"use strict";

import init, * as talc from "./pkg/talc_web.js";
await init();

/*
 *  DOM
 */

const $ = (q) => document.querySelector(q);

function newEl(tag, attrs, children) {
	const el = document.createElement(tag);
	for (const attr in attrs) {
		el.setAttribute(attr, attrs[attr]);
	}
	for (const child of children) {
		if (typeof(child) === "string") {
			el.appendChild(document.createTextNode(child));
		} else {
			el.appendChild(child);
		}
	}
	return el;
}

/*
 *  History
 */

let historyEntries = [""];
let historyIndex = 0;
let currentLine = "";

function prevHistory() {
	const inputEl = $("#input");
	if (historyIndex === 0) {
		currentLine = inputEl.innerText;
	}
	historyIndex = Math.min(historyIndex+1, historyEntries.length);
	const text = historyEntries[historyEntries.length - historyIndex];
	inputEl.innerText = text;

	document.getSelection().setPosition(inputEl, inputEl.childNodes.length);
}

function nextHistory() {
	const inputEl = $("#input");
	historyIndex = Math.max(historyIndex-1, 0);
	let text;
	if (historyIndex === 0) {
		text = currentLine;
	} else {
		text = historyEntries[historyEntries.length - historyIndex];
	}
	inputEl.innerText = text;

	document.getSelection().setPosition(inputEl, inputEl.childNodes.length);
}

/*
 *  REPL
 */

function nextLine() {
	const newPrompt = newEl("div", {"class": "prompt"}, []);
	newPrompt.innerHTML = $("#prompt").innerHTML;

	const newInput = newEl("div", {}, []);
	newInput.innerHTML = $("#input").innerHTML;

	$("#history").appendChild(newEl(
		"div",
		{"class": "input_line"},
		[newPrompt, newInput]
	));

	$("#input").innerHTML = "";

	currentLine = "";
	historyIndex = 0;

}

function execLine() {
	const inputLine = $("#input").innerText;
	nextLine();
	historyEntries.push(inputLine);

	try {
		const fixedInput = inputLine.replaceAll("\u00a0", " ");
		const out = talc.eval_line(fixedInput);
		if (out !== undefined) {
			$("#history").appendChild(newEl("div", {}, [out]));
		}
	} catch (e) {
		$("#history").appendChild(newEl("div", {}, [
			newEl("span", {"class": "error"}, ["Error: "]),
			newEl("pre", {"class": "err_msg"}, [e.toString()])
		]));
	}
}

/*
 *  Input
 */

function handleCtrlKey(event) {
	switch (event.code) {
		case "KeyL":
			event.preventDefault();
			$("#history").innerHTML = "";
			break;
		case "KeyC":
			event.preventDefault();
			nextLine();
			break;
	}
}

function keyPressed(event) {
	if (event.key === "Enter" && !event.shiftKey && !event.altKey) {
		event.preventDefault();
		execLine()
	} else if (event.ctrlKey && !event.altKey) {
		handleCtrlKey(event);
	} else if (event.key === "ArrowUp" && !event.altKey) {
		event.preventDefault();
		prevHistory();
	} else if (event.key === "ArrowDown" && !event.altKey) {
		event.preventDefault();
		nextHistory();
	}

	window.scrollTo(0, document.body.scrollHeight);
}

/*
 *  Listeners
 */

$("#input").addEventListener("keydown", keyPressed);
$("#input").focus();

$("#terminal").addEventListener("click", (event) => {
	if (event.target.id === "terminal" || event.target.id === "input") {
		$("#input").focus();
	}
})

/*
 *  Query parameter
 */

const urlParams = new URLSearchParams(window.location.search);
const initialLine = urlParams.get("eval");

if (initialLine !== null) {
	$("#input").innerText = initialLine;
	execLine();
}