# vim: set et nosta sw=4 ts=4 ft=nim : 

#

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## Overview

## ============

##

## This is a pure-nim client library for interacting with Stomp 1.2

## compliant messaging brokers.

##

## https://stomp.github.io/stomp-specification-1.2.html

##

## Stomp is a simple protocol for message passing between clients, using a central

## broker.  It is a subset of other more elaborate protocols (like AMQP), supporting

## only the most used features of common brokers.

##

## Because this library is pure-nim, there are no external dependencies.  If you

## can compile a nim binary, you can participate in advanced messaging between processes.

##

## A list of broker support for Stomp can be found here:

## https://stomp.github.io/implementations.html.

##

## This library has been tested with recent versions of RabbitMQ.  If it

## works for you with another broker, please let the author know.

##

import

    strutils,

    nativesockets,

    net,

    os,

    times,

    uri

const

    NULL    = "\x00"  ## The NULL character.

    CR      = "\r"    ## The carriage return character.

    CRLF    = "\r\n"  ## Carriage return + Line feed (EOL).

# Exceptions

#

type

    StompError* = object of ValueError ## A generic Stomp error state.

    StompClient* = ref object of RootObj ## An object that represents a connection to a Stomp compatible server.

        socket:         Socket ## The socket object attached to this client.

        connected*:     bool ## Is the client currently connected?

        uri*:           Uri ## The URI used to instantiate this client.

        username:       string ## The Stomp server user, if any.

        password:       string ## The Stomp server password, if any.

        host:           string ## The host or IP address to connect to.

        port:           Port ## Optional, if Stomp is on a non-default port.

        vhost:          string ## Parsed from the URI path, a Stomp "virtual host".

        timeout*:       int ## Global socket timeout.

        last_msgtime*:  Time ## Timestamp of last seen server message.

        options:        tuple[ heartbeat: int ] ## Any supported client options, derived from the URI query string.

        subscriptions*: seq[ string ] ## Registered client subscriptions. Array position is the ID.

        transactions*:  seq[ string ] ## Any currently open transactions.

        serverinfo:     seq[ tuple[name: string, value: string] ] ## Server metadata, populated upon a successful connection.

        connected_callback*:        proc ( client: StompClient, response: StompResponse ): void

        error_callback*:            proc ( client: StompClient, response: StompResponse ): void

        heartbeat_callback*:        proc ( client: StompClient, response: StompResponse ): void

        message_callback*:          proc ( client: StompClient, response: StompResponse ): void

        missed_heartbeat_callback*: proc ( client: StompClient ): void

        receipt_callback*:          proc ( client: StompClient, response: StompResponse ): void

    StompResponse* = ref object of RootObj ## A parsed packet from a Stomp server.

        headers:  seq[ tuple[name: string, value: string] ] ## Any headers in the response.  Access with the `[]` proc.

        frame*:   string ## The Stomp frame type.

        payload*: string ## The message body, if any.

# convenience

proc printf( formatstr: cstring ) {.header: "<stdio.h>", varargs.}

#-------------------------------------------------------------------

# R E S P O N S E

#-------------------------------------------------------------------

proc is_eol( s: string ): bool =

    ## Convenience method, returns **true** if string is a Stomp EOF.

    return s == CR or s == CRLF

proc parse_headers( response: StompResponse, c: StompClient ): int =

    ## Parse response headers from a stream.

    ## Returns the content length of the response body, or 0.

    result = 0

    var line = ""

    c.socket.readline( line, c.timeout )

    while not line.is_eol:

        if defined( debug ): printf " <-- %s\n", line

        var header = line.split( ":" )

        if header.len < 2: break

        response.headers.add( (header[0], header[1]) )

        if cmpIgnoreCase( header[0], "content-length" ) == 0: result = header[1].parse_int

        c.socket.readline( line, c.timeout )

proc parse_payload( response: StompResponse, c: StompClient, bodylength = 0 ): void =

    ## Parse message payload from a stream.

    let bufsize = 8192

    var

        buf  = ""

        data = ""

    # If we already know the length of the body, just perform a buffered read.

    #

    if bodylength > 0:

        var

            readtotal = 0

            readamt   = 0

            remaining = 0

        while readtotal != bodylength:

            remaining = bodylength - readtotal

            if remaining < bufsize:

                readamt = remaining

            else:

                readamt = bufsize

            buf = newString( readamt )

            readtotal = readtotal + c.socket.recv( buf, readamt, c.timeout )

            data = data & buf

        # Eat the NULL terminator.

        discard c.socket.recv( buf, 1, c.timeout )

    # Inefficient path.

    #

    else:

        while buf != NULL:

            discard c.socket.recv( buf, 1, c.timeout )

            data = data & buf

    response.payload = data

proc newStompResponse( c: StompClient ): StompResponse =

    ## Initialize a response object, which parses and contains

    ## the Stomp headers and any additional important data from

    ## the broker socket.

    new( result )

    result.headers = @[]

    # Get the frame type, record last seen server activity time.

    #

    var line = ""

    c.socket.readline( line, c.timeout )

    c.last_msgtime = get_time()

    # Heartbeat packets (empties.)

    #

    # This could -also- parse optional EOLs from the prior

    # message (after the NULL separator), but since it is a no-op,

    # this seems harmless.

    #

    if line.is_eol:

        result.frame = "HEARTBEAT"

        return result

    # All other types.

    #

    result.frame = line

    if defined( debug ):

        printf " <-- %s\n", line

    # Parse headers and body.

    #

    var length = result.parse_headers( c )

    if result.frame == "MESSAGE" or result.frame == "ERROR":

        result.parse_payload( c, length )

    # If the response -could- have a body, the NULL has already

    # been removed from the stream while we checked for one.

    #

    if result.payload.len > 0:

        if result.payload == NULL: # We checked for a body, but there was none.

            if defined( debug ): printf " <--\n <-- ^@\n\n"

        else:

            if defined( debug ): printf " <--\n <-- (payload)^@\n\n"

    # Otherwise, pop off the NULL terminator now.

    #

    else:

        discard c.socket.recv( line, 1, c.timeout )

        if defined( debug ): printf " <--\n <-- ^@\n\n"

proc `$`*( r: StompResponse ): string =

    ## Represent a Stomp response as a string.

    result = r.frame & ": " & $r.headers

proc `[]`*( response: StompResponse, key: string ): string =

    ## Get a specific header from a Stomp response.

    for header in response.headers:

        if cmpIgnoreCase( key, header.name ) == 0:

            return header.value

#-------------------------------------------------------------------

# C A L L B A C K S

#-------------------------------------------------------------------

proc default_error_callback( c: StompClient, response: StompResponse ) =

    ## Something bad happened.  Disconnect from the server, build an error message,

    ## and raise an exception.

    c.socket.close

    c.connected = false

    var detail = response.payload

    var msg    = response[ "message" ]

    if $detail[ ^1 ] == "\n": detail = detail[ 0 .. ^2 ] # chomp

    if detail.len > 0: msg = msg & " (" & detail & ")"

    raise newException( StompError, "ERROR: " & msg )

proc default_missed_heartbeat_callback( c: StompClient ) =

    ## Timeout while connected to the broker.

    c.socket.close

    c.connected = false

    raise newException( StompError, "Heartbeat timeout.  Last activity: " & $c.last_msgtime )

#-------------------------------------------------------------------

# C L I E N T

#-------------------------------------------------------------------

proc newStompClient*( s: Socket, uri: string ): StompClient =

    ## Create a new Stomp client object from a preexisting **socket**,

    ## and a stomp **URI** string.

    ##

    ## .. code-block:: nim

    ##

    ##    var socket = newSocket()

    ##    var stomp  = newStompClient( socket, "stomp://test:test@example.com/%2Fvhost" )

    ##

    ## or if connecting with SSL, when compiled with -d:ssl:

    ##

    ## .. code-block:: nim

    ##

    ##    var socket = newSocket()

    ##    let sslContext = newContext( verifyMode = CVerifyNone )

    ##    sslContext.wrapSocket(socket)

    ##    var stomp = newStompClient( socket, "stomp+ssl://test:test@example.com/%2Fvhost" )

    ##

    new( result )

    result.socket        = s

    result.connected     = false

    result.uri           = parse_uri( uri )

    result.username      = result.uri.username

    result.password      = result.uri.password

    result.host          = result.uri.hostname

    result.vhost         = result.uri.path

    result.timeout       = 500

    result.subscriptions = @[]

    result.transactions  = @[]

    # Parse any supported options in the query string.

    #

    for pairs in result.uri.query.split( '&' ):

        let opt = pairs.split( '=' )

        try:

            case opt[0]:

                of "heartbeat":

                    result.options.heartbeat = opt[1].parse_int

                else:

                    discard

        except IndexError, ValueError:

            discard

    # Set default STOMP port if otherwise unset.

    #

    if not result.uri.scheme.contains( "stomp" ):

        raise newException( StompError, "Unknown scheme: " & result.uri.scheme  )

    var port: int

    if result.uri.port == "":

        if result.uri.scheme.contains( "+ssl" ):

            port = 61614

        else:

            port = 61613

    else:

        port = result.uri.port.parse_int

    result.port = Port( port )

    # Decode URI encoded slashes for vhosts.

    result.vhost = result.vhost.replace( "%2f", "/" ).replace( "%2F", "/" ).replace( "//", "/" )

proc socksend( c: StompClient, data: string ): void =

    ## Send data on the connected socket with optional debug output.

    c.socket.send( data )

    if defined( debug ): printf " --> %s", data

proc finmsg( c: StompClient ): void =

    ## Send data on the connected socket with optional debug output.

    c.socket.send( CRLF & NULL & CRLF )

    if defined( debug ): printf " --> \n --> ^@\n\n"

proc `[]`*( c: StompClient, key: string ): string =

    ## Get a specific value from the server metadata, set during the initial connection.

    for header in c.serverinfo:

        if cmpIgnoreCase( key, header.name ) == 0:

            return header.value

proc `$`*( c: StompClient ): string =

    ## Represent the stomp client as a string, after masking the password.

    let uri = ( $c.uri ).replace( ":" & c.uri.password & "@", "@" )

    result = "(NimStomp v" & VERSION & ( if c.connected: " connected" else: " not connected" ) & " to " & uri

    result.add( ")" )

proc connect*( c: StompClient ): void =

    ## Establish a connection to the Stomp server.

    if c.connected: return

    var headers: seq[ tuple[name: string, value: string] ] = @[]

    headers.add( ("accept-version", "1.2") )

    # Stomp 1.2 requires the Host: header.  Use the path as a vhost if

    # supplied, otherwise use the hostname of the server.

    #

    if c.vhost != "":

        headers.add( ("host", c.vhost) )

    else:

        headers.add( ("host", c.host) )

    if c.username != "": headers.add( ("login", c.username) )

    if c.password != "": headers.add( ("passcode", c.password) )

    if c.options.heartbeat > 0:

        let heartbeat = c.options.heartbeat * 1000

        headers.add( ("heart-beat", "0," & $heartbeat) )

    # Connect the socket and send the headers off.

    #

    c.socket.connect( c.host, c.port )

    c.socksend( "CONNECT" & CRLF )

    for header in headers:

        c.socksend( header.name & ":" & header.value & CRLF )

    c.finmsg

    # Retreive and copy server metadata to client object.

    #

    var response = newStompResponse( c )

    c.serverinfo = response.headers

    if response.frame != "CONNECTED":

        if not isNil( c.error_callback ):

            c.error_callback( c, response )

        else:

            c.default_error_callback( response )

    else:

        c.connected = true

        if not isNil( c.connected_callback ):

            c.connected_callback( c, response )

proc disconnect*( c: StompClient ): void =

    ## Break down the connection to the Stomp server nicely.

    if not c.connected: return

    c.socksend( "DISCONNECT" & CRLF )

    c.finmsg

    c.socket.close

    c.connected = false

proc add_txn( c: StompClient ): void =

    ## Add a transaction header if there is only a single open txn.

    if c.transactions.len != 1: return

    c.socksend( "transaction:" & c.transactions[0] & CRLF )

proc send*( c: StompClient,

            destination: string,

            headers:     seq[ tuple[name: string, value: string] ] = @[] ): void =

    ## Send a **message** to **destination**.

    ##

    ## A Content-Length header is automatically and always included.

    ## A **contenttype** is optional, but strongly recommended.

    ##

    ## Additionally, a transaction ID is automatically added if there is only

    ## one transaction active.  If you need to attach this message to a particular

    ## transaction ID, you'll need to add it yourself with the user defined

    ## **headers**.

    if not c.connected: raise newException( StompError, "Client is not connected." )

    c.socksend( "SEND" & CRLF )

    c.socksend( "destination:" & destination & CRLF )

    c.socksend( "content-length:" & $message.len & CRLF )

    # Add custom headers.  Add transaction header if one isn't manually

    # present (and a transaction is open.)

    #

    var txn_seen = false

    for header in headers:

        if header.name == "transaction": txn_seen = true

        c.socksend( header.name & ":" & header.value & CRLF )

    if not txn_seen: c.add_txn

        c.finmsg

    else:

        c.socket.send( CRLF & message & NULL )

        if defined( debug ): printf " -->\n --> (payload)^@\n\n"

proc subscribe*( c: StompClient,

            destination: string,

            ack        = "auto",

            headers:     seq[ tuple[name: string, value: string] ] = @[] ): void =

    ## Subscribe to messages at **destination**.

    ##

    ## Setting **ack** to "client" or "client-individual" enables client ACK/NACK mode.

    ## In this mode, incoming messages aren't considered processed by

    ## the server unless they receive ACK.  By default, the server

    ## considers the message processed if a client simply accepts it.

    ##

    ## You may optionally add any additional **headers** the server may support.

    if not c.connected: raise newException( StompError, "Client is not connected." )

    c.socksend( "SUBSCRIBE" & CRLF )

    c.socksend( "destination:" & destination & CRLF )

    c.socksend( "id:" & $c.subscriptions.len & CRLF )

    if ack == "client" or ack == "client-individual":

        c.socksend( "ack:" & ack & CRLF )

    else:

        if ack != "auto": raise newException( StompError, "Unknown ack type: " & ack )

    for header in headers:

        c.socksend( header.name & ":" & header.value & CRLF )

    c.finmsg

    c.subscriptions.add( destination )

proc unsubscribe*( c: StompClient,

            destination: string,

            headers:     seq[ tuple[name: string, value: string] ] = @[] ): void =

    ## Unsubscribe from messages at **destination**.

    ## You may optionally add any additional **headers** the server may support.

    if not c.connected: raise newException( StompError, "Client is not connected." )

    var

        sub_id: int

        i = 0

    # Find the ID of the subscription.

    #

    for sub in c.subscriptions:

        if sub == destination:

            sub_id = i

            break

        i = i + 1

    c.socksend( "UNSUBSCRIBE" & CRLF )

    c.socksend( "id:" & $sub_id & CRLF )

    for header in headers:

        c.socksend( header.name & ":" & header.value & CRLF )

    c.finmsg

    c.subscriptions[ sub_id ] = ""

proc begin*( c: StompClient, txn: string ): void =

    ## Begin a new transaction on the broker, using **txn** as the identifier.

    c.socksend( "BEGIN" & CRLF )

    c.socksend( "transaction:" & txn & CRLF )

    c.finmsg

    c.transactions.add( txn )

    ## Finish a specific transaction **txn**, or the most current if unspecified.

    var transaction = txn

    c.socksend( "COMMIT" & CRLF )

    c.socksend( "transaction:" & transaction & CRLF )

    c.finmsg