/**
 * this method is used in nodejs-environments.
 * The ipc is handled via sockets and file-writes to the tmp-folder
 */

import util from 'util';
import fs from 'fs';
import crypto from 'crypto';
import os from 'os';
import events from 'events';
import net from 'net';
import path from 'path';
import PQueue from 'p-queue';
const PQueueConstructor = PQueue.default ? PQueue.default : PQueue;
import {
    add as unloadAdd
} from 'unload';

import { fillOptionsWithDefaults } from '../options.js';
import {
    randomInt,
    randomToken,
    PROMISE_RESOLVED_VOID
} from '../util.js';
import { ObliviousSet } from 'oblivious-set';

/**
 * windows sucks, so we have handle windows-type of socket-paths
 * @link https://gist.github.com/domenic/2790533#gistcomment-331356
 */
export function cleanPipeName(str) {
    if (
        process.platform === 'win32' &&
        !str.startsWith('\\\\.\\pipe\\')
    ) {
        str = str.replace(/^\//, '');
        str = str.replace(/\//g, '-');
        return '\\\\.\\pipe\\' + str;
    } else {
        return str;
    }
}

const mkdir = util.promisify(fs.mkdir);
const writeFile = util.promisify(fs.writeFile);
const readFile = util.promisify(fs.readFile);
const unlink = util.promisify(fs.unlink);
const readdir = util.promisify(fs.readdir);
const chmod = util.promisify(fs.chmod);
const rmDir = util.promisify(fs.rm);

const removeDir = async (p) => {
    try {
        return await rmDir(p,
            {
                recursive: true
            }
        );
    } catch (err) {
        if (err.code !== 'ENOENT') {
            throw err;
        }
    }
};

const OTHER_INSTANCES = {};
const TMP_FOLDER_NAME = 'pubkey.bc';
export const TMP_FOLDER_BASE = path.join(
    os.tmpdir(),
    TMP_FOLDER_NAME
);
const getPathsCache = new Map();

export function getPaths(channelName) {
    if (!getPathsCache.has(channelName)) {
        /**
         * Use the hash instead of the channelName
         * to ensure we have no characters that cannot be used as filenames.
         * And also to ensure that trimming the string will not end up
         * in using the same folders for different channels.
         */
        const channelHash = crypto.createHash('sha256').update(channelName).digest('hex');

        /**
         * because the length of socket-paths is limited, we use only the first 20 chars
         * and also start with A to ensure we do not start with a number
         * @link https://serverfault.com/questions/641347/check-if-a-path-exceeds-maximum-for-unix-domain-socket
         */
        const channelFolder = 'A' + channelHash.substring(0, 20);

        const channelPathBase = path.join(
            TMP_FOLDER_BASE,
            channelFolder
        );
        const folderPathReaders = path.join(
            channelPathBase,
            'rdrs'
        );
        const folderPathMessages = path.join(
            channelPathBase,
            'msgs'
        );

        const ret = {
            channelBase: channelPathBase,
            readers: folderPathReaders,
            messages: folderPathMessages
        };
        getPathsCache.set(channelName, ret);
        return ret;
    }
    return getPathsCache.get(channelName);
}

let ENSURE_BASE_FOLDER_EXISTS_PROMISE = null;
async function ensureBaseFolderExists() {
    if (!ENSURE_BASE_FOLDER_EXISTS_PROMISE) {
        ENSURE_BASE_FOLDER_EXISTS_PROMISE = mkdir(TMP_FOLDER_BASE).catch(() => null);
    }
    return ENSURE_BASE_FOLDER_EXISTS_PROMISE;
}

export async function ensureFoldersExist(channelName, paths) {
    paths = paths || getPaths(channelName);

    await ensureBaseFolderExists();

    await mkdir(paths.channelBase).catch(() => null);
    await Promise.all([
        mkdir(paths.readers).catch(() => null),
        mkdir(paths.messages).catch(() => null)
    ]);

    // set permissions so other users can use the same channel
    const chmodValue = '777';
    await Promise.all([
        chmod(paths.channelBase, chmodValue),
        chmod(paths.readers, chmodValue),
        chmod(paths.messages, chmodValue)
    ]).catch(() => null);
}

/**
 * removes the tmp-folder
 * @return {Promise<true>}
 */
export async function clearNodeFolder() {
    if (!TMP_FOLDER_BASE || TMP_FOLDER_BASE === '' || TMP_FOLDER_BASE === '/') {
        throw new Error('BroadcastChannel.clearNodeFolder(): path is wrong');
    }
    ENSURE_BASE_FOLDER_EXISTS_PROMISE = null;
    await removeDir(TMP_FOLDER_BASE);
    ENSURE_BASE_FOLDER_EXISTS_PROMISE = null;
    return true;
}


export function socketPath(channelName, readerUuid, paths) {
    paths = paths || getPaths(channelName);
    const socketPath = path.join(
        paths.readers,
        readerUuid + '.s'
    );
    return cleanPipeName(socketPath);
}

export function socketInfoPath(channelName, readerUuid, paths) {
    paths = paths || getPaths(channelName);
    return path.join(
        paths.readers,
        readerUuid + '.json'
    );
}


/**
 * Because it is not possible to get all socket-files in a folder,
 * when used under fucking windows,
 * we have to set a normal file so other readers know our socket exists
 */
export function createSocketInfoFile(channelName, readerUuid, paths) {
    const pathToFile = socketInfoPath(channelName, readerUuid, paths);
    return writeFile(
        pathToFile,
        JSON.stringify({
            time: microSeconds()
        })
    ).then(() => pathToFile);
}

/**
 * returns the amount of channel-folders in the tmp-directory
 * @return {Promise<number>}
 */
export async function countChannelFolders() {
    await ensureBaseFolderExists();
    const folders = await readdir(TMP_FOLDER_BASE);
    return folders.length;
}


async function connectionError(originalError) {
    const count = await countChannelFolders();

    // we only show the augmented message if there are more than 30 channels
    // because we then assume that BroadcastChannel is used in unit-tests
    if (count < 30) return originalError;

    const addObj = {};
    Object.entries(originalError).forEach(([k, v]) => addObj[k] = v);
    const text = 'BroadcastChannel.create(): error: ' +
        'This might happen if you have created to many channels, ' +
        'like when you use BroadcastChannel in unit-tests.' +
        'Try using BroadcastChannel.clearNodeFolder() to clear the tmp-folder before each test.' +
        'See https://github.com/pubkey/broadcast-channel#clear-tmp-folder';
    return new Error(text + ': ' + JSON.stringify(addObj, null, 2));
}

/**
 * creates the socket-file and subscribes to it
 * @return {{emitter: EventEmitter, server: any}}
 */
export async function createSocketEventEmitter(channelName, readerUuid, paths) {
    const pathToSocket = socketPath(channelName, readerUuid, paths);

    const emitter = new events.EventEmitter();
    const server = net
        .createServer(stream => {
            stream.on('end', function () { });
            stream.on('data', function (msg) {
                emitter.emit('data', msg.toString());
            });
        });

    await new Promise((resolve, reject) => {
        server.on('error', async (err) => {
            const useErr = await connectionError(err);
            reject(useErr);
        });

        server.listen(pathToSocket, async (err, res) => {
            if (err) {
                const useErr = await connectionError(err);
                reject(useErr);
            } else resolve(res);
        });
    });

    return {
        path: pathToSocket,
        emitter,
        server
    };
}

export async function openClientConnection(channelName, readerUuid) {
    const pathToSocket = socketPath(channelName, readerUuid);
    const client = new net.Socket();
    return new Promise((res, rej) => {
        client.connect(
            pathToSocket,
            () => res(client)
        );
        client.on('error', err => rej(err));
    });
}


/**
 * writes the new message to the file-system
 * so other readers can find it
 * @return {Promise}
 */
export function writeMessage(channelName, readerUuid, messageJson, paths) {

    let time = messageJson.time;
    if (!time) {
        time = microSeconds();
    }

    paths = paths || getPaths(channelName);
    const writeObject = {
        uuid: readerUuid,
        data: messageJson
    };

    const token = randomToken();
    const fileName = time + '_' + readerUuid + '_' + token + '.json';

    const msgPath = path.join(
        paths.messages,
        fileName
    );

    return writeFile(
        msgPath,
        JSON.stringify(writeObject)
    ).then(() => {
        return {
            time,
            uuid: readerUuid,
            token,
            path: msgPath
        };
    });
}

/**
 * returns the uuids of all readers
 * @return {string[]}
 */
export async function getReadersUuids(channelName, paths) {
    paths = paths || getPaths(channelName);
    const readersPath = paths.readers;
    const files = await readdir(readersPath);

    return files
        .map(file => file.split('.'))
        .filter(split => split[1] === 'json') // do not scan .socket-files
        .map(split => split[0]);
}

export async function messagePath(channelName, time, token, writerUuid) {
    const fileName = time + '_' + writerUuid + '_' + token + '.json';

    return path.join(
        getPaths(channelName).messages,
        fileName
    );
}

export async function getAllMessages(channelName, paths) {
    paths = paths || getPaths(channelName);
    const messagesPath = paths.messages;
    const files = await readdir(messagesPath);
    return files.map(file => {
        const fileName = file.split('.')[0];
        const split = fileName.split('_');

        return {
            path: path.join(
                messagesPath,
                file
            ),
            time: parseInt(split[0]),
            senderUuid: split[1],
            token: split[2]
        };
    });
}

export function getSingleMessage(channelName, msgObj, paths) {
    paths = paths || getPaths(channelName);

    return {
        path: path.join(
            paths.messages,
            msgObj.t + '_' + msgObj.u + '_' + msgObj.to + '.json'
        ),
        time: msgObj.t,
        senderUuid: msgObj.u,
        token: msgObj.to
    };
}


export function readMessage(messageObj) {
    return readFile(messageObj.path, 'utf8')
        .then(content => JSON.parse(content));
}

export async function cleanOldMessages(messageObjects, ttl) {
    const olderThan = microSeconds() - (ttl * 1000); // convert ttl to microseconds
    await Promise.all(
        messageObjects
            .filter(obj => obj.time < olderThan)
            .map(obj => unlink(obj.path).catch(() => null))
    );
}

export const type = 'node';

/**
 * creates a new channelState
 * @return {Promise<any>}
 */
export async function create(channelName, options = {}) {
    options = fillOptionsWithDefaults(options);
    const time = microSeconds();
    const paths = getPaths(channelName);
    const ensureFolderExistsPromise = ensureFoldersExist(channelName, paths);
    const uuid = randomToken();

    const state = {
        time,
        channelName,
        options,
        uuid,
        paths,
        // contains all messages that have been emitted before
        emittedMessagesIds: new ObliviousSet(options.node.ttl * 2),
        /**
         * Used to ensure we do not write too many files at once
         * which could throw an error.
         * Must always be smaller than options.node.maxParallelWrites
         */
        writeFileQueue: new PQueueConstructor({ concurrency: options.node.maxParallelWrites }),
        messagesCallbackTime: null,
        messagesCallback: null,
        // ensures we do not read messages in parallel
        writeBlockPromise: PROMISE_RESOLVED_VOID,
        otherReaderClients: {},
        // ensure if process crashes, everything is cleaned up
        removeUnload: unloadAdd(() => close(state)),
        closed: false
    };

    if (!OTHER_INSTANCES[channelName]) OTHER_INSTANCES[channelName] = [];
    OTHER_INSTANCES[channelName].push(state);

    await ensureFolderExistsPromise;
    const [
        socketEE,
        infoFilePath
    ] = await Promise.all([
        createSocketEventEmitter(channelName, uuid, paths),
        createSocketInfoFile(channelName, uuid, paths),
        refreshReaderClients(state)
    ]);
    state.socketEE = socketEE;
    state.infoFilePath = infoFilePath;

    // when new message comes in, we read it and emit it
    socketEE.emitter.on('data', data => {

        // if the socket is used fast, it may appear that multiple messages are flushed at once
        // so we have to split them before
        const singleOnes = data.split('|');
        singleOnes
            .filter(single => single !== '')
            .forEach(single => {
                try {
                    const obj = JSON.parse(single);
                    handleMessagePing(state, obj);
                } catch (err) {
                    throw new Error('could not parse data: ' + single);
                }
            });
    });

    return state;
}

export function _filterMessage(msgObj, state) {
    if (msgObj.senderUuid === state.uuid) return false; // not send by own
    if (state.emittedMessagesIds.has(msgObj.token)) return false; // not already emitted
    if (!state.messagesCallback) return false; // no listener
    if (msgObj.time < state.messagesCallbackTime) return false; // not older than onMessageCallback
    if (msgObj.time < state.time) return false; // msgObj is older than channel

    state.emittedMessagesIds.add(msgObj.token);
    return true;
}

/**
 * when the socket pings, so that we now new messages came,
 * run this
 */
export async function handleMessagePing(state, msgObj) {

    /**
     * when there are no listener, we do nothing
     */
    if (!state.messagesCallback) return;

    let messages;
    if (!msgObj) {
        // get all
        messages = await getAllMessages(state.channelName, state.paths);
    } else {
        // get single message
        messages = [
            getSingleMessage(state.channelName, msgObj, state.paths)
        ];
    }

    const useMessages = messages
        .filter(msgObj => _filterMessage(msgObj, state))
        .sort((msgObjA, msgObjB) => msgObjA.time - msgObjB.time); // sort by time


    // if no listener or message, so not do anything
    if (!useMessages.length || !state.messagesCallback) return;

    // read contents
    await Promise.all(
        useMessages
            .map(
                msgObj => readMessage(msgObj).then(content => msgObj.content = content)
            )
    );

    useMessages.forEach(msgObj => {
        state.emittedMessagesIds.add(msgObj.token);

        if (state.messagesCallback) {
            // emit to subscribers
            state.messagesCallback(msgObj.content.data);
        }
    });
}

/**
 * ensures that the channelState is connected with all other readers
 * @return {Promise<void>}
 */
export function refreshReaderClients(channelState) {
    return getReadersUuids(channelState.channelName, channelState.paths)
        .then(otherReaders => {
            // remove subscriptions to closed readers
            Object.keys(channelState.otherReaderClients)
                .filter(readerUuid => !otherReaders.includes(readerUuid))
                .forEach(async (readerUuid) => {
                    try {
                        await channelState.otherReaderClients[readerUuid].destroy();
                    } catch (err) { }
                    delete channelState.otherReaderClients[readerUuid];
                });

            // add new readers
            return Promise.all(
                otherReaders
                    .filter(readerUuid => readerUuid !== channelState.uuid) // not own
                    .filter(readerUuid => !channelState.otherReaderClients[readerUuid]) // not already has client
                    .map(async (readerUuid) => {
                        try {
                            if (channelState.closed) return;
                            try {
                                const client = await openClientConnection(channelState.channelName, readerUuid);
                                channelState.otherReaderClients[readerUuid] = client;
                            } catch (err) {
                                // this can throw when the cleanup of another channel was interrupted
                                // or the socket-file does not exist yet
                            }
                        } catch (err) {
                            // this might throw if the other channel is closed at the same time when this one is running refresh
                            // so we do not throw an error
                        }
                    })
            );
        });
}


/**
 * post a message to the other readers
 * @return {Promise<void>}
 */
export async function postMessage(channelState, messageJson) {
    const writePromise = channelState.writeFileQueue.add(
        () => writeMessage(
            channelState.channelName,
            channelState.uuid,
            messageJson,
            channelState.paths
        )
    );
    channelState.writeBlockPromise = channelState.writeBlockPromise.then(async () => {

        // w8 one tick to let the buffer flush
        await new Promise(res => setTimeout(res, 0));

        const [msgObj] = await Promise.all([
            writePromise,
            refreshReaderClients(channelState)
        ]);
        emitOverFastPath(channelState, msgObj, messageJson);
        const pingStr = '{"t":' + msgObj.time + ',"u":"' + msgObj.uuid + '","to":"' + msgObj.token + '"}|';

        const writeToReadersPromise = Promise.all(
            Object.values(channelState.otherReaderClients)
                .filter(client => client.writable) // client might have closed in between
                .map(client => {
                    return new Promise(res => {
                        client.write(pingStr, res);
                    });
                })
        );

        /**
         * clean up old messages
         * to not waste resources on cleaning up,
         * only if random-int matches, we clean up old messages
         */
        if (randomInt(0, 20) === 0) {
            /* await */
            getAllMessages(channelState.channelName, channelState.paths)
                .then(allMessages => cleanOldMessages(allMessages, channelState.options.node.ttl));
        }

        return writeToReadersPromise;
    });

    return channelState.writeBlockPromise;
}

/**
 * When multiple BroadcastChannels with the same name
 * are created in a single node-process, we can access them directly and emit messages.
 * This might not happen often in production
 * but will speed up things when this module is used in unit-tests.
 */
export function emitOverFastPath(state, msgObj, messageJson) {
    if (!state.options.node.useFastPath) {
        // disabled
        return;
    }
    const others = OTHER_INSTANCES[state.channelName].filter(s => s !== state);

    const checkObj = {
        time: msgObj.time,
        senderUuid: msgObj.uuid,
        token: msgObj.token
    };

    others
        .filter(otherState => _filterMessage(checkObj, otherState))
        .forEach(otherState => {
            otherState.messagesCallback(messageJson);
        });
}


export function onMessage(channelState, fn, time = microSeconds()) {
    channelState.messagesCallbackTime = time;
    channelState.messagesCallback = fn;
    handleMessagePing(channelState);
}

/**
 * closes the channel
 * @return {Promise}
 */
export function close(channelState) {
    if (channelState.closed) return PROMISE_RESOLVED_VOID;
    channelState.closed = true;
    channelState.emittedMessagesIds.clear();
    OTHER_INSTANCES[channelState.channelName] = OTHER_INSTANCES[channelState.channelName].filter(o => o !== channelState);

    if (channelState.removeUnload) {
        channelState.removeUnload.remove();
    }

    return new Promise((res) => {

        if (channelState.socketEE)
            channelState.socketEE.emitter.removeAllListeners();

        Object.values(channelState.otherReaderClients)
            .forEach(client => client.destroy());

        if (channelState.infoFilePath) {
            try {
                fs.unlinkSync(channelState.infoFilePath);
            } catch (err) { }
        }

        /**
         * the server get closed lazy because others might still write on it
         * and have not found out that the infoFile was deleted
         */
        setTimeout(() => {
            channelState.socketEE.server.close();
            res();
        }, 200);
    });
}


export function canBeUsed() {
    return typeof fs.mkdir === 'function';
}

/**
 * on node we use a relatively high averageResponseTime,
 * because the file-io might be in use.
 * Also it is more important that the leader-election is reliable,
 * than to have a fast election.
 */
export function averageResponseTime() {
    return 200;
}

export function microSeconds() {
    // convert nano to micro seconds
    return parseInt(now() / 1000);
}

function now() {
    return Number(process.hrtime.bigint()); // returns nanoseconds
}