// ============================================================================
// API Client
// ============================================================================

import { API_URL, STORAGE_KEYS } from "@/lib/utils/constants";
import type { ApiError } from "@/lib/types/api";

// ============================================================================
// Types
// ============================================================================

interface RequestOptions extends RequestInit {
  params?: Record<string, any>;
  requireAuth?: boolean;
}

// ============================================================================
// Helper Functions
// ============================================================================

/**
 * Build URL with query parameters
 */
const buildUrl = (endpoint: string, params?: Record<string, any>): string => {
  if (!params || Object.keys(params).length === 0) {
    return endpoint;
  }

  const searchParams = new URLSearchParams();
  Object.entries(params).forEach(([key, value]) => {
    if (value !== undefined && value !== null) {
      if (Array.isArray(value)) {
        value.forEach((v) => searchParams.append(key, String(v)));
      } else {
        searchParams.append(key, String(value));
      }
    }
  });

  const queryString = searchParams.toString();
  return queryString ? `${endpoint}?${queryString}` : endpoint;
};

/**
 * Get auth token from storage
 */
const getAuthToken = (): string | null => {
  if (typeof window === "undefined") return null;
  return localStorage.getItem(STORAGE_KEYS.ACCESS_TOKEN);
};

/**
 * Clear auth tokens from storage
 */
export const clearAuthTokens = (): void => {
  if (typeof window === "undefined") return;
  localStorage.removeItem(STORAGE_KEYS.ACCESS_TOKEN);
  localStorage.removeItem(STORAGE_KEYS.REFRESH_TOKEN);
  localStorage.removeItem(STORAGE_KEYS.USER);
};

/**
 * Save auth tokens to storage
 */
export const saveAuthTokens = (
  accessToken: string,
  refreshToken?: string
): void => {
  if (typeof window === "undefined") return;
  localStorage.setItem(STORAGE_KEYS.ACCESS_TOKEN, accessToken);
  if (refreshToken) {
    localStorage.setItem(STORAGE_KEYS.REFRESH_TOKEN, refreshToken);
  }
};

// ============================================================================
// API Client
// ============================================================================

/**
 * Main API request function
 */
export const apiRequest = async <T = any>(
  endpoint: string,
  options: RequestOptions = {}
): Promise<T> => {
  const { params, requireAuth = true, ...fetchOptions } = options;
  const body = fetchOptions.body;

  // Build URL
  const url = buildUrl(`${API_URL}${endpoint}`, params);

  const headers: HeadersInit = {
    ...fetchOptions.headers,
  };

  // Don't set Content-Type for FormData - browser will set it with boundary
  if (!(body instanceof FormData)) {
    (headers as Record<string, string>)["Content-Type"] = "application/json";
  }

  // Add auth token if required
  if (requireAuth) {
    const token = getAuthToken();
    if (token) {
      (headers as Record<string, string>)["Authorization"] = `Bearer ${token}`;
    }
  }

  try {
    // Serialize body to JSON if it's an object (not FormData or string)
    let serializedBody = body;
    if (body && typeof body === 'object' && !(body instanceof FormData) && !(body instanceof String)) {
      serializedBody = JSON.stringify(body);
    }

    const response = await fetch(url, {
      ...fetchOptions,
      headers,
      body: serializedBody,
    });

    // Handle 204 No Content
    if (response.status === 204) {
      return undefined as T;
    }

    // Parse response
    const data = await response.json();

    // Handle errors
    if (!response.ok) {
      // FastAPI returns errors in format { "detail": "..." }
      const error: ApiError = {
        detail: data.detail || "An error occurred",
      };
      throw error;
    }

    return data as T;
  } catch (error: any) {
    // Network error or parsing error
    if (!error.detail) {
      throw {
        detail: error.message || "Network error occurred",
      } as ApiError;
    }
    throw error;
  }
};

// ============================================================================
// Convenience Methods
// ============================================================================

export const api = {
  get: <T = any>(endpoint: string, options?: RequestOptions) =>
    apiRequest<T>(endpoint, { ...options, method: "GET" }),

  post: <T = any>(endpoint: string, body?: any, options?: RequestOptions) =>
    apiRequest<T>(endpoint, {
      ...options,
      method: "POST",
      body,
    }),

  put: <T = any>(endpoint: string, body?: any, options?: RequestOptions) =>
    apiRequest<T>(endpoint, {
      ...options,
      method: "PUT",
      body,
    }),

  patch: <T = any>(endpoint: string, body?: any, options?: RequestOptions) =>
    apiRequest<T>(endpoint, {
      ...options,
      method: "PATCH",
      body,
    }),

  delete: <T = any>(endpoint: string, options?: RequestOptions) =>
    apiRequest<T>(endpoint, { ...options, method: "DELETE" }),
};