'use strict';

/*
TODO:
- detect duplicate widget names
- forbid . , ; : in widget names
- widgets:
	- comparator
	- circle
	- rotate 2D
*/

let gl;
let program_main;
let program_post;
let vertex_buffer_rect;
let vertex_buffer_main;
let vertex_data_main;
let page;
let canvas;
let ui_canvas;
let ui_ctx;
let framebuffer;
let framebuffer_color_texture;
let sampler_texture;
let current_time;
let ui_shown = true;
let ui_div;
let viewport_width, viewport_height;
let shift_key = false, ctrl_key = false;
let html_id = 0;
let widget_choices;
let widget_search;

let width = 1920, height = 1920;

const widget_info = {
	'mix': {
		name: 'Mix',
		tooltip: 'weighted average of two inputs',
		inputs: [
			{name: 'source 1', id: 'src1'},
			{name: 'source 2', id: 'src2'},
			{name: 'mix', id: 'mix'},
		],
		controls: [
			{name: 'clamp mix', id: 'clamp', type: 'checkbox', tooltip: 'clamp the mix input to the [0, 1] range'}
		],
		outputs: [
			{name: 'out', id: 'out', tooltip: 'mix × (source 1) + (1 - mix) × (source 2)'}
		],
		func: function(state, inputs) {
			let src1 = inputs.src1;
			let src2 = inputs.src2;
			let mix = inputs.mix;
			let types_good = type_base_type(src1.type) === 'float' &&
				type_base_type(src2.type) === 'float' &&
				type_base_type(mix.type) === 'float' &&
				type_component_count(src1.type) === type_component_count(src2.type) &&
				(type_component_count(mix.type) === type_component_count(src1.type) ||
				 type_component_count(mix.type) === 1);
			if (!types_good) {
				return {error: 'bad types for mix: ' + [src1, src2, mix].map(function (x) { return x.type; }).join(', ')};
			}
			
			let mix_code = mix.code;
			if (inputs.clamp) {
				mix_code = `clamp(${mix_code},0.0,1.0)`;
			}
			
			let type = src1.type;
			let v = state.next_variable();
			state.add_code(`${type} ${v} = mix(${src1.code}, ${src2.code}, ${mix_code});\n`);
			return {out: {type: type, code: v}};
		},
	},
	'prev': {
		name: 'Last frame',
		tooltip: 'sample from the previous frame',
		inputs: [{name: 'pos', id: 'pos', tooltip: 'position to sample — bottom-left corner is (0, 0), top-right corner is (1, 1)'}],
		controls: [
			{name: 'wrap mode', id: 'wrap', type: 'select:clamp|wrap', tooltip: 'how to deal with the input components if they go outside [0, 1]'},
			{name: 'sample mode', id: 'sample', type: 'select:linear|nearest', tooltip: 'how positions in between pixels should be sampled'},
		],
		outputs: [{name: 'out', id: 'out', tooltip: 'the color from the previous frame'}],
		func: function(state, inputs) {
			let pos = inputs.pos;
			if (pos.type !== 'vec2') {
				return {error: 'bad type for sample position: ' + pos.type};
			}
			let vpos = state.next_variable();
			state.add_code(`vec2 ${vpos} = ${pos.code};\n`);
			switch (inputs.wrap) {
			case 'wrap':
				state.add_code(`${vpos} = mod(${vpos}, 1.0);\n`);
				break;
			case 'clamp':
				state.add_code(`${vpos} = clamp(${vpos}, 0.0, 1.0);\n`);
				break;
			default:
				console.error('bad wrap mode:', inputs.wrap);
				break;
			}
			
			switch (inputs.sample) {
			case 'linear': break;
			case 'nearest':
				state.add_code(`${vpos} = floor(0.5 + ${vpos} * u_texture_size) * (1.0 / u_texture_size);\n`);
				break;
			default:
				console.error('bad sample method:', inputs.sample);
				break;
			}
			let v = state.next_variable();
			state.add_code(`vec3 ${v} = texture2D(u_texture, ${vpos}).xyz;\n`);
			return {out: {type: 'vec3', code: v}};
		},
	},
	'output': {
		name: 'Output color',
		inputs: [{name: 'value', id: 'value'}],
		controls: [],
		outputs: [],
		func: function(state, inputs) {
			return {out: inputs.value};
		}
	},
	'mul': {
		name: 'Multiply',
		tooltip: 'multiply two numbers, scale a vector by a number, or perform component-wise multiplication between vectors',
		inputs: [{name: 'a', id: 'a'}, {name: 'b', id: 'b'}],
		controls: [],
		outputs: [{name: 'out', id: 'out'}],
		func: function(state, inputs) {
			let a = inputs.a;
			let b = inputs.b;
			if (a.type !== b.type && a.type !== type_base_type(b.type) && b.type !== type_base_type(a.type)) {
				return {error: `cannot multiply types ${a.type} and ${b.type}`};
			}
			let output_type = a.type === type_base_type(b.type) ? b.type : a.type;
			let v = state.next_variable();
			state.add_code(`${output_type} ${v} = ${a.code} * ${b.code};\n`);
			return {out: {code: v, type: output_type}};
		},
	},
	'mod': {
		name: 'Modulo',
		tooltip: 'wrap a value at a certain limit',
		inputs: [{name: 'a', id: 'a'}, {name: 'b', id: 'b'}],
		controls: [],
		outputs: [{name: 'out', id: 'out'}],
		func: function(state, inputs) {
			let a = inputs.a;
			let b = inputs.b;
			if (a.type !== b.type && a.type !== type_base_type(b.type) && b.type !== type_base_type(a.type)) {
				return {error: `cannot take type ${a.type} modulo type ${b.type}`};
			}
			
			let output_type = a.type === type_base_type(b.type) ? b.type : a.type;
			let v = state.next_variable();
			state.add_code(`${output_type} ${v} = mod(${output_type}(${a.code}), ${output_type}(${b.code}));\n`);
			return {out: {code: v, type: output_type}};
		}
	},
	'square': {
		name: 'Square',
		tooltip: 'select between two inputs depending on whether a point lies within a square (or cube in 3D)',
		inputs: [
			{name: 'pos', id: 'pos', tooltip: 'point to test'},
			{name: 'inside', id: 'inside', tooltip: 'source to use if pos lies inside the square'},
			{name: 'outside', id: 'outside', tooltip: 'source to use if pos lies outside the square'},
			{name: 'size', id: 'size', tooltip: 'radius of the square'},
		],
		controls: [],
		outputs: [{name: 'out', id: 'out'}],
		func: function(state, inputs) {
			let pos = inputs.pos;
			let inside = inputs.inside;
			let outside = inputs.outside;
			let size = inputs.size;
			if (type_base_type(pos.type) !== 'float') {
				return {error: 'bad type for input pos: ' + pos.type};
			}
			let output_type = inside.type;
			if (output_type !== outside.type) {
				return {error: `selector input types ${inside.type} and ${outside.type} do not match`};
			}
			if (size.type !== 'float' && size.type !== pos.type) {
				return {error: `bad type for square size: ${size.type}`};
			}
			let a = state.next_variable();
			let b = state.next_variable();
			let v = state.next_variable();
			state.add_code(`${pos.type} ${a} = abs(${pos.code} / ${size.code});\n`);
			switch (type_component_count(pos.type)) {
			case 1:
				b = a;
				break;
			case 2:
				state.add_code(`float ${b} = max(${a}.x,${a}.y);\n`);
				break;
			case 3:
				state.add_code(`float ${b} = max(${a}.x,max(${a}.y,${a}.z));\n`);
				break;
			case 4:
				state.add_code(`float ${b} = max(${a}.x,max(${a}.y,max(${a}.z,${a}.w)));\n`);
				break;
			}
			state.add_code(`${output_type} ${v} = ${b} < 1.0 ? ${inside.code} : ${outside.code};\n`);
			return {out: {code: v, type: output_type}};
		},
	},
};
let widget_ids_sorted_by_name = [];
for (let id in widget_info) { 
	widget_ids_sorted_by_name.push(id);
}
widget_ids_sorted_by_name.sort(function (a, b) {
	a = widget_info[a].name;
	b = widget_info[b].name;
	return a.localeCompare(b);
});

window.addEventListener('load', startup);

function set_ui_shown(to) {
	ui_shown = to;
	ui_div.style.visibility = to ? 'visible' : 'collapse';
	page.dataset.uiShown = to ? '1' : '0';
}

function rgba_hex_to_float(hex) {
	let r;
	let g;
	let b;
	let a;
	
	if (hex.length === 7 || hex.length === 9) {
		// #rrggbb or #rrggbbaa
		r = parseInt(hex.substr(1, 2), 16) / 255;
		g = parseInt(hex.substr(3, 2), 16) / 255;
		b = parseInt(hex.substr(5, 2), 16) / 255;
		a = hex.length === 7 ? 1 : parseInt(hex.substr(7, 2), 16) / 255;
	} else if (hex.length === 4 || hex.length === 5) {
		// #rgb or #rgba
		r = parseInt(hex.substr(1, 1), 16) / 15;
		g = parseInt(hex.substr(2, 1), 16) / 15;
		b = parseInt(hex.substr(3, 1), 16) / 15;
		a = hex.length === 4 ? 1 : parseInt(hex.substr(4, 1), 16) / 15;
	}

	if (isNaN(r) || isNaN(g) || isNaN(b) || isNaN(a)) {
		return null;
	}
	
	let color = {
		r: r,
		g: g,
		b: b,
		a: a,
	};
	Object.preventExtensions(color);
	return color;
}

function rgba_float_to_hex(flt) {
	function comp(x) {
		x = Math.round(x * 255);
		if (x < 0) x = 0;
		if (x > 255) x = 255;
		let s = x.toString(16);
		while (s.length < 2) {
			s = '0' + s;
		}
		return s;
	}
	return '#' + comp(flt.r) + comp(flt.g) + comp(flt.b) + comp(flt.a);
}

function update_key_modifiers_from_event(e) {
	shift_key = e.shiftKey;
	ctrl_key = e.ctrlKey;
}

function update_shader() {
	let source = get_shader_source();
	if (source === null)
		return;
	let fragment_code = `
#ifdef GL_ES
precision highp float;
#endif

uniform sampler2D u_texture;
uniform float u_time;
uniform vec2 u_texture_size;
varying vec2 pos;

vec3 get_color() {
	${source}
}

void main() {
	gl_FragColor = vec4(get_color(), 1.0);
}
`;
	const vertex_code = `
attribute vec2 v_pos;
varying vec2 pos;
void main() {
	pos = v_pos;
	gl_Position = vec4(v_pos, 0.0, 1.0);
}
`;
	program_main = compile_program('main', {'vertex': vertex_code, 'fragment': fragment_code});
}

function on_key_press(e) {
	update_key_modifiers_from_event(e);
	let code = e.keyCode;
	if (e.target.tagName === 'INPUT' || e.target.tagName === 'BUTTON') {
		return;
	}
	console.log('key press', code);
	
	switch (code) {
	case 32: // space
		if (canvas_is_target)
			perform_step();
		break;
	case 9: // tab
		set_ui_shown(!ui_shown);
		e.preventDefault();
		break;
	case 13: // return
		update_shader();
		e.preventDefault();
		break;
	}
}

function on_key_release(e) {
	update_key_modifiers_from_event(e);
}


function on_mouse_move(e) {
	update_key_modifiers_from_event(e);
}

function distance(p0, p1) {
	let dx = p0.x - p1.x;
	let dy = p0.y - p1.y;
	return Math.sqrt(dx * dx + dy * dy);
}

function on_click(e) {
	update_key_modifiers_from_event(e);
	if (!ui_shown) {
		return;
	}
}


function float_glsl(f) {
	if (isNaN(f)) return '(0.0 / 0.0)';
	if (f === Infinity) return '1e+1000';
	if (f === -Infinity) return '-1e+1000';
	let s = f + '';
	if (s.indexOf('.') !== -1 || s.indexOf('e') !== -1)
		return s;
	return s + '.0';
}

function type_component_count(type) {
	switch (type) {
	case 'float': return 1;
	case 'vec2': return 2;
	case 'vec3': return 3;
	case 'vec4': return 4;
	default:
		return 0;
	}
}

function type_base_type(type) {
	switch (type) {
	case 'float':
	case 'vec2':
	case 'vec3':
	case 'vec4':
		return 'float';
	default:
		return null;
	}
}

function type_vec(base_type, component_count) {
	switch (base_type) {
	case 'float':
		switch (component_count) {
		case 1: return 'float';
		case 2: return 'vec2';
		case 3: return 'vec3';
		case 4: return 'vec4';
		default:
			return null;
		}
	default:
		return null;
	}
}

function add_widget(func) {
	let info = widget_info[func];
	console.assert(info !== undefined, 'bad widget name: ' + func);
	let root = document.createElement('div');
	root.dataset.func = func;
	root.classList.add('widget');
	
	{ // title
		let title = document.createElement('div');
		title.classList.add('widget-title');
		if ('tooltip' in info) {
			title.title = info.tooltip;
		}
		title.appendChild(document.createTextNode(info.name));
		if (func !== 'output') {
			let name_input = document.createElement('input');
			name_input.placeholder = 'Name';
			name_input.classList.add('widget-name');
			title.appendChild(name_input);
		}
		root.appendChild(title);
	}
	
	if (func !== 'output') {
		// delete button
		let delete_button = document.createElement('button');
		let delete_img = document.createElement('img');
		delete_img.src = 'x.svg';
		delete_img.alt = 'delete';
		delete_button.appendChild(delete_img);
		delete_button.classList.add('widget-delete');
		delete_button.addEventListener('click', function (e) {
			root.remove();
		});
		root.appendChild(delete_button);
	}
	
	// inputs
	info.inputs.forEach(function (input) {
		let container = document.createElement('div');
		container.classList.add('in');
		console.assert('id' in input, 'input missing ID', input);
		container.dataset.id = input.id;
		let input_element = document.createElement('input');
		input_element.type = 'text';
		input_element.id = 'gen-input-' + (++html_id);
		let label = document.createElement('label');
		label.htmlFor = input_element.id;
		if ('tooltip' in input) {
			label.title = input.tooltip;
		}
		label.appendChild(document.createTextNode(input.name));
		container.appendChild(input_element);
		container.appendChild(document.createTextNode(' '));
		container.appendChild(label);
		root.appendChild(container);
	});
	
	// controls
	for (let control of info.controls) {
		let container = document.createElement('div');
		container.classList.add('control');
		console.assert('id' in control, 'control missing ID', control);
		container.dataset.id = control.id;
		let type = control.type;
		let input;
		if (type === 'checkbox') {
			input = document.createElement('input');
			input.type = 'checkbox';
		} else if (type.startsWith('select:')) {
			let options = type.substr('select:'.length).split('|');
			
			input = document.createElement('select');
			for (let opt of options) {
				let option = document.createElement('option');
				option.appendChild(document.createTextNode(opt));
				option.value = opt;
				input.appendChild(option);
			}
		} else {
			console.error('bad control type');
		}
		
		input.id = 'gen-control-' + (++html_id);
		input.classList.add('control-input');
		let label = document.createElement('label');
		label.htmlFor = input.id;
		label.appendChild(document.createTextNode(control.name));
		if ('tooltip' in control) {
			label.title = control.tooltip;
		}
		container.appendChild(input);
		container.appendChild(document.createTextNode(' '));
		container.appendChild(label);
		root.appendChild(container);
	}
	
	{ // outputs
		let container = document.createElement('div');
		container.classList.add('outs');
		info.outputs.forEach(function (output, i) {
			if (i > 0) {
				container.appendChild(document.createTextNode(', '));
			}
			let span = document.createElement('span');
			span.classList.add('out');
			span.appendChild(document.createTextNode(output.name));
			if ('tooltip' in output) {
				span.title = output.tooltip;
			}
			container.appendChild(span);
		});
		root.appendChild(container);
	}
	
	ui_div.appendChild(root);
	return true;
}

class GLSLGenerationState {
	constructor(widgets) {
		this.widgets = widgets;
		this.code = [];
		this.computing_inputs = {};
		this.variable = 0;
	}
	
	next_variable() {
		this.variable += 1;
		return 'v' + this.variable;
	}
	
	add_code(code) {
		this.code.push(code);
	}
	
	get_code() {
		return this.code.join('');
	}
	
	compute_input(input) {
		input = input.trim();
		if (input.length === 0) {
			return {error: 'empty input'};
		}
		if (!isNaN(input)) {
			return { code: float_glsl(parseFloat(input)), type: 'float' };
		}
		
		if (input.indexOf(',') !== -1) {
			// vector construction
			let items = input.split(',');
			console.assert(items.length >= 2, 'huhhhhh??');
			let components = [];
			for (let item of items) {
				let input = this.compute_input(item);
				if ('error' in input) {
					return {error: input.error};
				}
				components.push(input);
			}
			let component_count = 0;
			let base_type = undefined;
			for (let component of components) {
				let type = component.type;
				let c = type_component_count(type);
				if (c === 0) {
					return {error: `cannot use type ${type} with ,`};
				}
				component_count += c;
				if (base_type === undefined) {
					base_type = type_base_type(type);
				}
				if (base_type !== type_base_type(type)) {
					return {error: 'bad combination of types for ,'};
				}
			}
			let type = type_vec(base_type, component_count);
			if (type === null) {
				// e.g. trying to combine 5 floats
				return {error: 'bad combination of types for ,'};
			}
			let v = this.next_variable();
			let component_values = components.map(function (c) { return c.code; });
			this.add_code(`${type} ${v} = ${type}(${component_values.join()});\n`);
			return {type: type, code: v};
		}
		
		if (input[0] === '#') {
			let color = rgba_hex_to_float(input);
			if (color === null) {
				return {error: 'bad color: ' + input};
			}
			return input.length === 4 || input.length === 7 ?
				{ code: `vec3(${float_glsl(color.r)},${float_glsl(color.g)},${float_glsl(color.b)})`, type: 'vec3' } :
				{ code: `vec4(${float_glsl(color.r)},${float_glsl(color.g)},${float_glsl(color.b)},${float_glsl(color.a)})`, type: 'vec4' };
		}
		
		let dot = input.lastIndexOf('.');
		let field = dot === -1 ? 'out' : input.substr(dot + 1);
		
		if (field.length === 0) {
			return {error: 'inputs should not end in .'};
		}
		
		if (field.length >= 1 && field.length <= 4 && field.split('').every(function (c) { return 'xyzw'.indexOf(c) !== -1 })) {
			// swizzle
			let vector = this.compute_input(input.substr(0, dot));
			let base = type_base_type(vector.type);
			let count = type_component_count(vector.type);
			
			for (let c of field) {
				let i = 'xyzw'.indexOf(c);
				if (i >= count) {
					return {error: `type ${vector.type} has no field ${c}.`};
				}
			}
			
			return {code: `(${vector.code}).${field}`, type: type_vec(base, field.length)};
		}
		
		if (dot === 0) {
			switch (input) {
			case '.pos':
				return {code: 'pos', type: 'vec2'};
			case '.pos01':
				return {code: '(0.5+0.5*pos)', type: 'vec2'};
			case '.time':
				return {code: 'u_time', type: 'float'};
			default:
				return {error: `no such builtin: ${input}`};
			}
		}
		
		if (dot !== -1) {
			input = input.substr(0, dot);
		}
		let esc_input = '-' + input; // prevent wacky stuff if input is an Object built-in
		let widget = this.widgets[esc_input];
		if (widget === undefined) {
			return {error: 'cannot find ' + input};
		}
		
		if (esc_input in this.computing_inputs) {
			return {error: 'circular dependency at ' + input};
		}
		this.computing_inputs[esc_input] = true;
		let value = this.compute_widget_output(widget, field);
		delete this.computing_inputs[esc_input];
		return value;
	}
	
	compute_widget_output(widget, output) {
		if (!('outputs' in widget)) {
			let info = widget_info[widget.func];
			let inputs = {};
			for (let input in widget.inputs) {
				let value = this.compute_input(widget.inputs[input]);
				if ('error' in value) {
					widget.outputs = {error: value.error};
					return {error: value.error};
				}
				inputs[input] = value;	
			}
			for (let control in widget.controls) {
				inputs[control] = widget.controls[control];
			}
			let outputs = info.func(this, inputs);
			widget.outputs = outputs;
		}
		
		let outputs = widget.outputs;
		if ('error' in outputs) {
			return {error: outputs.error};
		}
		if (!(output in outputs)) {
			return {error: `function ${widget.func} has no output ${output}`};
		}
		return outputs[output];
	}
}

function parse_widgets() {
	let widgets = {};
	for (let widget_div of document.getElementsByClassName('widget')) {
		let names = widget_div.getElementsByClassName('widget-name');
		console.assert(names.length <= 1, 'multiple name inputs for widget');
		let name = names.length > 0 ? names[0].value : null;
		let func = widget_div.dataset.func;
		let inputs = {};
		let controls = {};
		for (let input of widget_div.getElementsByClassName('in')) {
			let id = input.dataset.id;
			inputs[id] = input.getElementsByTagName('input')[0].value;
		}
		for (let control of widget_div.getElementsByClassName('control')) {
			let id = control.dataset.id;
			let input = control.getElementsByClassName('control-input')[0];
			let value;
			if (input.tagName === 'INPUT' && input.type == 'checkbox') {
				value = input.checked;
			} else {
				value = input.value;
			}
			controls[id] = value;
		}
		let widget = {
			func: func,
			inputs: inputs,
			controls: controls,
		};
		if (name !== null) {
			widgets['-' + name] = widget;
		}
		if (func === 'output') {
			widgets.output = widget;
		}
	}
	return widgets;
}

function export_widgets(widgets) {
	let data = [];
	for (let name in widgets) {
		let widget = widgets[name];
		data.push(widget.func);
		data.push(';');
		data.push('n:');
		data.push(name);
		data.push(';');
		for (let input in widget.inputs) {
			data.push('i');
			data.push(input);
			data.push(':');
			data.push(widget.inputs[input]);
			data.push(';');
		}
		for (let control in widget.controls) {
			data.push('c');
			data.push(control);
			data.push(':');
			data.push(widget.controls[control]);
			data.push(';');
		}
		data.pop(); // remove terminal separator
		data.push(';;');
	}
	data.pop(); // remove terminal separator
	return data.join('');
}

function import_widgets(string) {
	let widgets = {};
	for (let widget_str of string.split(';;')) {
		let widget = {};
		let name = null;
		let parts = widget_str.split(';');
		let func = parts[0];
		let info = widget_info[func];
		parts.splice(0, 1);
		
		for (let part of parts) {
			let kv = part.split(':');
			if (kv.length !== 2) {
				return {error: `bad key-value pair (kv count ${kv.length})`};
			}
			let type = kv[0][0];
			let key = kv[0].substr(1);
			let value = kv[1];
			if (type === 'n') {
				// name
				name = key;
			} else if (type === 'i') {
				// input
				widget.inputs[key] = value;
			} else if (type === 'c') {
				// control
				widget.controls[key] = value;
			} else {
				return {error: `bad widget part type: '${type}'`};
			}
		}
		
		if (name === null) {
			return {error: 'widget has no name'};
		}
		widgets[name] = widget;
	}
	return widgets;
}

function get_shader_source() {
	let widgets = parse_widgets();
	let output_widget = widgets.output;
	let state = new GLSLGenerationState(widgets);
	if (output_widget === undefined) {
		show_error('no output color');
		return null;
	}
	let output = state.compute_widget_output(output_widget, 'out');
	if ('error' in output) {
		show_error(output.error);
		return null;
	}
	if (output.type !== 'vec3') {
		show_error('output color should have type vec3, but it has type ' + output.type);
		return null;
	}
	state.add_code(`return ${output.code};\n`);
	let code = state.get_code();
	console.log(code);
	console.log(export_widgets(widgets));
	return code;
}

function update_widget_choices() {
	let search_term = widget_search.value.toLowerCase();
	let choices = widget_choices.getElementsByClassName('widget-choice');
	widget_ids_sorted_by_name.forEach(function (id, i) {
		let name = widget_info[id].name;
		let choice = choices[i];
		let shown = name.toLowerCase().indexOf(search_term) !== -1;
		if (id === 'output') {
			shown = false;
		}
		choice.style.display = shown ? 'block' : 'none';
	});
}

function startup() {
	page = document.getElementById('page');
	canvas = document.getElementById('canvas');
	ui_div = document.getElementById('ui');
	widget_choices = document.getElementById('widget-choices');
	widget_search = document.getElementById('widget-search');
	
	gl = canvas.getContext('webgl');
	if (gl === null) {
		// support for very-old-but-not-ancient browsers
		gl = canvas.getContext('experimental-webgl');
		if (gl === null) {
			show_error('your browser doesnt support webgl.\noh well.');
			return;
		}
	}
	
	program_main = compile_program('main', {
		'vertex': `
attribute vec2 v_pos;
varying vec2 uv;
void main() {
	uv = v_pos * 0.5 + 0.5;
	gl_Position = vec4(v_pos, 0.0, 1.0);
}`,
		'fragment': `
#ifdef GL_ES
precision highp float;
#endif

uniform sampler2D u_texture;
uniform float u_time;
varying vec2 uv;

void main() {
	vec2 u = pow(uv,vec2(1.2 + 0.4 * sin(u_time)));
	vec2 k =floor(3.0 * u); 
	int i = int(k.y * 3.0 + k.x);
	if (i == 4) discard;
	vec3 sample = texture2D(u_texture, mod(3.0*u, 1.0)).xyz;
	float h = mod(float(i) * 5.0, 8.0) / 8.0;
	sample = vec3(
		mix(sample.x, sample.z, h),
		mix(sample.y, sample.x, h),
		mix(sample.z, sample.y, h)
	);
	gl_FragColor = vec4(mix(sample, vec3(1.0,0.0,0.0), 0.2),1.0);
}
`
	});
	if (program_main === null) {
		return;
	}
	
	program_post = compile_program('post', {
		'vertex': `
attribute vec2 v_pos;
varying vec2 uv;
void main() {
	uv = v_pos * 0.5 + 0.5;
	gl_Position = vec4(v_pos, 0.0, 1.0);
}
`,
		'fragment': `
#ifdef GL_ES
precision highp float;
#endif
uniform sampler2D u_texture;
varying vec2 uv;
void main() {
	gl_FragColor = texture2D(u_texture, uv);
}
`,
	});
	if (program_post === null) {
		return;
	}
	
	vertex_buffer_rect = gl.createBuffer();
	gl.bindBuffer(gl.ARRAY_BUFFER, vertex_buffer_rect);
	gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([
		-1.0, -1.0, 1.0, -1.0, 1.0, 1.0,
		-1.0, -1.0, 1.0, 1.0, -1.0, 1.0
	]), gl.STATIC_DRAW);
	
	vertex_buffer_main = gl.createBuffer();
	gl.bindBuffer(gl.ARRAY_BUFFER, vertex_buffer_main);
	gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([
		-1.0, -1.0, 1.0, -1.0, 1.0, 1.0,
		-1.0, -1.0, 1.0, 1.0, -1.0, 1.0
	]), gl.STATIC_DRAW);
	
	framebuffer_color_texture = gl.createTexture();
	sampler_texture = gl.createTexture();
	
	// add widget buttons
	for (let id of widget_ids_sorted_by_name) {
		let widget = widget_info[id];
		let button = document.createElement('button');
		button.classList.add('widget-choice');
		if ('tooltip' in widget) {
			button.title = widget.tooltip;
		}
		button.appendChild(document.createTextNode(widget.name));
		widget_choices.appendChild(button);
		button.addEventListener('click', function (e) {
			add_widget(id);
		});
	}
	
	set_up_framebuffer();
	add_widget('output');
	update_widget_choices();
	widget_search.addEventListener('input', function (e) {
		update_widget_choices();
	});
	
	frame(0.0);
	window.addEventListener('keydown', on_key_press);
	window.addEventListener('keyup', on_key_release);
	window.addEventListener('mousemove', on_mouse_move);
	window.addEventListener('click', on_click);
}

function frame(time) {
	current_time = time * 1e-3;
	let ui_width = ui_shown ? ui_div.offsetWidth : 0;
	let page_width = page.offsetWidth - ui_width;
	let page_height = page.offsetHeight;
	
	let aspect_ratio = width / height;
	let canvas_x = 0, canvas_y = 0;
	if (page_width / aspect_ratio < page_height) {
		// landscape mode
		canvas_y = Math.floor((page_height - viewport_height) * 0.5);
		viewport_width = page_width;
		viewport_height = Math.floor(page_width / aspect_ratio);
	} else {
		// portrait mode
		canvas_x = Math.floor((page_width - viewport_width) * 0.5);
		viewport_width = Math.floor(page_height * aspect_ratio);
		viewport_height = page_height;
	}
	
	canvas.width = viewport_width;
	canvas.height = viewport_height;
	canvas.style.left = ui_width + canvas_x + 'px';
	canvas.style.top = canvas_y + 'px';
	
	let step = true;
	if (step) {
		perform_step();
	}
	
	gl.bindFramebuffer(gl.FRAMEBUFFER, null);
	gl.viewport(0, 0, viewport_width, viewport_height);
	gl.clearColor(0.0, 0.0, 0.0, 1.0);
	gl.clear(gl.COLOR_BUFFER_BIT);
	
	gl.useProgram(program_post);
	gl.bindBuffer(gl.ARRAY_BUFFER, vertex_buffer_rect);
	gl.activeTexture(gl.TEXTURE0);
	gl.bindTexture(gl.TEXTURE_2D, sampler_texture);
	gl.uniform1i(gl.getUniformLocation(program_post, 'u_texture'), 0);
	let v_pos = gl.getAttribLocation(program_post, 'v_pos');
	gl.enableVertexAttribArray(v_pos);
	gl.vertexAttribPointer(v_pos, 2, gl.FLOAT, false, 0, 0);
	gl.drawArrays(gl.TRIANGLES, 0, 6);
	
	if (requestAnimationFrame == null) {
		show_error('your browser doesnt support requestAnimationFrame.\noh well.');
		return;
	}
	requestAnimationFrame(frame);
}

function perform_step() {
	if (width === -1) {
		// not properly loaded yet
		return;
	}
	
	gl.bindFramebuffer(gl.FRAMEBUFFER, framebuffer);
	gl.viewport(0, 0, width, height);
	gl.clearColor(0.0, 0.0, 0.0, 1.0);
	gl.clear(gl.COLOR_BUFFER_BIT);
	
	gl.useProgram(program_main);
	gl.activeTexture(gl.TEXTURE0);
	gl.bindTexture(gl.TEXTURE_2D, sampler_texture);
	gl.uniform1i(gl.getUniformLocation(program_main, 'u_texture'), 0);
	gl.uniform1f(gl.getUniformLocation(program_main, 'u_time'), current_time % 3600);
	gl.uniform2f(gl.getUniformLocation(program_main, 'u_texture_size'), width, height);
	
	gl.bindBuffer(gl.ARRAY_BUFFER, vertex_buffer_main);
	let v_pos = gl.getAttribLocation(program_main, 'v_pos');
	gl.enableVertexAttribArray(v_pos);
	gl.vertexAttribPointer(v_pos, 2, gl.FLOAT, false, 8, 0);
	gl.drawArrays(gl.TRIANGLES, 0, 6);
	
	gl.bindTexture(gl.TEXTURE_2D, sampler_texture);
	gl.copyTexImage2D(gl.TEXTURE_2D, 0, gl.RGBA, 0, 0, width, height, 0);
}
	
function compile_program(name, shaders) {
	let program = gl.createProgram();
	for (let type in shaders) {
		let source = shaders[type];
		let gl_type;
		if (type === 'vertex') {
			gl_type = gl.VERTEX_SHADER;
		} else if (type === 'fragment') {
			gl_type = gl.FRAGMENT_SHADER;
		} else {
			show_error('unrecognized shader type: ' + type);
		}
		let shader = compile_shader(name + ' ' + type, gl_type, source);
		if (shader === null)
			return null;
		gl.attachShader(program, shader);
	}
	
	gl.linkProgram(program);
	if (!gl.getProgramParameter(program, gl.LINK_STATUS)) {
		show_error('Error linking shader program:\n' + gl.getProgramInfoLog(program));
		return null;
	}
	return program;
}

function set_up_framebuffer() {
	framebuffer = gl.createFramebuffer();
	let sampler_pixels = new Uint8Array(width * height * 4);
	sampler_pixels.fill(0);
	set_up_rgba_texture(sampler_texture, width, height, sampler_pixels);
	set_up_rgba_texture(framebuffer_color_texture, width, height, null);
	gl.bindFramebuffer(gl.FRAMEBUFFER, framebuffer);
	gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, framebuffer_color_texture, 0);
	let status = gl.checkFramebufferStatus(gl.FRAMEBUFFER);
	if (status !== gl.FRAMEBUFFER_COMPLETE) {
		show_error('Error: framebuffer incomplete (status ' + status + ')');
		return;
	}
}

function set_up_rgba_texture(texture, width, height, pixels) {
	gl.bindTexture(gl.TEXTURE_2D, texture);
	gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, width, height, 0,
		gl.RGBA, gl.UNSIGNED_BYTE, pixels);
	gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
	gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
	gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
	gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
}

function compile_shader(name, type, source) {
	let shader = gl.createShader(type);
	gl.shaderSource(shader, source);
	gl.compileShader(shader);
	
	if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
		show_error('Error compiling shader ' + name + ':\n' +
			gl.getShaderInfoLog(shader));
		return null;
	}
	return shader;
}

function show_error(error) {
	document.getElementById('error-message').innerText = error;
	document.getElementById('error-dialog').showModal();
}