'use strict';

const packageData = require('../../package.json');
const shared = require('../shared');

/**
 * Generates a Transport object for streaming
 *
 * Possible options can be the following:
 *
 *  * **buffer** if true, then returns the message as a Buffer object instead of a stream
 *  * **newline** either 'windows' or 'unix'
 *
 * @constructor
 * @param {Object} optional config parameter
 */
class StreamTransport {
    constructor(options) {
        options = options || {};

        this.options = options;

        this.name = 'StreamTransport';
        this.version = packageData.version;

        this.logger = shared.getLogger(this.options, {
            component: this.options.component || 'stream-transport'
        });

        this.winbreak = ['win', 'windows', 'dos', '\r\n'].includes((options.newline || '').toString().toLowerCase());
    }

    /**
     * Compiles a mailcomposer message and forwards it to handler that sends it
     *
     * @param {Object} emailMessage MailComposer object
     * @param {Function} callback Callback function to run when the sending is completed
     */
    send(mail, done) {
        // We probably need this in the output
        mail.message.keepBcc = true;

        const envelope = mail.data.envelope || mail.message.getEnvelope();
        const messageId = mail.message.messageId();

        const recipients = [].concat(envelope.to || []);
        if (recipients.length > 3) {
            recipients.push('...and ' + recipients.splice(2).length + ' more');
        }
        this.logger.info(
            {
                tnx: 'send',
                messageId
            },
            'Sending message %s to <%s> using %s line breaks',
            messageId,
            recipients.join(', '),
            this.winbreak ? '<CR><LF>' : '<LF>'
        );

        setImmediate(() => {
            let stream;

            try {
                stream = mail.message.createReadStream();
            } catch (E) {
                this.logger.error(
                    {
                        err: E,
                        tnx: 'send',
                        messageId
                    },
                    'Creating send stream failed for %s. %s',
                    messageId,
                    E.message
                );
                return done(E);
            }

            if (!this.options.buffer) {
                stream.once('error', err => {
                    this.logger.error(
                        {
                            err,
                            tnx: 'send',
                            messageId
                        },
                        'Failed creating message for %s. %s',
                        messageId,
                        err.message
                    );
                });
                return done(null, {
                    envelope,
                    messageId,
                    message: stream
                });
            }

            const chunks = [];
            let chunklen = 0;
            stream.on('readable', () => {
                let chunk;
                while ((chunk = stream.read()) !== null) {
                    chunks.push(chunk);
                    chunklen += chunk.length;
                }
            });

            stream.once('error', err => {
                this.logger.error(
                    {
                        err,
                        tnx: 'send',
                        messageId
                    },
                    'Failed creating message for %s. %s',
                    messageId,
                    err.message
                );
                return done(err);
            });

            stream.on('end', () =>
                done(null, {
                    envelope,
                    messageId,
                    message: Buffer.concat(chunks, chunklen)
                })
            );
        });
    }
}

module.exports = StreamTransport;
