"""
Cache management utilities for download plans.
Handles caching, loading, and cleanup of download plan data.
"""

import hashlib

import json
from datetime import datetime, timedelta
from pathlib import Path

# Constants
DEFAULT_CACHE_EXPIRATION_DAYS = 1
DEFAULT_CACHE_FILENAME_LENGTH_LIMIT = 200  # Increased from 60
DEFAULT_CACHE_FILENAME_PREFIX_LENGTH = 100  # Increased from 40


def get_download_plan_cache_file(mode, **kwargs):
    """Generate a unique cache filename based on mode and key parameters."""
    parts = [f"plan_{mode}"]

    # Handle parameters in a more readable way
    for k, v in sorted(kwargs.items()):
        if k == "channels_hash":
            # Use a shorter version of the hash for readability
            parts.append(f"hash{v[:8]}")
        else:
            parts.append(f"{k}{v}")

    base = "_".join(parts)

    # Hash for safety if string is still too long
    if len(base) > DEFAULT_CACHE_FILENAME_LENGTH_LIMIT:
        base = (
            base[:DEFAULT_CACHE_FILENAME_PREFIX_LENGTH]
            + "_"
            + hashlib.md5(base.encode()).hexdigest()[:8]
        )

    return Path(f"data/{base}.json")


def load_cached_plan(cache_file, max_age_days=DEFAULT_CACHE_EXPIRATION_DAYS):
    """Load a cached download plan if it exists and is not expired."""
    if not cache_file.exists():
        return None, None

    try:
        with open(cache_file, "r", encoding="utf-8") as f:
            cache_data = json.load(f)
        cache_time = datetime.fromisoformat(cache_data.get("timestamp"))
        if datetime.now() - cache_time < timedelta(days=max_age_days):
            print(
                f"🗂️  Using cached download plan from {cache_time} ({cache_file.name})."
            )
            return cache_data["download_plan"], cache_data["unmatched"]
    except Exception as e:
        print(f"⚠️ Could not load download plan cache: {e}")

    return None, None


def save_plan_cache(cache_file, download_plan, unmatched):
    """Save a download plan to cache."""
    if download_plan:
        cache_data = {
            "timestamp": datetime.now().isoformat(),
            "download_plan": download_plan,
            "unmatched": unmatched,
        }
        with open(cache_file, "w", encoding="utf-8") as f:
            json.dump(cache_data, f, indent=2, ensure_ascii=False)
        print(f"🗂️  Saved new download plan cache: {cache_file.name}")
    else:
        if cache_file.exists():
            cache_file.unlink()
        print("🗂️  No matches found, not saving download plan cache.")


def delete_plan_cache(cache_file):
    """Delete a download plan cache file."""
    if cache_file.exists():
        try:
            cache_file.unlink()
            print(f"🗑️  Deleted download plan cache: {cache_file.name}")
        except Exception as e:
            print(f"⚠️ Could not delete download plan cache: {e}")