'use strict';

const stream = require('stream'),
    { StringDecoder } = require('string_decoder'),
    TransformStream = stream.Transform;

class LogStream extends TransformStream {
    constructor(options) {
        super();
        this._options = Object.assign({ source: 'unknown', format: 'json' }, options);
        this._decoder = new StringDecoder();
        this._soFar = '';
    }

    _format(line) {
        if (this._options.format !== 'json') return line + '\n';

        const data = line.split(' '); // logs are <ISOtimestamp> <msg>
        let timestamp = (new Date(data[0])).getTime();
        if (isNaN(timestamp)) timestamp = 0;
        const message = line.slice(data[0].length+1);

        // ignore faulty empty logs
        if (!timestamp && !message) return;

        return JSON.stringify({
            realtimeTimestamp: timestamp * 1000,
            message: message,
            source: this._options.source
        }) + '\n';
    }

    _transform(chunk, encoding, callback) {
        const data = this._soFar + this._decoder.write(chunk);
        let start = this._soFar.length, end = -1;
        while ((end = data.indexOf('\n', start)) !== -1) {
            const line = data.slice(start, end); // does not include end
            this.push(this._format(line));
            start = end + 1;
        }
        this._soFar = data.slice(start);
        callback(null);
    }

    _flush(callback) {
        const line = this._soFar + this._decoder.end();
        this.push(this._format(line));
        callback(null);
    }
}

exports = module.exports = LogStream;