"""
Input Validation Utilities
===========================

Validation functions for user inputs in Nano Banana Streamlit.
Ensures data integrity and provides clear error messages.
"""

from typing import Optional, List, Tuple
from pathlib import Path
from PIL import Image

from config.settings import Settings
from utils.logging_utils import get_logger


logger = get_logger(__name__)


# =============================================================================
# PARAMETER VALIDATION
# =============================================================================

def validate_temperature(temperature: float) -> Tuple[bool, Optional[str]]:
    """
    Validate temperature parameter.

    Args:
        temperature: Temperature value to validate

    Returns:
        Tuple of (is_valid, error_message)
        error_message is None if valid
    """
    if not isinstance(temperature, (int, float)):
        return False, "Temperature must be a number"

    if temperature < Settings.MIN_TEMPERATURE or temperature > Settings.MAX_TEMPERATURE:
        return False, f"Temperature must be between {Settings.MIN_TEMPERATURE} and {Settings.MAX_TEMPERATURE}"

    return True, None


def validate_aspect_ratio(aspect_ratio: str) -> Tuple[bool, Optional[str]]:
    """
    Validate aspect ratio parameter.

    Args:
        aspect_ratio: Aspect ratio string (display name or value)

    Returns:
        Tuple of (is_valid, error_message)
    """
    if not isinstance(aspect_ratio, str):
        return False, "Aspect ratio must be a string"

    # Check if it's a display name
    if aspect_ratio in Settings.ASPECT_RATIOS:
        return True, None

    # Check if it's a ratio value
    if aspect_ratio in Settings.ASPECT_RATIOS.values():
        return True, None

    return False, f"Invalid aspect ratio: {aspect_ratio}"


def validate_backend(backend: str) -> Tuple[bool, Optional[str]]:
    """
    Validate backend parameter.

    Args:
        backend: Backend name

    Returns:
        Tuple of (is_valid, error_message)
    """
    if not isinstance(backend, str):
        return False, "Backend must be a string"

    if backend not in Settings.AVAILABLE_BACKENDS:
        return False, f"Invalid backend: {backend}. Must be one of {Settings.AVAILABLE_BACKENDS}"

    return True, None


def validate_prompt(prompt: str, min_length: int = 1, max_length: int = 5000) -> Tuple[bool, Optional[str]]:
    """
    Validate text prompt.

    Args:
        prompt: Text prompt
        min_length: Minimum required length (default: 1)
        max_length: Maximum allowed length (default: 5000)

    Returns:
        Tuple of (is_valid, error_message)
    """
    if not isinstance(prompt, str):
        return False, "Prompt must be a string"

    prompt = prompt.strip()

    if len(prompt) < min_length:
        return False, f"Prompt must be at least {min_length} character(s)"

    if len(prompt) > max_length:
        return False, f"Prompt must be at most {max_length} characters"

    return True, None


def validate_character_name(name: str) -> Tuple[bool, Optional[str]]:
    """
    Validate character name.

    Args:
        name: Character name

    Returns:
        Tuple of (is_valid, error_message)
    """
    if not isinstance(name, str):
        return False, "Character name must be a string"

    name = name.strip()

    if len(name) < 1:
        return False, "Character name cannot be empty"

    if len(name) > 100:
        return False, "Character name must be at most 100 characters"

    return True, None


# =============================================================================
# IMAGE VALIDATION
# =============================================================================

def validate_image(image: Image.Image) -> Tuple[bool, Optional[str]]:
    """
    Validate PIL Image object.

    Checks:
    - Is valid Image instance
    - Has reasonable dimensions
    - Is in supported format

    Args:
        image: PIL Image to validate

    Returns:
        Tuple of (is_valid, error_message)
    """
    if not isinstance(image, Image.Image):
        return False, "Invalid image object"

    # Check dimensions
    width, height = image.size

    if width < 1 or height < 1:
        return False, "Image has invalid dimensions"

    if width > 8192 or height > 8192:
        return False, "Image is too large (max 8192x8192 pixels)"

    # Check mode (format)
    if image.mode not in ['RGB', 'RGBA', 'L', 'P']:
        return False, f"Unsupported image mode: {image.mode}"

    return True, None


def validate_image_file(file_path: Path) -> Tuple[bool, Optional[str]]:
    """
    Validate image file path and format.

    Args:
        file_path: Path to image file

    Returns:
        Tuple of (is_valid, error_message)
    """
    if not isinstance(file_path, Path):
        try:
            file_path = Path(file_path)
        except Exception:
            return False, "Invalid file path"

    # Check exists
    if not file_path.exists():
        return False, f"File not found: {file_path}"

    # Check is file (not directory)
    if not file_path.is_file():
        return False, f"Not a file: {file_path}"

    # Check extension
    valid_extensions = {'.png', '.jpg', '.jpeg', '.webp', '.bmp'}
    if file_path.suffix.lower() not in valid_extensions:
        return False, f"Unsupported file format: {file_path.suffix}"

    # Try to open as image
    try:
        with Image.open(file_path) as img:
            return validate_image(img)
    except Exception as e:
        return False, f"Cannot open as image: {e}"


def validate_image_upload_size(file_size_bytes: int) -> Tuple[bool, Optional[str]]:
    """
    Validate uploaded file size.

    Args:
        file_size_bytes: File size in bytes

    Returns:
        Tuple of (is_valid, error_message)
    """
    max_bytes = Settings.MAX_IMAGE_UPLOAD_SIZE * 1024 * 1024  # Convert MB to bytes

    if file_size_bytes > max_bytes:
        max_mb = Settings.MAX_IMAGE_UPLOAD_SIZE
        actual_mb = file_size_bytes / (1024 * 1024)
        return False, f"File too large: {actual_mb:.1f}MB (max: {max_mb}MB)"

    return True, None


# =============================================================================
# GENERATION REQUEST VALIDATION
# =============================================================================

def validate_generation_request(
    prompt: str,
    backend: str,
    aspect_ratio: str,
    temperature: float,
    input_images: Optional[List[Image.Image]] = None
) -> Tuple[bool, Optional[str]]:
    """
    Validate a complete generation request.

    Validates all parameters required for image generation.

    Args:
        prompt: Text prompt
        backend: Backend name
        aspect_ratio: Aspect ratio
        temperature: Temperature value
        input_images: Optional list of input images

    Returns:
        Tuple of (is_valid, error_message)
        error_message is None if valid
    """
    # Validate prompt
    valid, error = validate_prompt(prompt)
    if not valid:
        return False, f"Invalid prompt: {error}"

    # Validate backend
    valid, error = validate_backend(backend)
    if not valid:
        return False, f"Invalid backend: {error}"

    # Validate aspect ratio
    valid, error = validate_aspect_ratio(aspect_ratio)
    if not valid:
        return False, f"Invalid aspect ratio: {error}"

    # Validate temperature
    valid, error = validate_temperature(temperature)
    if not valid:
        return False, f"Invalid temperature: {error}"

    # Validate input images if provided
    if input_images:
        if not isinstance(input_images, list):
            return False, "Input images must be a list"

        if len(input_images) > 3:
            return False, "Maximum 3 input images allowed"

        for idx, img in enumerate(input_images, 1):
            valid, error = validate_image(img)
            if not valid:
                return False, f"Invalid input image {idx}: {error}"

    return True, None


def validate_character_forge_request(
    character_name: str,
    initial_image: Optional[Image.Image],
    face_image: Optional[Image.Image],
    body_image: Optional[Image.Image],
    image_type: str,
    backend: str
) -> Tuple[bool, Optional[str]]:
    """
    Validate a Character Forge generation request.

    Args:
        character_name: Name for character
        initial_image: Initial image (for Face Only / Full Body modes)
        face_image: Face image (for Face+Body Separate mode)
        body_image: Body image (for Face+Body Separate mode)
        image_type: Type of input ("Face Only", "Full Body", "Face + Body (Separate)")
        backend: Backend to use

    Returns:
        Tuple of (is_valid, error_message)
    """
    # Validate character name
    valid, error = validate_character_name(character_name)
    if not valid:
        return False, error

    # Validate backend
    valid, error = validate_backend(backend)
    if not valid:
        return False, error

    # Validate images based on mode
    if image_type == "Face + Body (Separate)":
        if face_image is None:
            return False, "Face image is required for Face+Body Separate mode"
        if body_image is None:
            return False, "Body image is required for Face+Body Separate mode"

        valid, error = validate_image(face_image)
        if not valid:
            return False, f"Invalid face image: {error}"

        valid, error = validate_image(body_image)
        if not valid:
            return False, f"Invalid body image: {error}"

    else:  # Face Only or Full Body
        if initial_image is None:
            return False, f"Initial image is required for {image_type} mode"

        valid, error = validate_image(initial_image)
        if not valid:
            return False, f"Invalid initial image: {error}"

    return True, None


# =============================================================================
# BACKEND AVAILABILITY VALIDATION
# =============================================================================

def validate_backend_available(backend: str, api_key: Optional[str] = None) -> Tuple[bool, Optional[str]]:
    """
    Check if a backend is available and properly configured.

    Args:
        backend: Backend name
        api_key: API key (for Gemini backend)

    Returns:
        Tuple of (is_available, error_message)
    """
    # Validate backend name first
    valid, error = validate_backend(backend)
    if not valid:
        return False, error

    # Check Gemini API
    if backend == Settings.BACKEND_GEMINI:
        if not api_key:
            return False, "Gemini API key not configured. Please set GEMINI_API_KEY or enter it in settings."
        return True, None

    # Check OmniGen2
    if backend == Settings.BACKEND_OMNIGEN2:
        # Try to check if server is running
        try:
            import requests
            response = requests.get(f"{Settings.OMNIGEN2_BASE_URL}/health", timeout=2)
            if response.ok:
                data = response.json()
                if data.get('status') == 'healthy':
                    return True, None
                else:
                    return False, "OmniGen2 server is not healthy. Check server.log for details."
            else:
                return False, f"OmniGen2 server returned error: {response.status_code}"
        except Exception as e:
            return False, f"OmniGen2 server not responding. Start it with: omnigen2_plugin/server.bat start"

    return False, f"Unknown backend: {backend}"


# =============================================================================
# HELPER FUNCTIONS
# =============================================================================

def raise_if_invalid(is_valid: bool, error_message: Optional[str], exception_type=ValueError):
    """
    Raise an exception if validation failed.

    Helper function for turning validation results into exceptions.

    Args:
        is_valid: Validation result
        error_message: Error message (if invalid)
        exception_type: Exception class to raise (default: ValueError)

    Raises:
        exception_type: If is_valid is False
    """
    if not is_valid:
        logger.error(f"Validation failed: {error_message}")
        raise exception_type(error_message)


def log_validation_error(validation_result: Tuple[bool, Optional[str]], context: str = ""):
    """
    Log a validation error if validation failed.

    Args:
        validation_result: Result tuple from validation function
        context: Optional context string for the log message
    """
    is_valid, error_message = validation_result
    if not is_valid:
        if context:
            logger.warning(f"Validation failed [{context}]: {error_message}")
        else:
            logger.warning(f"Validation failed: {error_message}")