/**
 * API service layer for backend communication.
 * Provides functions for all API endpoints with error handling.
 * Includes JWT token management and automatic token refresh.
 * 
 * Requirements: 10.1, 10.3, 2.1, 3.1, 4.1, 4.4
 */
import axios, { AxiosInstance, AxiosError, InternalAxiosRequestConfig } from 'axios';
import type { Project } from '../atoms/project-atoms';
import type { Task } from '../atoms/task-atoms';
import type { Annotation } from '../atoms/annotation-atoms';
import { toast } from './toast';

/**
 * API base URL - defaults to localhost:8002 for development
 */
const API_BASE_URL = process.env.NX_API_BASE_URL || 'http://localhost:8002';

/**
 * Axios instance with default configuration
 */
const apiClient: AxiosInstance = axios.create({
  baseURL: API_BASE_URL,
  timeout: 30000,
  headers: {
    'Content-Type': 'application/json',
  },
});

/**
 * Flag to prevent multiple simultaneous token refresh requests
 */
let isRefreshing = false;

/**
 * Queue of failed requests waiting for token refresh
 */
let failedQueue: Array<{
  resolve: (value?: any) => void;
  reject: (error?: any) => void;
}> = [];

/**
 * Process queued requests after token refresh
 */
const processQueue = (error: any = null) => {
  failedQueue.forEach((promise) => {
    if (error) {
      promise.reject(error);
    } else {
      promise.resolve();
    }
  });
  failedQueue = [];
};

/**
 * Get stored authentication tokens from localStorage
 */
const getStoredTokens = () => {
  try {
    const tokensStr = localStorage.getItem('auth_tokens');
    return tokensStr ? JSON.parse(tokensStr) : null;
  } catch {
    return null;
  }
};

/**
 * Update stored authentication tokens in localStorage
 */
const updateStoredTokens = (tokens: any) => {
  localStorage.setItem('auth_tokens', JSON.stringify(tokens));
};

/**
 * Clear stored authentication data
 */
const clearStoredAuth = () => {
  localStorage.removeItem('auth_tokens');
  localStorage.removeItem('current_user');
};

/**
 * Request interceptor to automatically attach JWT token
 */
apiClient.interceptors.request.use(
  (config: InternalAxiosRequestConfig) => {
    // Skip token attachment for auth endpoints
    if (
      config.url?.includes('/api/auth/register') ||
      config.url?.includes('/api/auth/login') ||
      config.url?.includes('/api/auth/refresh')
    ) {
      return config;
    }

    // Get tokens from localStorage
    const tokens = getStoredTokens();

    // Attach access token to Authorization header
    if (tokens?.access_token) {
      config.headers.Authorization = `Bearer ${tokens.access_token}`;
    }

    return config;
  },
  (error) => {
    return Promise.reject(error);
  }
);

/**
 * Response interceptor for error handling and automatic token refresh
 */
apiClient.interceptors.response.use(
  (response) => response,
  async (error: AxiosError) => {
    const originalRequest = error.config as InternalAxiosRequestConfig & {
      _retry?: boolean;
    };

    // Handle network errors (CORS, connection refused, etc.)
    if (!error.response) {
      console.error('Network Error:', error.message);
      
      // Check if it's a CORS error or connection error
      if (error.message === 'Network Error' || error.code === 'ERR_NETWORK') {
        // Check if user has auth tokens - if yes, might be a CORS issue with expired token
        const tokens = getStoredTokens();
        if (tokens) {
          // Clear auth data and redirect to login
          clearStoredAuth();
          toast.error('网络连接失败或登录已过期，请重新登录', '连接错误', 2000);
          
          setTimeout(() => {
            window.location.href = '/login';
          }, 500);
        } else {
          toast.error('无法连接到服务器，请检查网络连接', '网络错误');
        }
      }
      
      return Promise.reject({
        status: 0,
        message: error.message || '网络错误',
        originalError: error,
      });
    }

    // Handle 401 Unauthorized errors (token expired or invalid)
    if (error.response?.status === 401) {
      const errorData = error.response.data as any;

      // If not a retry and error is due to token expiration, try to refresh
      if (!originalRequest._retry && errorData?.error_type === 'token_expired') {
        // Prevent infinite retry loop
        originalRequest._retry = true;

        // If already refreshing, queue this request
        if (isRefreshing) {
          return new Promise((resolve, reject) => {
            failedQueue.push({ resolve, reject });
          })
            .then(() => {
              // Retry original request with new token
              return apiClient(originalRequest);
            })
            .catch((err) => {
              return Promise.reject(err);
            });
        }

        // Start token refresh process
        isRefreshing = true;

        try {
          const tokens = getStoredTokens();

          if (!tokens?.refresh_token) {
            throw new Error('No refresh token available');
          }

          // Call refresh token endpoint
          const response = await axios.post(
            `${API_BASE_URL}/api/auth/refresh`,
            {
              refresh_token: tokens.refresh_token,
            }
          );

          const newTokens = {
            access_token: response.data.access_token,
            refresh_token: response.data.refresh_token,
            token_type: response.data.token_type,
          };

          // Update stored tokens
          updateStoredTokens(newTokens);

          // Update user info if provided
          if (response.data.user) {
            localStorage.setItem(
              'current_user',
              JSON.stringify(response.data.user)
            );
          }

          // Process queued requests
          processQueue();

          // Retry original request with new token
          originalRequest.headers.Authorization = `Bearer ${newTokens.access_token}`;
          return apiClient(originalRequest);
        } catch (refreshError) {
          // Token refresh failed - clear auth data and redirect to login
          processQueue(refreshError);
          clearStoredAuth();

          // Show error message and wait a bit before redirecting
          toast.error('登录已过期，请重新登录', '认证失败', 2000);

          // Redirect to login page after a short delay to allow toast to show
          setTimeout(() => {
            window.location.href = '/login';
          }, 500);

          return Promise.reject(refreshError);
        } finally {
          isRefreshing = false;
        }
      } else {
        // 401 error but not token expiration (invalid credentials, etc.)
        // OR token refresh already attempted but still failed
        // Clear auth data and redirect to login
        clearStoredAuth();
        
        // Show error message and wait a bit before redirecting
        toast.error('认证失败，请重新登录', '认证失败', 2000);
        
        // Redirect to login page after a short delay to allow toast to show
        setTimeout(() => {
          window.location.href = '/login';
        }, 500);
        
        return Promise.reject(error);
      }
    }

    // Extract error message from response
    let errorMessage = '发生了意外错误';

    if (error.response?.data) {
      const data = error.response.data as any;

      // Handle FastAPI validation errors (array of error objects)
      if (Array.isArray(data.detail)) {
        // Format validation errors into readable message
        errorMessage = data.detail
          .map((err: any) => {
            const field = err.loc?.join('.') || '字段';
            return `${field}: ${err.msg}`;
          })
          .join('; ');
      }
      // Handle simple string error message
      else if (typeof data.detail === 'string') {
        errorMessage = data.detail;
      }
      // Handle object error message
      else if (typeof data.detail === 'object' && data.detail !== null) {
        errorMessage = JSON.stringify(data.detail);
      }
      // Fallback to error message
      else if (data.message) {
        errorMessage = data.message;
      }
    } else if (error.message) {
      errorMessage = error.message;
    }

    // Log error for debugging
    console.error('API Error:', {
      url: error.config?.url,
      method: error.config?.method,
      status: error.response?.status,
      message: errorMessage,
      originalData: error.response?.data,
    });

    // Show error toast (skip for 401 errors as they're handled above with their own messages)
    if (error.response?.status !== 401) {
      // Determine toast type based on status code
      if (error.response?.status === 403) {
        toast.warning(errorMessage, '权限不足');
      } else if (error.response?.status === 404) {
        toast.warning(errorMessage, '资源不存在');
      } else if (error.response?.status && error.response.status >= 500) {
        toast.error(errorMessage, '服务器错误');
      } else {
        toast.error(errorMessage, '请求失败');
      }
    }

    // Return a rejected promise with formatted error
    return Promise.reject({
      status: error.response?.status,
      message: errorMessage,
      originalError: error,
    });
  }
);

// ============================================================================
// Project API Functions
// ============================================================================

/**
 * Project creation data
 */
export interface ProjectCreateData {
  name: string;
  description: string;
  config: string;
}

/**
 * Project update data
 */
export interface ProjectUpdateData {
  name?: string;
  description?: string;
  config?: string;
}

/**
 * List all projects
 */
export async function listProjects(): Promise<Project[]> {
  const response = await apiClient.get<Project[]>('/api/projects');
  return response.data;
}

/**
 * Create a new project
 */
export async function createProject(
  data: ProjectCreateData
): Promise<Project> {
  const response = await apiClient.post<Project>('/api/projects', data);
  return response.data;
}

/**
 * Get project by ID
 */
export async function getProject(projectId: string): Promise<Project> {
  const response = await apiClient.get<Project>(`/api/projects/${projectId}`);
  return response.data;
}

/**
 * Update project
 */
export async function updateProject(
  projectId: string,
  data: ProjectUpdateData
): Promise<Project> {
  const response = await apiClient.put<Project>(
    `/api/projects/${projectId}`,
    data
  );
  return response.data;
}

/**
 * Delete project
 */
export async function deleteProject(projectId: string): Promise<void> {
  await apiClient.delete(`/api/projects/${projectId}`);
}

/**
 * Get tasks for a specific project
 */
export async function getProjectTasks(projectId: string): Promise<Task[]> {
  return listTasks({ project_id: projectId });
}

// ============================================================================
// Task API Functions
// ============================================================================

/**
 * Task creation data
 */
export interface TaskCreateData {
  project_id: string;
  name: string;
  data: Record<string, any>;
  assigned_to?: string | null;
}

/**
 * Task update data
 */
export interface TaskUpdateData {
  name?: string;
  data?: Record<string, any>;
  status?: 'pending' | 'in_progress' | 'completed';
  assigned_to?: string | null;
}

/**
 * Task list filters
 */
export interface TaskListFilters {
  project_id?: string;
  status?: string;
  assigned_to?: string;
}

/**
 * List all tasks with optional filters
 */
export async function listTasks(filters?: TaskListFilters): Promise<Task[]> {
  const params = new URLSearchParams();
  if (filters?.project_id) params.append('project_id', filters.project_id);
  if (filters?.status) params.append('status', filters.status);
  if (filters?.assigned_to) params.append('assigned_to', filters.assigned_to);

  const response = await apiClient.get<Task[]>('/api/tasks', { params });
  return response.data;
}

/**
 * Create a new task
 */
export async function createTask(data: TaskCreateData): Promise<Task> {
  const response = await apiClient.post<Task>('/api/tasks', data);
  return response.data;
}

/**
 * Get task by ID
 */
export async function getTask(taskId: string): Promise<Task> {
  const response = await apiClient.get<Task>(`/api/tasks/${taskId}`);
  return response.data;
}

/**
 * Update task
 */
export async function updateTask(
  taskId: string,
  data: TaskUpdateData
): Promise<Task> {
  const response = await apiClient.put<Task>(`/api/tasks/${taskId}`, data);
  return response.data;
}

/**
 * Delete task
 */
export async function deleteTask(taskId: string): Promise<void> {
  await apiClient.delete(`/api/tasks/${taskId}`);
}

// ============================================================================
// Annotation API Functions
// ============================================================================

/**
 * Annotation creation data
 */
export interface AnnotationCreateData {
  task_id: string;
  user_id: string;
  result: Record<string, any>;
}

/**
 * Annotation update data
 */
export interface AnnotationUpdateData {
  result: Record<string, any>;
}

/**
 * Annotation list filters
 */
export interface AnnotationListFilters {
  task_id?: string;
  user_id?: string;
}

/**
 * List all annotations with optional filters
 */
export async function listAnnotations(
  filters?: AnnotationListFilters
): Promise<Annotation[]> {
  const params = new URLSearchParams();
  if (filters?.task_id) params.append('task_id', filters.task_id);
  if (filters?.user_id) params.append('user_id', filters.user_id);

  const response = await apiClient.get<Annotation[]>('/api/annotations', {
    params,
  });
  return response.data;
}

/**
 * Create a new annotation
 */
export async function createAnnotation(
  data: AnnotationCreateData
): Promise<Annotation> {
  const response = await apiClient.post<Annotation>('/api/annotations', data);
  return response.data;
}

/**
 * Get annotation by ID
 */
export async function getAnnotation(annotationId: string): Promise<Annotation> {
  const response = await apiClient.get<Annotation>(
    `/api/annotations/${annotationId}`
  );
  return response.data;
}

/**
 * Update annotation
 */
export async function updateAnnotation(
  annotationId: string,
  data: AnnotationUpdateData
): Promise<Annotation> {
  const response = await apiClient.put<Annotation>(
    `/api/annotations/${annotationId}`,
    data
  );
  return response.data;
}

/**
 * Get annotations by task ID
 */
export async function getTaskAnnotations(taskId: string): Promise<Annotation[]> {
  const response = await apiClient.get<Annotation[]>(
    `/api/annotations/tasks/${taskId}/annotations`
  );
  return response.data;
}

/**
 * Export the configured axios instance for advanced usage
 */
export { apiClient };