import { API_ENDPOINTS } from "@/lib/api_urls";
import type {
  RegisterInput,
  VerifyOtpInput,
  LoginInput,
  ResendOtpInput,
  ForgotPasswordInput,
  VerifyPasswordResetOtpInput,
  ResetPasswordInput,
  TokenRefreshInput,
} from "@/lib/schema/auth";
import type { AuthResponse, ApiError, AuthTokens, User } from "@/lib/models/auth";

// Helper function to extract error message from API response
function extractErrorMessage(error: ApiError): string {
  // Check for main error messages
  if (error.detail) {
    // Handle both string and array formats
    if (Array.isArray(error.detail)) {
      return error.detail.join(", ");
    }
    return String(error.detail);
  }
  
  if (error.message) {
    if (Array.isArray(error.message)) {
      return error.message.join(", ");
    }
    return String(error.message);
  }
  
  if (error.error) {
    if (Array.isArray(error.error)) {
      return error.error.join(", ");
    }
    return String(error.error);
  }

  // Check for field-specific errors (common in Django REST Framework)
  const fieldErrors: string[] = [];
  Object.keys(error).forEach((key) => {
    if (key !== "detail" && key !== "message" && key !== "error") {
      const fieldError = error[key];
      if (Array.isArray(fieldError)) {
        fieldErrors.push(`${key}: ${fieldError.join(", ")}`);
      } else if (typeof fieldError === "string") {
        fieldErrors.push(`${key}: ${fieldError}`);
      }
    }
  });

  if (fieldErrors.length > 0) {
    return fieldErrors.join(". ");
  }

  return "An error occurred";
}

// Helper function to handle API responses
async function handleResponse<T>(response: Response): Promise<T> {
  let data: any;
  
  try {
    data = await response.json();
  } catch {
    // If response is not JSON, use status text
    throw new Error(response.statusText || "An error occurred");
  }

  if (!response.ok) {
    const error: ApiError = data;
    const errorMessage = extractErrorMessage(error);
    throw new Error(errorMessage);
  }

  return data as T;
}

// Helper function to normalize auth response
function normalizeAuthResponse(data: AuthResponse): AuthResponse {
  // Normalize tokens: if tokens are at root level, move them to tokens object
  if (data.access && data.refresh && !data.tokens) {
    data.tokens = {
      access: data.access,
      refresh: data.refresh,
    };
  }
  
  // Normalize user: only map isVerified to is_verified if needed
  if (data.user) {
    const user = data.user as any;
    if (user.isVerified !== undefined && user.is_verified === undefined) {
      user.is_verified = user.isVerified;
    }
    data.user = user;
  }
  
  return data;
}

// Register a new user
export async function registerUser(input: RegisterInput): Promise<AuthResponse> {
  const response = await fetch(API_ENDPOINTS.auth.register, {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
    },
    body: JSON.stringify(input),
  });

  // Handle response - check if it's a 500 error that might indicate OTP sending failure
  // but user registration might have succeeded
  if (!response.ok && response.status === 500) {
    try {
      const data = await response.json();
      // If the error message mentions OTP or email sending, it might be a partial success
      const errorMessage = extractErrorMessage(data);
      if (errorMessage.toLowerCase().includes("otp") || 
          errorMessage.toLowerCase().includes("email") ||
          errorMessage.toLowerCase().includes("send") ||
          errorMessage.toLowerCase().includes("ssl") ||
          errorMessage.toLowerCase().includes("certificate")) {
        // Return a partial success response - user might be created, allow OTP resend
        // This allows the user to proceed to OTP verification and use resend OTP
        return {
          message: "User registered, but OTP email could not be sent. Please use resend OTP.",
        } as AuthResponse;
      }
    } catch {
      // If we can't parse the error, continue to normal error handling
    }
  }

  return handleResponse<AuthResponse>(response);
}

// Verify OTP
export async function verifyOtp(input: VerifyOtpInput): Promise<AuthResponse> {
  const response = await fetch(API_ENDPOINTS.auth.verifyOtp, {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
    },
    body: JSON.stringify(input),
  });

  const data = await handleResponse<AuthResponse>(response);
  return normalizeAuthResponse(data);
}

// Login user
export async function loginUser(input: LoginInput): Promise<AuthResponse> {
  const response = await fetch(API_ENDPOINTS.auth.login, {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
    },
    body: JSON.stringify(input),
  });

  const data = await handleResponse<AuthResponse>(response);
  return normalizeAuthResponse(data);
}

// Resend OTP
export async function resendOtp(input: ResendOtpInput): Promise<AuthResponse> {
  const response = await fetch(API_ENDPOINTS.auth.resendOtp, {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
    },
    body: JSON.stringify(input),
  });

  return handleResponse<AuthResponse>(response);
}

// Forgot password
export async function forgotPassword(input: ForgotPasswordInput): Promise<AuthResponse> {
  const response = await fetch(API_ENDPOINTS.auth.forgotPassword, {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
    },
    body: JSON.stringify(input),
  });

  return handleResponse<AuthResponse>(response);
}

// Verify password reset OTP
export async function verifyPasswordResetOtp(
  input: VerifyPasswordResetOtpInput
): Promise<AuthResponse> {
  const response = await fetch(API_ENDPOINTS.auth.verifyPasswordResetOtp, {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
    },
    body: JSON.stringify(input),
  });

  return handleResponse<AuthResponse>(response);
}

// Reset password
export async function resetPassword(input: ResetPasswordInput): Promise<AuthResponse> {
  const response = await fetch(API_ENDPOINTS.auth.resetPassword, {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
    },
    body: JSON.stringify(input),
  });

  return handleResponse<AuthResponse>(response);
}

// Refresh access token
export async function refreshToken(input: TokenRefreshInput): Promise<AuthTokens> {
  const response = await fetch(API_ENDPOINTS.auth.tokenRefresh, {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
    },
    body: JSON.stringify(input),
  });

  return handleResponse<AuthTokens>(response);
}

// Decode JWT token to check expiration
function decodeJWT(token: string): { exp?: number; [key: string]: any } | null {
  try {
    const parts = token.split(".");
    if (parts.length !== 3) return null;
    
    const payload = parts[1];
    const decoded = JSON.parse(atob(payload.replace(/-/g, "+").replace(/_/g, "/")));
    return decoded;
  } catch (error) {
    return null;
  }
}

// Check if token is expired
export function isTokenExpired(token: string | null): boolean {
  if (!token) return true;
  
  const decoded = decodeJWT(token);
  if (!decoded || !decoded.exp) return true;
  
  // exp is in seconds, Date.now() is in milliseconds
  const expirationTime = decoded.exp * 1000;
  const currentTime = Date.now();
  
  // Consider token expired if it expires within the next 5 seconds (buffer)
  return currentTime >= (expirationTime - 5000);
}

// Get stored tokens
export function getStoredTokens(): { access: string | null; refresh: string | null } {
  if (typeof window === "undefined") {
    return { access: null, refresh: null };
  }

  return {
    access: localStorage.getItem("auth_access_token"),
    refresh: localStorage.getItem("auth_refresh_token"),
  };
}

// Check if user has valid authentication
export function hasValidAuth(): boolean {
  const tokens = getStoredTokens();
  if (!tokens.access) return false;
  
  return !isTokenExpired(tokens.access);
}

// Store tokens
export function storeTokens(tokens: AuthTokens): void {
  if (typeof window === "undefined") return;

  localStorage.setItem("auth_access_token", tokens.access);
  localStorage.setItem("auth_refresh_token", tokens.refresh);

  // Also set cookies for middleware
  document.cookie = `auth_access_token=${tokens.access}; path=/; max-age=${7 * 24 * 60 * 60}; SameSite=Lax`;
  document.cookie = `auth_refresh_token=${tokens.refresh}; path=/; max-age=${30 * 24 * 60 * 60}; SameSite=Lax`;
}

// Store user
export function storeUser(user: User): void {
  if (typeof window === "undefined") return;

  localStorage.setItem("auth_user", JSON.stringify(user));
  document.cookie = `auth_user=${encodeURIComponent(JSON.stringify(user))}; path=/; max-age=${7 * 24 * 60 * 60}; SameSite=Lax`;
}

// Get stored user
export function getStoredUser(): User | null {
  if (typeof window === "undefined") return null;

  const userStr = localStorage.getItem("auth_user");
  if (!userStr) return null;

  try {
    return JSON.parse(userStr) as User;
  } catch {
    return null;
  }
}

// Clear auth data
export function clearAuthData(): void {
  if (typeof window === "undefined") return;

  localStorage.removeItem("auth_access_token");
  localStorage.removeItem("auth_refresh_token");
  localStorage.removeItem("auth_user");

  // Also clear cookies
  document.cookie = "auth_access_token=; path=/; max-age=0";
  document.cookie = "auth_refresh_token=; path=/; max-age=0";
  document.cookie = "auth_user=; path=/; max-age=0";
}

// Get auth header for API requests
export function getAuthHeader(): { Authorization: string } | {} {
  const tokens = getStoredTokens();
  if (tokens.access && !isTokenExpired(tokens.access)) {
    return { Authorization: `Bearer ${tokens.access}` };
  }
  return {};
}

// Get all users (Admin only)
export async function getAllUsers(): Promise<User[]> {
  const tokens = getStoredTokens();
  
  if (!tokens.access) {
    throw new Error("Authentication required.");
  }

  const response = await fetch(API_ENDPOINTS.auth.allUsers, {
    method: "GET",
    headers: {
      "Content-Type": "application/json",
      Authorization: `Bearer ${tokens.access}`,
    },
  });

  const data = await response.json();

  if (!response.ok) {
    const errorMessage = extractErrorMessage(data);
    throw new Error(errorMessage);
  }

  // Handle different response formats
  if (data.users) {
    return data.users;
  }
  if (Array.isArray(data)) {
    return data;
  }
  
  return [];
}