"""Sens'it Discovery payload decoder — all 6 modes."""

MODES = {
    0: "Standby / Button",
    1: "Temperature",
    2: "Light",
    3: "Door",
    4: "Vibration",
    5: "Magnet",
}


def decode(payload_hex: str) -> dict:
    """
    Decode a 4-byte Sens'it Discovery payload.

    Format (per Sens'it Discovery v3.1.0+ spec):
        Byte 0: bits 7-3 = battery level, bits 2-0 = reserved (0b110)
        Byte 1: bits 7-3 = mode, bits 2-1 = mode-specific / spare, bit 0 = button flag
        Byte 2-3: mode-specific data

    Battery formula: V = (raw × 0.05) + 2.7
    """
    payload_hex = payload_hex.strip().lower().replace("0x", "").replace(" ", "")
    if len(payload_hex) != 8:
        return {"error": f"payload must be 4 bytes (8 hex chars), got '{payload_hex}'"}

    try:
        b0, b1, b2, b3 = (int(payload_hex[i : i + 2], 16) for i in range(0, 8, 2))
    except ValueError as e:
        return {"error": str(e)}

    # Common fields
    battery_raw = (b0 >> 3) & 0x1F
    battery_volts = round(battery_raw * 0.05 + 2.7, 2)
    reserved = b0 & 0x07
    mode = (b1 >> 3) & 0x1F
    button_alert = bool(b1 & 0x01)

    result = {
        "raw": payload_hex,
        "battery": battery_volts,
        "battery_raw": battery_raw,
        "reserved_ok": reserved == 0b110,
        "mode": MODES.get(mode, f"Unknown ({mode})"),
        "mode_id": mode,
        "button_alert": button_alert,
    }

    # Mode-specific decoding
    if mode == 1:  # Temperature
        temp_msb = (b1 >> 2) & 0x01
        temp_raw = (temp_msb << 8) | b2
        result["temperature_c"] = round((temp_raw - 200) / 8, 2)
        result["humidity_pct"] = round(b3 / 2, 1)

    elif mode == 2:  # Light
        brightness_msb = (b1 >> 2) & 0x01
        brightness_raw = (brightness_msb << 8) | b2
        result["brightness_lux"] = round(brightness_raw / 96, 2)

    elif mode == 3:  # Door
        door_status_bits = (b1 >> 1) & 0x03
        door_map = {0: "closed", 1: "opened", 2: "opening_alert", 3: "closing_alert"}
        result["door_status"] = door_map.get(door_status_bits, "unknown")
        result["event_count"] = (b2 << 8) | b3

    elif mode == 4:  # Vibration
        vib_status_bits = (b1 >> 1) & 0x03
        vib_map = {0: "no_vibration", 1: "vibration_detected"}
        result["vibration_status"] = vib_map.get(vib_status_bits, "unknown")
        result["event_count"] = (b2 << 8) | b3

    elif mode == 5:  # Magnet
        mag_status_bits = (b1 >> 1) & 0x03
        mag_map = {0: "no_magnet", 1: "magnet_detected"}
        result["magnet_status"] = mag_map.get(mag_status_bits, "unknown")
        result["event_count"] = (b2 << 8) | b3

    return result


if __name__ == "__main__":
    # Sanity checks with the payloads we captured
    for h in ("b60dc86e", "a60dc271", "b6043081"):
        print(h, "→", decode(h))