#!/usr/bin/env python

# Copyright (c) 2009
#      Daniel O'Connor <darius@dons.net.au>.  All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
# 1. Redistributions of source code must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
#    notice, this list of conditions and the following disclaimer in the
#    documentation and/or other materials provided with the distribution.
#
# THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND
# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED.  IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
# SUCH DAMAGE.
#

# Reverse engineered from the Linux library & example program at
# http://epsrv.astro.umk.pl/~ep/irbene/rsib/library/RSIB-Linux.zip
#
# There are 2 socket connections for some reason.
# The first seems to do [nearly] all the work
#
# Packets to the instrument
# On connection:
# -> 00 00 00 40
# <- 00 00 00 40 a0 04 00 00
#
# We need to echo back the last 4 bytes of the reply to a second
# socket opened to the same port. I don't know what that socket is for
# though.
#
# Send a command:
# -> 00 00 00 05 90 00 01 2a  49 44 4e 3f             .......* IDN?
#
# Offs	Value	Meaning
# 00	00	?
# 01	00	?
# 02	00	?
# 03	05	Length
# 04	90	MsgID
# 05	00	?
# 06	03	Seq number
# 07	2a (*)	Cmd byte 0
# 08	49 (I)	Cmd byte 1
# 09	44 (D)	Cmd byte 2
# 10	4a (N)	Cmd byte 3
# 10	3f (?)	Cmd byte 4
#
# Interactive program seems to cap length at 0x99 but perhaps the
# first 4 bytes are length.
#
# Reply to command:
# <- 00 00 00 23 80 00 01 52 6f 68 ...
#
# Offs	Value	Meaning
# 00	00	Length 31..24
# 01	00	       23..16
# 02	00	       15..8
# 03	23	        7..0
# 04	80	MsgID
# 05	00	?
# 06	01	Seq number

MSG_HELLO = 0x40   # We send this on connect
MSG_CMDREP = 0x80  # Reply from the instrument to us
MSG_CMD = 0x90     # Command to the instrument
MSG_SRQ = 0x91	   # Query SRQ

import socket

class RSIBDevice(object):
    hello = '\x00\x00\x00\x40'
    docmd = '\x00\x00\x00\x05\x90\x00\x01'

    def __init__(self, host, port = None):
        if port == None:
            port = 2525
        self.host = host
        self.port = port

        s1 = socket.socket()
        s1.settimeout(5)
        s1.connect((self.host, self.port))
        s1.send(b'\x00\x00\x00\x40')
        rx = b''
        while len(rx) < 8:
            rx = rx + s1.recv(8)
            if rx == b'':
                raise IOError("EOF from device")

        s2 = socket.socket()
        s2.settimeout(5)
        s2.connect((self.host, self.port))
        s2.send(rx[4:])

        self.s1 = s1
        self.s2 = s2
        self.tag = 0
        
    def write(self, cmd, timeout = 0.5):
        """Send data (string) to the instrument"""
        self.s1.settimeout(timeout)

        if len(cmd) > 0x99:
            raise ValueError("Command too long")
        
        # Pre-increment for easy comparison in read
        self.tag = (self.tag + 1) & 0xff
        msg = b'\x00\x00\x00' + bytes([len(cmd)]) + b'\x90\x00' + bytes([self.tag]) + cmd.encode('ascii')
        self.s1.send(msg)
        
    def read(self, timeout = 0.5):
        """Read data from the device, waits for up to timeout seconds for each TCP read"""

        self.s1.settimeout(timeout)
        
        # Fetch the header
        rx = b''
        while len(rx) < 7:
            rx = self.s1.recv(7)
            if rx == b'':
                raise IOError("EOF from device")
        
        if self.tag != rx[6]:
            raise IOError("Reply out of order, got 0x%02x expected 0x%02x" % (ord(rx[6]), self.tag))

        rxlen = rx[0] << 24 | rx[1] << 16 | rx[2] << 8 | rx[3]
        #print "Msg ID 0x%02x" % (rx[4])
        if False and rx[4] != MSG_CMDREP:
            raise IOError("Unexpected Msg ID 0x%02x" % (rx[4]))
        
        if rx[5] != 0:
            print("Mystery byte %d != 0" % (rx[5]))
        # Fetch the actual reply now we know the length
        reply = b''
        while len(reply) < rxlen:
            rx = self.s1.recv(rxlen)
            if rx == b'':
                raise IOError("EOF from device")
            reply += rx
            
        return(reply)

    def queryrsb(self):
        msg = b'\x00\x00\x00\x00\xd1\x18\x00'
        self.s2.send(msg)
        
        reply = b''
        while len(reply) < 7:
            rx = self.s2.recv(7)
            if rx == b'':
                raise IOError("EOF from device")
            reply += rx

        # '\x00\x00\x00\x00\x80\x04\x01' => STB = 4
        if rx[4] != b'\x80':
            raise IOError("Incorrect Msg ID in response to STB query")
        
        return rx[5]

    def waitsrq(self):
        msg = b'\x00\x00\x00\x00\xb1\x00\x00'
        
    def testsrq(self):
        msg = b'\x00\x00\x00\x00\x91\x00\x00'
        self.s2.send(msg)
        reply = b''
        while len(reply) < 7:
            rx = self.s2.recv(7)
            if rx == b'':
                raise IOError("EOF from device")
            reply += rx
            
        # 00 00 00 00 80 14 08 - SRQ = 0
        # 00 00 00 00 a0 64 07 - SRQ = 1
        if rx == b'\x00\x00\x00\x00\x80\x14\x08':
            return False
        elif rx == b'\x00\x00\x00\x00\xa0\x64\x07':
            return True
        else:
            raise IOError("Unknown SRQ byte sequence - " + str(rx))