"""Send AMI 0x182 display values through a python-can adapter (no motor actuation)."""
import argparse
from decimal import Decimal, InvalidOperation
import os
import struct
import time


def temperature_raw(value):
    try:
        scaled = Decimal(value) * 10
        if not scaled.is_finite() or scaled != scaled.to_integral_value():
            raise ValueError('temperature must have at most one decimal place')
        raw = int(scaled)
    except (InvalidOperation, OverflowError) as exc:
        raise ValueError('invalid temperature') from exc
    if not -32768 <= raw <= 32767:
        raise ValueError('temperature must be -3276.8..3276.7 degC')
    return raw


def build_payload(torque, motor_temp, mcu_temp, valid=7):
    if not -1000 <= torque <= 1000:
        raise ValueError('torque must be -1000..1000 permille')
    if not 0 <= valid <= 7:
        raise ValueError('valid must be 0..7 (bit0 torque, bit1 motor, bit2 MCU)')
    return struct.pack('<hhhBB', torque, temperature_raw(motor_temp),
                       temperature_raw(mcu_temp), valid, 1)


def main():
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument('--torque', type=int, required=True)
    parser.add_argument('--motor-temp', required=True, help='degC, up to one decimal place')
    parser.add_argument('--mcu-temp', required=True, help='motor-controller temperature, degC')
    parser.add_argument('--valid', type=int, default=7, help='validity mask 0..7, default all valid')
    parser.add_argument('--interface', default='pcan')
    parser.add_argument('--channel', default='PCAN_USBBUS1')
    parser.add_argument('--bitrate', type=int, choices=(250000, 500000), default=250000)
    parser.add_argument('--period', type=float, default=0.1, help='seconds, default 100 ms')
    parser.add_argument('--duration', type=float, default=10, help='seconds; finite transmission')
    parser.add_argument('--dll-dir', help='Windows adapter DLL directory, if required')
    parser.add_argument('--dry-run', action='store_true', help='print payload without opening CAN')
    args = parser.parse_args()
    try:
        payload = build_payload(args.torque, args.motor_temp, args.mcu_temp, args.valid)
    except ValueError as exc:
        parser.error(str(exc))
    if not (0 < args.period <= 2 and 0 < args.duration < float('inf')):
        parser.error('period must be >0 and <=2 seconds; duration must be positive and finite')
    print(f'Standard ID 0x182, DLC 8, data {payload.hex(" ").upper()}, bitrate {args.bitrate}', flush=True)
    if args.dry_run:
        return
    dll_handle = None
    if args.dll_dir:
        path = os.path.abspath(args.dll_dir)
        os.environ['PATH'] = path + os.pathsep + os.environ['PATH']
        if hasattr(os, 'add_dll_directory'):
            dll_handle = os.add_dll_directory(path)
    import can
    count = 0
    try:
        with can.Bus(interface=args.interface, channel=args.channel, bitrate=args.bitrate) as bus:
            message = can.Message(arbitration_id=0x182, is_extended_id=False, data=payload)
            started = time.monotonic()
            deadline = started
            while time.monotonic() < started + args.duration:
                bus.send(message, timeout=0.2)
                count += 1
                deadline += args.period
                time.sleep(max(0, min(deadline, started + args.duration) - time.monotonic()))
    finally:
        if dll_handle is not None:
            dll_handle.close()
    print(f'Sent {count} frames. Values expire after 2 seconds without valid input.')


if __name__ == '__main__':
    main()