"""Builders for the structured records SIGN_TX streams to the device.

Wire layouts are documented at the top of `src/handlers/sign_tx.rs`; the
covenant item layouts mirror `shd/Sources/Covenants/CovenantData.swift`.
"""

from hashlib import sha3_256
from typing import List, Sequence, Tuple

from ragger.bip import pack_derivation_path

SCRIPT_KIND_P2WPKH: int = 0x00
SCRIPT_KIND_P2WSH: int = 0x01

SIGHASH_ALL: int = 0x01
SIGHASH_NONE: int = 0x02
SIGHASH_SINGLE: int = 0x03
SIGHASH_SINGLEREVERSE: int = 0x04
SIGHASH_NOINPUT: int = 0x40
SIGHASH_ANYONECANPAY: int = 0x80

# Covenant types, matching shd/Sources/Protocol/CovenantType.swift.
COVENANT_NONE: int = 0
COVENANT_CLAIM: int = 1
COVENANT_OPEN: int = 2
COVENANT_BID: int = 3
COVENANT_REVEAL: int = 4
COVENANT_REDEEM: int = 5
COVENANT_REGISTER: int = 6
COVENANT_UPDATE: int = 7
COVENANT_RENEW: int = 8
COVENANT_TRANSFER: int = 9
COVENANT_FINALIZE: int = 10
COVENANT_REVOKE: int = 11


def encode_varint(n: int) -> bytes:
    if n < 0xFD:
        return bytes([n])
    if n <= 0xFFFF:
        return b"\xfd" + n.to_bytes(2, "little")
    if n <= 0xFFFFFFFF:
        return b"\xfe" + n.to_bytes(4, "little")
    return b"\xff" + n.to_bytes(8, "little")


def name_hash(name: bytes) -> bytes:
    """`shd` NameRules.hashName: SHA3-256, not Keccak."""
    return sha3_256(name).digest()


def begin_payload(n_in: int, n_out: int, version: int = 0, locktime: int = 0) -> bytes:
    return (version.to_bytes(4, "little")
            + encode_varint(n_in)
            + encode_varint(n_out)
            + locktime.to_bytes(4, "little"))


def input_payload(path: str,
                  value: int,
                  txid: bytes = b"\x11" * 32,
                  vout: int = 0,
                  sequence: int = 0xFFFFFFFF,
                  sighash: int = SIGHASH_ALL,
                  script_kind: int = SCRIPT_KIND_P2WPKH) -> bytes:
    assert len(txid) == 32
    return (txid
            + vout.to_bytes(4, "little")
            + sequence.to_bytes(4, "little")
            + value.to_bytes(8, "little")
            + bytes([sighash])
            + pack_derivation_path(path)
            + bytes([script_kind]))


def output_payload(value: int,
                   addr_hash: bytes = b"\x22" * 20,
                   addr_version: int = 0,
                   covenant_kind: int = COVENANT_NONE,
                   covenant_items: Sequence[bytes] = ()) -> bytes:
    items = b"".join(encode_varint(len(i)) + i for i in covenant_items)
    return (value.to_bytes(8, "little")
            + bytes([addr_version, len(addr_hash)])
            + addr_hash
            + bytes([covenant_kind])
            + encode_varint(len(covenant_items))
            + items)


def uint32_le(n: int) -> bytes:
    return n.to_bytes(4, "little")


def open_items(name: bytes) -> List[bytes]:
    """OPEN: [nameHash, height, name] (CovenantData.makeOpen)."""
    return [name_hash(name), uint32_le(0), name]


def bid_items(name: bytes, height: int = 0, blind: bytes = b"\x33" * 32) -> List[bytes]:
    """BID: [nameHash, startHeight, name, blind] (CovenantData.makeBid)."""
    return [name_hash(name), uint32_le(height), name, blind]


def reveal_items(name: bytes, height: int = 0, nonce: bytes = b"\x44" * 32) -> List[bytes]:
    """REVEAL: [nameHash, startHeight, nonce]. Carries no plaintext name."""
    return [name_hash(name), uint32_le(height), nonce]


def transfer_items(name: bytes,
                   dest_hash: bytes,
                   height: int = 0,
                   dest_version: int = 0) -> List[bytes]:
    """TRANSFER: [nameHash, startHeight, [version], addressHash].

    `items[3]` is the address the name is handed to, which is the whole point
    of the covenant and appears nowhere else in the output.
    """
    return [name_hash(name), uint32_le(height), bytes([dest_version]), dest_hash]