import { API_BASE_URL } from '../utils/constants';

interface ApiResponse<T = any> {
  data: T;
  status: number;
}

class ApiClient {
  private baseURL: string;

  constructor(baseURL: string) {
    this.baseURL = baseURL;
  }

  private getAuthHeaders(): Record<string, string> {
    const rawApiKey = localStorage.getItem('kb_api_key');
    const rawToken = localStorage.getItem('authToken') || localStorage.getItem('token');
    const activeTenantId = localStorage.getItem('kb_active_tenant_id');
    const language = localStorage.getItem('userLanguage') || 'ja';

    // Helper to filter out invalid values
    const isValid = (val: string | null) => {
        if (!val) return false;
        const v = val.trim().toLowerCase();
        return v !== '' && v !== 'undefined' && v !== 'null' && v !== '[object object]';
    };

    const apiKey = isValid(rawApiKey) ? rawApiKey : null;
    const token = isValid(rawToken) ? rawToken : null;

    const headers: Record<string, string> = {
      'Content-Type': 'application/json',
      'x-user-language': language,
    };

    if (apiKey) {
      if (apiKey.startsWith('kb_')) {
        headers['x-api-key'] = apiKey;
      } else {
        headers['Authorization'] = `Bearer ${apiKey}`;
      }
    } else if (token) {
      headers['Authorization'] = `Bearer ${token}`;
    }

    // Final fail-safe: Ensure no header is 'undefined' string
    Object.keys(headers).forEach(key => {
        if (headers[key]?.toLowerCase().includes('undefined')) {
            delete headers[key];
        }
    });

    if (activeTenantId && isValid(activeTenantId)) {
      headers['x-tenant-id'] = activeTenantId;
    }

    // DEBUG: Only log first few chars
    console.log('[ApiClient] Auth Headers:', {
        hasApiKey: !!headers['x-api-key'],
        hasAuth: !!headers['Authorization'],
        authPreview: headers['Authorization']?.substring(0, 20),
        tenantId: headers['x-tenant-id']
    });

    return headers;
  }

  // New API call method, returns { data, status }
  async get<T = any>(url: string): Promise<ApiResponse<T>> {
    const response = await fetch(`${this.baseURL}${url}`, {
      method: 'GET',
      headers: this.getAuthHeaders(),
    });

    const data = await response.json();
    if (response.status === 401) {
        this.handleUnauthorized();
        throw new Error(data.message || 'Unauthorized');
    }
    if (!response.ok) {
        throw new Error(data.message || 'Request failed');
    }

    return { data, status: response.status };
  }

  async post<T = any>(url: string, body?: any): Promise<ApiResponse<T>> {
    const response = await fetch(`${this.baseURL}${url}`, {
      method: 'POST',
      headers: this.getAuthHeaders(),
      body: body ? JSON.stringify(body) : undefined,
    });

    const data = await response.json();
    if (response.status === 401) {
        this.handleUnauthorized();
        throw new Error(data.message || 'Unauthorized');
    }
    if (!response.ok) {
        throw new Error(data.message || 'Request failed');
    }

    return { data, status: response.status };
  }

  async put<T = any>(url: string, body?: any): Promise<ApiResponse<T>> {
    const response = await fetch(`${this.baseURL}${url}`, {
      method: 'PUT',
      headers: this.getAuthHeaders(),
      body: body ? JSON.stringify(body) : undefined,
    });

    const data = await response.json();
    if (response.status === 401) {
        this.handleUnauthorized();
        throw new Error(data.message || 'Unauthorized');
    }
    if (!response.ok) {
        throw new Error(data.message || 'Request failed');
    }

    return { data, status: response.status };
  }

  async delete<T = any>(url: string): Promise<ApiResponse<T>> {
    const response = await fetch(`${this.baseURL}${url}`, {
      method: 'DELETE',
      headers: this.getAuthHeaders(),
    });

    const data = await response.json();
    if (response.status === 401) {
        this.handleUnauthorized();
        throw new Error(data.message || 'Unauthorized');
    }
    if (!response.ok) {
        throw new Error(data.message || 'Request failed');
    }

    return { data, status: response.status };
  }

  // Legacy compatibility method — returns raw Response for streaming and other special cases
  async request(path: string, options: RequestInit = {}): Promise<Response> {
    const authHeaders = this.getAuthHeaders();
    const headers = new Headers(options.headers);
    Object.entries(authHeaders).forEach(([k, v]) => headers.set(k, v));

    const language = localStorage.getItem('userLanguage') || 'ja';
    headers.set('x-user-language', language);

    let url = path;
    if (!path.startsWith('http')) {
      const cleanPath = path.startsWith('/') ? path : `/${path}`;
      url = `${this.baseURL}${cleanPath}`;
    }

    const response = await fetch(url, {
      ...options,
      headers,
    });

    if (response.status === 401) {
      this.handleUnauthorized();
      throw new Error('Unauthorized');
    }

    return response;
  }

  private handleUnauthorized() {
    console.warn('[ApiClient] 401 Unauthorized detected. Cleaning up and redirecting to login...');
    localStorage.removeItem('kb_api_key');
    localStorage.removeItem('authToken');
    localStorage.removeItem('token');
    localStorage.removeItem('kb_active_tenant_id');
    // Only redirect if we are not already on the login page
    if (window.location.pathname !== '/login') {
        window.location.href = '/login';
    }
  }
}

export const apiClient = new ApiClient(API_BASE_URL);