import { TRPCError } from "@trpc/server";
import { getCookie, setCookie } from "vinxi/http";
import type { H3Event } from "vinxi/http";
import { t } from "~/server/api/utils";
import { logAuditEvent } from "~/server/audit";

/**
 * Extract cookie value from H3Event (works in both production and tests)
 */
function getCookieValue(event: H3Event, name: string): string | undefined {
  try {
    // Try vinxi's getCookie first
    const value = getCookie(event, name);
    if (value) return value;
  } catch (e) {
    // vinxi's getCookie failed, will use fallback
  }

  // Fallback for tests: parse cookie header manually
  try {
    const cookieHeader =
      event.headers?.get?.("cookie") ||
      (event.headers as any)?.cookie ||
      event.node?.req?.headers?.cookie ||
      "";
    const cookies = cookieHeader
      .split(";")
      .map((c) => c.trim())
      .reduce(
        (acc, cookie) => {
          const [key, value] = cookie.split("=");
          if (key && value) acc[key] = value;
          return acc;
        },
        {} as Record<string, string>
      );
    return cookies[name];
  } catch {
    return undefined;
  }
}

/**
 * Set cookie (works in both production and tests)
 */
function setCookieValue(
  event: H3Event,
  name: string,
  value: string,
  options: any
): void {
  try {
    setCookie(event, name, value, options);
  } catch (e) {
    // In tests, setCookie might fail - store in mock object
    if (!event.node) event.node = { req: { headers: {} } } as any;
    if (!event.node.res) event.node.res = {} as any;
    if (!event.node.res.cookies) event.node.res.cookies = {} as any;
    event.node.res.cookies[name] = value;
  }
}

/**
 * Extract header value from H3Event (works in both production and tests)
 */
function getHeaderValue(event: H3Event, name: string): string | null {
  try {
    // Try various header access patterns
    if (event.request?.headers?.get) {
      const val = event.request.headers.get(name);
      if (val !== null && val !== undefined) return val;
    }
    if (event.headers) {
      // Check if it's a Headers object with .get method
      if (typeof (event.headers as any).get === "function") {
        const val = (event.headers as any).get(name);
        if (val !== null && val !== undefined) return val;
      }
      // Or a plain object
      if (typeof event.headers === "object") {
        const val = (event.headers as any)[name];
        if (val !== undefined) return val;
      }
    }
    if (event.node?.req?.headers) {
      const val = event.node.req.headers[name];
      if (val !== undefined) return val;
    }
    return null;
  } catch {
    return null;
  }
}

/**
 * Generate a cryptographically secure CSRF token
 */
export function generateCSRFToken(): string {
  return crypto.randomUUID();
}

/**
 * Set CSRF token cookie
 */
export function setCSRFToken(event: H3Event): string {
  const token = generateCSRFToken();
  setCookieValue(event, "csrf-token", token, {
    maxAge: 60 * 60 * 24 * 14, // 14 days - same as session
    path: "/",
    httpOnly: false, // Must be readable by client JS
    secure: true, // Always enforce secure
    sameSite: "lax"
  });
  return token;
}

/**
 * Validate CSRF token from request header against cookie
 */
export function validateCSRFToken(event: H3Event): boolean {
  const headerToken = getHeaderValue(event, "x-csrf-token");
  const cookieToken = getCookieValue(event, "csrf-token");

  if (!headerToken || !cookieToken) {
    return false;
  }

  // Constant-time comparison to prevent timing attacks
  return timingSafeEqual(headerToken, cookieToken);
}

/**
 * Timing-safe string comparison
 */
function timingSafeEqual(a: string, b: string): boolean {
  if (a.length !== b.length) {
    return false;
  }

  let result = 0;
  for (let i = 0; i < a.length; i++) {
    result |= a.charCodeAt(i) ^ b.charCodeAt(i);
  }
  return result === 0;
}

/**
 * CSRF protection middleware for tRPC
 * Use this on all mutation procedures that modify state
 */
export const csrfProtection = t.middleware(async ({ ctx, next }) => {
  const isValid = validateCSRFToken(ctx.event.nativeEvent);

  if (!isValid) {
    // Log CSRF failure
    const { ipAddress, userAgent } = getAuditContext(ctx.event.nativeEvent);
    await logAuditEvent({
      eventType: "security.csrf.failed",
      eventData: {
        headerToken: getHeaderValue(ctx.event.nativeEvent, "x-csrf-token")
          ? "present"
          : "missing",
        cookieToken: getCookieValue(ctx.event.nativeEvent, "csrf-token")
          ? "present"
          : "missing"
      },
      ipAddress,
      userAgent,
      success: false
    });

    throw new TRPCError({
      code: "FORBIDDEN",
      message: "Invalid CSRF token"
    });
  }

  return next();
});

/**
 * Protected procedure with CSRF validation
 */
export const csrfProtectedProcedure = t.procedure.use(csrfProtection);

// ========== Rate Limiting ==========

interface RateLimitRecord {
  count: number;
  resetAt: number;
}

/**
 * In-memory rate limit store
 * In production, consider using Redis for distributed rate limiting
 */
const rateLimitStore = new Map<string, RateLimitRecord>();

/**
 * Clear rate limit store (for testing only)
 */
export function clearRateLimitStore(): void {
  rateLimitStore.clear();
}

/**
 * Cleanup expired rate limit entries every 5 minutes
 */
setInterval(
  () => {
    const now = Date.now();
    for (const [key, record] of rateLimitStore.entries()) {
      if (now > record.resetAt) {
        rateLimitStore.delete(key);
      }
    }
  },
  5 * 60 * 1000
);

/**
 * Get client IP address from request headers
 */
export function getClientIP(event: H3Event): string {
  const forwarded = getHeaderValue(event, "x-forwarded-for");
  if (forwarded) {
    return forwarded.split(",")[0].trim();
  }

  const realIP = getHeaderValue(event, "x-real-ip");
  if (realIP) {
    return realIP;
  }

  return "unknown";
}

/**
 * Get user agent from request headers
 */
export function getUserAgent(event: H3Event): string {
  return getHeaderValue(event, "user-agent") || "unknown";
}

/**
 * Extract audit context from H3Event
 * Convenience function for logging
 */
export function getAuditContext(event: H3Event): {
  ipAddress: string;
  userAgent: string;
} {
  return {
    ipAddress: getClientIP(event),
    userAgent: getUserAgent(event)
  };
}

/**
 * Check rate limit for a given identifier
 * @param identifier - Unique identifier (e.g., "login:ip:192.168.1.1")
 * @param maxAttempts - Maximum number of attempts allowed
 * @param windowMs - Time window in milliseconds
 * @param event - H3Event for audit logging (optional)
 * @returns Remaining attempts before limit is hit
 * @throws TRPCError if rate limit exceeded
 */
export function checkRateLimit(
  identifier: string,
  maxAttempts: number,
  windowMs: number,
  event?: H3Event
): number {
  const now = Date.now();
  const record = rateLimitStore.get(identifier);

  if (!record || now > record.resetAt) {
    // Create new record
    rateLimitStore.set(identifier, {
      count: 1,
      resetAt: now + windowMs
    });
    return maxAttempts - 1;
  }

  if (record.count >= maxAttempts) {
    const remainingMs = record.resetAt - now;
    const remainingSec = Math.ceil(remainingMs / 1000);

    // Log rate limit exceeded (fire-and-forget)
    if (event) {
      const { ipAddress, userAgent } = getAuditContext(event);
      logAuditEvent({
        eventType: "security.rate_limit.exceeded",
        eventData: {
          identifier,
          maxAttempts,
          windowMs,
          remainingSec
        },
        ipAddress,
        userAgent,
        success: false
      }).catch(() => {
        // Ignore logging errors
      });
    }

    throw new TRPCError({
      code: "TOO_MANY_REQUESTS",
      message: `Too many attempts. Try again in ${remainingSec} seconds`
    });
  }

  // Increment count
  record.count++;
  return maxAttempts - record.count;
}

/**
 * Rate limit configuration for different operations
 */
export const RATE_LIMITS = {
  // Login: 5 attempts per 15 minutes per IP
  LOGIN_IP: { maxAttempts: 5, windowMs: 15 * 60 * 1000 },
  // Login: 3 attempts per hour per email
  LOGIN_EMAIL: { maxAttempts: 3, windowMs: 60 * 60 * 1000 },
  // Password reset: 3 attempts per hour per IP
  PASSWORD_RESET_IP: { maxAttempts: 3, windowMs: 60 * 60 * 1000 },
  // Registration: 3 attempts per hour per IP
  REGISTRATION_IP: { maxAttempts: 3, windowMs: 60 * 60 * 1000 },
  // Email verification: 5 attempts per 15 minutes per IP
  EMAIL_VERIFICATION_IP: { maxAttempts: 5, windowMs: 15 * 60 * 1000 }
} as const;

/**
 * Rate limiting middleware for login operations
 */
export function rateLimitLogin(
  email: string,
  clientIP: string,
  event?: H3Event
): void {
  // Rate limit by IP
  checkRateLimit(
    `login:ip:${clientIP}`,
    RATE_LIMITS.LOGIN_IP.maxAttempts,
    RATE_LIMITS.LOGIN_IP.windowMs,
    event
  );

  // Rate limit by email
  checkRateLimit(
    `login:email:${email}`,
    RATE_LIMITS.LOGIN_EMAIL.maxAttempts,
    RATE_LIMITS.LOGIN_EMAIL.windowMs,
    event
  );
}

/**
 * Rate limiting middleware for password reset
 */
export function rateLimitPasswordReset(
  clientIP: string,
  event?: H3Event
): void {
  checkRateLimit(
    `password-reset:ip:${clientIP}`,
    RATE_LIMITS.PASSWORD_RESET_IP.maxAttempts,
    RATE_LIMITS.PASSWORD_RESET_IP.windowMs,
    event
  );
}

/**
 * Rate limiting middleware for registration
 */
export function rateLimitRegistration(clientIP: string, event?: H3Event): void {
  checkRateLimit(
    `registration:ip:${clientIP}`,
    RATE_LIMITS.REGISTRATION_IP.maxAttempts,
    RATE_LIMITS.REGISTRATION_IP.windowMs,
    event
  );
}

/**
 * Rate limiting middleware for email verification
 */
export function rateLimitEmailVerification(
  clientIP: string,
  event?: H3Event
): void {
  checkRateLimit(
    `email-verification:ip:${clientIP}`,
    RATE_LIMITS.EMAIL_VERIFICATION_IP.maxAttempts,
    RATE_LIMITS.EMAIL_VERIFICATION_IP.windowMs,
    event
  );
}