"""WLED-compatible UDP packet encoders — DRGB, DRGBW, DNRGB.

Source: https://kno.wled.ge/interfaces/udp-realtime/
"""
import struct

WLED_PORT = 21324
PROTOCOL_DRGB = 2
PROTOCOL_DRGBW = 3
PROTOCOL_DNRGB = 4
TIMEOUT_BYTE = 2  # seconds before device returns to normal mode

# Max pixels per packet (stays under 1472-byte UDP payload limit)
# Standard Ethernet MTU = 1500; IP header = 20; UDP header = 8 → max payload = 1472
DRGB_MAX_PX = 490    # (1472 - 2) // 3
DRGBW_MAX_PX = 367   # (1472 - 2) // 4
DNRGB_MAX_PX = 489   # (1472 - 4) // 3


def encode_drgb(pixels: list[tuple[int, int, int]]) -> bytes:
    """Encode up to 490 RGB pixels into a DRGB UDP packet.

    Format: [0x02][timeout][R0][G0][B0]...[Rn][Gn][Bn]
    Truncates silently to DRGB_MAX_PX if more pixels are provided.
    """
    header = bytes([PROTOCOL_DRGB, TIMEOUT_BYTE])
    body = bytearray()
    for r, g, b in pixels[:DRGB_MAX_PX]:
        body.extend([r & 0xFF, g & 0xFF, b & 0xFF])
    return header + bytes(body)


def encode_drgbw(pixels: list[tuple[int, int, int, int]]) -> bytes:
    """Encode up to 367 RGBW pixels into a DRGBW UDP packet.

    Format: [0x03][timeout][R0][G0][B0][W0]...[Rn][Gn][Bn][Wn]
    Truncates silently to DRGBW_MAX_PX if more pixels are provided.
    """
    header = bytes([PROTOCOL_DRGBW, TIMEOUT_BYTE])
    body = bytearray()
    for r, g, b, w in pixels[:DRGBW_MAX_PX]:
        body.extend([r & 0xFF, g & 0xFF, b & 0xFF, w & 0xFF])
    return header + bytes(body)


def encode_dnrgb_packets(
    pixels: list[tuple[int, int, int]],
    start_index: int = 0,
) -> list[bytes]:
    """Split a large RGB pixel array into DNRGB UDP packets, each under MTU.

    Format per packet: [0x04][timeout][start_hi][start_lo][R0][G0][B0]...[Rn][Gn][Bn]
    Start index is 16-bit big-endian per WLED spec.

    Args:
        pixels: Full list of (R, G, B) pixel tuples.
        start_index: LED strip offset for the first pixel (default 0).

    Returns:
        List of byte strings, one per chunk of up to DNRGB_MAX_PX pixels.
    """
    packets = []
    for offset in range(0, len(pixels), DNRGB_MAX_PX):
        chunk = pixels[offset:offset + DNRGB_MAX_PX]
        idx = start_index + offset
        header = struct.pack(">BBH", PROTOCOL_DNRGB, TIMEOUT_BYTE, idx)
        body = bytearray()
        for r, g, b in chunk:
            body.extend([r & 0xFF, g & 0xFF, b & 0xFF])
        packets.append(header + bytes(body))
    return packets