''' Module that implements OSC '''

import asyncio
import struct

_TASK = None
_Q = asyncio.Queue()

def __string_to_osc(s: str) -> bytes:
    ''' Convert python string to OSC-string '''
    data = s.encode('ascii')
    to_append = 4 - (len(data) % 4)
    data += b'\0' * to_append
    return data

async def __serve() -> None:
    ''' Task that manages OSC sending '''
    # log
    print('[I] OSC: task is running')
    # task loop
    while True:
        # get value from queue
        val = await _Q.get()
        # stop
        if val == 0:
            break
        # host, port, OSC address and data
        host = val['host']
        port = val['port']
        addr = val['addr']
        data = val['data']
        # OSC type tag string
        type_tag = ','
        # OSC data to append to the final packet
        osc_data = bytes()
        # check if data is correct
        for d in data:
            d_type = type(d)
            # process the value
            if d_type is int:
                type_tag += 'i'
                osc_data += struct.pack('>i', d)
            elif d_type is str:
                type_tag += 's'
                osc_data += __string_to_osc(d)
            # unsupported
            else:
                print('[!] OSC: unsupported data type was provided! The packet is discarded.')
                print('      * host: %s' % host)
                print('      * port: %s' % port)
                print('      * address: %s' % addr)
                print('      * data: %s' % data)
                print('         (bad type is %s)' % d_type)
                type_tag = None
                break
        # no type tag
        if type_tag is None:
            continue
        # convert type tag to OSC-string
        type_tag = __string_to_osc(type_tag)
        # create OSC packet
        packet = __string_to_osc(addr) + type_tag + osc_data

        # send the packet
        trans, prot = await asyncio.get_running_loop().create_datagram_endpoint(
            asyncio.DatagramProtocol,
            remote_addr=(host, port)
        )
        try:
            trans.sendto(packet)
            print('[I] OSC: sent data to %s:%s' % (host, port))
        except:
            print('[!] OSC: failed to send to %s:%s!' % (host, port))
            print('      * address: %s' % addr)
            print('      * data: %s' % data)
        finally:
            trans.close()

    # log
    print('[I] OSC: task is stopped')

async def start() -> None:
    ''' Starts OSC task '''
    global _TASK
    # already started
    if _TASK is not None:
        return
    _TASK = asyncio.create_task(__serve())

async def stop() -> None:
    ''' Stops OSC task '''
    global _TASK
    # not started
    if _TASK is None:
        return
    # stop
    await _Q.put(0)
    await _TASK
    # reset
    _TASK = None

async def send(host: str, port: str, addr: str, values: list) -> None:
    ''' Schedule packet transmission '''
    # not started
    if _TASK is None:
        return
    # create
    d = {
        'host': host,
        'port': port,
        'addr': addr,
        'data': values
    }
    await _Q.put(d)