# sid.py

from __future__ import annotations
from typing import List, Dict, Any
from sid_hashers import StructureHashStrategy
from sid_canonical import encode_str, encode_kv_pairs


# ---------------------------------------------------------------------
# SID computation
# ---------------------------------------------------------------------

def compute_sid(
    *,
    op: str,
    child_sids: List[str],
    params: Dict[str, Any],
    hasher: StructureHashStrategy,
    ordered_children: bool = True,
    domain: str = "artifact.sid.v1",
) -> str:
    """
    Compute a deterministic Merkle-style SID for an artifact.

    Parameters
    ----------
    op: str
        Operation name (e.g., "tensor", "splice", "leaf.bits").
    child_sids: List[str]
        List of SIDs of children artifacts.
    params: Dict[str, Any]
        Canonicalized parameters for the operation.
    hasher: StructureHashStrategy
        Hash strategy to use (default SHA-256 SID hasher).
    ordered_children: bool
        Whether child order matters (tensor vs commutative ops).
    domain: str
        Domain/version for domain separation.

    Returns
    -------
    sid: str
        Hex string representing the structural ID.
    """

    payload = b""

    # -----------------------------------------------------------------
    # Domain/version separation
    # -----------------------------------------------------------------
    payload += encode_str(domain)

    # -----------------------------------------------------------------
    # Operation name
    # -----------------------------------------------------------------
    payload += encode_str(op)

    # -----------------------------------------------------------------
    # Children SIDs
    # -----------------------------------------------------------------
    children = list(child_sids)
    if not ordered_children:
        children.sort()

    payload += len(children).to_bytes(4, "big")
    for c in children:
        payload += encode_str(c)

    # -----------------------------------------------------------------
    # Canonicalized parameters
    # -----------------------------------------------------------------
    param_pairs = sorted((str(k), str(v)) for k, v in params.items())
    payload += encode_kv_pairs(param_pairs)

    # -----------------------------------------------------------------
    # Compute structural hash
    # -----------------------------------------------------------------
    return hasher.hash_struct(payload)