1 files changed, 380 insertions, 0 deletions
diff --git a/background/storage.mjs b/background/storage.mjs
new file mode 100644
index 0000000..00b1ace
--- /dev/null
+++ b/background/storage.mjs
@@ -0,0 +1,380 @@
+/**
+* Myext storage manager
+*
+* Copyright (C) 2021 Wojtek Kosior
+*
+* Dual-licensed under:
+*   - 0BSD license
+*   - GPLv3 or (at your option) any later version
+*/
+
+import {TYPE_PREFIX, TYPE_NAME, list_prefixes} from '/common/stored_types.mjs';
+import {make_lock, lock, unlock} from '/common/lock.mjs';
+import make_once from '/common/once.mjs';
+import browser from '/common/browser.mjs';
+
+"use strict";
+
+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 = window.browser === undefined ?
+	    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 a 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 same as for bundles. 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);
+}
+
+export default make_once(init);