"""Hash computation utilities for model files."""

from __future__ import annotations

import hashlib
import os
from pathlib import Path
from typing import Optional, Callable, Union


def compute_sha256(file_path: Union[str, Path], chunk_size: int = 8192) -> str:
    """
    Compute SHA256 hash of a file.

    Args:
        file_path: Path to the file to hash
        chunk_size: Size of chunks to read (default 8KB)

    Returns:
        Hexadecimal SHA256 hash string
    """
    sha256 = hashlib.sha256()
    with open(file_path, "rb") as f:
        while chunk := f.read(chunk_size):
            sha256.update(chunk)
    return sha256.hexdigest()


def compute_sha256_chunked(
    file_path: Union[str, Path],
    progress_callback: Optional[Callable[[int, int], None]] = None,
    chunk_size: int = 1024 * 1024  # 1MB chunks for progress
) -> str:
    """
    Compute SHA256 hash with progress reporting.

    Args:
        file_path: Path to the file to hash
        progress_callback: Callable(bytes_processed, total_bytes) for progress
        chunk_size: Size of chunks to read (default 1MB for better progress)

    Returns:
        Hexadecimal SHA256 hash string
    """
    file_path = Path(file_path)
    total_size = file_path.stat().st_size
    processed = 0

    sha256 = hashlib.sha256()
    with open(file_path, "rb") as f:
        while chunk := f.read(chunk_size):
            sha256.update(chunk)
            processed += len(chunk)
            if progress_callback:
                progress_callback(processed, total_size)

    return sha256.hexdigest()


def verify_file_hash(file_path: Union[str, Path], expected_hash: str) -> bool:
    """
    Verify a file matches an expected SHA256 hash.

    Args:
        file_path: Path to the file to verify
        expected_hash: Expected SHA256 hash (hex string)

    Returns:
        True if hash matches, False otherwise
    """
    actual_hash = compute_sha256(file_path)
    return actual_hash.lower() == expected_hash.lower()


def get_file_info(file_path: Union[str, Path]) -> dict:
    """
    Get file information including size and modification time.

    Args:
        file_path: Path to the file

    Returns:
        Dict with size, mtime, and exists keys
    """
    path = Path(file_path)
    if not path.exists():
        return {"exists": False, "size": 0, "mtime": None}

    stat = path.stat()
    return {
        "exists": True,
        "size": stat.st_size,
        "mtime": stat.st_mtime,
    }