"use strict";

const assert = require("assert");
const types = require("@babel/types");
const template = require("@babel/template").default;
const unreachable = require("@joepie91/unreachable")("jsnix");

const NoChange = require("../astformer/actions/no-change");
const ConsumeNode = require("../astformer/actions/consume-node");
const RemoveNode = require("../astformer/actions/remove-node");

const asExpression = require("as-expression");
const unpackExpression = require("./_unpack-expression");
const printAst = require("../print-ast");



// FIXME: Make strict mode! Otherwise objects will inherit from `global`
let tmplModule = template(`
	module.exports = function({ builtins, $$jsNix$extend }) {
		return %%contents%%;
	};
`);


let tmplLetIn = template(`
	(() => {
		%%letBindings%%

		return %%expression%%;
	})()
`);

let tmplObjectDynamic = template(`
	(() => {
		let $$nixJS_object = {};

		%%entries%%

		return $$nixJS_object;
	})()
`);

let tmplObjectDynamicEntry = template(`
	if ($$nixJS_object[%%key%%] !== undefined) { throw new Error(\`Duplicate key '\${%%key%%}' in attribute set\`); }
	$$nixJS_object[%%key%%] = %%wrappedExpression%%;
`);

let tmplIdentifierReference = template(`(
	(this?.%%name%% ?? %%name%%)()
)`);

function generateDynamicObject(bindings, recursive) {
	let generatedBindings = bindings.map((binding) => {
		let wrapper = (recursive)
			? tmplLazyWrapperRecursive
			: tmplLazyWrapper;

		let key = isDynamicBinding(binding)
			? binding.attrpath.attr[0]
			: binding.attrpath.attr[0].name;

		return tmplObjectDynamicEntry({
			key: key,
			wrappedExpression: wrapper({ expression: binding.expression })
		});
	});

	return tmplObjectDynamic({ entries: generatedBindings.flat() })
}

let trivial = {
	name: "trivial-transforms",
	visitors: {
		// Trivial transforms
		NixParenthesizedExpression: (node) => node.expression,
		Program: (_node, { setContext, defer }) => {
			setContext(null, "identifierType", "reference");

			return defer((node) => {
				assert(node.body.length === 1);
				return tmplModule({ contents: node.body[0] });
			});
		},
		NixIdentifier: (node, { getContext }) => {
			// FIXME: Mangle reserved keywords like `const`
			if (getContext("identifierType") === "define") {
				return types.identifier(node.name);
			} else { // reference
				return unpackExpression(tmplIdentifierReference({ name: node.name }));
			}
		},
		NixBinaryOperation: (_node, { defer }) => {
			return defer((node) => {
				// FIXME: Verify that all the 'operator' values match between Nix and JS!
				return types.binaryExpression(node.operator, node.left, node.right);
			});
		}
	}
};

module.exports = [
	require("./desugar-attrsets"),
	require("./literals"),
	require("./functions"),
	require("./attribute-sets"),
	trivial,
];