import struct

from app.fit.crc import fit_crc


def make_fit(data_records: bytes, *, header_size: int = 14) -> bytes:
    if header_size not in {12, 14}:
        raise ValueError(header_size)
    header = bytearray(header_size)
    header[0] = header_size
    header[1] = 0x20
    struct.pack_into("<H", header, 2, 0x0100)
    struct.pack_into("<I", header, 4, len(data_records))
    header[8:12] = b".FIT"
    if header_size == 14:
        struct.pack_into("<H", header, 12, fit_crc(header[:12]))
    body = header + data_records
    return bytes(body + struct.pack("<H", fit_crc(body)))


def definition(local: int, global_num: int, fields: list[tuple[int, int, int]], *, endian: str = "<") -> bytes:
    architecture = 1 if endian == ">" else 0
    payload = bytearray([0, architecture])
    payload.extend(struct.pack(f"{endian}H", global_num))
    payload.append(len(fields))
    for num, size, base_type in fields:
        payload.extend(bytes([num, size, base_type]))
    return bytes([0x40 | local]) + bytes(payload)


def data(local: int, payload: bytes) -> bytes:
    return bytes([local]) + payload