1 files changed, 397 insertions, 0 deletions
diff --git a/background/storage.js b/background/storage.js
new file mode 100644
index 0000000..ea390ef
--- /dev/null
+++ b/background/storage.js
@@ -0,0 +1,397 @@
+/**
+* Myext storage manager
+*
+* Copyright (C) 2021 Wojtek Kosior
+*
+* Dual-licensed under:
+*   - 0BSD license
+*   - GPLv3 or (at your option) any later version
+*/
+
+"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 bundles;
+    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 bundles, item name is chosen by user, data is an array of 2-element
+     * arrays with type prefix and script/bundle 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);
+})();