# /// script
# requires-python = ">=3.10"
# dependencies = ["requests"]
# ///
"""
@effect dog
@version 1.0.0
@author @giles@artdag.rose-ash.com
@temporal true

@description
Returns dog.mkv regardless of input. This is a constant effect that
fetches from an immutable URL and verifies the content hash.
Demonstrates a whole-video effect that ignores its input.

@example
  (fx dog)
"""

import hashlib
import logging
import shutil
from pathlib import Path
from typing import Any, Dict, List

import requests

logger = logging.getLogger(__name__)

# Immutable source URL (commit-pinned)
DOG_URL = "https://git.rose-ash.com/art-dag/art-source/raw/3cb70f9aab6c5e9473e5ce34c59fb1d7dca4bdaa/dog.mkv"
DOG_HASH = "772f26f9b4e80984788bc48f7c6eee0a1974966b2d4ee56a72d7c6586b3ac9d8"


def file_hash(path: Path) -> str:
    """Compute SHA3-256 hash of a file."""
    hasher = hashlib.sha3_256()
    with open(path, "rb") as f:
        for chunk in iter(lambda: f.read(65536), b""):
            hasher.update(chunk)
    return hasher.hexdigest()


def process(input_paths: List[Path], output_path: Path, params: Dict[str, Any], ctx) -> Path:
    """
    Whole-video API: ignores input, returns dog.mkv.

    Downloads from immutable URL and verifies hash.
    """
    output_path = Path(output_path)
    output_path.parent.mkdir(parents=True, exist_ok=True)

    # Output with correct extension
    actual_output = output_path.with_suffix(".mkv")
    if actual_output.exists():
        actual_output.unlink()

    # Check cache first
    cache_dir = Path.home() / ".artdag" / "effect_cache"
    cache_dir.mkdir(parents=True, exist_ok=True)
    cached_file = cache_dir / f"{DOG_HASH}.mkv"

    if cached_file.exists():
        # Verify cached file
        if file_hash(cached_file) == DOG_HASH:
            logger.debug(f"EFFECT dog: using cached {cached_file}")
            shutil.copy2(cached_file, actual_output)
            return actual_output
        else:
            # Cache corrupted, remove it
            cached_file.unlink()

    # Download from immutable URL
    logger.info(f"EFFECT dog: downloading from {DOG_URL}")
    response = requests.get(DOG_URL, stream=True)
    response.raise_for_status()

    # Write to cache
    with open(cached_file, "wb") as f:
        for chunk in response.iter_content(chunk_size=65536):
            f.write(chunk)

    # Verify hash
    downloaded_hash = file_hash(cached_file)
    if downloaded_hash != DOG_HASH:
        cached_file.unlink()
        raise ValueError(f"Hash mismatch! Expected {DOG_HASH}, got {downloaded_hash}")

    # Copy to output
    shutil.copy2(cached_file, actual_output)
    logger.debug(f"EFFECT dog: -> {actual_output} (input ignored)")

    return actual_output