Haketilo

/**

 * This file is part of Haketilo.

 *

 * Function: Facilitate use of IndexedDB within Haketilo.

 *

 * Copyright (C) 2021 Wojtek Kosior <koszko@koszko.org>

 *

 * This program is free software: you can redistribute it and/or modify

 * it under the terms of the GNU General Public License as published by

 * the Free Software Foundation, either version 3 of the License, or

 * (at your option) any later version.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * As additional permission under GNU GPL version 3 section 7, you

 * may distribute forms of that code without the copy of the GNU

 * GPL normally required by section 4, provided you include this

 * license notice and, in case of non-source distribution, a URL

 * through which recipients can access the Corresponding Source.

 * If you modify file(s) with this exception, you may extend this

 * exception to your version of the file(s), but you are not

 * obligated to do so. If you do not wish to do so, delete this

 * exception statement from your version.

 *

 * As a special exception to the GPL, any HTML file which merely

 * makes function calls to this code, and for that purpose

 * includes it by reference shall be deemed a separate work for

 * copyright law purposes. If you modify this code, you may extend

 * this exception to your version of the code, but you are not

 * obligated to do so. If you do not wish to do so, delete this

 * exception statement from your version.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program.  If not, see <https://www.gnu.org/licenses/>.

 *

 * I, Wojtek Kosior, thereby promise not to sue for violation of this file's

 * license. Although I request that you do not make use of this code in a

 * proprietary program, I am not going to enforce this in court.

 */

#IMPORT common/entities.js

#IMPORT common/broadcast.js

let initial_data = (

#IF UNIT_TEST

    {}

#ELSE

#INCLUDE default_settings.json

#ENDIF

);

/* Update when changes are made to database schema. Must have 3 elements */

const db_version = [1, 0, 0];

const nr_reductor = ([i, s], num) => [i - 1, s + num * 1024 ** i];

const version_nr = ver => Array.reduce(ver.slice(0, 3), nr_reductor, [2, 0])[1];

const stores = 	[

    ["files",     {keyPath: "hash_key"}],

    ["file_uses", {keyPath: "hash_key"}],

    ["resource",  {keyPath: "identifier"}],

    ["mapping",   {keyPath: "identifier"}],

    ["settings",  {keyPath: "name"}],

    ["blocking",  {keyPath: "pattern"}],

    ["repos",     {keyPath: "url"}]

];

let db = null;

/* Generate a Promise that resolves when an IndexedDB request succeeds. */

async function wait_request(idb_request)

{

    let resolve, reject;

    const waiter = new Promise((...cbs) => [resolve, reject] = cbs);

    [idb_request.onsuccess, idb_request.onerror] = [resolve, reject];

    return waiter;

}

/* asynchronous wrapper for IDBObjectStore's get() method. */

async function idb_get(transaction, store_name, key)

{

    const req = transaction.objectStore(store_name).get(key);

    return (await wait_request(req)).target.result;

}

#EXPORT idb_get

/* asynchronous wrapper for IDBObjectStore's put() method. */

async function idb_put(transaction, store_name, object)

{

    return wait_request(transaction.objectStore(store_name).put(object));

}

/* asynchronous wrapper for IDBObjectStore's delete() method. */

async function idb_del(transaction, store_name, key)

{

    return wait_request(transaction.objectStore(store_name).delete(key));

}

/* Open haketilo database, asynchronously return an IDBDatabase object. */

async function get_db()

{

    if (db)

	return db;

    let resolve, reject;

    const waiter = new Promise((...cbs) => [resolve, reject] = cbs);

    const request = indexedDB.open("haketilo", version_nr(db_version));

    request.onsuccess       = resolve;

    request.onerror         = ev => reject("db error: " + ev.target.errorCode);

    request.onupgradeneeded = resolve;

    const event = await waiter;

    const opened_db = event.target.result;

    if (event instanceof IDBVersionChangeEvent) {

	/*

	 * When we move to a new database schema, we will add upgrade logic

	 * here.

	 */

	if (event.oldVersion > 0)

	    throw "bad db version: " + event.oldVersion;

	let store;

	for (const [store_name, key_mode] of stores)

	    store = opened_db.createObjectStore(store_name, key_mode);

	const ctx = make_context(store.transaction, initial_data.files);

	await _save_items(initial_data.resources, initial_data.mappings, ctx);

    }

    if (db)

	opened_db.close();

    else

	db = opened_db;

    return db;

}

#EXPORT  get_db  AS get

/* Helper function used by make_context(). */

function reject_discard(context)

{

    broadcast.discard(context.sender);

    broadcast.close(context.sender);

    context.reject();

}

/* Helper function used by make_context(). */

function resolve_flush(context)

{

    broadcast.close(context.sender);

    context.resolve();

}

/* Helper function used by start_items_transaction() and get_db(). */

function make_context(transaction, files)

{

    const sender = broadcast.sender_connection();

    files = files || {};

    let resolve, reject;

    const result = new Promise((...cbs) => [resolve, reject] = cbs);

    const context =

	  {sender, transaction, resolve, reject, result, files, file_uses: {}};

    transaction.oncomplete = () => resolve_flush(context);

    transaction.onerror = () => reject_discard(context);

    return context;

}

/*

 * item_store_names should be an array with either string "mapping", string

 * "resource" or both. files should be an object with values being contents of

 * files that are to be possibly saved in this transaction and keys of the form

 * `sha256-<file's-sha256-sum>`.

 *

 * Returned is a context object wrapping the transaction and handling the

 * counting of file references in IndexedDB.

 */

async function start_items_transaction(item_store_names, files)

{

    const db = await get_db();

    const scope = [...item_store_names, "files", "file_uses"];

    return make_context(db.transaction(scope, "readwrite"), files);

}

#EXPORT start_items_transaction

async function incr_file_uses(context, file_ref, by=1)

{

    const hash_key = file_ref.hash_key;

    let uses = context.file_uses[hash_key];

    if (uses === undefined) {

	uses = await idb_get(context.transaction, "file_uses", hash_key);

	if (uses)

	    [uses.new, uses.initial] = [false, uses.uses];

	else

	    uses = {hash_key, uses: 0, new: true, initial: 0};

	context.file_uses[hash_key] = uses;

    }

    uses.uses = uses.uses + by;

}

const decr_file_uses = (ctx, file_ref) => incr_file_uses(ctx, file_ref, -1);

async function finalize_transaction(context)

{

    for (const uses of Object.values(context.file_uses)) {

	if (uses.uses < 0)

	    console.error("internal error: uses < 0 for file " + uses.hash_key);

	const is_new       = uses.new;

	const initial_uses = uses.initial;

	const hash_key     = uses.hash_key;

	delete uses.new;

	delete uses.initial;

	if (uses.uses < 1) {

	    if (!is_new) {

		idb_del(context.transaction, "file_uses", hash_key);

		idb_del(context.transaction, "files",     hash_key);

	    }

	    continue;

	}

	if (uses.uses === initial_uses)

	    continue;

	idb_put(context.transaction, "file_uses", uses);

	if (initial_uses > 0)

	    continue;

	const file = context.files[hash_key];

	if (file === undefined) {

	    context.transaction.abort();

	    throw "file not present: " + hash_key;

	}

	idb_put(context.transaction, "files", {hash_key, contents: file});

    }

    return context.result;

}

#EXPORT finalize_transaction

/*

 * How a sample data argument to the function below might look like:

 *

 * data = {

 *     resources: {

 *         "resource1": {

 *             "1": {

 *                 // some stuff

 *             },

 *             "1.1": {

 *                 // some stuff

 *             }

 *         },

 *         "resource2": {

 *             "0.4.3": {

 *                 // some stuff

 *             }

 *         },

 *     },

 *     mappings: {

 *         "mapping1": {

 *             "2": {

 *                 // some stuff

 *             }

 *         },

 *         "mapping2": {

 *             "0.1": {

 *                 // some stuff

 *             }

 *         },

 *     },

 *     files: {

 *         "sha256-f9444510dc7403e41049deb133f6892aa6a63c05591b2b59e4ee5b234d7bbd99": "console.log(\"hello\");\n",

 *         "sha256-b857cd521cc82fff30f0d316deba38b980d66db29a5388eb6004579cf743c6fd": "console.log(\"bye\");"

 *     }

 * }

 */

async function save_items(data)

{

    const item_store_names = ["resource", "mapping"];

    const context = await start_items_transaction(item_store_names, data.files);

    return _save_items(data.resources, data.mappings, context);

}

#EXPORT save_items

async function _save_items(resources, mappings, context)

{

    resources = Object.values(resources || {}).map(entities.get_newest);

    mappings  = Object.values(mappings  || {}).map(entities.get_newest);

    for (const item of resources.concat(mappings))

	await save_item(item, context);

    await finalize_transaction(context);

}

/*

 * Save given definition of a resource/mapping to IndexedDB. If the definition

 * (passed as `item`) references files that are not already present in

 * IndexedDB, those files should be provided as values of the `files' object

 * used to create the transaction context.

 *

 * context should be one returned from start_items_transaction() and should be

 * later passed to finalize_transaction() so that files depended on are added to

 * IndexedDB and files that are no longer depended on after this operation are

 * removed from IndexedDB.

 */

async function save_item(item, context)

{

    for (const file_ref of entities.get_files(item))

	await incr_file_uses(context, file_ref);

    broadcast.prepare(context.sender, `idb_changes_${item.type}`,

		      item.identifier);

    await _remove_item(item.type, item.identifier, context, false);

    await idb_put(context.transaction, item.type, item);

}

#EXPORT save_item

/* Helper function used by remove_item() and save_item(). */

async function _remove_item(store_name, identifier, context)

{

    const item = await idb_get(context.transaction, store_name, identifier);

    if (item !== undefined) {

	for (const file_ref of entities.get_files(item))

	    await decr_file_uses(context, file_ref);

    }

}

/*

 * Remove definition of a resource/mapping from IndexedDB.

 *

 * context should be one returned from start_items_transaction() and should be

 * later passed to finalize_transaction() so that files depended on are added to

 * IndexedDB and files that are no longer depended on after this operation are

 * removed from IndexedDB.

 */

async function remove_item(store_name, identifier, context)

{

    broadcast.prepare(context.sender, `idb_changes_${store_name}`, identifier);

    await _remove_item(store_name, identifier, context);

    await idb_del(context.transaction, store_name, identifier);

}

const remove_resource = (id, ctx) => remove_item("resource", id, ctx);

#EXPORT remove_resource

const remove_mapping = (id, ctx) => remove_item("mapping",  id, ctx);

#EXPORT remove_mapping

/* Function to retrieve all items from a given store. */

async function get_all(store_name)

{

    const transaction = (await get_db()).transaction([store_name]);

    const all_req = transaction.objectStore(store_name).getAll();

    return (await wait_request(all_req)).target.result;

}

#EXPORT get_all

/*

 * A simplified kind of transaction for modifying stores without special

 * inter-store integrity constraints ("settings", "blocking", "repos").

 */

async function start_simple_transaction(store_name)

{

    const db = await get_db();

    return make_context(db.transaction(store_name, "readwrite"), {});

}

/* Functions to access the "settings" store. */

async function set_setting(name, value)

{

    const context = await start_simple_transaction("settings");

    broadcast.prepare(context.sender, "idb_changes_settings", name);

    await idb_put(context.transaction, "settings", {name, value});

    return finalize_transaction(context);

}

#EXPORT set_setting

async function get_setting(name)

{

    const transaction = (await get_db()).transaction("settings");

    return ((await idb_get(transaction, "settings", name)) || {}).value;

}

#EXPORT get_setting

/* Functions to access the "blocking" store. */

async function set_allowed(pattern, allow=true)

{

    const context = await start_simple_transaction("blocking");

    broadcast.prepare(context.sender, "idb_changes_blocking", pattern);

    if (allow === null)

	await idb_del(context.transaction, "blocking", pattern);

    else

	await idb_put(context.transaction, "blocking", {pattern, allow});

    return finalize_transaction(context);

}

#EXPORT set_allowed

const set_disallowed = pattern => set_allowed(pattern, false);

#EXPORT set_disallowed

const set_default_allowing = pattern => set_allowed(pattern, null);

#EXPORT set_default_allowing

async function get_allowing(pattern)

{

    const transaction = (await get_db()).transaction("blocking");

    return ((await idb_get(transaction, "blocking", pattern)) || {}).allow;

}

#EXPORT get_allowing

/* Functions to access the "repos" store. */

async function set_repo(url, remove=false)

{

    const context = await start_simple_transaction("repos");

    broadcast.prepare(context.sender, "idb_changes_repos", url);

    if (remove)

	await idb_del(context.transaction, "repos", url);

    else

	await idb_put(context.transaction, "repos", {url});

    return finalize_transaction(context);

}

#EXPORT set_repo

const del_repo = url => set_repo(url, true);

#EXPORT del_repo

const get_repos = () => get_all("repos").then(list => list.map(obj => obj.url));

#EXPORT get_repos

/* Callback used when listening to broadcasts while tracking db changes. */

async function track_change(tracking, key)

{

    const transaction = (await get_db()).transaction([tracking.store_name]);

    const new_val = await idb_get(transaction, tracking.store_name, key);

    tracking.onchange({key, new_val});

}

/*

 * Monitor changes to `store_name` IndexedDB object store.

 *

 * `store_name` should be either "resource", "mapping", "settings", "blocking"

 * or "repos".

 *

 * `onchange` should be a callback that will be called when an item is added,

 * modified or removed from the store. The callback will be passed an object

 * representing the change as its first argument. This object will have the

 * form:

 * {

 *     key: "the identifier of modified resource/mapping or settings key",

 *     new_val: undefined // `undefined` if item removed, item object otherwise

 * }

 *

 * Returns a [tracking, all_current_items] array where `tracking` is an object

 * that can be later passed to untrack() to stop tracking changes and

 * `all_current_items` is an array of items currently present in the object

 * store.

 *

 * It is possible that `onchange` gets spuriously fired even when an item is not

 * actually modified or that it only gets called once after multiple quick

 * changes to an item.

 */

async function start_tracking(store_name, onchange)

{

    const tracking = {store_name, onchange};

    tracking.listener =

	broadcast.listener_connection(msg => track_change(tracking, msg[1]));

    broadcast.subscribe(tracking.listener, `idb_changes_${store_name}`);

    return [tracking, await get_all(store_name)];

}

const track = {};

const trackable = ["resource", "mapping", "settings", "blocking", "repos"];

for (const store_name of trackable)

    track[store_name] = onchange => start_tracking(store_name, onchange);

#EXPORT track

const untrack = tracking => broadcast.close(tracking.listener);

#EXPORT untrack