/**
 * Sync Server Client - HTTP client for sync-server communication.
 * 
 * Handles:
 * - Creating/updating invitations on the server
 * - Fetching invitations by ID
 * - ExtJSON encoding/decoding for data transfer
 */

import type { XOInvitation } from '@xo-cash/types';
import { encodeExtendedJson, decodeExtendedJson } from '../utils/ext-json.js';

/**
 * Response from the sync server.
 */
export interface SyncServerResponse<T> {
  success: boolean;
  data?: T;
  error?: string;
}

/**
 * HTTP client for sync-server communication.
 */
export class SyncClient {
  /** Base URL of the sync server */
  private baseUrl: string;

  /**
   * Creates a new sync client.
   * @param baseUrl - Base URL of the sync server (e.g., http://localhost:3000)
   */
  constructor(baseUrl: string) {
    // Remove trailing slash if present
    this.baseUrl = baseUrl.replace(/\/$/, '');
  }

  /**
   * Makes an HTTP request to the sync server.
   * @param method - HTTP method
   * @param path - Request path
   * @param body - Optional request body
   * @returns Response data
   */
  private async request<T>(
    method: 'GET' | 'POST' | 'PUT' | 'DELETE',
    path: string,
    body?: unknown,
  ): Promise<T> {
    const url = `${this.baseUrl}${path}`;
    
    const headers: Record<string, string> = {
      'Content-Type': 'application/json',
      'Accept': 'application/json',
    };

    const options: RequestInit = {
      method,
      headers,
    };

    if (body !== undefined) {
      // Encode body using ExtJSON for proper BigInt and Uint8Array serialization
      options.body = encodeExtendedJson(body);
    }

    const response = await fetch(url, options);

    if (!response.ok) {
      const errorText = await response.text();
      throw new Error(`HTTP ${response.status}: ${errorText}`);
    }

    const responseText = await response.text();
    
    // Return empty object if no response body
    if (!responseText) {
      return {} as T;
    }

    // Decode response using ExtJSON
    return decodeExtendedJson(responseText) as T;
  }

  // ============================================================================
  // Invitation Operations
  // ============================================================================

  /**
   * Posts an invitation to the sync server (create or update).
   * @param invitation - Invitation to post
   * @returns The stored invitation
   */
  async postInvitation(invitation: XOInvitation): Promise<XOInvitation> {
    return this.request<XOInvitation>('POST', '/invitations', invitation);
  }

  /**
   * Gets an invitation from the sync server.
   * @param invitationIdentifier - Invitation ID to fetch
   * @returns The invitation or undefined if not found
   */
  async getInvitation(invitationIdentifier: string): Promise<XOInvitation | undefined> {
    try {
      // Use query parameter for GET request (can't have body)
      const response = await this.request<XOInvitation>(
        'GET', 
        `/invitations?invitationIdentifier=${encodeURIComponent(invitationIdentifier)}`
      );
      return response;
    } catch (error) {
      // Return undefined if not found (404)
      if (error instanceof Error && error.message.includes('404')) {
        return undefined;
      }
      throw error;
    }
  }

  /**
   * Updates an invitation on the sync server.
   * @param invitation - Updated invitation
   * @returns The updated invitation
   */
  async updateInvitation(invitation: XOInvitation): Promise<XOInvitation> {
    // Uses the same POST endpoint which handles both create and update
    return this.postInvitation(invitation);
  }

  // ============================================================================
  // Health Check
  // ============================================================================

  /**
   * Checks if the sync server is healthy.
   * @returns True if server is healthy
   */
  async isHealthy(): Promise<boolean> {
    try {
      const response = await this.request<{ status: string }>('GET', '/health');
      return response.status === 'ok';
    } catch {
      return false;
    }
  }

  /**
   * Gets the base URL of the sync server.
   */
  getBaseUrl(): string {
    return this.baseUrl;
  }

  /**
   * Gets the SSE endpoint URL for an invitation.
   * @param invitationId - Invitation ID to subscribe to
   * @returns SSE endpoint URL
   */
  getSSEUrl(invitationIdentifier: string): string {
    return `${this.baseUrl}/invitations?invitationIdentifier=${encodeURIComponent(invitationIdentifier)}`;
  }
}