/**
 * This file is part of Haketilo.
 *
 * Function: Storage manager, lighter than the previous one.
 *
 * Copyright (C) 2021 Wojtek Kosior
 * Redistribution terms are gathered in the `copyright' file.
 */

/*
 * IMPORTS_START
 * IMPORT TYPE_PREFIX
 * IMPORT raw_storage
 * IMPORT is_mozilla
 * IMPORT observables
 */

const reg_spec = new Set(["\\", "[", "]", "(", ")", "{", "}", ".", "*", "+"]);
const escape_reg_special = c => reg_spec.has(c) ? "\\" + c : c;

function make_regex(name)
{
    return new RegExp(`^${name.split("").map(escape_reg_special).join("")}\$`);
}

const listeners_by_callback = new Map();

function listen(callback, prefix, name)
{
    let by_prefix = listeners_by_callback.get(callback);
    if (!by_prefix) {
	by_prefix = new Map();
	listeners_by_callback.set(callback, by_prefix);
    }

    let by_name = by_prefix.get(prefix);
    if (!by_name) {
	by_name = new Map();
	by_prefix.set(prefix, by_name);
    }

    let name_reg = by_name.get(name);
    if (!name_reg) {
	name_reg = name.test ? name : make_regex(name);
	by_name.set(name, name_reg);
    }
}

function no_listen(callback, prefix, name)
{
    const by_prefix = listeners_by_callback.get(callback);
    if (!by_prefix)
	return;

    const by_name = by_prefix.get(prefix);
    if (!by_name)
	return;

    const name_reg = by_name.get(name);
    if (!name_reg)
	return;

    by_name.delete(name);

    if (by_name.size === 0)
	by_prefix.delete(prefix);

    if (by_prefix.size === 0)
	listeners_by_callback.delete(callback);
}

function storage_change_callback(changes, area)
{
    if (is_mozilla && area !== "local")
    {console.log("area", area);return;}

    for (const item of Object.keys(changes)) {
	for (const [callback, by_prefix] of listeners_by_callback.entries()) {
	    const by_name = by_prefix.get(item[0]);
	    if (!by_name)
		continue;

	    for (const reg of by_name.values()) {
		if (!reg.test(item.substring(1)))
		    continue;

		try {
		    callback(item, changes[item]);
		} catch(e) {
		    console.error(e);
		}
	    }
	}
    }
}

raw_storage.listen(storage_change_callback);


const created_observables = new Map();

async function observe(prefix, name)
{
    const observable = observables.make();
    const callback = (it, ch) => observables.set(observable, ch.newValue);
    listen(callback, prefix, name);
    created_observables.set(observable, [callback, prefix, name]);
    observables.silent_set(observable, await raw_storage.get(prefix + name));

    return observable;
}

const observe_var = name => observe(TYPE_PREFIX.VAR, name);

function no_observe(observable)
{
    no_listen(...created_observables.get(observable) || []);
    created_observables.delete(observable);
}

const light_storage = {};
Object.assign(light_storage, raw_storage);
Object.assign(light_storage,
	      {listen, no_listen, observe, observe_var, no_observe});

/*
 * EXPORTS_START
 * EXPORT light_storage
 * EXPORTS_END
 */