messagestream.js

'use strict';

const fs     = require('fs');
const Stream = require('stream').Stream;
const utils  = require('haraka-utils');

const ChunkEmitter = require('./chunkemitter');

const STATE_HEADERS = 1;
const STATE_BODY = 2;

class MessageStream extends Stream {
    constructor (cfg, id, headers) {
        super();
        if (!id) throw new Error('id required');
        this.uuid = id;
        this.write_ce = null;
        this.read_ce = null;
        this.bytes_read = 0;
        this.state = STATE_HEADERS;
        this.idx = {};
        this.end_called = false;
        this.end_callback = null;
        this.buffered = 0;
        this._queue = [];
        this.max_data_inflight = 0;
        this.buffer_max = (!isNaN(cfg.main.spool_after) ?
            Number(cfg.main.spool_after) : -1);
        this.spooling = false;
        this.fd = null;
        this.open_pending = false;
        this.spool_dir = cfg.main.spool_dir || '/tmp';
        this.filename = this.spool_dir + '/' + id + '.eml';
        this.write_pending = false;

        this.readable = true;
        this.paused = false;
        this.headers = headers || [];
        this.headers_done = false;
        this.headers_found_eoh = false;
        this.line_endings = "\r\n";
        this.dot_stuffing = false;
        this.ending_dot = false;
        this.buffer_size = (1024 * 64);
        this.start = 0;
        this.write_complete = false;
        this.ws = null;
        this.rs = null;
        this.in_pipe = false;
    }

    add_line (line) {
        const self = this;

        if (typeof line === 'string') {
            line = Buffer.from(line);
        }

        // create a ChunkEmitter
        if (!this.write_ce) {
            this.write_ce = new ChunkEmitter();
            this.write_ce.on('data', chunk => {
                self._write(chunk);
            });
        }

        this.bytes_read += line.length;

        // Build up an index of 'interesting' data on the fly
        if (this.state === STATE_HEADERS) {
            // Look for end of headers line
            if (line.length === 2 && line[0] === 0x0d && line[1] === 0x0a) {
                this.idx.headers = { start: 0, end: this.bytes_read-line.length };
                this.state = STATE_BODY;
                this.idx.body = { start: this.bytes_read };
            }
        }

        if (this.state === STATE_BODY) {
            // Look for MIME boundaries
            if (line.length > 4 && line[0] === 0x2d && line[1] == 0x2d) {
                let boundary = line.slice(2).toString().replace(/\s*$/,'');
                if (/--\s*$/.test(line)) {
                    // End of boundary?
                    boundary = boundary.slice(0, -2);
                    if (this.idx[boundary]) {
                        this.idx[boundary].end = this.bytes_read;
                    }
                }
                else {
                    // Start of boundary?
                    if (!this.idx[boundary]) {
                        this.idx[boundary] = { start: this.bytes_read-line.length };
                    }
                }
            }
        }

        this.write_ce.fill(line);
    }

    add_line_end (cb) {
        // Record body end position
        if (this.idx.body) {
            this.idx.body.end = this.bytes_read;
        }
        this.end_called = true;
        if (cb && typeof cb === 'function') {
            this.end_callback = cb;
        }
        // Call _write() only if no new data was emitted
        // This might happen if the message size matches
        // the size of the chunk buffer.
        if (!this.write_ce.end()) {
            this._write();
        }
    }

    _write (data) {
        const self = this;
        if (data) {
            this.buffered += data.length;
            this._queue.push(data);
        }
        // Stats
        if (this.buffered > this.max_data_inflight) {
            this.max_data_inflight = this.buffered;
        }
        // Abort if we have pending disk operations
        if (this.open_pending || this.write_pending) return false;
        // Do we need to spool to disk?
        if (this.buffer_max !== -1 && this.buffered > this.buffer_max) {
            this.spooling = true;
        }
        // Have we completely finished writing all data?
        if (this.end_called && (!this.spooling || (this.spooling && !this._queue.length))) {
            if (this.end_callback) this.end_callback();
            // Do we have any waiting readers?
            if (this.listeners('data').length && !this.write_complete) {
                this.write_complete = true;
                setImmediate(() => {
                    if (self.readable && !self.paused)
                        self._read();
                });
            }
            else {
                this.write_complete = true;
            }
            return true;
        }
        if (this.buffer_max === -1 || (this.buffered < this.buffer_max && !this.spooling)) {
            return true;
        }
        else {
            // We're spooling to disk
            if (!this._queue.length) {
                return false;
            }
        }

        // Open file descriptor if needed
        if (!this.fd && !this.open_pending) {
            this.open_pending = true;
            this.ws = fs.createWriteStream(this.filename, { flags: 'wx+', end: false })
            this.ws.on('open', fd => {
                self.fd = fd;
                self.open_pending = false;
                setImmediate(() => {
                    self._write();
                });
            });
            this.ws.on('error', error => {
                self.emit('error', error);
            });
        }

        if (!this.fd) return false;
        const to_send = this._queue.shift();
        this.buffered -= to_send.length;
        // TODO: try and implement backpressure
        if (!this.ws.write(to_send)) {
            this.write_pending = true;
            this.ws.once('drain', () => {
                self.write_pending = false;
                setImmediate(() => {
                    self._write();
                });
            });
            return false;
        }
        else {
            if (this.end_called && (!this.spooling || (this.spooling && !this._queue.length))) {
                return self._write();
            }
            return true;
        }
    }

    /*
    ** READABLE STREAM
    */

    _read () {
        const self = this;
        if (!this.end_called) {
            throw new Error('end not called!');
        }

        if (!this.readable || this.paused || !this.write_complete) {
            return;
        }

        // Buffer and send headers first.
        //
        // Headers are always stored in an array of strings
        // as they are heavily read and modified throughout
        // the reception of a message.
        //
        // Typically headers will be < 32Kb (Sendmail limit)
        // so we do all of them in one operation before we
        // loop around again (and check for pause).
        if (this.headers.length && !this.headers_done) {
            this.headers_done = true;
            for (let i=0; i<this.headers.length; i++) {
                this.read_ce.fill(this.headers[i].replace(/\r?\n/g,this.line_endings));
            }
            // Add end of headers marker
            this.read_ce.fill(this.line_endings);
            // Loop
            setImmediate(() => {
                if (self.readable && !self.paused)
                    self._read();
            });
        }
        else {
            // Read the message body by line
            // If we have queued entries, then we didn't
            // create a queue file, so we read from memory.
            if (this._queue.length > 0) {
                // TODO: implement start/end offsets
                for (let i=0; i<this._queue.length; i++) {
                    this.process_buf(this._queue[i].slice(0));
                }
                this._read_finish();
            }
            else {
                this.rs = fs.createReadStream(null, { fd: this.fd, start: 0 });
                // Prevent the file descriptor from being closed
                this.rs.destroy = () => {};
                this.rs.on('error', error => {
                    self.emit('error', error);
                });
                this.rs.on('data', chunk => {
                    self.process_buf(chunk);
                });
                this.rs.on('end', () => {
                    self._read_finish();
                });
            }
        }
    }

    process_buf (buf) {
        let offset = 0;
        while ((offset = utils.indexOfLF(buf)) !== -1) {
            let line = buf.slice(0, offset+1);
            buf = buf.slice(line.length);
            // Don't output headers if they where sent already
            if (this.headers_done && !this.headers_found_eoh) {
                // Allow \r\n or \n here...
                if (
                    (line.length === 2 && line[0] === 0x0d && line[1] === 0x0a) ||
                    (line.length === 1 && line[0] === 0x0a)
                ) {
                    this.headers_found_eoh = true;
                }
                continue;
            }
            // Remove dot-stuffing if required
            if (!this.dot_stuffing && line.length >= 4 &&
                line[0] === 0x2e && line[1] === 0x2e
            ) {
                line = line.slice(1);
            }
            // We store lines in native CRLF format; so strip CR if requested
            if (this.line_endings === '\n' && line.length >= 2 &&
                line[line.length-1] === 0x0a && line[line.length-2] === 0x0d
            ) {
                // We copy the line to a new buffer before modifying the copy
                line = Buffer.from(line);
                line[line.length-2] = 0x0a;
                line = line.slice(0, line.length-1);
            }
            this.read_ce.fill(line);
        }
        // Check for data left in the buffer
        if (buf.length > 0) {
            this.read_ce.fill(buf);
        }
    }

    _read_finish () {
        const self = this;
        // End dot required?
        if (this.ending_dot) {
            this.read_ce.fill('.' + this.line_endings);
        }
        // Tell the chunk emitter to send whatever is left
        // We don't close the fd here so we can re-use it later.
        this.read_ce.end(() => {
            if (self.clamd_style) {
                // Add 0 length to notify end
                const buf = Buffer.alloc(4);
                buf.writeUInt32BE(0, 0);
                self.emit('data', buf);
            }
            self.in_pipe = false;
            self.emit('end');
        });
    }

    pipe (destination, options) {
        const self = this;
        if (this.in_pipe) {
            throw new Error('Cannot pipe while currently piping');
        }
        Stream.prototype.pipe.call(this, destination, options);
        // Options
        this.line_endings = ((options && options.line_endings) ? options.line_endings : "\r\n");
        this.dot_stuffing = ((options && options.dot_stuffing) ? options.dot_stuffing : false);
        this.ending_dot   = ((options && options.ending_dot) ? options.ending_dot : false);
        this.clamd_style  = ((options && options.clamd_style) ? true : false);
        this.buffer_size  = ((options && options.buffer_size) ? options.buffer_size : 1024 * 64);
        this.start        = ((options && parseInt(options.start)) ? parseInt(options.start) : 0);
        // Reset
        this.in_pipe = true;
        this.readable = true;
        this.paused = false;
        this.headers_done = false;
        this.headers_found_eoh = false;
        this.rs = null;
        this.read_ce = new ChunkEmitter(this.buffer_size);
        this.read_ce.on('data', chunk => {
            if (self.clamd_style) {
                // Prefix data length to the beginning of line
                const buf = Buffer.alloc(chunk.length+4);
                buf.writeUInt32BE(chunk.length, 0);
                chunk.copy(buf, 4);
                self.emit('data', buf);
            }
            else {
                self.emit('data', chunk);
            }
        });
        // Stream won't be readable until we've finished writing and add_line_end() has been called.
        // As we've registered for events above, the _write() function can now detect that we
        // are waiting for the data and will call _read() automatically when it is finished.
        if (!this.write_complete) return destination;
        // Create this.fd only if it doesn't already exist
        // This is so we can re-use the already open descriptor
        if (!this.fd && !(this._queue.length > 0)) {
            fs.open(this.filename, 'r', null, (err, fd) => {
                if (err) throw err;
                self.fd = fd;
                self._read();
            });
        }
        else {
            self._read();
        }
        return destination;
    }

    pause () {
        this.paused = true;
        if (this.rs) this.rs.pause();
    }

    resume () {
        this.paused = false;
        if (this.rs) {
            this.rs.resume();
        }
        else {
            this._read();
        }
    }

    destroy () {
        const self = this;
        try {
            if (this.fd) {
                fs.close(this.fd, err => {
                    fs.unlink(self.filename, () => {});
                });
            }
            else {
                fs.unlink(this.filename, () => {});
            }
        }
        catch (err) {
            // Ignore any errors
        }
    }

    get_data (options, cb) { // Or: (cb)
        if (arguments.length === 1) {
            cb = arguments[0];
            options = {};
        }
        const ws = new GetDataStream(cb);
        this.pipe(ws, options);
    }
}

module.exports = MessageStream;

class GetDataStream extends Stream {
    constructor (cb) {
        super();
        this.cb = cb;
        this.buf = Buffer.alloc(0);
        this.writable = true;
    }

    write (obj, enc) {
        this.buf = Buffer.concat([this.buf, obj]);
        return true;
    }

    end (obj, enc) {
        if (obj) this.buf = Buffer.concat([this.buf, obj]);
        this.cb(this.buf);
    }

    destroy () {
        // ignore
    }

    destroySoon () {
        // ignore
    }
}