/// @ts-check

/** @return {never} */
function never() { throw new Error() }

/**@type{WebAssembly.Instance}*/ let hbcInstance;
/**@type{Promise<WebAssembly.WebAssemblyInstantiatedSource>}*/ let hbcInstaceFuture;
async function getHbcInstance() {
	hbcInstaceFuture ??= WebAssembly.instantiateStreaming(fetch("/hbc.wasm"), {});
	return hbcInstance ??= (await hbcInstaceFuture).instance;
}

const stack_pointer_offset = 1 << 20;

/** @param {WebAssembly.Instance} instance @param {Uint8Array} code @param {number} fuel
 * @returns {string} */
function compileCode(instance, code, fuel) {
	let {
		INPUT, INPUT_LEN,
		LOG_MESSAGES, LOG_MESSAGES_LEN,
		memory, compile_and_run,
	} = instance.exports;

	if (!(true
		&& memory instanceof WebAssembly.Memory
		&& INPUT instanceof WebAssembly.Global
		&& INPUT_LEN instanceof WebAssembly.Global
		&& LOG_MESSAGES instanceof WebAssembly.Global
		&& LOG_MESSAGES_LEN instanceof WebAssembly.Global
		&& typeof compile_and_run === "function"
	)) never();

	const dw = new DataView(memory.buffer);
	dw.setUint32(INPUT_LEN.value, code.length, true);
	new Uint8Array(memory.buffer, INPUT.value).set(code);

	runWasmFunction(instance, compile_and_run, fuel);
	return bufToString(memory, LOG_MESSAGES, LOG_MESSAGES_LEN);
}

/**@type{WebAssembly.Instance}*/ let fmtInstance;
/**@type{Promise<WebAssembly.WebAssemblyInstantiatedSource>}*/ let fmtInstaceFuture;
/** @param {string} code @param {"fmt" | "minify"} action
 * @returns {Promise<string>} */
async function modifyCode(code, action) {
	fmtInstaceFuture ??= WebAssembly.instantiateStreaming(fetch("/hbfmt.wasm"), {});
	fmtInstance ??= (await fmtInstaceFuture).instance;

	let {
		INPUT, INPUT_LEN,
		OUTPUT, OUTPUT_LEN,
		memory, fmt, minify
	} = fmtInstance.exports;

	if (!(true
		&& memory instanceof WebAssembly.Memory
		&& INPUT instanceof WebAssembly.Global
		&& INPUT_LEN instanceof WebAssembly.Global
		&& OUTPUT instanceof WebAssembly.Global
		&& OUTPUT_LEN instanceof WebAssembly.Global
		&& typeof fmt === "function"
		&& typeof minify === "function"
	)) never();

	if (action !== "fmt") {
		INPUT = OUTPUT;
		INPUT_LEN = OUTPUT_LEN;
	}

	let dw = new DataView(memory.buffer);
	dw.setUint32(INPUT_LEN.value, code.length, true);
	new Uint8Array(memory.buffer, INPUT.value).set(new TextEncoder().encode(code));

	return runWasmFunction(fmtInstance, action === "fmt" ? fmt : minify) ?
		bufToString(memory, OUTPUT, OUTPUT_LEN) : "invalid code";
}


/** @param {WebAssembly.Instance} instance @param {CallableFunction} func @param {any[]} args
 * @returns {boolean} */
function runWasmFunction(instance, func, ...args) {
	const prev = performance.now();
	const { PANIC_MESSAGE, PANIC_MESSAGE_LEN, memory, stack_pointer } = instance.exports;
	if (!(true
		&& memory instanceof WebAssembly.Memory
		&& stack_pointer instanceof WebAssembly.Global
	)) never();
	const ptr = stack_pointer.value;
	try {
		func(...args);
		return true;
	} catch (error) {
		if (error instanceof WebAssembly.RuntimeError && error.message == "unreachable") {
			if (PANIC_MESSAGE instanceof WebAssembly.Global
				&& PANIC_MESSAGE_LEN instanceof WebAssembly.Global) {
				console.error(bufToString(memory, PANIC_MESSAGE, PANIC_MESSAGE_LEN), error);
			}
		} else {
			console.error(error);
		}
		stack_pointer.value = ptr;
		return false;
	} finally {
		console.log("compiletion took:", performance.now() - prev);
	}
}

/** @typedef {Object} Post
 * @property {string} path 
 * @property {string} code */

/** @param {Post[]} posts @returns {Uint8Array} */
function packPosts(posts) {
	let len = 0; for (const post of posts) len += 2 + post.path.length + 2 + post.code.length;

	const buf = new Uint8Array(len), view = new DataView(buf.buffer), enc = new TextEncoder();
	len = 0; for (const post of posts) {
		view.setUint16(len, post.path.length, true); len += 2;
		buf.set(enc.encode(post.path), len); len += post.path.length;
		view.setUint16(len, post.code.length, true); len += 2;
		buf.set(enc.encode(post.code), len); len += post.code.length;
	}

	return buf;
}

/** @param {WebAssembly.Memory} mem
 * @param {WebAssembly.Global} ptr
 * @param {WebAssembly.Global} len
 * @return {string} */
function bufToString(mem, ptr, len) {
	const res = new TextDecoder()
		.decode(new Uint8Array(mem.buffer, ptr.value,
			new DataView(mem.buffer).getUint32(len.value, true)));
	new DataView(mem.buffer).setUint32(len.value, 0, true);
	return res;
}

/** @param {HTMLElement} target */
function wireUp(target) {
	execApply(target);
	cacheInputs(target);
	bindTextareaAutoResize(target);
	bindCodeEdit(target);
}

/** @type {{ [key: string]: (content: string) => Promise<string> | string }} */
const applyFns = {
	timestamp: (content) => new Date(parseInt(content) * 1000).toLocaleString(),
	fmt: (content) => modifyCode(content, "fmt").then(c => c),
};

/** @param {HTMLElement} target */
async function bindCodeEdit(target) {
	const edit = target.querySelector("#code-edit");
	if (!(edit instanceof HTMLTextAreaElement)) return;
	const errors = target.querySelector("#compiler-output");
	if (!(errors instanceof HTMLPreElement)) never();

	const hbc = await getHbcInstance();

	const debounce = 100;
	let timeout = 0;
	edit.addEventListener("input", () => {
		if (timeout) clearTimeout(timeout);
		timeout = setTimeout(() => {
			const buf = packPosts([
				{ path: "local.hb", code: edit.value },
				{ path: "lam.hb", code: "foo:=10" },
			]);
			errors.textContent = compileCode(hbc, buf, 1);
			timeout = 0;
		}, debounce);
	});
	edit.dispatchEvent(new InputEvent("input"));
}

/** @param {HTMLElement} target */
function execApply(target) {
	for (const elem of target.querySelectorAll('[apply]')) {
		if (!(elem instanceof HTMLElement)) continue;
		const funcname = elem.getAttribute('apply') ?? never();
		let res = applyFns[funcname](elem.textContent ?? "");
		if (res instanceof Promise) res.then(c => elem.textContent = c);
		else elem.textContent = res;
	}
}

/** @param {HTMLElement} target */
function bindTextareaAutoResize(target) {
	for (const textarea of target.querySelectorAll("textarea")) {
		if (!(textarea instanceof HTMLTextAreaElement)) never();

		const taCssMap = window.getComputedStyle(textarea);
		const padding = parseInt(taCssMap.getPropertyValue('padding-top') ?? "0")
			+ parseInt(taCssMap.getPropertyValue('padding-top') ?? "0");
		textarea.style.height = "auto";
		textarea.style.height = (textarea.scrollHeight - padding) + "px";
		textarea.style.overflowY = "hidden";
		textarea.addEventListener("input", function() {
			let top = window.scrollY;
			textarea.style.height = "auto";
			textarea.style.height = (textarea.scrollHeight - padding) + "px";
			window.scrollTo({ top });
		});

		textarea.onkeydown = (ev) => {
			if (ev.key === "Tab") {
				ev.preventDefault();
				document.execCommand('insertText', false, "\t");
			}
		}
	}
}

/** @param {HTMLElement} target */
function cacheInputs(target) {
	/**@type {HTMLFormElement}*/ let form;
	for (form of target.querySelectorAll('form')) {
		const path = form.getAttribute('hx-post') || form.getAttribute('hx-delete');
		if (!path) {
			console.warn('form does not have a hx-post or hx-delete attribute', form);
			continue;
		}

		for (const input of form.elements) {
			if (input instanceof HTMLInputElement || input instanceof HTMLTextAreaElement) {
				if ('password submit button'.includes(input.type)) continue;
				const key = path + input.name;
				input.value = localStorage.getItem(key) ?? '';
				input.addEventListener("input", () => localStorage.setItem(key, input.value));
			} else {
				console.warn("unhandled form element: ", input);
			}
		}
	}
}

if (window.location.hostname === 'localhost') {
	let id; setInterval(async () => {
		let new_id = await fetch('/hot-reload').then(reps => reps.text());
		id ??= new_id;
		if (id !== new_id) window.location.reload();
	}, 300);

	(async function test() {
		{
			const code = "main:=fn():void{return}";
			const fmtd = await modifyCode(code, "fmt") ?? never();
			const prev = await modifyCode(fmtd, "minify") ?? never();
			if (code != prev) console.error(code, prev);
		}
		{
			const posts = [{
				path: "foo.hb",
				code: "main:=fn():int{return 42}",
			}];
			const buf = packPosts(posts);
			const res = compileCode(await getHbcInstance(), buf, 1) ?? never();
			const expected = "exit code: 42\n";
			if (expected != res) console.error(expected, res);
		}
	})()
}

document.body.addEventListener('htmx:afterSwap', (ev) => {
	if (!(ev.target instanceof HTMLElement)) never();
	wireUp(ev.target);
});

wireUp(document.body);