path: root/background/storage.js

/**
 * Myext storage manager
 *
 * Copyright (C) 2021 Wojtek Kosior
 * Redistribution terms are gathered in the `copyright' file.
 */

"use strict";

(() => {
    const TYPE_PREFIX = window.TYPE_PREFIX;
    const TYPE_NAME = window.TYPE_NAME;
    const list_prefixes = window.list_prefixes;
    const make_lock = window.make_lock;
    const lock = window.lock;
    const unlock = window.unlock;
    const make_once = window.make_once;
    const browser = window.browser;
    const is_chrome = window.is_chrome;

    var exports = {};

    /* We're yet to decide how to handle errors... */

    /* Here are some basic wrappers for storage API functions */

    async function get(key)
    {
	try {
	    /* Fix for fact that Chrome does not use promises here */
	    let promise = is_chrome ?
		new Promise((resolve, reject) =>
			    chrome.storage.local.get(key,
						     val => resolve(val))) :
		browser.storage.local.get(key);

	    return (await promise)[key];
	} catch (e) {
	    console.log(e);
	}
    }

    async function set(key, value)
    {
	try {
	    return browser.storage.local.set({[key]: value});
	} catch (e) {
	    console.log(e);
	}
    }

    async function setn(keys_and_values)
    {
	let obj = Object();
	while (keys_and_values.length > 1) {
	    let value = keys_and_values.pop();
	    let key = keys_and_values.pop();
	    obj[key] = value;
	}

	try {
	    return browser.storage.local.set(obj);
	} catch (e) {
	    console.log(e);
	}
    }

    async function set_var(name, value)
    {
	return set(TYPE_PREFIX.VAR + name, value);
    }

    async function get_var(name)
    {
	return get(TYPE_PREFIX.VAR + name);
    }

    /*
     * A special case of persisted variable is one that contains list
     * of items.
     */

    async function get_list_var(name)
    {
	let list = await get_var(name);

	return list === undefined ? [] : list;
    }

    /* We maintain in-memory copies of some stored lists. */

    async function list(prefix)
    {
	let name = TYPE_NAME[prefix] + "s"; /* Make plural. */
	let map = new Map();

	for (let item of await get_list_var(name))
	    map.set(item, await get(prefix + item));

	return {map, prefix, name, listeners : new Set(), lock : make_lock()};
    }

    var pages;
    var bags;
    var scripts;

    var list_by_prefix = {};

    async function init()
    {
	for (let prefix of list_prefixes)
	    list_by_prefix[prefix] = await list(prefix);

	return exports;
    }

    /*
     * 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);
    }

    function broadcast_change(change, list)
    {
	for (let listener_callback of list.listeners)
	    listener_callback(change);
    }

    /* 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);
    }

    /*
     * Below we make additional effort to update map of given kind of items
     * every time an item is added/removed to keep everything coherent.
     */
    async function set_item(item, value, list)
    {
	await lock(list.lock);
	let result = await _set_item(...arguments);
	unlock(list.lock)
	return result;
    }
    async function _set_item(item, value, list)
    {
	let key = list.prefix + item;
	let old_val = list.map.get(item);
	if (old_val === undefined) {
	    let items = list_items(list);
	    items.push(item);
	    await setn([key, value, "_" + list.name, items]);
	} else {
	    await set(key, value);
	}

	list.map.set(item, value)

	let change = {
	    prefix : list.prefix,
	    item,
	    old_val,
	    new_val : value
	};

	broadcast_change(change, list);

	return old_val;
    }

    // TODO: The actual idea to set value to undefined is good - this way we can
    //       also set a new list of items in the same API call. But such key
    //       is still stored in the storage. We need to somehow remove it later.
    //       For that, we're going to have to store 1 more list of each kind.
    async function remove_item(item, list)
    {
	await lock(list.lock);
	let result = await _remove_item(...arguments);
	unlock(list.lock)
	return result;
    }
    async function _remove_item(item, list)
    {
	let old_val = list.map.get(item);
	if (old_val === undefined)
	    return;

	let key = list.prefix + item;
	let items = list_items(list);
	let index = items.indexOf(item);
	items.splice(index, 1);

	await setn([key, undefined, "_" + list.name, items]);

	list.map.delete(item);

	let change = {
	    prefix : list.prefix,
	    item,
	    old_val,
	    new_val : undefined
	};

	broadcast_change(change, list);

	return old_val;
    }

    // TODO: same as above applies here
    async function replace_item(old_item, new_item, list, new_val=undefined)
    {
	await lock(list.lock);
	let result = await _replace_item(...arguments);
	unlock(list.lock)
	return result;
    }
    async function _replace_item(old_item, new_item, list, new_val=undefined)
    {
	let old_val = list.map.get(old_item);
	if (new_val === undefined) {
	    if (old_val === undefined)
		return;
	    new_val = old_val
	} else if (new_val === old_val && new_item === old_item) {
	    return old_val;
	}

	if (old_item === new_item || old_val === undefined) {
	    await _set_item(new_item, new_val, list);
	    return old_val;
	}

	let new_key = list.prefix + new_item;
	let old_key = list.prefix + old_item;
	let items = list_items(list);
	let index = items.indexOf(old_item);
	items[index] = new_item;
	await setn([old_key, undefined, new_key, new_val,
		    "_" + list.name, items]);

	list.map.delete(old_item);

	let change = {
	    prefix : list.prefix,
	    item : old_item,
	    old_val,
	    new_val : undefined
	};

	broadcast_change(change, list);

	list.map.set(new_item, new_val);

	change.item = new_item;
	change.old_val = undefined;
	change.new_val = new_val;

	broadcast_change(change, list);

	return old_val;
    }

    /*
     * For scripts, item name is chosen by user, data should be
     * an object containing:
     * - script's url and hash or
     * - script's text or
     * - all three
     */

    /*
     * For bags, item name is chosen by user, data is an array of 2-element
     * arrays with type prefix and script/bag names.
     */

    /*
     * For pages data argument is an object with properties `allow'
     * and `components'. Item name is url.
     */

    exports.set = async function (prefix, item, data)
    {
	return set_item(item, data, list_by_prefix[prefix]);
    }

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

    exports.remove = async function (prefix, item)
    {
	return remove_item(item, list_by_prefix[prefix]);
    }

    exports.replace = async function (prefix, old_item, new_item,
				      new_data=undefined)
    {
	return replace_item(old_item, new_item, list_by_prefix[prefix],
			    new_data);
    }

    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]);
    }

    /* Finally, a quick way to wipe all the data. */
    // TODO: maybe delete items in such order that none of them ever references
    // an already-deleted one?
    exports.clear = async function ()
    {
	let lists = list_prefixes.map((p) => list_by_prefix[p]);

	for (let list of lists)
	    await lock(list.lock);

	for (let list of lists) {

	    let change = {
		prefix : list.prefix,
		new_val : undefined
	    };

	    for (let [item, val] of list_entries_it(list)) {
		change.item = item;
		change.old_val = val;
		broadcast_change(change, list);
	    }

	    list.map = new Map();
	}

	await browser.storage.local.clear();

	for (let list of lists)
	    unlock(list.lock);
    }

    window.get_storage = make_once(init);
})();