'use strict';

const spawn = require('child_process').spawn;
const packageData = require('../../package.json');
const LeWindows = require('./le-windows');
const LeUnix = require('./le-unix');
const shared = require('../shared');

/**
 * Generates a Transport object for Sendmail
 *
 * Possible options can be the following:
 *
 *  * **path** optional path to sendmail binary
 *  * **newline** either 'windows' or 'unix'
 *  * **args** an array of arguments for the sendmail binary
 *
 * @constructor
 * @param {Object} optional config parameter for the AWS Sendmail service
 */
class SendmailTransport {
    constructor(options) {
        options = options || {};

        // use a reference to spawn for mocking purposes
        this._spawn = spawn;

        this.options = options || {};

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

        this.path = 'sendmail';
        this.args = false;
        this.winbreak = false;

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

        if (options) {
            if (typeof options === 'string') {
                this.path = options;
            } else if (typeof options === 'object') {
                if (options.path) {
                    this.path = options.path;
                }
                if (Array.isArray(options.args)) {
                    this.args = options.args;
                }
                this.winbreak = ['win', 'windows', 'dos', '\r\n'].includes((options.newline || '').toString().toLowerCase());
            }
        }
    }

    /**
     * <p>Compiles a mailcomposer message and forwards it to handler that sends it.</p>
     *
     * @param {Object} emailMessage MailComposer object
     * @param {Function} callback Callback function to run when the sending is completed
     */
    send(mail, done) {
        // Sendmail strips this header line by itself
        mail.message.keepBcc = true;

        let envelope = mail.data.envelope || mail.message.getEnvelope();
        let messageId = mail.message.messageId();
        let args;
        let sendmail;
        let returned;
        let transform;

        if (this.args) {
            // force -i to keep single dots
            args = ['-i'].concat(this.args).concat(envelope.to);
        } else {
            args = ['-i'].concat(envelope.from ? ['-f', envelope.from] : []).concat(envelope.to);
        }

        let callback = err => {
            if (returned) {
                // ignore any additional responses, already done
                return;
            }
            returned = true;
            if (typeof done === 'function') {
                if (err) {
                    return done(err);
                } else {
                    return done(null, {
                        envelope: mail.data.envelope || mail.message.getEnvelope(),
                        messageId,
                        response: 'Messages queued for delivery'
                    });
                }
            }
        };

        try {
            sendmail = this._spawn(this.path, args);
        } catch (E) {
            this.logger.error(
                {
                    err: E,
                    tnx: 'spawn',
                    messageId
                },
                'Error occurred while spawning sendmail. %s',
                E.message
            );
            return callback(E);
        }

        if (sendmail) {
            sendmail.on('error', err => {
                this.logger.error(
                    {
                        err,
                        tnx: 'spawn',
                        messageId
                    },
                    'Error occurred when sending message %s. %s',
                    messageId,
                    err.message
                );
                callback(err);
            });

            sendmail.once('exit', code => {
                if (!code) {
                    return callback();
                }
                let err;
                if (code === 127) {
                    err = new Error('Sendmail command not found, process exited with code ' + code);
                } else {
                    err = new Error('Sendmail exited with code ' + code);
                }

                this.logger.error(
                    {
                        err,
                        tnx: 'stdin',
                        messageId
                    },
                    'Error sending message %s to sendmail. %s',
                    messageId,
                    err.message
                );
                callback(err);
            });
            sendmail.once('close', callback);

            sendmail.stdin.on('error', err => {
                this.logger.error(
                    {
                        err,
                        tnx: 'stdin',
                        messageId
                    },
                    'Error occurred when piping message %s to sendmail. %s',
                    messageId,
                    err.message
                );
                callback(err);
            });

            let 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>',
                messageId,
                recipients.join(', ')
            );

            transform = this.winbreak ? new LeWindows() : new LeUnix();
            let sourceStream = mail.message.createReadStream();

            transform.once('error', err => {
                this.logger.error(
                    {
                        err,
                        tnx: 'stdin',
                        messageId
                    },
                    'Error occurred when generating message %s. %s',
                    messageId,
                    err.message
                );
                sendmail.kill('SIGINT'); // do not deliver the message
                callback(err);
            });

            sourceStream.once('error', err => transform.emit('error', err));
            sourceStream.pipe(transform).pipe(sendmail.stdin);
        } else {
            return callback(new Error('sendmail was not found'));
        }
    }
}

module.exports = SendmailTransport;