"""
Input validation utilities for NeuroSAM 3 application.
Provides validation functions for user inputs, files, and parameters.
"""

import os
from typing import Optional, Tuple
from pathlib import Path
from logger_config import logger
from config import (
    MAX_FILE_SIZE_BYTES,
    ALLOWED_IMAGE_EXTENSIONS,
    ALLOWED_ANNOTATION_EXTENSIONS,
    MIN_THRESHOLD,
    MAX_THRESHOLD,
    MIN_MASK_THRESHOLD,
    MAX_MASK_THRESHOLD,
    MAX_COORDINATE_VALUE,
    MIN_NUM_MASKS,
    MAX_NUM_MASKS,
)


class ValidationError(Exception):
    """Custom exception for validation errors."""
    pass


def validate_file_path(file_path: Optional[str]) -> Tuple[bool, Optional[str]]:
    """
    Validate that a file path exists and is accessible.
    
    Args:
        file_path: Path to validate
    
    Returns:
        Tuple of (is_valid, error_message)
    """
    if file_path is None:
        return False, "File path is None"
    
    if not isinstance(file_path, (str, Path)):
        return False, f"Invalid file path type: {type(file_path)}"
    
    file_path = str(file_path)
    
    if not os.path.exists(file_path):
        return False, f"File not found: {file_path}"
    
    if not os.path.isfile(file_path):
        return False, f"Path is not a file: {file_path}"
    
    return True, None


def validate_file_size(file_path: str) -> Tuple[bool, Optional[str]]:
    """
    Validate that a file size is within limits.
    
    Args:
        file_path: Path to file to validate
    
    Returns:
        Tuple of (is_valid, error_message)
    """
    try:
        file_size = os.path.getsize(file_path)
        if file_size > MAX_FILE_SIZE_BYTES:
            size_mb = file_size / (1024 * 1024)
            max_mb = MAX_FILE_SIZE_BYTES / (1024 * 1024)
            return False, f"File size ({size_mb:.2f} MB) exceeds maximum ({max_mb} MB)"
        return True, None
    except OSError as e:
        return False, f"Could not check file size: {e}"


def validate_file_extension(file_path: str, allowed_extensions: tuple = ALLOWED_IMAGE_EXTENSIONS) -> Tuple[bool, Optional[str]]:
    """
    Validate file extension.
    
    Args:
        file_path: Path to file
        allowed_extensions: Tuple of allowed extensions (default: image extensions)
    
    Returns:
        Tuple of (is_valid, error_message)
    """
    ext = os.path.splitext(file_path)[1].lower()
    if ext not in allowed_extensions:
        return False, f"File extension '{ext}' not allowed. Allowed: {', '.join(allowed_extensions)}"
    return True, None


def validate_image_file(file_path: Optional[str]) -> Tuple[bool, Optional[str]]:
    """
    Comprehensive validation for image files.
    
    Args:
        file_path: Path to image file
    
    Returns:
        Tuple of (is_valid, error_message)
    """
    # Check if path is valid
    is_valid, error = validate_file_path(file_path)
    if not is_valid:
        return False, error
    
    file_path = str(file_path)
    
    # Check extension
    is_valid, error = validate_file_extension(file_path, ALLOWED_IMAGE_EXTENSIONS)
    if not is_valid:
        return False, error
    
    # Check file size
    is_valid, error = validate_file_size(file_path)
    if not is_valid:
        return False, error
    
    return True, None


def validate_threshold(threshold: float) -> Tuple[bool, Optional[str]]:
    """
    Validate threshold value.
    
    Args:
        threshold: Threshold value to validate
    
    Returns:
        Tuple of (is_valid, error_message)
    """
    if not isinstance(threshold, (int, float)):
        return False, f"Threshold must be a number, got {type(threshold)}"
    
    if threshold < MIN_THRESHOLD or threshold > MAX_THRESHOLD:
        return False, f"Threshold must be between {MIN_THRESHOLD} and {MAX_THRESHOLD}, got {threshold}"
    
    return True, None


def validate_mask_threshold(mask_threshold: float) -> Tuple[bool, Optional[str]]:
    """
    Validate mask threshold value.
    
    Args:
        mask_threshold: Mask threshold value to validate
    
    Returns:
        Tuple of (is_valid, error_message)
    """
    if not isinstance(mask_threshold, (int, float)):
        return False, f"Mask threshold must be a number, got {type(mask_threshold)}"
    
    if mask_threshold < MIN_MASK_THRESHOLD or mask_threshold > MAX_MASK_THRESHOLD:
        return False, f"Mask threshold must be between {MIN_MASK_THRESHOLD} and {MAX_MASK_THRESHOLD}, got {mask_threshold}"
    
    return True, None


def validate_coordinates(x: float, y: float, max_value: int = MAX_COORDINATE_VALUE) -> Tuple[bool, Optional[str]]:
    """
    Validate coordinate values.
    
    Args:
        x: X coordinate
        y: Y coordinate
        max_value: Maximum allowed coordinate value
    
    Returns:
        Tuple of (is_valid, error_message)
    """
    if not isinstance(x, (int, float)) or not isinstance(y, (int, float)):
        return False, f"Coordinates must be numbers, got x={type(x)}, y={type(y)}"
    
    if x < 0 or y < 0:
        return False, f"Coordinates must be non-negative, got x={x}, y={y}"
    
    if x > max_value or y > max_value:
        return False, f"Coordinates exceed maximum value ({max_value}), got x={x}, y={y}"
    
    return True, None


def validate_bounding_box(x1: float, y1: float, x2: float, y2: float) -> Tuple[bool, Optional[str]]:
    """
    Validate bounding box coordinates.
    
    Args:
        x1, y1: Top-left corner coordinates
        x2, y2: Bottom-right corner coordinates
    
    Returns:
        Tuple of (is_valid, error_message)
    """
    # Validate individual coordinates
    for coord, name in [(x1, 'x1'), (y1, 'y1'), (x2, 'x2'), (y2, 'y2')]:
        if not isinstance(coord, (int, float)):
            return False, f"{name} must be a number, got {type(coord)}"
        if coord < 0:
            return False, f"{name} must be non-negative, got {coord}"
        if coord > MAX_COORDINATE_VALUE:
            return False, f"{name} exceeds maximum ({MAX_COORDINATE_VALUE}), got {coord}"
    
    # Validate box dimensions
    if x2 <= x1:
        return False, f"x2 ({x2}) must be greater than x1 ({x1})"
    
    if y2 <= y1:
        return False, f"y2 ({y2}) must be greater than y1 ({y1})"
    
    return True, None


def validate_num_masks(num_masks: int) -> Tuple[bool, Optional[str]]:
    """
    Validate number of masks parameter.
    
    Args:
        num_masks: Number of masks to generate
    
    Returns:
        Tuple of (is_valid, error_message)
    """
    if not isinstance(num_masks, int):
        return False, f"Number of masks must be an integer, got {type(num_masks)}"
    
    if num_masks < MIN_NUM_MASKS or num_masks > MAX_NUM_MASKS:
        return False, f"Number of masks must be between {MIN_NUM_MASKS} and {MAX_NUM_MASKS}, got {num_masks}"
    
    return True, None


def validate_prompt_text(prompt_text: Optional[str]) -> Tuple[bool, Optional[str], str]:
    """
    Validate and sanitize prompt text.
    
    Args:
        prompt_text: Text prompt to validate
    
    Returns:
        Tuple of (is_valid, error_message, sanitized_prompt)
    """
    if prompt_text is None:
        return True, None, "brain"  # Default prompt
    
    if not isinstance(prompt_text, str):
        return False, f"Prompt must be a string, got {type(prompt_text)}", ""
    
    # Sanitize: strip whitespace
    sanitized = prompt_text.strip()
    
    # Check length (reasonable limit)
    if len(sanitized) > 500:
        return False, "Prompt text is too long (max 500 characters)", ""
    
    # Use default if empty
    if not sanitized:
        sanitized = "brain"
    
    return True, None, sanitized


def validate_modality(modality: Optional[str]) -> Tuple[bool, Optional[str]]:
    """
    Validate imaging modality.
    
    Args:
        modality: Modality string (CT or MRI)
    
    Returns:
        Tuple of (is_valid, error_message)
    """
    if modality is None:
        return False, "Modality is required"
    
    if not isinstance(modality, str):
        return False, f"Modality must be a string, got {type(modality)}"
    
    modality_upper = modality.upper()
    if modality_upper not in ("CT", "MRI"):
        return False, f"Modality must be 'CT' or 'MRI', got '{modality}'"
    
    return True, None


def validate_transparency(transparency: float) -> Tuple[bool, Optional[str]]:
    """
    Validate transparency value.
    
    Args:
        transparency: Transparency value (0.0-1.0)
    
    Returns:
        Tuple of (is_valid, error_message)
    """
    if not isinstance(transparency, (int, float)):
        return False, f"Transparency must be a number, got {type(transparency)}"
    
    if transparency < 0.0 or transparency > 1.0:
        return False, f"Transparency must be between 0.0 and 1.0, got {transparency}"
    
    return True, None


def validate_brightness_contrast(value: float, name: str = "value") -> Tuple[bool, Optional[str]]:
    """
    Validate brightness or contrast value.
    
    Args:
        value: Brightness or contrast value
        name: Name of the parameter for error messages
    
    Returns:
        Tuple of (is_valid, error_message)
    """
    if not isinstance(value, (int, float)):
        return False, f"{name} must be a number, got {type(value)}"
    
    if value < 0.0 or value > 3.0:
        return False, f"{name} must be between 0.0 and 3.0, got {value}"
    
    return True, None