wojtek Kosior
 *
 * This program 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.
 *
 * This program 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.
 *
 * As additional permission under GNU GPL version 3 section 7, you
 * may distribute forms of that code without the copy of the GNU
 * GPL normally required by section 4, provided you include this
 * license notice and, in case of non-source distribution, a URL
 * through which recipients can access the Corresponding Source.
 * If you modify file(s) with this exception, you may extend this
 * exception to your version of the file(s), but you are not
 * obligated to do so. If you do not wish to do so, delete this
 * exception statement from your version.
 *
 * As a special exception to the GPL, any HTML file which merely
 * makes function calls to this code, and for that purpose
 * includes it by reference shall be deemed a separate work for
 * copyright law purposes. If you modify this code, you may extend
 * this exception to your version of the code, but you are not
 * obligated to do so. If you do not wish to do so, delete this
 * exception statement from your version.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 *
 * I, Wojtek Kosior, thereby promise not to sue for violation of this file's
 * license. Although I request that you do not make use this code in a
 * proprietary program, I am not going to enforce this in court.
 */

/*
 * IMPORTS_START
 * IMPORT CONNECTION_TYPE
 * IMPORT list_prefixes
 * IMPORT make_once
 * IMPORT browser
 * IMPORTS_END
 */

var call_id = 0;
var port;
var calls_waiting = new Map();

function set_call_callback(resolve, reject, func, args)
{
    port.postMessage([call_id, func, args]);
    calls_waiting.set(call_id++, [resolve, reject]);
}

async function remote_call(func, args)
{
    return new Promise((resolve, reject) =>
		       set_call_callback(resolve, reject, func, args));
}

function handle_message(message)
{
    let callbacks = calls_waiting.get(message.call_id);
    if (callbacks === undefined) {
	handle_change(message);
	return;
    }

    let [resolve, reject] = callbacks;
    calls_waiting.delete(message.call_id);
    if (message.error !== undefined)
	setTimeout(reject, 0, message.error);
    else
	setTimeout(resolve, 0, message.result);
}

const list_by_prefix = {};

for (const prefix of list_prefixes)
    list_by_prefix[prefix] = {prefix, listeners : new Set()};

var resolve_init;

function handle_first_message(message)
{
    for (let prefix of Object.keys(message))
	list_by_prefix[prefix].map = new Map(message[prefix]);

    port.onMessage.removeListener(handle_first_message);
    port.onMessage.addListener(handle_message);

    resolve_init();
}

function handle_change(change)
{
    let list = list_by_prefix[change.prefix];

    if (change.new_val === undefined)
	list.map.delete(change.item);
    else
	list.map.set(change.item, change.new_val);

    for (let listener_callback of list.listeners)
	listener_callback(change);
}

var exports = {};

function start_connection(resolve)
{
    resolve_init = resolve;
    port = browser.runtime.connect({name : CONNECTION_TYPE.REMOTE_STORAGE});
    port.onMessage.addListener(handle_first_message);
}

async function init() {
    await new Promise((resolve, reject) => start_connection(resolve));
    return exports;
}

for (let call_name of ["set", "remove", "replace", "clear"])
    exports [call_name] = (...args) => remote_call(call_name, args);

// TODO: Much of the code below is copy-pasted from /background/storage.mjs.
//       This should later be refactored into a separate module
//       to avoid duplication.

/*
 * Facilitate listening to changes
 */

exports.add_change_listener = function (cb, prefixes=list_prefixes)
{
    if (typeof(prefixes) === "string")
	prefixes = [prefixes];

    for (let prefix of prefixes)
	list_by_prefix[prefix].listeners.add(cb);
}

exports.remove_change_listener = function (cb, prefixes=list_prefixes)
{
    if (typeof(prefixes) === "string")
	prefixes = [prefixes];

    for (let prefix of prefixes)
	list_by_prefix[prefix].listeners.delete(cb);
}

/* Prepare some hepler functions to get elements of a list */

function list_items_it(list, with_values=false)
{
    return with_values ? list.map.entries() : list.map.keys();
}

function list_entries_it(list)
{
    return list_items_it(list, true);
}

function list_items(list, with_values=false)
{
    let array = [];

    for (let item of list_items_it(list, with_values))
	array.push(item);

    return array;
}

function list_entries(list)
{
    return list_items(list, true);
}

exports.get = function (prefix, item)
{
    return list_by_prefix[prefix].map.get(item);
}

exports.get_all_names = function (prefix)
{
    return list_items(list_by_prefix[prefix]);
}

exports.get_all_names_it = function (prefix)
{
    return list_items_it(list_by_prefix[prefix]);
}

exports.get_all = function (prefix)
{
    return list_entries(list_by_prefix[prefix]);
}

exports.get_all_it = function (prefix)
{
    return list_entries_it(list_by_prefix[prefix]);
}

const get_remote_storage = make_once(init);

/*
 * EXPORTS_START
 * EXPORT get_remote_storage
 * EXPORTS_END
 */