import type { IRustBridgeLogger } from './interfaces/index.js';

/**
 * Buffer-based newline scanner for streaming binary data.
 * Accumulates chunks and emits complete lines via callback.
 * Used by both StdioTransport and SocketTransport.
 */
export class LineScanner {
  private buffer: Buffer = Buffer.alloc(0);
  private maxPayloadSize: number;
  private logger: IRustBridgeLogger;

  constructor(maxPayloadSize: number, logger: IRustBridgeLogger) {
    this.maxPayloadSize = maxPayloadSize;
    this.logger = logger;
  }

  /**
   * Feed a chunk of data. Calls onLine for each complete newline-terminated line found.
   */
  public push(chunk: Buffer, onLine: (line: string) => void): void {
    this.buffer = Buffer.concat([this.buffer, chunk]);

    let newlineIndex: number;
    while ((newlineIndex = this.buffer.indexOf(0x0A)) !== -1) {
      const lineBuffer = this.buffer.subarray(0, newlineIndex);
      this.buffer = this.buffer.subarray(newlineIndex + 1);

      if (lineBuffer.length > this.maxPayloadSize) {
        this.logger.log('error', `Inbound message exceeds maxPayloadSize (${lineBuffer.length} bytes), dropping`);
        continue;
      }

      const line = lineBuffer.toString('utf8').trim();
      if (line) {
        onLine(line);
      }
    }

    // Prevent OOM if sender never sends newline
    if (this.buffer.length > this.maxPayloadSize) {
      this.logger.log('error', `Buffer exceeded maxPayloadSize (${this.buffer.length} bytes) without newline, clearing`);
      this.buffer = Buffer.alloc(0);
    }
  }

  /** Reset the internal buffer. */
  public clear(): void {
    this.buffer = Buffer.alloc(0);
  }
}