"""
Template utility functions for size parsing and template management
"""

import os
from pathlib import Path
from typing import List, Tuple, Optional


def parse_template_size(template_path: str) -> Tuple[int, int]:
    """
    Parse video size from template path
    
    Args:
        template_path: Template path like "templates/1080x1920/default.html"
                      or "1080x1920/default.html"
    
    Returns:
        Tuple of (width, height) in pixels
    
    Raises:
        ValueError: If template path format is invalid
    
    Examples:
        >>> parse_template_size("templates/1080x1920/default.html")
        (1080, 1920)
        >>> parse_template_size("1920x1080/modern.html")
        (1920, 1080)
    """
    path = Path(template_path)
    
    # Get parent directory name (should be like "1080x1920")
    dir_name = path.parent.name
    
    # Special case: if parent is "templates", go up one more level
    if dir_name == "templates":
        # This shouldn't happen in new structure, but handle it
        raise ValueError(
            f"Invalid template path format: {template_path}. "
            f"Expected format: 'WIDTHxHEIGHT/template.html' or 'templates/WIDTHxHEIGHT/template.html'"
        )
    
    # Parse size from directory name
    if 'x' not in dir_name:
        raise ValueError(
            f"Invalid size format in path: {template_path}. "
            f"Directory name should be 'WIDTHxHEIGHT' (e.g., '1080x1920')"
        )
    
    try:
        width_str, height_str = dir_name.split('x')
        width = int(width_str)
        height = int(height_str)
        
        # Sanity check
        if width < 100 or height < 100 or width > 10000 or height > 10000:
            raise ValueError(f"Invalid size dimensions: {width}x{height}")
        
        return (width, height)
    except ValueError as e:
        raise ValueError(
            f"Failed to parse size from path: {template_path}. "
            f"Expected format: 'WIDTHxHEIGHT/template.html' (e.g., '1080x1920/default.html'). "
            f"Error: {e}"
        )


def list_available_sizes() -> List[str]:
    """
    List all available video sizes
    
    Returns:
        List of size strings like ["1080x1920", "1920x1080", "1080x1080"]
    
    Examples:
        >>> list_available_sizes()
        ['1080x1920', '1920x1080', '1080x1080']
    """
    templates_dir = Path("templates")
    
    if not templates_dir.exists():
        return []
    
    sizes = []
    for item in templates_dir.iterdir():
        if item.is_dir() and 'x' in item.name:
            # Validate it's a proper size format
            try:
                width, height = item.name.split('x')
                int(width)
                int(height)
                sizes.append(item.name)
            except (ValueError, AttributeError):
                # Skip invalid directories
                continue
    
    return sorted(sizes)


def list_templates_for_size(size: str) -> List[str]:
    """
    List all templates available for a given size
    
    Args:
        size: Size string like "1080x1920"
    
    Returns:
        List of template filenames (without path) like ["default.html", "modern.html"]
    
    Examples:
        >>> list_templates_for_size("1080x1920")
        ['cartoon.html', 'default.html', 'elegant.html', 'modern.html', ...]
    """
    size_dir = Path("templates") / size
    
    if not size_dir.exists() or not size_dir.is_dir():
        return []
    
    templates = []
    for item in size_dir.iterdir():
        if item.is_file() and item.suffix == '.html':
            templates.append(item.name)
    
    return sorted(templates)


def get_template_full_path(size: str, template_name: str) -> str:
    """
    Get full template path from size and template name
    
    Args:
        size: Size string like "1080x1920"
        template_name: Template filename like "default.html"
    
    Returns:
        Full path like "templates/1080x1920/default.html"
    
    Raises:
        FileNotFoundError: If template file doesn't exist
    
    Examples:
        >>> get_template_full_path("1080x1920", "default.html")
        'templates/1080x1920/default.html'
    """
    template_path = Path("templates") / size / template_name
    
    if not template_path.exists():
        available_templates = list_templates_for_size(size)
        raise FileNotFoundError(
            f"Template not found: {template_path}\n"
            f"Available templates for size {size}: {available_templates}"
        )
    
    return str(template_path)


def resolve_template_path(template_input: Optional[str]) -> str:
    """
    Resolve template input to full path with validation
    
    Args:
        template_input: Can be:
            - None: Use default "1080x1920/default.html"
            - "template.html": Use default size + this template
            - "1080x1920/template.html": Full relative path
            - "templates/1080x1920/template.html": Absolute-ish path
    
    Returns:
        Resolved full path like "templates/1080x1920/default.html"
    
    Raises:
        FileNotFoundError: If template doesn't exist
    
    Examples:
        >>> resolve_template_path(None)
        'templates/1080x1920/default.html'
        >>> resolve_template_path("modern.html")
        'templates/1080x1920/modern.html'
        >>> resolve_template_path("1920x1080/default.html")
        'templates/1920x1080/default.html'
    """
    # Default case
    if template_input is None:
        template_input = "1080x1920/default.html"
    
    # If already starts with "templates/", use as-is
    if template_input.startswith("templates/"):
        template_path = Path(template_input)
    # If contains size directory (e.g., "1080x1920/default.html")
    elif '/' in template_input and 'x' in template_input.split('/')[0]:
        template_path = Path("templates") / template_input
    # Just template name (e.g., "default.html")
    else:
        # Use default size
        template_path = Path("templates") / "1080x1920" / template_input
    
    # Validate existence
    if not template_path.exists():
        available_sizes = list_available_sizes()
        raise FileNotFoundError(
            f"Template not found: {template_path}\n"
            f"Available sizes: {available_sizes}\n"
            f"Hint: Use format 'SIZExSIZE/template.html' (e.g., '1080x1920/default.html')"
        )
    
    return str(template_path)