"""
Template integration utilities for FastAPI application.

This module provides utilities for template rendering with common context
and helper functions.

Series Identifier Convention:
    - `key`: Primary identifier for all series operations
      (URL-safe, e.g., "attack-on-titan")
    - `folder`: Metadata only for filesystem operations and display
      (e.g., "Attack on Titan (2013)")

All template helpers that handle series data use `key` for identification and
provide `folder` as display metadata only.
"""
import logging
import time
from pathlib import Path
from typing import Any, Dict, List, Optional

from fastapi import Request
from fastapi.templating import Jinja2Templates

from src.server.utils.version import APP_VERSION

logger = logging.getLogger(__name__)

# Configure templates directory
TEMPLATES_DIR = Path(__file__).parent.parent / "web" / "templates"
templates = Jinja2Templates(directory=str(TEMPLATES_DIR))

# Version token for static asset cache-busting; changes on every server start.
STATIC_VERSION: str = str(int(time.time()))


def get_base_context(
    request: Request, title: str = "Aniworld"
) -> Dict[str, Any]:
    """
    Get base context for all templates.
    
    Args:
        request: FastAPI request object
        title: Page title
        
    Returns:
        Dictionary with base context variables
    """
    return {
        "request": request,
        "title": title,
        "app_name": "Aniworld Download Manager",
        "version": APP_VERSION,
        "static_v": STATIC_VERSION,
    }


def render_template(
    template_name: str,
    request: Request,
    context: Optional[Dict[str, Any]] = None,
    title: Optional[str] = None
):
    """
    Render a template with base context.
    
    Args:
        template_name: Name of the template file
        request: FastAPI request object
        context: Additional context variables
        title: Page title (optional)
        
    Returns:
        TemplateResponse object
    """
    base_context = get_base_context(
        request,
        title or template_name.replace('.html', '').replace('_', ' ').title()
    )
    
    if context:
        base_context.update(context)
    
    return templates.TemplateResponse(template_name, base_context)


def validate_template_exists(template_name: str) -> bool:
    """
    Check if a template file exists.
    
    Args:
        template_name: Name of the template file
        
    Returns:
        True if template exists, False otherwise
    """
    template_path = TEMPLATES_DIR / template_name
    return template_path.exists()


def list_available_templates() -> list[str]:
    """
    Get list of all available template files.

    Returns:
        List of template file names
    """
    if not TEMPLATES_DIR.exists():
        return []

    return [
        f.name
        for f in TEMPLATES_DIR.glob("*.html")
        if f.is_file()
    ]


def prepare_series_context(
    series_data: List[Dict[str, Any]],
    sort_by: str = "name"
) -> List[Dict[str, Any]]:
    """
    Prepare series data for template rendering.

    This function ensures series data follows the identifier convention:
    - `key` is used as the primary identifier for all operations
    - `folder` is included as metadata for display purposes

    Args:
        series_data: List of series dictionaries from the API
        sort_by: Field to sort by ("name", "key", or "folder")

    Returns:
        List of series dictionaries prepared for template use

    Raises:
        ValueError: If series_data contains items without required 'key' field

    Example:
        >>> series = [
        ...     {"key": "attack-on-titan", "name": "Attack on Titan",
        ...      "folder": "Attack on Titan (2013)"},
        ...     {"key": "one-piece", "name": "One Piece",
        ...      "folder": "One Piece (1999)"}
        ... ]
        >>> prepared = prepare_series_context(series, sort_by="name")
    """
    if not series_data:
        return []

    prepared = []
    for series in series_data:
        if "key" not in series:
            logger.warning(
                "Series data missing 'key' field: %s",
                series.get("name", "unknown")
            )
            continue

        prepared_item = {
            "key": series["key"],
            "name": series.get("name", series["key"]),
            "folder": series.get("folder", ""),
            **{k: v for k, v in series.items()
               if k not in ("key", "name", "folder")}
        }
        prepared.append(prepared_item)

    # Sort by specified field
    if sort_by in ("name", "key", "folder"):
        prepared.sort(key=lambda x: x.get(sort_by, "").lower())

    return prepared


def get_series_by_key(
    series_data: List[Dict[str, Any]],
    key: str
) -> Optional[Dict[str, Any]]:
    """
    Find a series in the data by its key.

    Uses `key` as the identifier (not `folder`) following the project
    identifier convention.

    Args:
        series_data: List of series dictionaries
        key: The unique series key to search for

    Returns:
        The series dictionary if found, None otherwise

    Example:
        >>> series = [{"key": "attack-on-titan", "name": "Attack on Titan"}]
        >>> result = get_series_by_key(series, "attack-on-titan")
        >>> result["name"]
        'Attack on Titan'
    """
    for series in series_data:
        if series.get("key") == key:
            return series
    return None


def filter_series_by_missing_episodes(
    series_data: List[Dict[str, Any]]
) -> List[Dict[str, Any]]:
    """
    Filter series to only include those with missing episodes.

    Args:
        series_data: List of series dictionaries with 'missing_episodes' field

    Returns:
        Filtered list containing only series with missing episodes

    Note:
        Identification uses `key`, not `folder`.
    """
    return [
        series for series in series_data
        if series.get("missing_episodes")
        and any(episodes for episodes in series["missing_episodes"].values())
    ]