"""ESP-NOW wire format (MicroPython). See docs/espnow-binary-protocol.md in led-controller."""

import struct

WIRE_MAGIC = 0x4C
MAX_ESPNOW_PAYLOAD = 250

MSG_ANNOUNCE = 0x01
MSG_GROUPS = 0x02
MSG_CMD = 0x03
MSG_GROUP_CMD = 0x04
MSG_PING_REQ = 0x05
MSG_PING_RSP = 0x06

BROADCAST_MAC = b"\xff\xff\xff\xff\xff\xff"

COLOR_ORDER_TO_ENUM = {
    "rgb": 0,
    "rbg": 1,
    "grb": 2,
    "gbr": 3,
    "brg": 4,
    "bgr": 5,
}
STARTUP_MODE_TO_ENUM = {"default": 0, "last": 1, "off": 2}


def _pack_header(msg_type, body):
    pkt = bytes([WIRE_MAGIC, msg_type]) + body
    if len(pkt) > MAX_ESPNOW_PAYLOAD:
        raise ValueError("packet too large")
    return pkt


def pack_announce(
    name,
    num_leds,
    color_order="rgb",
    startup_mode="default",
    brightness=32,
    device_type=0,
):
    name_b = name.encode("utf-8")
    co = COLOR_ORDER_TO_ENUM.get(str(color_order).lower(), 0)
    sm = STARTUP_MODE_TO_ENUM.get(str(startup_mode).lower(), 0)
    body = (
        bytes([len(name_b)])
        + name_b
        + struct.pack("<H", int(num_leds))
        + bytes([co & 7, sm & 3, max(0, min(255, int(brightness))), device_type & 255])
    )
    return _pack_header(MSG_ANNOUNCE, body)


def parse_groups(payload):
    if len(payload) >= 2 and payload[0] == WIRE_MAGIC:
        if payload[1] != MSG_GROUPS:
            return None
        body = payload[2:]
    else:
        body = payload
    if not body:
        return []
    off = 0
    count = body[off]
    off += 1
    out = []
    for _ in range(count):
        gl = body[off]
        off += 1
        out.append(body[off : off + gl].decode("utf-8"))
        off += gl
    return out


def parse_group_cmd(payload):
    if len(payload) < 2 or payload[0] != WIRE_MAGIC or payload[1] != MSG_GROUP_CMD:
        return None
    body = payload[2:]
    gl = body[0]
    gid = body[1 : 1 + gl].decode("utf-8")
    env = body[1 + gl :]
    return gid, env


HEADER_LEN = 5


def _envelope_size(env):
    if len(env) < HEADER_LEN:
        return len(env)
    lp, ls, ld = env[2], env[3], env[4]
    return HEADER_LEN + lp + ls + ld


def cmd_envelope(payload):
    if len(payload) < 2 or payload[0] != WIRE_MAGIC or payload[1] != MSG_CMD:
        return None, False
    env = payload[2:]
    if not env:
        return None, False
    need = _envelope_size(env)
    if need > len(env):
        return None, False
    save = len(env) > need and env[need] == 1
    return env[:need], save


def pack_ping_req(ping_id):
    body = struct.pack("<I", int(ping_id) & 0xFFFFFFFF)
    return _pack_header(MSG_PING_REQ, body)


def parse_ping_req(payload):
    if len(payload) >= 2 and payload[0] == WIRE_MAGIC:
        if payload[1] != MSG_PING_REQ:
            return None
        body = payload[2:]
    else:
        body = payload
    if len(body) < 4:
        return None
    return struct.unpack("<I", body[:4])[0]


def pack_ping_rsp(ping_id, name):
    name_b = name.encode("utf-8")
    body = struct.pack("<I", int(ping_id) & 0xFFFFFFFF) + bytes([len(name_b)]) + name_b
    return _pack_header(MSG_PING_RSP, body)


def wire_msg_type(payload):
    if len(payload) >= 2 and payload[0] == WIRE_MAGIC:
        return payload[1]
    return None