import readline from 'node:readline';
import fs from 'node:fs';
import net from 'node:net';

export class Stream_Relay {

	#target_stream = null;
	#line_buffer_tally = 0;
	#connecting = false;

	constructor(source_stream, target_socket, line_buffer=[], line_buffer_max_size=1024**2) {
		Object.assign(this, { source_stream, target_socket, line_buffer, line_buffer_max_size });
	}
	serve() {

		const rli = readline.createInterface({
			input: this.source_stream,
			crlfDelay: Infinity
		});

		rli.on('line', (line) => this.log_line(line));
	}

	buffer_line(line) {

		this.#line_buffer_tally += line.length + 1;
		this.line_buffer.push(line);	// NOTE: We may of course briefly overshoot here but we are not expecting or caring about huge oneliners for now

		while (this.line_buffer.length && (this.#line_buffer_tally > this.line_buffer_max_size)) {
			const discarded = this.line_buffer.shift();
			this.#line_buffer_tally -= discarded.length + 1;
			console.log({ discarded });
		}

	}

	log_line(line) {
		this.buffer_line(line);

		if (this.#target_stream) {
			this.#flush();
		} else {
			this.#connect_target();
		}

	}



	#connect_target() {

		if (this.#target_stream || this.#connecting) {
			return;
		}

		this.#connecting = true;

		const socket = net.createConnection(this.target_socket.connect_options);

		socket.on('connect', () => {
			this.#connecting = false;
			this.#target_stream = socket;
			this.#flush();
		});

		socket.on('error', (err) => {
			console.log("target error", { err });
			socket.destroy();
			this.#connecting = false;
		});

		socket.on('close', () => {
			this.#target_stream = null;
		});
	}


	#flush() {

		while (this.line_buffer.length && this.#target_stream) {

			const line = this.line_buffer[0];
			const ok = this.#target_stream.write(line + '\n');

			if (ok === false) {
				return;
			}

			this.line_buffer.shift();
		}
	}



}