"""
Input validation utilities for mobile app backend.
"""

import re
from typing import Tuple, Optional
from config import Config


class Validators:
    """Input validation utilities."""
    
    EMAIL_PATTERN = re.compile(
        r'^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$'
    )
    
    PASSWORD_MIN_LENGTH = 8
    PASSWORD_MAX_LENGTH = 128
    
    @staticmethod
    def validate_email(email: str) -> Tuple[bool, Optional[str]]:
        """Validate email format."""
        if not email:
            return False, "Email is required"
        
        email = email.strip().lower()
        
        if len(email) > 254:
            return False, "Email is too long"
        
        if not Validators.EMAIL_PATTERN.match(email):
            return False, "Invalid email format"
        
        return True, None
    
    @staticmethod
    def validate_password(password: str) -> Tuple[bool, Optional[str]]:
        """
        Validate password strength.
        Requirements: 8+ chars, 1 uppercase, 1 lowercase, 1 number.
        """
        if not password:
            return False, "Password is required"
        
        if len(password) < Validators.PASSWORD_MIN_LENGTH:
            return False, f"Password must be at least {Validators.PASSWORD_MIN_LENGTH} characters"
        
        if len(password) > Validators.PASSWORD_MAX_LENGTH:
            return False, "Password is too long"
        
        if not re.search(r'[A-Z]', password):
            return False, "Password must contain at least one uppercase letter"
        
        if not re.search(r'[a-z]', password):
            return False, "Password must contain at least one lowercase letter"
        
        if not re.search(r'\d', password):
            return False, "Password must contain at least one number"
        
        return True, None
    
    @staticmethod
    def validate_name(name: str) -> Tuple[bool, Optional[str]]:
        """Validate user name."""
        if not name:
            return False, "Name is required"
        
        name = name.strip()
        
        if len(name) < 2:
            return False, "Name must be at least 2 characters"
        
        if len(name) > 100:
            return False, "Name is too long"
        
        if not re.match(r"^[a-zA-Z\s\-']+$", name):
            return False, "Name contains invalid characters"
        
        return True, None
    
    @staticmethod
    def validate_otp(otp: str) -> Tuple[bool, Optional[str]]:
        """Validate OTP format."""
        if not otp:
            return False, "Verification code is required"
        
        otp = otp.strip()
        
        if len(otp) != Config.OTP_LENGTH:
            return False, f"Verification code must be {Config.OTP_LENGTH} digits"
        
        if not otp.isdigit():
            return False, "Verification code must contain only numbers"
        
        return True, None
    
    @staticmethod
    def validate_document_type(doc_type: str) -> Tuple[bool, Optional[str]]:
        """Validate document type."""
        valid_types = ['insurance', 'academic', 'id', 'financial', 'medical', 'general']
        
        if not doc_type:
            return False, "Document type is required"
        
        if doc_type.lower() not in valid_types:
            return False, f"Invalid document type. Must be one of: {', '.join(valid_types)}"
        
        return True, None
    
    @staticmethod
    def validate_file(file, max_size: int = None) -> Tuple[bool, Optional[str]]:
        """Validate uploaded file."""
        if not file or not file.filename:
            return False, "File is required"
        
        filename = file.filename.lower()
        allowed = Config.ALLOWED_EXTENSIONS
        
        if not any(filename.endswith(f'.{ext}') for ext in allowed):
            return False, f"File type not allowed. Allowed types: {', '.join(allowed)}"
        
        if max_size:
            try:
                file.seek(0, 2)
                size = file.tell()
                file.seek(0)
                
                if size > max_size:
                    max_mb = max_size / (1024 * 1024)
                    return False, f"File size exceeds {max_mb:.1f}MB limit"
            except Exception:
                pass
        
        return True, None
    
    @staticmethod
    def validate_device_id(device_id: str) -> Tuple[bool, Optional[str]]:
        """Validate device identifier."""
        if not device_id:
            return False, "Device ID is required"
        
        device_id = device_id.strip()
        
        if len(device_id) < 8:
            return False, "Device ID is too short"
        
        if len(device_id) > 256:
            return False, "Device ID is too long"
        
        return True, None
    
    @staticmethod
    def validate_fcm_token(token: str) -> Tuple[bool, Optional[str]]:
        """Validate Firebase Cloud Messaging token."""
        if not token:
            return False, "FCM token is required"
        
        token = token.strip()
        
        if len(token) < 32:
            return False, "Invalid FCM token format"
        
        if len(token) > 512:
            return False, "FCM token is too long"
        
        return True, None
    
    @staticmethod
    def sanitize_string(value: str, max_length: int = 255) -> str:
        """Sanitize a string input."""
        if not value:
            return ""
        
        value = value.strip()
        
        if len(value) > max_length:
            value = value[:max_length]
        
        return value