/**
 * Move SvelteKit's inline bootstrap script to an external file for CSP (no unsafe-inline).
 * Run after vite build; reads/writes build/.
 * Finds <script>...</script> containing __sveltekit_, minifies it, writes to _app/immutable/entry/bootstrap.js,
 * and replaces the inline script with <script src="...">.
 */
import { readFileSync, writeFileSync, readdirSync, mkdirSync } from 'fs';
import { join, dirname } from 'path';
import { fileURLToPath } from 'url';
import { minify } from 'terser';

const __dirname = dirname(fileURLToPath(import.meta.url));
const buildDir = join(__dirname, '..', 'build');
const entryDir = join(buildDir, '_app', 'immutable', 'entry');
const bootstrapPath = join(entryDir, 'bootstrap.js');
const scriptSrc = './_app/immutable/entry/bootstrap.js';

function getFiles(dir, ext, files = []) {
	for (const name of readdirSync(dir, { withFileTypes: true })) {
		const full = join(dir, name.name);
		if (name.isDirectory()) getFiles(full, ext, files);
		else if (name.name.endsWith(ext)) files.push(full);
	}
	return files;
}

// Find first <script>...</script> that contains __sveltekit_
function findInlineBootstrap(html) {
	const scriptOpen = html.indexOf('<script>');
	if (scriptOpen === -1) return null;
	const scriptClose = html.indexOf('</script>', scriptOpen);
	if (scriptClose === -1) return null;
	const content = html.slice(scriptOpen + '<script>'.length, scriptClose);
	if (!content.includes('__sveltekit_')) return null;
	return { content: content.trim(), start: scriptOpen, end: scriptClose + '</script>'.length };
}

const SCRIPT_TAG = `<script src="${scriptSrc}"></script>`;

async function main() {
	const htmlFiles = getFiles(buildDir, '.html');
	let bootstrapWritten = false;
	let count = 0;
	for (const htmlFile of htmlFiles) {
		let html = readFileSync(htmlFile, 'utf8');
		const found = findInlineBootstrap(html);
		if (!found) continue;

		if (!bootstrapWritten) {
			// Imports relative to script location when in _app/immutable/entry/
			let scriptContent = found.content.replace(
				/import\("\.\/_app\/immutable\/entry\/([^"]+)"\)/g,
				'import("./$1")'
			);
			const result = await minify(scriptContent, {
				format: { comments: false },
				compress: { passes: 1 }
			});
			if (result.code) scriptContent = result.code;
			mkdirSync(entryDir, { recursive: true });
			writeFileSync(bootstrapPath, scriptContent, 'utf8');
			bootstrapWritten = true;
		}

		html = html.slice(0, found.start) + SCRIPT_TAG + html.slice(found.end);
		writeFileSync(htmlFile, html, 'utf8');
		count++;
	}
	if (count > 0) {
		console.log('Bootstrap script externalized (minified):', scriptSrc, `(${count} HTML file(s))`);
	} else if (htmlFiles.length > 0) {
		console.log('No SvelteKit inline script found in HTML (bootstrap already external?)');
	}
}

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