"""Security headers and CORS middleware.

Implements security hardening:
- HSTS (HTTP Strict Transport Security)
- CSP (Content Security Policy)
- X-Frame-Options
- CORS strict configuration
- Additional security headers
"""

from typing import Optional
from fastapi import Request, Response
from fastapi.middleware.cors import CORSMiddleware
from starlette.middleware.base import BaseHTTPMiddleware

from src.core.config import settings


# Security headers configuration
SECURITY_HEADERS = {
    # HTTP Strict Transport Security
    "Strict-Transport-Security": "max-age=31536000; includeSubDomains; preload",
    # Content Security Policy
    "Content-Security-Policy": (
        "default-src 'self'; "
        "script-src 'self' 'unsafe-inline' 'unsafe-eval'; "
        "style-src 'self' 'unsafe-inline'; "
        "img-src 'self' data: https:; "
        "font-src 'self' data:; "
        "connect-src 'self' https:; "
        "frame-ancestors 'none'; "
        "base-uri 'self'; "
        "form-action 'self';"
    ),
    # X-Frame-Options
    "X-Frame-Options": "DENY",
    # X-Content-Type-Options
    "X-Content-Type-Options": "nosniff",
    # Referrer Policy
    "Referrer-Policy": "strict-origin-when-cross-origin",
    # Permissions Policy
    "Permissions-Policy": (
        "accelerometer=(), "
        "camera=(), "
        "geolocation=(), "
        "gyroscope=(), "
        "magnetometer=(), "
        "microphone=(), "
        "payment=(), "
        "usb=()"
    ),
    # X-XSS-Protection (legacy browsers)
    "X-XSS-Protection": "1; mode=block",
    # Cache control for sensitive data
    "Cache-Control": "no-store, max-age=0",
}


class SecurityHeadersMiddleware(BaseHTTPMiddleware):
    """Middleware to add security headers to all responses."""

    async def dispatch(self, request: Request, call_next):
        response = await call_next(request)

        # Add security headers
        for header, value in SECURITY_HEADERS.items():
            response.headers[header] = value

        return response


class CORSSecurityMiddleware:
    """CORS middleware with strict security configuration."""

    @staticmethod
    def get_middleware():
        """Get CORS middleware with strict configuration."""

        # Get allowed origins from settings
        allowed_origins = getattr(
            settings,
            "cors_allowed_origins",
            ["http://localhost:3000", "http://localhost:5173"],
        )

        # In production, enforce strict origin checking
        if not getattr(settings, "debug", False):
            allowed_origins = getattr(
                settings,
                "cors_allowed_origins_production",
                allowed_origins,
            )

        return CORSMiddleware(
            allow_origins=allowed_origins,
            allow_credentials=True,
            allow_methods=["GET", "POST", "PUT", "DELETE", "PATCH", "OPTIONS"],
            allow_headers=[
                "Authorization",
                "Content-Type",
                "X-Request-ID",
                "X-Correlation-ID",
                "X-API-Key",
                "X-Scenario-ID",
            ],
            expose_headers=[
                "X-Request-ID",
                "X-Correlation-ID",
                "X-RateLimit-Limit",
                "X-RateLimit-Remaining",
                "X-RateLimit-Reset",
            ],
            max_age=600,  # 10 minutes
        )


# Content Security Policy for different contexts
CSP_POLICIES = {
    "default": SECURITY_HEADERS["Content-Security-Policy"],
    "api": ("default-src 'none'; frame-ancestors 'none'; base-uri 'none';"),
    "reports": (
        "default-src 'self'; "
        "script-src 'self'; "
        "style-src 'self' 'unsafe-inline'; "
        "img-src 'self' data:; "
        "frame-ancestors 'none';"
    ),
}


def get_csp_header(context: str = "default") -> str:
    """Get Content Security Policy for specific context.

    Args:
        context: Context type (default, api, reports)

    Returns:
        CSP header value
    """
    return CSP_POLICIES.get(context, CSP_POLICIES["default"])


class SecurityContextMiddleware(BaseHTTPMiddleware):
    """Middleware to add context-aware security headers."""

    async def dispatch(self, request: Request, call_next):
        response = await call_next(request)

        # Determine context based on path
        path = request.url.path

        if path.startswith("/api/"):
            context = "api"
        elif path.startswith("/reports/"):
            context = "reports"
        else:
            context = "default"

        # Set context-specific CSP
        response.headers["Content-Security-Policy"] = get_csp_header(context)

        return response


# Input validation security


class InputValidator:
    """Input validation helpers for security."""

    # Maximum allowed sizes
    MAX_STRING_LENGTH = 10000
    MAX_JSON_SIZE = 1024 * 1024  # 1MB
    MAX_QUERY_PARAMS = 50
    MAX_HEADER_SIZE = 8192  # 8KB

    @classmethod
    def validate_string(
        cls, value: str, field_name: str, max_length: Optional[int] = None
    ) -> str:
        """Validate string input.

        Args:
            value: String value to validate
            field_name: Name of the field for error messages
            max_length: Maximum allowed length

        Returns:
            Validated string

        Raises:
            ValueError: If validation fails
        """
        max_len = max_length or cls.MAX_STRING_LENGTH

        if not isinstance(value, str):
            raise ValueError(f"{field_name} must be a string")

        if len(value) > max_len:
            raise ValueError(f"{field_name} exceeds maximum length of {max_len}")

        # Check for potential XSS
        if cls._contains_xss_patterns(value):
            raise ValueError(f"{field_name} contains invalid characters")

        return value

    @classmethod
    def _contains_xss_patterns(cls, value: str) -> bool:
        """Check if string contains potential XSS patterns."""
        xss_patterns = [
            "<script",
            "javascript:",
            "onerror=",
            "onload=",
            "onclick=",
            "eval(",
            "document.cookie",
        ]

        value_lower = value.lower()
        return any(pattern in value_lower for pattern in xss_patterns)

    @classmethod
    def sanitize_html(cls, value: str) -> str:
        """Sanitize HTML content to prevent XSS.

        Args:
            value: HTML string to sanitize

        Returns:
            Sanitized string
        """
        import html

        # Escape HTML entities
        sanitized = html.escape(value)

        return sanitized


def setup_security_middleware(app):
    """Setup all security middleware for FastAPI app.

    Args:
        app: FastAPI application instance
    """
    # Note: CORS middleware is configured in main.py
    # Add security headers middleware
    app.add_middleware(SecurityHeadersMiddleware)

    # Add context-aware security middleware
    app.add_middleware(SecurityContextMiddleware)