/*
 * SPDX-FileCopyrightText: syuilo and misskey-project
 * SPDX-License-Identifier: AGPL-3.0-only
 */

export function loadShader(gl: WebGL2RenderingContext, type: GLenum, source: string): WebGLShader {
	const shader = gl.createShader(type);
	if (shader == null) {
		throw new Error('falied to create shader');
	}

	gl.shaderSource(shader, source);
	gl.compileShader(shader);

	if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
		console.error(`falied to compile shader: ${gl.getShaderInfoLog(shader)}`);
		gl.deleteShader(shader);
		throw new Error(`falied to compile shader: ${gl.getShaderInfoLog(shader)}`);
	}

	return shader;
}

export function initShaderProgram(gl: WebGL2RenderingContext, vsSource: string, fsSource: string): WebGLProgram {
	const vertexShader = loadShader(gl, gl.VERTEX_SHADER, vsSource);
	const fragmentShader = loadShader(gl, gl.FRAGMENT_SHADER, fsSource);

	const shaderProgram = gl.createProgram();

	gl.attachShader(shaderProgram, vertexShader);
	gl.attachShader(shaderProgram, fragmentShader);
	gl.linkProgram(shaderProgram);

	if (!gl.getProgramParameter(shaderProgram, gl.LINK_STATUS)) {
		console.error(`failed to init shader: ${gl.getProgramInfoLog(shaderProgram)}`);
		throw new Error('failed to init shader');
	}

	return shaderProgram;
}

export const GLSL_LIB_SNOISE = `
// Description : Array and textureless GLSL 2D/3D/4D simplex
//               noise functions.
//      Author : Ian McEwan, Ashima Arts.
//  Maintainer : stegu
//     Lastmod : 20201014 (stegu)
//     License : Copyright (C) 2011 Ashima Arts. All rights reserved.
//               Distributed under the MIT License. See LICENSE file.
//               https://github.com/ashima/webgl-noise
//               https://github.com/stegu/webgl-noise

vec3 mod289(vec3 x) {
	return x - floor(x * (1.0 / 289.0)) * 289.0;
}

vec4 mod289(vec4 x) {
	return x - floor(x * (1.0 / 289.0)) * 289.0;
}

vec4 permute(vec4 x) {
	return mod289(((x * 34.0) + 10.0) * x);
}

vec4 taylorInvSqrt(vec4 r) {
	return 1.79284291400159 - 0.85373472095314 * r;
}

float snoise(vec3 v) {
	const vec2 C = vec2(1.0/6.0, 1.0/3.0);
	const vec4 D = vec4(0.0, 0.5, 1.0, 2.0);

	vec3 i = floor(v + dot(v, C.yyy));
	vec3 x0 = v - i + dot(i, C.xxx);

	vec3 g = step(x0.yzx, x0.xyz);
	vec3 l = 1.0 - g;
	vec3 i1 = min(g.xyz, l.zxy);
	vec3 i2 = max(g.xyz, l.zxy);

	vec3 x1 = x0 - i1 + C.xxx;
	vec3 x2 = x0 - i2 + C.yyy;
	vec3 x3 = x0 - D.yyy;

	i = mod289(i);
	vec4 p = permute(permute(permute(
						i.z + vec4(0.0, i1.z, i2.z, 1.0))
					+ i.y + vec4(0.0, i1.y, i2.y, 1.0))
					+ i.x + vec4(0.0, i1.x, i2.x, 1.0));

	float n_ = 0.142857142857;
	vec3 ns = n_ * D.wyz - D.xzx;

	vec4 j = p - 49.0 * floor(p * ns.z * ns.z);

	vec4 x_ = floor(j * ns.z);
	vec4 y_ = floor(j - 7.0 * x_);

	vec4 x = x_ * ns.x + ns.yyyy;
	vec4 y = y_ * ns.x + ns.yyyy;
	vec4 h = 1.0 - abs(x) - abs(y);

	vec4 b0 = vec4(x.xy, y.xy);
	vec4 b1 = vec4(x.zw, y.zw);

	vec4 s0 = floor(b0) * 2.0 + 1.0;
	vec4 s1 = floor(b1) * 2.0 + 1.0;
	vec4 sh = -step(h, vec4(0.0));

	vec4 a0 = b0.xzyw + s0.xzyw * sh.xxyy;
	vec4 a1 = b1.xzyw + s1.xzyw * sh.zzww;

	vec3 p0 = vec3(a0.xy, h.x);
	vec3 p1 = vec3(a0.zw, h.y);
	vec3 p2 = vec3(a1.xy, h.z);
	vec3 p3 = vec3(a1.zw, h.w);

	vec4 norm = taylorInvSqrt(vec4(dot(p0, p0), dot(p1, p1), dot(p2, p2), dot(p3, p3)));
	p0 *= norm.x;
	p1 *= norm.y;
	p2 *= norm.z;
	p3 *= norm.w;

	vec4 m = max(0.5 - vec4(dot(x0, x0), dot(x1, x1), dot(x2, x2), dot(x3, x3)), 0.0);
	m = m * m;
	return 105.0 * dot(m * m, vec4(dot(p0, x0), dot(p1, x1), dot(p2, x2), dot(p3, x3)));
}
`;