/*
 * PixelED.js - simple pixel-like editor for the browser
 *
 * This project is primarily just practice for The Odin Project's curriculum.
 * (Found at https://theodinproject.com/) It claims this project is difficult,
 * but the requirements are quite well-defined, so it doesn't strike me as
 * difficult. Just tedious.
 *
 * This project was a good fit for TOP because it shows the student the
 * difficulties in building intuitive and effective interfaces in the Web
 * environment.
 *
 * Scope:
 * [x] Erase button (sets all canvas pixels to white)
 * [x] Black button, sets current color to black
 * [x] White button, sets current color to white
 * [x] 'Current color' indicator, clicking color box brings up dialog.
 * [-] Reset button (sets canvas to 16x16, current color to black)
 *	'-> Refreshing the page does the same damn thing. YAGNI
 * [x] Range slider for canvas size, with numeric indicator
 * [x] Rainbow drawing mode that randomizes the color on every draw
 * [x] Darken drawing mode that darkens the color by 10% on every draw
 *  '-> BONUS: Added a Lighten mode based on the reverse of Darken
 * [x] 'Clear' button, to make the entire canvas white
 */

/* GOALS
 *
 * [*] discrete drawing states
 * [*] click-and-drag to draw, not hover
 * [ ] right click to copy color under cursor (and switch to it)
 *
 * STRETCH GOAL
 *
 * [ ] better UI layout
 * [ ] possible export to PNG or GIF format (!!! :D)
 */

/* disable right click's default behavior */
document.body.addEventListener("contextmenu",
	(e) => {
		e.preventDefault();
	}
);
/* Target element for the application */
const root = document.getElementById('app_area');
const dstates = Object.freeze({
	BLACK: 0,
	WHITE: 1,
	CUSTOM: 2,
	RAINBOW: 3,
	DARKEN: 4,
	LIGHTEN: 5
});
current_color = "#000000";
custom_color = "#2564b8";
draw_state = dstates["BLACK"];
do_draw = false;

function clean_element(node) {
	while (node.firstChild) {
		node.removeChild(node.firstChild);
	}
}

function resetCanvas(size) {
	clean_element(grid);
	grid.style.gridTemplateColumns = `repeat(${size}, 1fr)`;
	rebuildCanvas(size);
}

function rebuildCanvas(size) {
	size = lintCanvasSize(size);
	for (i=0; i<(size*size); i++) {
		box = grid.appendChild(document.createElement("div"));
		box.addEventListener("mouseover", function(e) {
			if (do_draw) {
				drawColor(e.target, current_color);
			}
		});
		box.addEventListener("mousedown", function(e) {
			console.log(e);
			if (e.which == 3 || e.button == 2) {
				console.log(e);
				setCustom();
				custom_color = rgb_to_hex(e.target.style.backgroundColor);
				document.querySelector("#custom_color").value = custom_color;
				current_color = custom_color;
			} else {
				do_draw = true;
				drawColor(e.target, current_color);
			}
		}, { "passive": false, "capture": true } );
		box.addEventListener("mouseup", function(e) {
			do_draw = false;
		}, { "passive": false } );
	}
}

function clearCanvas() {
	pixels = document.querySelectorAll("#grid_container div");
	pixels.forEach(function(i) {
		i.removeAttribute("style");
	});
}

function handler() {
	initialSetup();
}

function initialSetup() {
	workspace = document.createElement("div");
	workspace.id = ["workspace"];

	/* generate a 16x16 grid of divs */
	grid = document.createElement("div");
	grid.id = ["grid_container"];
	/* turn the pen off when you leave the canvas */
	grid.addEventListener("mouseleave",
		(e) => {
			do_draw = false;
		}, { "passive": false }
	);

	grid_caption = document.createElement("div");
	grid_caption.id = ["grid_caption"];
	grid_caption.textContent = 'an app by ZLG';

	resetCanvas(16);
	/* we should have 256 divs appended to the grid. */

	toolbox = document.createElement("div");
	toolbox.id = ["toolbox"];
	/* This is somewhat hackish, but takes up fewer lines of code than accomplishing
	 * the same thing in pure JS. It's all scaffolding anyway. */
	toolbox.innerHTML = `
	<header>pixelED</header>
	<section id="color_picker">
		<div id="black_pick">
			<span class="swatch"></span>
			<span class="sw_label">black</span>
		</div>
		<div id="white_pick">
			<span class="swatch"></span>
			<span class="sw_label">white</span>
		</div>
		<div id="custom_pick">
			<input class="swatch" type="color" value="" name="custom_color" id="custom_color"></input>
			<span class="sw_label">custom</span>
		</div>
	</section>
	<section id="canvas_opts">
		<label>canvas size</label>
		<input type="range" min="8" max="100" value="16" name="canvas_size" id="canvas_size" list="sizes"></input>
		<input type="text" value="16"></input>
	</section>
	<button id="rainbow">rainbow</button>
	<button id="darken">darken</button>
	<button id="lighten">lighten</button>
	<button id="erase">erase</button>
	<datalist id="sizes">
		<option value="16"></option>
		<option value="32"></option>
		<option value="48"></option>
		<option value="64"></option>
		<option value="80"></option>
	</datalist>
	`;

	/* elements must be added to the page in order to be queried */
	root.appendChild(toolbox);
	root.appendChild(workspace);
	workspace.appendChild(grid);
	workspace.appendChild(grid_caption);

	/* initial settings */
	setBlack();
	document.querySelector("#custom_color").value = custom_color;

	/* add events, AFTER added to DOM above */
	document.getElementById("rainbow").addEventListener("click", setRainbow);
	document.getElementById("darken").addEventListener("click", setDarken);
	document.getElementById("lighten").addEventListener("click", setLighten);
	document.getElementById("erase").addEventListener("click", clearCanvas);

	/* The canvas slider */
	document.querySelector("#canvas_size").addEventListener(
		"input",
		(e) => {
			let size = lintCanvasSize(e.target.value);
			document.querySelector('#canvas_opts input[type="text"]').value = size;
			e.target.value = size;
			resetCanvas(size);
		}
	);

	document.querySelector('#canvas_opts > input[type="text"]').addEventListener(
		"change",
		(e) => {
			let size = lintCanvasSize(e.target.value);
			document.querySelector("#canvas_size").value = size;
			e.target.value = size;
			resetCanvas(size);
		}
	);
	document.querySelector('#canvas_opts > input[type="text"]').addEventListener(
		"keydown",
		(e) => {
			let size = lintCanvasSize(e.target.value);
			/* todo switch case */
			if (e.key == "ArrowDown") {
				if (size > 8) {
					size -= 1;
					e.target.value = size;
					document.querySelector("#canvas_size").value = size;
					resetCanvas(size);
				}
				// parseInt(e.target.value) -= 1;
			} else if (e.key == "ArrowUp") {
				if (size < 100) {
					size += 1;
					e.target.value = size;
					document.querySelector("#canvas_size").value = size;
					resetCanvas(size);
				}
				// parseInt(e.target.value) += 1;
			}
		}
	);

	/* The Black color option */
	document.querySelectorAll('#black_pick > span').forEach(
		(i) => {
			i.addEventListener("click", setBlack);
		}
	);
	document.querySelector('#black_pick').addEventListener("click", setBlack);

	/* The White color option */
	document.querySelectorAll('#white_pick > span').forEach(
		(i) => {
			i.addEventListener("click", setWhite);
		}
	);
	document.querySelector('#white_pick').addEventListener("click", setWhite);

	/* The Custom color option */
	document.querySelector('#custom_color').addEventListener("input", setCustom);
	document.querySelector('#custom_pick > span').addEventListener("click", setCustom);
	document.querySelector('#custom_pick').addEventListener("click", setCustom);
}

function drawColor(e, c) {
	switch (draw_state) {
		case dstates["BLACK"]:
			e.style.backgroundColor = "#000000";
			break;
		case dstates["WHITE"]:
			e.style.backgroundColor = "#ffffff";
			break;
		case dstates["CUSTOM"]:
			current_color = document.querySelector("#custom_color").value;
			e.style.backgroundColor = current_color;
			break;
		case dstates["RAINBOW"]:
			e.style.backgroundColor = gen_rainbow();
			break;
		case dstates["DARKEN"]:
			e.style.backgroundColor = gen_darken(e.style.backgroundColor);
			break;
		case dstates["LIGHTEN"]:
			e.style.backgroundColor = gen_lighten(e.style.backgroundColor);
			break;
	}
}

function setRainbow() {
	draw_state = dstates["RAINBOW"];
	clearSelected();
	document.querySelector("#rainbow").classList.toggle("selected");
}

function setDarken() {
	draw_state = dstates["DARKEN"];
	clearSelected();
	document.querySelector("#darken").classList.toggle("selected");
}

function setLighten() {
	draw_state = dstates["LIGHTEN"];
	clearSelected();
	document.querySelector("#lighten").classList.toggle("selected");
}

function lintCanvasSize(s) {
	s = parseInt(s);
	if (s < 8) {
		s = 8;
	} else if(s > 100) {
		s = 100;
	}
	return s;
}

function clearSelected() {
	document.querySelectorAll(".selected").forEach(
		(i) => {
			i.classList.toggle("selected");
		}
	);
}

function getRGBTriplet(str) {
	if (str[0] == "#") {
		return hex_to_rgb(str);
	}
	return str.match(new RegExp("rgb\\((.*)\\)"))[1].split(", ");
}

/* transform a hex color into rgb(x, y, z) format */
function hex_to_rgb(str) {
	/* there are two main formats I want to support, though the third would be best, too:
	 *
	 * - "#abcdef": the typical hex color
	 * - "#ade"   : shorthand for "#aaddee"
	 * - "#abcdef99": an alpha-aware hexcode, whose fourth set represents opacity
	 */
	if (str[0] == "#") {
		str = str.substr(1);
		console.log(str);
	}
	switch (str.length) {
		case 3:
			/* shorthand hex */
			break;
		case 6:
			/* standard hex */
			let red = parseInt(str.substr(0,2),16);
			let grn = parseInt(str.substr(2,2),16);
			let blu = parseInt(str.substr(4,2),16);
			return [red, grn, blu];
			break;
		case 8:
			/* 32-bit hex color */
			break;
	}
}

function rgb_to_hex(str) {
	if (str.length == 0) {
		return "#ffffff";
	}
	let trp = getRGBTriplet(str);
	let red = parseInt(trp[0],10).toString(16).padStart(2, '0');
	let grn = parseInt(trp[1],10).toString(16).padStart(2, '0');
	let blu = parseInt(trp[2],10).toString(16).padStart(2, '0');
	return `#${red}${grn}${blu}`;
}

function setBlack() {
	clearSelected();
	document.querySelector("#black_pick").classList.toggle("selected");
	draw_state = dstates["BLACK"];
}

function setWhite() {
	clearSelected();
	document.querySelector("#white_pick").classList.toggle("selected");
	draw_state = dstates["WHITE"];
}

/* You have to click the <input> itself to change the color. */
function setCustom() {
	clearSelected();
	document.querySelector("#custom_pick").classList.toggle("selected");
	draw_state = dstates["CUSTOM"];
}

/* generate a random color and return its six digit hex code, with octothorpe (#) */
function gen_rainbow() {
	let r = Math.floor(Math.random()*255);
	let g = Math.floor(Math.random()*255);
	let b = Math.floor(Math.random()*255);
	let hr = r.toString(16).padStart(2, '0');
	let hg = g.toString(16).padStart(2, '0');
	let hb = b.toString(16).padStart(2, '0');
	current_color = `#${hr}${hg}${hb}`;
	document.querySelector("#custom_color").value = current_color;
	return current_color;
}

/* accept a given 'rgb(r, g, b)' sequence, darken each color channel by 26, and return it */
function gen_darken(c) {
	/* this happens on un-touched pixels, generally white by convention */
	if (!c) {
		return "rgb(224, 224, 224)";
	}
	let nc_array = [];
	let c_array = getRGBTriplet(c);
	c_array.forEach((i) => {
		let num = parseInt(i);
		num -= 26;
		if (num < 0) {
			num = 0;
		}
		nc_array.push(num);
	});
	let is = nc_array.join(", ");
	return `rgb(${is})`;
}

/* accept a given 'rgb(r, g, b)' sequence, lighten each color channel by 26, and return it */
function gen_lighten(c) {
	/* this happens on un-touched pixels, generally white by convention */
	if (!c) {
		return "rgb(255, 255, 255)";
	}
	let nc_array = [];
	let c_array = getRGBTriplet(c);
	c_array.forEach((i) => {
		let num = parseInt(i);
		num += 26;
		if (num > 255) {
			num = 255;
		}
		nc_array.push(num);
	});
	let is = nc_array.join(", ");
	return `rgb(${is})`;
}