/**
 * Live render check. Not a unit test — this draws to your real terminal.
 *
 *   node --experimental-strip-types test/render-demo.ts
 *
 * Pass: a red rectangle appears, then the text below it redraws 20 times
 * without the image blinking or the screen clearing.
 */

import { resolveCellSize } from "../src/cell-size.ts";
import { imageDimensions } from "../src/dimensions.ts";
import { deleteVirtual, fitToGrid, placeholderRows, transmitVirtual } from "../src/placeholder.ts";
import { allocateImageId } from "../src/placeholder.ts";

import { deflateSync } from "node:zlib";

function png(w: number, h: number, rgb: [number, number, number]): Buffer {
	const crcTable = Array.from({ length: 256 }, (_, n) => {
		let c = n;
		for (let k = 0; k < 8; k++) c = c & 1 ? 0xedb88320 ^ (c >>> 1) : c >>> 1;
		return c >>> 0;
	});
	const crc32 = (buf: Buffer) => {
		let c = 0xffffffff;
		for (const byte of buf) c = crcTable[(c ^ byte) & 0xff]! ^ (c >>> 8);
		return (c ^ 0xffffffff) >>> 0;
	};
	const chunk = (type: string, data: Buffer) => {
		const body = Buffer.concat([Buffer.from(type, "ascii"), data]);
		const len = Buffer.alloc(4);
		len.writeUInt32BE(data.length);
		const crc = Buffer.alloc(4);
		crc.writeUInt32BE(crc32(body));
		return Buffer.concat([len, body, crc]);
	};
	const ihdr = Buffer.alloc(13);
	ihdr.writeUInt32BE(w, 0);
	ihdr.writeUInt32BE(h, 4);
	ihdr[8] = 8;
	ihdr[9] = 2;
	const row = Buffer.concat([Buffer.from([0]), Buffer.from(Array(w).fill(rgb).flat())]);
	const raw = Buffer.concat(Array(h).fill(row));
	return Buffer.concat([
		Buffer.from([0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a]),
		chunk("IHDR", ihdr),
		chunk("IDAT", deflateSync(raw)),
		chunk("IEND", Buffer.alloc(0)),
	]);
}

const bytes = png(240, 160, [220, 60, 60]);
const cell = await resolveCellSize();
const dims = imageDimensions(bytes);
const grid = fitToGrid(dims.widthPx, dims.heightPx, cell, 30, 15);
const id = allocateImageId();

console.log(`cell=${cell.widthPx}x${cell.heightPx}px  image=${dims.widthPx}x${dims.heightPx}px  grid=${grid.cols}x${grid.rows} cells  id=${id}`);
console.log("");

process.stdout.write(transmitVirtual(bytes.toString("base64"), id, grid));
for (const row of placeholderRows(id, grid)) console.log(row);

// Redraw the line under the image repeatedly. The image must not flicker,
// because nothing about it is retransmitted or cleared.
let n = 0;
const timer = setInterval(() => {
	n++;
	process.stdout.write(`\rredraw ${n}/20 — image should be rock steady   `);
	if (n >= 20) {
		clearInterval(timer);
		console.log("\n\nPass if the red block never blinked.");
		console.log("Press enter to free the image.");
		process.stdin.once("data", () => {
			process.stdout.write(deleteVirtual(id));
			process.exit(0);
		});
		process.stdin.resume();
	}
}, 100);