/* v8 ignore start */

import {Transform, type TransformCallback, type TransformOptions} from "node:stream";

import {logger} from "../../utils/logger";
import {SIGNATURE} from "./consts";

const NS = "zh:zboss:read";

export class ZBOSSReader extends Transform {
    private buffer: Buffer;

    public constructor(opts?: TransformOptions) {
        super(opts);

        this.buffer = Buffer.alloc(0);
    }

    override _transform(chunk: Buffer, _encoding: BufferEncoding, cb: TransformCallback): void {
        let data = Buffer.concat([this.buffer, chunk]);
        let position: number;

        logger.debug(`<<<  DATA [${chunk.toString("hex")}]`, NS);
        // SIGNATURE - start of package
        // biome-ignore lint/suspicious/noAssignInExpressions: shorter
        while ((position = data.indexOf(SIGNATURE)) !== -1) {
            // need for read length
            if (data.length > position + 3) {
                const len = data.readUInt16LE(position + 1);
                if (data.length >= position + 1 + len) {
                    const frame = data.subarray(position + 1, position + 1 + len);
                    logger.debug(`<<< FRAME [${frame.toString("hex")}]`, NS);
                    // emit the frame via 'data' event
                    this.push(frame);

                    // if position not 1 - try to convert buffer before position to text - chip console output
                    if (position > 1) {
                        logger.debug(`<<< CONSOLE:\n\r${data.subarray(0, position - 1).toString()}`, NS);
                    }
                    // remove the frame from internal buffer (set below)
                    data = data.subarray(position + 1 + len);
                    if (data.length) logger.debug(`<<< TAIL [${data.toString("hex")}]`, NS);
                } else {
                    logger.debug(`<<< Not enough data. Length=${data.length}, frame length=${len}. Waiting`, NS);
                    break;
                }
            } else {
                logger.debug(`<<< Not enough data. Length=${data.length}. Waiting`, NS);
                break;
            }
        }

        this.buffer = data;

        cb();
    }

    override _flush(cb: TransformCallback): void {
        this.push(this.buffer);

        this.buffer = Buffer.alloc(0);

        cb();
    }
}