"use strict";

/**
 * Generate the demo fixtures that test4node.js reads from the (gitignored)
 * `test/` directory: a source PDF for every rotation the manual demo walks
 * through, a stamp image, and a self-signed PKCS#12 certificate.
 *
 * Usage: node testutil/make-demo.js [pfxPassword]
 */

const m_fs = require("fs");
const m_path = require("path");
const m_zlib = require("zlib");
const Zga = require("../lib/zganode.js");
const {makeP12} = require("./fixtures.js");

/** @type {string} Output directory, matching the `workpath` of test4node.js. */
const outDir = m_path.join(__dirname, "..", "test");
/** @type {Array<number>} Page rotations the manual demo iterates over. */
const ROTATIONS = [0, 90, 180, 270];
/** @type {string} */
const DEFAULT_PWD = "zgatest";
/** @type {number} CCN-STIC-221 requires at least 3000 bits. */
const RSA_BITS = 3072;

/**
 * Build a one-page demo PDF with the given page rotation.
 *
 * @param {number} angle Page rotation in degrees.
 * @return {Promise<Uint8Array>}
 */
async function makePdf(angle){
	const doc = await Zga.PDFLib.PDFDocument.create();
	const font = await doc.embedFont(Zga.PDFLib.StandardFonts.Helvetica);
	const page = doc.addPage([595, 842]);
	page.drawText("zgapdfsigner demo document", {x: 60, y: 760, size: 18, font: font});
	page.drawText("Page rotation: " + angle + " degrees", {x: 60, y: 730, size: 12, font: font});
	page.drawText("Generated by testutil/make-demo.js", {x: 60, y: 710, size: 10, font: font});
	if(angle){
		page.setRotation(Zga.PDFLib.degrees(angle));
	}
	return doc.save();
}

/**
 * CRC-32 as specified by the PNG format.
 *
 * @param {Buffer} buf
 * @return {number}
 */
function crc32(buf){
	let crc = 0xffffffff;
	for(let i = 0; i < buf.length; i++){
		crc ^= buf[i];
		for(let bit = 0; bit < 8; bit++){
			crc = (crc >>> 1) ^ (0xedb88320 & -(crc & 1));
		}
	}
	return (crc ^ 0xffffffff) >>> 0;
}

/**
 * Wrap a payload into a length-prefixed, CRC-suffixed PNG chunk.
 *
 * @param {string} type Four-character chunk type.
 * @param {Buffer} data
 * @return {Buffer}
 */
function pngChunk(type, data){
	const head = Buffer.alloc(4);
	head.writeUInt32BE(data.length, 0);
	const body = Buffer.concat([Buffer.from(type, "ascii"), data]);
	const tail = Buffer.alloc(4);
	tail.writeUInt32BE(crc32(body), 0);
	return Buffer.concat([head, body, tail]);
}

/**
 * Build a small solid-color PNG, used as the signature stamp image.
 *
 * @return {Buffer}
 */
function makePng(){
	const size = 64;
	const stride = 1 + size * 3;
	const raw = Buffer.alloc(size * stride);
	for(let y = 0; y < size; y++){
		const row = y * stride;
		raw[row] = 0; // filter type: none
		for(let x = 0; x < size; x++){
			const px = row + 1 + x * 3;
			const edge = x < 4 || y < 4 || x >= size - 4 || y >= size - 4;
			raw[px] = edge ? 0x1f : 0x8a;
			raw[px + 1] = edge ? 0x6f : 0xc8;
			raw[px + 2] = edge ? 0xd5 : 0xf0;
		}
	}
	const ihdr = Buffer.alloc(13);
	ihdr.writeUInt32BE(size, 0);
	ihdr.writeUInt32BE(size, 4);
	ihdr[8] = 8; // bit depth
	ihdr[9] = 2; // color type: truecolor
	return Buffer.concat([
		Buffer.from([0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a]),
		pngChunk("IHDR", ihdr),
		pngChunk("IDAT", m_zlib.deflateSync(raw)),
		pngChunk("IEND", Buffer.alloc(0)),
	]);
}

async function main(){
	const pwd = process.argv[2] || DEFAULT_PWD;
	m_fs.mkdirSync(outDir, {recursive: true});

	for(const angle of ROTATIONS){
		const name = "_test" + (angle ? "_" + angle : "") + ".pdf";
		m_fs.writeFileSync(m_path.join(outDir, name), await makePdf(angle));
		console.log("Wrote " + m_path.join(outDir, name));
	}

	const pngPath = m_path.join(outDir, "_test.png");
	m_fs.writeFileSync(pngPath, makePng());
	console.log("Wrote " + pngPath);

	const pfxPath = m_path.join(outDir, "_test.pfx");
	m_fs.writeFileSync(pfxPath, Buffer.from(makeP12(RSA_BITS, pwd), "latin1"));
	console.log("Wrote " + pfxPath + " (password: " + pwd + ")");

	console.log("\nRun the manual demo with: npm run test:manual -- " + pwd);
}

main().catch(function(err){
	console.error(err);
	process.exit(1);
});