Haketilo

/**

 * 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);

})();