// Mechanical CommonJS -> ESM conversion of desktop LS Tools modules (no logic changes).
// usage: node tools/port-module.mjs <reference file> <output file>
//   const x = require("y");            -> import x from "y";
//   const { a, b: c } = require("y");  -> import { a, b as c } from "y";
//   module.exports = { A, B: C };       -> export { A, C as B };
//   module.exports = X;                 -> export default X;
// Relative requires get ".js" added. Anything else that is not this simple is reported, so it
// gets ported by hand instead of guessed.
import fs from "node:fs";
import * as acorn from "acorn";

const [src, dst] = process.argv.slice(2);
let text = fs.readFileSync(src, "utf8");
const problems = [];

const fixSpec = (s) => (s.startsWith(".") && !s.endsWith(".js") && !s.endsWith(".json") ? s + ".js" : s);

text = text.replace(/^const (\w+) = require\("([^"]+)"\);?$/gm, (_, name, spec) => `import ${name} from "${fixSpec(spec)}";`);
text = text.replace(/^const \{([^}]+)\} = require\("([^"]+)"\);?$/gm, (_, names, spec) => {
	const list = names.split(",").map((n) => n.trim()).filter(Boolean).map((n) => n.replace(/^(\w+)\s*:\s*(\w+)$/, "$1 as $2"));
	return `import { ${list.join(", ")} } from "${fixSpec(spec)}";`;
});
// module.exports = { ... } is parsed (acorn), not split on commas: values can be whole arrow
// functions or methods with commas inside.
{
	const ast = acorn.parse(text, { ecmaVersion: "latest", sourceType: "module", allowReturnOutsideFunction: true, allowAwaitOutsideFunction: true });
	const st = ast.body.find(
		(n) =>
			n.type === "ExpressionStatement" &&
			n.expression.type === "AssignmentExpression" &&
			n.expression.left.type === "MemberExpression" &&
			n.expression.left.object.name === "module" &&
			n.expression.left.property.name === "exports" &&
			n.expression.right.type === "ObjectExpression",
	);
	if (st) {
		const consts = [];
		const list = [];
		for (const p of st.expression.right.properties) {
			if (p.type !== "Property" || p.computed) {
				problems.push(`module.exports: unsupported property ${text.slice(p.start, p.end).slice(0, 60)}`);
				continue;
			}
			const key = p.key.type === "Identifier" ? p.key.name : String(p.key.value);
			if (p.shorthand) list.push([key, key]);
			else if (!p.method && p.value.type === "Identifier") list.push([p.value.name, key]);
			else if (p.method || p.kind !== "init") {
				// method shorthand / getter: keep the exact source inside a one-property object
				consts.push(`const __export_${key} = ({ ${text.slice(p.start, p.end)} }).${key};`);
				list.push([`__export_${key}`, key]);
			} else {
				// key: expression (e.g. texture: assets.texture, save: async (...) => {...})
				consts.push(`const __export_${key} = ${text.slice(p.value.start, p.value.end)};`);
				list.push([`__export_${key}`, key]);
			}
		}
		const named = list.map(([local, key]) => (local === key ? key : `${local} as ${key}`));
		// default export too: other modules do `const x = require("./y")` -> `import x from "./y.js"`
		const defaults = list.map(([local, key]) => (local === key ? key : `${key}: ${local}`));
		const out = `${consts.join("\n")}${consts.length ? "\n" : ""}export { ${named.join(", ")} };\nexport default { ${defaults.join(", ")} };\n`;
		text = text.slice(0, st.start) + out + text.slice(st.end);
	}
}
text = text.replace(/^module\.exports = (\w+);?\s*$/m, "export default $1;\n");

for (const [i, line] of text.split("\n").entries()) {
	if (/\brequire\(/.test(line)) problems.push(`${i + 1}: require left: ${line.trim()}`);
	if (/\bmodule\.exports\b|\bexports\.\w+\s*=/.test(line)) problems.push(`${i + 1}: exports left: ${line.trim()}`);
	if (/\b__dirname\b|\b__filename\b|process\.(env|platform|argv)/.test(line)) problems.push(`${i + 1}: node global: ${line.trim()}`);
}
fs.mkdirSync(dst.replace(/[\\/][^\\/]+$/, ""), { recursive: true });
fs.writeFileSync(dst, `// Ported from LS Tools desktop: ${src.replace(/\\/g, "/").split("/src/").pop()} (mechanical CJS -> ESM)\n` + text);
console.log(`${dst}: ${problems.length ? problems.length + " to check" : "ok"}`);
for (const p of problems) console.log("  " + p);