# Copyright (C) 2012 Vermeer Manufacturing Co.
# License: GPLv3 with additional permissions (see README).

import socket
import os
import sys
import struct

if sys.platform == "win32":
    header_len = 2

#
# Message classes
#

class Int32(int):
    pass


class Message:
    def __init__(self, *pvalues):
        for parameter, value in zip(self.parameters, pvalues):
            setattr(self, parameter[1], parameter[0](value))

    def __str__(self):
        p = []
        for parameter in self.parameters:
            p.append(parameter[1] + "=" + str(getattr(self, parameter[1])))
        if p:
            pf = " " + " ".join(p)
        else:
            pf = ""
        return "<" + self.__class__.__name__ + pf + ">"


class MessageTick(Message):
    code = 0
    parameters = []


class MessageGo(Message):
    code = 1
    parameters = []


class MessageWrite(Message):
    code = 2
    parameters = [(str, "name"), (Int32, "index"), (int, "value")]


class MessageRead(Message):
    code = 3
    parameters = [(str, "name"), (Int32, "index")]


class MessageReadReply(Message):
    code = 4
    parameters = [(int, "value")]

message_classes = [MessageTick, MessageGo, MessageWrite, MessageRead, MessageReadReply]


#
# Packing
#

def _pack_int(v):
    if v == 0:
        p = [1, 0]
    else:
        p = []
        while v != 0:
            p.append(v & 0xff)
            v >>= 8
        p.insert(0, len(p))
    return p


def _pack_str(v):
    p = [ord(c) for c in v]
    p.append(0)
    return p


def _pack_int16(v):
    return [v & 0xff,
            (v & 0xff00) >> 8]


def _pack_int32(v):
    return [
        v & 0xff,
        (v & 0xff00) >> 8,
        (v & 0xff0000) >> 16,
        (v & 0xff000000) >> 24
    ]


def _pack(message):
    r = [message.code]
    for t, p in message.parameters:
        value = getattr(message, p)
        assert(isinstance(value, t))
        if t == int:
            r += _pack_int(value)
        elif t == str:
            r += _pack_str(value)
        elif t == Int32:
            r += _pack_int32(value)
        else:
            raise TypeError
    if sys.platform == "win32":
        size = _pack_int16(len(r) + header_len)
        r = size + r
    return bytes(r)


#
# Unpacking
#

def _unpack_int(i, nchunks=None):
    v = 0
    power = 1
    if nchunks is None:
        nchunks = next(i)
    for j in range(nchunks):
        v += power*next(i)
        power *= 256
    return v


def _unpack_str(i):
    v = ""
    c = next(i)
    while c:
        v += chr(c)
        c = next(i)
    return v


def _unpack(message):
    i = iter(message)
    code = next(i)
    msgclass = next(filter(lambda x: x.code == code, message_classes))
    pvalues = []
    for t, p in msgclass.parameters:
        if t == int:
            v = _unpack_int(i)
        elif t == str:
            v = _unpack_str(i)
        elif t == Int32:
            v = _unpack_int(i, 4)
        else:
            raise TypeError
        pvalues.append(v)
    return msgclass(*pvalues)


#
# I/O
#

class PacketTooLarge(Exception):
    pass


class Initiator:
    def __init__(self, sockaddr):
        self.sockaddr = sockaddr
        if sys.platform == "win32":
            self.socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        else:
            self.socket = socket.socket(socket.AF_UNIX, socket.SOCK_SEQPACKET)
            self._cleanup_file()
        self.socket.bind(self.sockaddr)
        self.socket.listen(1)

        self.ipc_rxbuffer = bytearray()

    def _cleanup_file(self):
        try:
            os.remove(self.sockaddr)
        except OSError:
            pass

    def accept(self):
        self.conn, addr = self.socket.accept()

    def send(self, message):
        self.conn.send(_pack(message))

    def recv_packet(self, maxlen):
        if sys.platform == "win32":
            while len(self.ipc_rxbuffer) < header_len:
                self.ipc_rxbuffer += self.conn.recv(maxlen)
            packet_len = struct.unpack("<H", self.ipc_rxbuffer[:header_len])[0]
            while len(self.ipc_rxbuffer) < packet_len:
                self.ipc_rxbuffer += self.conn.recv(maxlen)
            packet = self.ipc_rxbuffer[header_len:packet_len]
            self.ipc_rxbuffer = self.ipc_rxbuffer[packet_len:]
        else:
            packet = self.conn.recv(maxlen)
        return packet

    def recv(self):
        maxlen = 2048
        packet = self.recv_packet(maxlen)
        if len(packet) < 1:
            return None
        if len(packet) >= maxlen:
            raise PacketTooLarge
        return _unpack(packet)

    def close(self):
        if hasattr(self, "conn"):
            self.conn.shutdown(socket.SHUT_RDWR)
            self.conn.close()
        if hasattr(self, "socket"):
            if sys.platform == "win32":
                # don't shutdown our socket since closing connection
                # seems to already have done it. (trigger an error
                # otherwise)
                self.socket.close()
            else:
                self.socket.shutdown(socket.SHUT_RDWR)
                self.socket.close()
                self._cleanup_file()