from __future__ import annotations

import hashlib
import json
from typing import List

from .contracts import Signal


class MerkleProvenance:
    @staticmethod
    def hash_item(item: dict) -> str:
        return hashlib.sha256(json.dumps(item, sort_keys=True).encode()).hexdigest()

    @staticmethod
    def merkle_root(values: List[Signal]) -> str:
        # Build a simple Merkle tree over serialized signals
        leaves = [MerkleProvenance.hash_item(signal_to_dict(s)) for s in values]
        if not leaves:
            return ""  # empty root
        level = leaves
        while len(level) > 1:
            next_level = []
            for i in range(0, len(level), 2):
                left = level[i]
                right = level[i + 1] if i + 1 < len(level) else left
                next_level.append(hashlib.sha256((left + right).encode()).hexdigest())
            level = next_level
        return level[0]


def signal_to_dict(s: Signal) -> dict:
    return {
        "venue": s.venue,
        "timestamp": s.timestamp,
        "metrics": s.metrics,
        "version": s.version,
    }