/*
 * 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 GOALS
 *
 * [*] better UI layout
 * [ ] possible export to GIF format (!!! :D)
 */

/* POST-COMPLETION
 *
 * This project has helped me understand what goes into making modern Web apps,
 * and the value that some frameworks can bring when you're building something
 * with somewhat complex UI language, like an editing tool. There is a lot of
 * event and state syncing, for lack of a better explanation, which increases
 * the complexity of the task you're carrying out. Web apps can be convenient
 * to visit and use, but building them is a challenge. I think I would be more
 * at home in a persistent ticking environment like a video game, or somewhat
 * predictable backend code. The moving target of HTML5 and CSS3 and JS, while
 * fun in some respects, adds to the ever-increasing complexity that developers
 * face when building for the Web.
 *
 * I would prefer to build on a platform that is less prone to change. There's
 * bound to be a middle ground between low-level tedium and a gargantuan
 * virtual machine.
 */

/* CREDITS
 *
 * Wikipedia for the GIF information
 * MDN for endless Web and Javascript info
 * The Command Line Fanatic, who wrote two great articles on GIF:
 *		https://commandlinefanatic.com/cgi-bin/showarticle.cgi?article=art010
 *		https://commandlinefanatic.com/cgi-bin/showarticle.cgi?article=art011
 *
 * Implementing GIF would have been more of a hassle without these resources.
 */

/* 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;
do_move = 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) {
			if (e.which == 3 || e.button == 2) {
				if (e.target.style.backgroundColor == 'rgb(0, 0, 0)') {
					setBlack();
				} else if (e.target.style.backgroundColor == 'rgb(255, 255, 255)' || e.target.style.backgroundColor == '') {
					setWhite();
				} else {
					custom_color = rgb_to_hex(e.target.style.backgroundColor);
					document.querySelector("#custom_color").value = custom_color;
					current_color = custom_color;
					setCustom();
				}
			} 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() {
	if (window.confirm("Clear the entire canvas?")) {
		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"];
	grid.classList = ["show_grid"];
	/* turn the pen off when you leave the canvas */
	// grid.addEventListener("mouseleave",
	// 	(e) => {
	// 		do_draw = false;
	// 	}, { "passive": false }
	// );

	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="tool_palette">
		<div id="black_pick">
			<span class="swatch"></span>
		</div>
		<div id="white_pick">
			<span class="swatch"></span>
		</div>
		<div id="custom_pick">
			<input class="swatch" type="color" value="" name="custom_color" id="custom_color"></input>
		</div>
		<div id="rainbow">
			<span class="swatch"></span>
		</div>
		<div id="darken">
			<span class="swatch"></span>
		</div>
		<div id="lighten">
			<span class="swatch"></span>
		</div>
		<div id="clear_canvas">
			<span class="swatch"></span>
		</div>
		<div id="grid_toggle" class="active">
			<span class="swatch"></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>
	`;

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

	/* the area behind the grid */
	workspace.addEventListener("mousedown", (e) => {
		do_draw = true;
	});
	/* the area behind the grid */
	workspace.addEventListener("mouseup", (e) => {
		do_draw = false;
	});

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

	/* click-and-drag for the toolbox */
	document.querySelector("#toolbox header").addEventListener("mousedown", (e) => {
		e.preventDefault();
		x1 = e.clientX;
		y1 = e.clientY;
		xoff = e.clientX - e.target.parentNode.offsetLeft;
		yoff = e.clientY - e.target.parentNode.offsetTop;
		do_move = true;
		document.addEventListener("mousemove", moveToolbox);
		document.addEventListener("mouseup", (e) => {
			e.preventDefault();
			do_move = false;
		}, { once: true });
	});

	/* 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("clear_canvas").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').addEventListener("click", setCustom);

	/* The Toggle Grid option */
	document.querySelector('#grid_toggle').addEventListener("click", toggleGrid);
}

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 toggleGrid(e) {
	document.querySelector("#grid_container").classList.toggle("show_grid");
	document.querySelector("#grid_toggle").classList.toggle("active");
}

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(s) {
	console.log(s);
	if (s.length == 0) {
		return [255, 255, 255];
	}
	if (s[0] == "#" || s.length == 6) {
		return hex_to_rgb(s);
	}
	triplet = s.match(new RegExp("rgb\\((.*)\\)"))[1].split(", ");
	nums = new Array();
	triplet.forEach(
		(c) => {
			nums.push(Number.parseInt(c));
		}
	);
	return nums;
}

/* 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})`;
}

function moveToolbox(e) {
	if (!do_move) {
		return 0;
	}
	e = e || window.event;
	e.preventDefault();
	let tb = document.querySelector("#toolbox");
	// console.log(`toolbar at ${tb.offsetLeft},${tb.offsetTop}`);
	tb.style.left = `${e.clientX - xoff}px`;
	tb.style.top = `${(e.clientY - yoff)}px`;
	boundToolbox();
}

function myMid(lowb, num, highb) {
	return Math.min(Math.max(lowb, num), highb);
}

function boundToolbox() {
	let tb = document.querySelector("#toolbox");
	let tbh = document.querySelector("#toolbox header");
	let gap = tbh.style.gap;
	tb.style.left = `${myMid(0,tb.offsetLeft,(window.innerWidth - tb.offsetWidth))}px`;
	tb.style.top = `${myMid(0,tb.offsetTop,(window.innerHeight - (tbh.offsetHeight + 16)))}px`;
}

/* Implement a simple GIF class to facilitate easy downloading of user's work
 *
 * Limitations include:
 *   * no animation
 *   * no sub-images for complex palettes
 *   * no transparency
 *   * no palette correction should the colorspace run out
 *
 * In short, please only use this as a way to get pixelED art into another
 * program.
 */
class GIFImage {
	#header = "GIF89a";
	#width;
	#height;
	#pixel_data;
	#pixel_view;
	raw_binary;
	theGCT;
	theIDS;

	constructor(height, width, pdata) {
		this.#width = width;
		this.#height = height;
		this.#pixel_data = new Uint8Array(3*(this.#width*this.#height));
		this.#pixel_view = new DataView(this.#pixel_data.buffer, 0);
		this.fill_buffer(pdata);
		this.build_gct();
	}

	// fill the data buffer with background color information from this element's children.
	fill_buffer(grid_area) {
		if (grid_area.children.length != (this.#pixel_data.length / 3) ) {
			console.log("pixelED Error: Size mismatch between canvas and GIF buffer size!");
			return;
		} else {
			// every pixel has three values, thus we can know offsets
			for (i=0; i<this.#pixel_data.length; i+=3) {
				let grid_index = i / 3;
				let pixel = getRGBTriplet(grid_area.children[grid_index].style.backgroundColor);
				this.#pixel_view.setUint8(i,pixel[0]);
				this.#pixel_view.setUint8(i+1,pixel[1]);
				this.#pixel_view.setUint8(i+2,pixel[2]);
			}
		}
	}

	// make the global color table, and add color indices to the image data section
	build_gct() {
		// setup the gct naively
		this.theGCT = new Array();
		this.theIDS = new Array();
		grid.childNodes.forEach(
			(p) => {
				let hex = rgb_to_hex(p.style.backgroundColor).substring(1);
				if (! this.theGCT.includes(hex)) {
					this.theGCT.push(hex);
				}
				let ci = this.theGCT.indexOf(hex);
				this.theIDS.push(ci);
			}
		);
	}

	gct_to_binary() {
		let buf = new Uint8Array(128*3);
		for (i=0; (i/3) <= this.theGCT.length; i+=3) {
			let rgb = getRGBTriplet(this.theGCT[i/3]);
			buf[i] = rgb[0];
			buf[i+1] = rgb[1];
			buf[i+2] = rgb[2];
		}
		return new DataView(buf.buffer, 0);
	}

	ids_to_binary() {
		let buf = new Uint8Array(this.theIDS.length);
		for (i=0; i < buf.byteLength; i++) {
			buf[i] = this.theIDS[i];
		}
		return new DataView(buf.buffer, 0);
	}

	// don't hurt me i'm still a babby
	writeData() {
		// we need to figure out the length of our information before we allocate a buffer.
		let size = 0;
		size += 6; // header: 'GIF89a'
		size += 2; // logical screen width
		size += 2; // logical screen height
		size += 1; // GCT (Global Color Table) information
		// -- u are here
		size += 1; // background color index
		size += 1; // pixel aspect ratio
		size += this.gct_to_binary().byteLength;
		// we'll try omitting the GCE
		size += 1; // image descriptor ','
		size += 4; // upper-left coord of image in logical screen
		size += 4; // image width and height
		size += 1; // local color table bit
		size += 1; // minimum LZW code size - 1 (7 for 8-bit indices)
		size += 1; // CLEAR code (80)
		size += this.ids_to_binary().byteLength;
		size += 1; // STOP code (81)
		size += 1; // last ';' in the file
		console.log("we need "+size+" bytes");
		
		// do the business
		this.raw_binary = new Uint8Array(size);
		let offset = 0;
		// write header
		for (i=0; i<this.#header.length; i++) {
			this.raw_binary[i] = this.#header[i].charCodeAt(0);
			offset++;
		}
		// write LS width and height
		this.raw_binary[offset] = (this.#width & 255);
		offset++;
		this.raw_binary[offset] = (this.#width) >> 8;
		offset++;
		this.raw_binary[offset] = (this.#height & 255);
		offset++;
		this.raw_binary[offset] = (this.#height) >> 8;
		offset++;

		// write BG index and aspect ratio
		this.raw_binary[offset++] = 0;
		this.raw_binary[offset++] = 0;

		let packed_field = 0b10110110;

		console.log(offset);
	}
}

/* vim: set foldmethod=syntax: */