const EventEmitter = require('events');
const { spawn } = require('child_process');
const createWriteStream = require('fs').createWriteStream;
const unlink = require('fs/promises').unlink;
const resolve = require('path').resolve;

class Player extends EventEmitter {

    constructor() {
        super();
        this.timestamp = Date.now();
        this.position = 0;
        this.events = [];
        this.tmp = {
            file: resolve(global.config?.tmp || '/tmp/kannon.tmp')
        };
    }

    async prepare(size, threshold) {
        logger.debug('preparing audio player...');
        await this.#reset();
        await this.#removeTemporaryFile();
        this.size = size;
        this.threshold = threshold;
        this.tmp.stream = createWriteStream(this.tmp.file);
    }

    async feed(buffer) {
        this.tmp.stream.write(buffer);
        if (this.tmp.announced === undefined && this.tmp.stream.bytesWritten >= this.threshold) {
            this.tmp.announced = true;
            this.#setState(constants.STATE_READY);
            logger.debug('threshold of ' + this.threshold + ' bytes reached after ' + (Date.now() - this.timestamp) + 'ms');
        }
    }

    stopFeed() {
        logger.debug('finished writing of ' + this.tmp.stream.bytesWritten + ' bytes after ' + (Date.now() - this.timestamp) + 'ms');
        this.tmp.stream.end();
        this.tmp.stream.close();
    }

    async play(position) {
        if (this.isPlaying()) {
            await this.stop();
        }
        await this.#spawnProcess(position);
        this.process.stderr.on('data', (data) => {
            data = data.toString();
            const position = data.toString().trim().split(' ')[0];
            if (position.length === 0 || isNaN(position)) {
                return;
            }
            this.position = position;
        });
        this.process.stdin.on('error', (error) => {
            this.#setState(constants.STATE_ERROR, error);
        });
    }

    async pause() {
        await this.#reset(true);
        this.#setState(constants.STATE_PAUSED);
    }

    async stop() {
        await this.#reset();
        this.#setState(constants.STATE_STOPPED);
    }

    isReady() {
        return this.state === constants.STATE_READY;
    }

    isPlaying() {
        return this.state === constants.STATE_PLAYING;
    }

    isPaused() {
        return this.state === constants.STATE_PAUSED;
    }

    isFinished() {
        return this.state === constants.STATE_STOPPED;
    }

    hasError() {
        return this.state === constants.STATE_ERROR;
    }

    getPosition() {
        return this.position;
    }

    async #spawnProcess(position) {
        return new Promise((resolve, reject) => {
            const args = [
                '-vn',
                '-nodisp'
            ];
            if (this.isPaused() && !isNaN(position)) {
                args.unshift('-ss', position);
            }
            args.push(this.tmp.file);
            this.process = spawn("ffplay", args);
            this.process.on('error', (error) => {
                this.#reset();
                // TODO: try/catch error
                reject('error spawning process \'ffplay\': ' + error);
            });
            this.process.on('spawn', () => {
                logger.info('spawned process \'ffplay\' (pid: ' + this.process.pid + ')...');
                this.#setState(constants.STATE_PLAYING);
                resolve();
            });
        });

    }

    #setState(state, data) {
        if (this.state === state) {
            return;
        }
        this.state = state;
        logger.debug('setting state of audio player to \'' + state + '\'...');
        if (this.events.includes(state)) {
            return;
        }
        logger.debug('emitting state \'' + state + '\' of audio player...');
        this.emit(this.state, { data: data });
        this.emit('statechange', { state: this.state });
        this.events.push(state);
    }

    async #killProcess() {
        if (this.process === undefined) {
            return;
        }
        const pid = this.process.pid;
        this.#closeStdIO();
        if (this.process?.killed === false) {
            this.process.kill('SIGTERM');
        }
        await new Promise((resolve, reject) => {
            this.process.on('close', (code, signal) => {
                let msg = 'process \'ffplay\' (pid: ' + pid + ') closed with';
                if (code !== undefined) {
                    msg += ' code \'' + code + '\'';
                } else {
                    msg += ' signal \'' + signal + '\'';
                }
                logger.debug(msg);
                this.process = undefined;
                resolve();
            });
        });
    }

    #closeStdIO() {
        if (this.process?.stdio === undefined) {
            return;
        }
        logger.debug('closing all stdio streams of process \'ffplay\' (pid: ' + this.process.pid + ')...');
        for (let index = 0; index < this.process.stdio.length; index++) {
            this.process.stdio[index].destroy();
        }
    }

    async #removeTemporaryFile() {
        try {
            await unlink(this.tmp.file);
        } catch (error) {
            if (error?.code === 'ENOENT') {
                return;
            }
            logger.error('error removing temporary file \'' + this.tmp.file + '\': ' + error);
        }
    }

    async #reset(paused) {
        await this.#killProcess();
        this.timestamp = Date.now();
        this.events = [];
        if (paused === true) {
            return;
        }
        this.position = 0;
    }

}

module.exports = Player;