"""AUTH1 command builder + Table 8-12 reader-signature input.

Mirrors applet/src/test/.../ReaderSide.java buildTable812 + buildAuth1Data.
"""

from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives.asymmetric import ec
from cryptography.hazmat.primitives.asymmetric.utils import decode_dss_signature

CLA = 0x80
INS_AUTH1 = 0x81

USAGE_READER_AUTH1 = bytes([0x41, 0x5D, 0x95, 0x69])
USAGE_UD_AUTH1 = bytes([0x4E, 0x88, 0x7B, 0x4C])


def build_table_812(
    *,
    reader_id_32: bytes,
    credential_ephem_pub_x: bytes,
    reader_ephem_pub_x: bytes,
    transaction_id: bytes,
) -> bytes:
    return _build_table_8_12_or_13(
        reader_id_32, credential_ephem_pub_x, reader_ephem_pub_x,
        transaction_id, USAGE_READER_AUTH1,
    )


def build_table_813(
    *,
    reader_id_32: bytes,
    credential_ephem_pub_x: bytes,
    reader_ephem_pub_x: bytes,
    transaction_id: bytes,
) -> bytes:
    """Same TLV shape as Table 8-12, only the usage tag differs."""
    return _build_table_8_12_or_13(
        reader_id_32, credential_ephem_pub_x, reader_ephem_pub_x,
        transaction_id, USAGE_UD_AUTH1,
    )


def _build_table_8_12_or_13(
    rid: bytes, cred_x: bytes, reader_x: bytes, txn: bytes, usage: bytes,
) -> bytes:
    # Match auth0.py / build_auth1_data discipline: validate fixed-length
    # inputs up front. Java callers get an ArrayIndexOutOfBoundsException
    # naturally; Python slicing would silently produce a wrong-length blob.
    if len(rid) != 32:
        raise ValueError(f"reader_id_32 must be 32B (got {len(rid)})")
    if len(cred_x) != 32:
        raise ValueError(f"credential_ephem_pub_x must be 32B (got {len(cred_x)})")
    if len(reader_x) != 32:
        raise ValueError(f"reader_ephem_pub_x must be 32B (got {len(reader_x)})")
    if len(txn) != 16:
        raise ValueError(f"transaction_id must be 16B (got {len(txn)})")
    return (
        bytes([0x4D, 0x20]) + rid
        + bytes([0x86, 0x20]) + cred_x
        + bytes([0x87, 0x20]) + reader_x
        + bytes([0x4C, 0x10]) + txn
        + bytes([0x93, 0x04]) + usage
    )


def sign_table_812_raw(table_812: bytes, reader_priv: ec.EllipticCurvePrivateKey) -> bytes:
    """Returns 64B raw r||s ECDSA-SHA-256 signature."""
    der = reader_priv.sign(table_812, ec.ECDSA(hashes.SHA256()))
    r, s = decode_dss_signature(der)
    return r.to_bytes(32, "big") + s.to_bytes(32, "big")


def build_auth1_data(raw_sig_64: bytes, command_parameters: int = 0x01) -> bytes:
    """AUTH1 command data field per spec Table 8-10. cmd_params bit 0 = 1
    means 'return credential_PubK' (simpler than the SHA-1 key_slot path)."""
    if len(raw_sig_64) != 64:
        raise ValueError("reader signature must be 64B raw r||s")
    return (
        bytes([0x41, 0x01, command_parameters])
        + bytes([0x9E, 0x40]) + raw_sig_64
    )


def build_auth1_apdu(data: bytes) -> bytes:
    return bytes([CLA, INS_AUTH1, 0x00, 0x00, len(data)]) + data