Haketilo

/**

 * Hachette storage manager

 *

 * Copyright (C) 2021 Wojtek Kosior

 * Redistribution terms are gathered in the `copyright' file.

 */

/*

 * IMPORTS_START

 * IMPORT TYPE_PREFIX

 * IMPORT TYPE_NAME

 * IMPORT list_prefixes

 * IMPORT make_lock

 * IMPORT lock

 * IMPORT unlock

 * IMPORT make_once

 * IMPORT browser

 * IMPORT is_chrome

 * IMPORT observables

 * IMPORTS_END

 */

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, observable: observables.make(),

	    lock: make_lock()};

}

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)

	observables.subscribe(list_by_prefix[prefix].observable, cb);

}

exports.remove_change_listener = function (cb, prefixes=list_prefixes)

{

    if (typeof(prefixes) === "string")

	prefixes = [prefixes];

    for (let prefix of prefixes)

	observables.unsubscribe(list_by_prefix[prefix].observable, 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);

}

/*

 * 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

    };

    observables.broadcast(list.observable, change);

    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

    };

    observables.broadcast(list.observable, change);

    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

    };

    observables.broadcast(list.observable, change);

    list.map.set(new_item, new_val);

    change.item = new_item;

    change.old_val = undefined;

    change.new_val = new_val;

    observables.broadcast(list.observable, change);

    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;

	    observables.broadcast(list.observable, change);

	}

	list.map = new Map();

    }

    await browser.storage.local.clear();

    for (let list of lists)

	unlock(list.lock);

}

const get_storage = make_once(init);

/*

 * EXPORTS_START

 * EXPORT get_storage

 * EXPORTS_END

 */