import { SSEClient, SSEClientOptions, SSEvent } from './sse-client';

import { unpackMultiple } from 'msgpackr';

/**
 * SSEClientMsgpackr is a subclass of SSEClient that uses msgpackr to parse the events.
 */
export class SSEClientMsgpackr extends SSEClient {

    /**
   * Creates a new SSEClientMsgpackr instance.
   * @param {string} url The URL to connect to
   * @param {SSEClientOptions} options The options for the SSEClient
   * @returns {SSEClientMsgpackr} A new SSEClientMsgpackr instance
   */
  public static async from(url: string, options: SSEClientOptions) {
    const client = new SSEClientMsgpackr(url, options);
    await client.connect();
    return client;
  }

  /**
   * Parses the events from the msgpackr message buffer.
   * @param {Uint8Array} chunk The chunk to parse
   * @returns {SSEvent[]} The parsed events
   */
  protected parseEvents(chunk: Uint8Array): SSEvent[] {
    // Append new chunk to existing buffer
    this.messageBuffer = new Uint8Array([...this.messageBuffer, ...chunk]);

    // Create an array to store the parsed events
    const events: SSEvent[] = [];

    try {
      // Try to decode the entire buffer as msgPackr messages
      unpackMultiple(this.messageBuffer, (value, start, end) => {
        // Remove the event from the buffer
        this.messageBuffer = this.messageBuffer.slice(end);

        // Add the event to the events array
        events.push(value);
      });
    } catch (error) {
      // If we can't decode the buffer, it might be incomplete
      // Keep the entire buffer for next time
    } finally {
      // Update buffer with any remaining unprocessed content
      this.messageBuffer = new Uint8Array(this.messageBuffer);

      // Return the events
      return events;
    }
  }
}