#!/usr/bin/env python3

import evdev
import argparse
import os
import sys

scan_to_hid = {
    evdev.ecodes.KEY_A: 0x04,
    evdev.ecodes.KEY_B: 0x05,
    evdev.ecodes.KEY_C: 0x06,
    evdev.ecodes.KEY_D: 0x07,
    evdev.ecodes.KEY_E: 0x08,
    evdev.ecodes.KEY_F: 0x09,
    evdev.ecodes.KEY_G: 0x0a,
    evdev.ecodes.KEY_H: 0x0b,
    evdev.ecodes.KEY_I: 0x0c,
    evdev.ecodes.KEY_J: 0x0d,
    evdev.ecodes.KEY_K: 0x0e,
    evdev.ecodes.KEY_L: 0x0f,
    evdev.ecodes.KEY_M: 0x10,
    evdev.ecodes.KEY_N: 0x11,
    evdev.ecodes.KEY_O: 0x12,
    evdev.ecodes.KEY_P: 0x13,
    evdev.ecodes.KEY_Q: 0x14,
    evdev.ecodes.KEY_R: 0x16,
    evdev.ecodes.KEY_S: 0x15,
    evdev.ecodes.KEY_T: 0x17,
    evdev.ecodes.KEY_U: 0x18,
    evdev.ecodes.KEY_V: 0x19,
    evdev.ecodes.KEY_W: 0x1a,
    evdev.ecodes.KEY_X: 0x1b,
    evdev.ecodes.KEY_Y: 0x1c,
    evdev.ecodes.KEY_Z: 0x1d,
}

LEFT_CTRL = 1 << 0
LEFT_SHIFT = 1 << 1
LEFT_ALT = 1 << 2
LEFT_GUI = 1 << 3
RIGHT_CTRL = 1 << 4
RIGHT_SHIFT = 1 << 5
RIGHT_ALT = 1 << 6
RIGHT_GUI = 1 << 7


if __name__ == '__main__':
    parser = argparse.ArgumentParser(description='Forward input events to a USB descriptor')
    parser.add_argument('input', type=str, help='The source evdev device')
    parser.add_argument('output', type=str, help='The output HID device')

    args = parser.parse_args()

    dst = os.open(args.output, os.O_WRONLY)
    src = evdev.InputDevice(args.input)
    src.grab()

    modifiers = 0
    keys_down = set()

    for event in src.read_loop():
        if event.type != evdev.ecodes.EV_KEY:
            continue

        data = evdev.categorize(event)
        print("Got key", data.scancode)

        code = scan_to_hid.get(data.scancode, None)
        if code is None:
            print("Ignoring unknown key")
            continue

        if data.keystate == data.key_down:
            if len(keys_down) >= 6:
                print("Ignoring key due to rollover")
                continue
            print("Adding key")
            keys_down.add(code)

        if data.keystate == data.key_up:
            print("Removing key")
            keys_down.remove(code)

        # Build the packet
        packet = [0] + [0] + [k for k in keys_down]
        packet += [0] * (8 - len(packet))

        assert(len(packet) == 8)

        print("Sending", packet)
        os.write(dst, bytes(packet))