import { Transform } from 'stream';

export default class LoraStream extends Transform {
    constructor(options) {
        super(options);
        this.byteBuffer = new Uint8Array([]);
        this.textDecoder = new TextDecoder();
    }

    _transform(chunk, encoding, callback) {
        this.byteBuffer = new Uint8Array([
            ...this.byteBuffer,
            ...chunk,
        ]);
        let processingExhausted = false;
        while (this.byteBuffer.length !== 0 && !processingExhausted) {
            const framingIndex = this.byteBuffer.findIndex((byte) => byte === 0x94);
            const framingByte2 = this.byteBuffer[framingIndex + 1];
            if (framingByte2 === 0xc3) {
                if (this.byteBuffer.subarray(0, framingIndex).length) {
                    this.byteBuffer = this.byteBuffer.subarray(framingIndex);
                }
                const msb = this.byteBuffer[2];
                const lsb = this.byteBuffer[3];
                if (msb !== undefined && lsb !== undefined && this.byteBuffer.length >= 4 + (msb << 8) + lsb) {
                    const packet = this.byteBuffer.subarray(4, 4 + (msb << 8) + lsb);
      
                    const malformedDetectorIndex = packet.findIndex(
                      (byte) => byte === 0x94,
                    );
                    if (malformedDetectorIndex !== -1 && packet[malformedDetectorIndex + 1] === 0xc3) {
                        // malformed
                        this.byteBuffer = this.byteBuffer.subarray(malformedDetectorIndex);
                    } else {
                        this.byteBuffer = this.byteBuffer.subarray(3 + (msb << 8) + lsb + 1);
                        this.push(packet);
                    }
                } else {
                    /** Only partioal message in buffer, wait for the rest */
                    processingExhausted = true;
                }
            } else {
                /** Message not complete, only 1 byte in buffer */
                processingExhausted = true;
            }
        }

        callback();
    }
    _flush(callback) {
        try {
          if (this._buffer) {
            this.push(this._buffer.trim());
          }
          callback();
        } catch (err) {
          callback(err);
        }
    }
}