#version 450

//#extension GL_ARB_gpu_shader5 : require

layout (location = 0) in vec4 v_color;
layout (location = 1) in vec4 v_texcoord;



layout (std140, binding = 0) uniform uniforms_t
{ 
  mat4 ViewProjectionMatrix;
  mat4 ModelMatrix;
  vec4 param1;     
} ub;


//layout (binding = 1) uniform sampler2D tex;

/*
layout(push_constant) uniform push_block_t
{
  float time;
} cb;
*/


layout (location = 0) out vec4 FragColor;


// Original code: https://www.shadertoy.com/view/MdGGzy
/*
"Seascape" by Alexander Alekseev aka TDM - 2014
License Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.
Contact: tdmaav@gmail.com
*/


const int NUM_STEPS = 8;
const float PI	 	= 3.1415;
const float EPSILON	= 1e-3;
//float EPSILON_NRM	= 0.1 / iResolution.x;
//float EPSILON_NRM	= 0.1 / ub.param1.x;
float EPSILON_NRM	= 0.1;

// sea
const int ITER_GEOMETRY = 3;
const int ITER_FRAGMENT = 5;
const float SEA_HEIGHT = 0.6;
const float SEA_CHOPPY = 4.0;
const float SEA_SPEED = 0.8;
const float SEA_FREQ = 0.16;
const vec3 SEA_BASE = vec3(0.1,0.19,0.22);
const vec3 SEA_WATER_COLOR = vec3(0.8,0.9,0.6);
//float SEA_TIME = iGlobalTime * SEA_SPEED;
//float SEA_TIME = ub.param1.z * SEA_SPEED;
float SEA_TIME = 0;
mat2 octave_m = mat2(1.6,1.2,-1.2,1.6);

// math
mat3 fromEuler(vec3 ang) {
	vec2 a1 = vec2(sin(ang.x),cos(ang.x));
    vec2 a2 = vec2(sin(ang.y),cos(ang.y));
    vec2 a3 = vec2(sin(ang.z),cos(ang.z));
    mat3 m;
    m[0] = vec3(a1.y*a3.y+a1.x*a2.x*a3.x,a1.y*a2.x*a3.x+a3.y*a1.x,-a2.y*a3.x);
	m[1] = vec3(-a2.y*a1.x,a1.y*a2.y,a2.x);
	m[2] = vec3(a3.y*a1.x*a2.x+a1.y*a3.x,a1.x*a3.x-a1.y*a3.y*a2.x,a2.y*a3.y);
	return m;
}



/*
float hash( vec2 p ) {
	float h = dot(p,vec2(127.1,311.7));	
    return fract(sin(h)*43758.5453123);
}
*/

/*
//
// Corruptions on Intel GPUs:  https://www.geeks3d.com/forums/index.php/topic,5859.0.html
//
float dot_precise(vec2 a, vec2 b)
{
    precise float result = 0;
    result += a.x * b.x;
    result += a.y * b.y;
    return result;
}

float hash(vec2 p)
{
  float h = dot_precise(p, vec2(127.09999847412109375, 311.70001220703125));
  return fract(sin(h) * 43758.546875);
}
*/

void dot_precise(vec2 a, vec2 b, precise out float result)
{
    result = 0;
    result += a.x * b.x;
    result += a.y * b.y;
}

float hash(vec2 p)
{
  float h = 0;
  dot_precise(p, vec2(127.09999847412109375, 311.70001220703125), h);
  return fract(sin(h) * 43758.546875);
}







float noise( in vec3 uvt ) {
    vec2 p = uvt.xy;
    vec2 ft = fract(uvt.z * vec2(1.0, 1.0));
    vec2 i = floor(p+ft) + floor(uvt.z);
    vec2 f = fract( p +ft );
	vec2 u = f*f*(3.0-2.0*f);
    return -1.0+2.0*mix( mix( hash( i + vec2(0.0,0.0) ), 
                     hash( i + vec2(1.0,0.0) ), u.x),
                mix( hash( i + vec2(0.0,1.0) ), 
                     hash( i + vec2(1.0,1.0) ), u.x), u.y);
}

// lighting
float diffuse(vec3 n,vec3 l,float p) 
{
    //return pow(dot(n,l) * 0.4 + 0.6,p);

    //  https://www.geeks3d.com/forums/index.php/topic,5973.0.html
    return pow(max(dot(n,l) * 0.4 + 0.6, 0.0),p);
}

float specular(vec3 n,vec3 l,vec3 e,float s) 
{    
    float nrm = (s + 8.0) / (3.1415 * 8.0);
    return pow(max(dot(reflect(e,n),l),0.0),s) * nrm;
}

// sky
vec3 getSkyColor(vec3 e) 
{
    e.y = max(e.y,0.0);
    vec3 ret;

    //ret.x = pow(1.0-e.y,2.0);

    //  https://www.geeks3d.com/forums/index.php/topic,5973.0.html
    ret.x = pow(max(1.0-e.y, 0.0),2.0);

    ret.y = 1.0-e.y;
    ret.z = 0.6+(1.0-e.y)*0.4;
    return ret;
}

// sea
float sea_octave(vec3 uvt, float choppy) 
{
    vec2 uv = uvt.xy;// + uvt.z;
    uv += noise(uvt);
    vec2 cost = cos(uvt.z * vec2(1.0, 1.0));
    vec2 sint = sin(uvt.z * vec2(1.0, 1.0));
    vec2 wv = 1.0-abs(sin(uv)*cost  + sint*cos(uv) );
    vec2 swv = abs(cos(uv)*cost - sin(uv)*sint);    
    
    wv = mix(wv,swv,wv);
    //return pow(1.0-pow(wv.x * wv.y,0.65),choppy);

    //  https://www.geeks3d.com/forums/index.php/topic,5973.0.html
    return pow(max(1.0-pow(max(wv.x * wv.y, 0.0),0.65), 0.0),choppy);
}

float map(vec3 p) {
    float freq = SEA_FREQ;
    float amp = SEA_HEIGHT;
    float choppy = SEA_CHOPPY;
    SEA_TIME = ub.param1.z * SEA_SPEED;

    vec3 uvt = vec3(p.xz, SEA_TIME); uvt.x *= 0.75;
    
    float d, h = 0.0;    
    for(int i = 0; i < ITER_GEOMETRY; i++) {        
    	d = sea_octave((uvt)*freq,choppy);
    	d += sea_octave((uvt)*freq,choppy);
        h += d * amp;        
    	uvt.xy *= octave_m; freq *= 1.9; amp *= 0.22;
        choppy = mix(choppy,1.0,0.2);
    }
    return p.y - h;
}

float map_detailed(vec3 p) {
    float freq = SEA_FREQ;
    float amp = SEA_HEIGHT;
    float choppy = SEA_CHOPPY;
    SEA_TIME = ub.param1.z * SEA_SPEED;
    vec3 uvt = vec3(p.xz, SEA_TIME); uvt.x *= 0.75;
    
    float d, h = 0.0;    
    for(int i = 0; i < ITER_FRAGMENT; i++) {        
    	d = sea_octave((uvt)*freq,choppy);
    	d += sea_octave((uvt)*freq,choppy);
        h += d * amp;        
    	uvt.xy*= octave_m; freq *= 1.9; amp *= 0.22;
        choppy = mix(choppy,1.0,0.2);
    }
    return p.y - h;
}

vec3 getSeaColor(vec3 p, vec3 n, vec3 l, vec3 eye, vec3 dist) {  
    float fresnel = 1.0 - max(dot(n,-eye),0.0);

    //fresnel = pow(fresnel,3.0) * 0.65;

    //https://www.geeks3d.com/forums/index.php/topic,5973.0.html
    fresnel = pow(max(fresnel, 0.0),3.0) * 0.65;
        
    vec3 reflected = getSkyColor(reflect(eye,n));    
    vec3 refracted = SEA_BASE + diffuse(n,l,80.0) * SEA_WATER_COLOR * 0.12; 
    
    vec3 color = mix(refracted,reflected,fresnel);
    
    float atten = max(1.0 - dot(dist,dist) * 0.001, 0.0);
    color += SEA_WATER_COLOR * (p.y - SEA_HEIGHT) * 0.18 * atten;
    
    color += vec3(specular(n,l,eye,60.0));
    
    return color;
}

// tracing
vec3 getNormal(vec3 p, float eps) {
    vec3 n;
    n.y = map_detailed(p);    
    n.x = map_detailed(vec3(p.x+eps,p.y,p.z)) - n.y;
    n.z = map_detailed(vec3(p.x,p.y,p.z+eps)) - n.y;
    n.y = eps;
    return normalize(n);
}


// Error:  Seascape: uninitialized out variable
// https://www.geeks3d.com/forums/index.php/topic,5693.0.html
//float heightMapTracing(vec3 ori, vec3 dir, out vec3 p) {  

float heightMapTracing(vec3 ori, vec3 dir, inout vec3 p) {  
    float tm = 0.0;
    float tx = 1000.0;    
    float hx = map(ori + dir * tx);
    if(hx > 0.0) return tx;   
    float hm = map(ori + dir * tm);    
    float tmid = 0.0;
    for(int i = 0; i < NUM_STEPS; i++) {
        tmid = mix(tm,tx, hm/(hm-hx));                   
        p = ori + dir * tmid;                   
    	float hmid = map(p);
		if(hmid < 0.0) {
        	tx = tmid;
            hx = hmid;
        } else {
            tm = tmid;
            hm = hmid;
        }
    }
    return tmid;
}

// main
void mainImage( out vec4 fragColor, in vec2 fragCoord ) {

  EPSILON_NRM	= 0.1 / ub.param1.x;

  vec2 uv = v_texcoord.xy;
	//vec2 uv = fragCoord.xy / ub.param1.xy;
  uv = uv * 2.0 - 1.0;
  uv.x *= ub.param1.x / ub.param1.y;    
  float time = ub.param1.z * 0.3;
        
  // ray
  vec3 ang = vec3(sin(time*3.0)*0.1,sin(time)*0.2+0.3,time);    
  vec3 ori = vec3(0.0,3.5,time*5.0);
  vec3 dir = normalize(vec3(uv.xy,-2.0)); dir.z += length(uv) * 0.15;
  dir = normalize(dir) * fromEuler(ang);
  
  // tracing
  // Error:  Seascape: uninitialized out variable
  // https://www.geeks3d.com/forums/index.php/topic,5693.0.html
  vec3 p = vec3(0.0);

  heightMapTracing(ori,dir,p);
  vec3 dist = p - ori;
  vec3 n = getNormal(p, dot(dist,dist) * EPSILON_NRM);
  vec3 light = normalize(vec3(0.0,1.0,0.8)); 
           
  // color
  vec3 color = mix( getSkyColor(dir),  getSeaColor(p,n,light,dir,dist), pow(smoothstep(0.0,-0.05,dir.y),0.3));
      
  // post
  // fragColor = vec4(pow(color,vec3(0.75)), 1.0);

  //https://www.geeks3d.com/forums/index.php/topic,5973.0.html
  fragColor = vec4(pow(max(color, vec3(0.0)),vec3(0.75)), 1.0);

}

void main( void ){vec4 color = vec4(0.0,0.0,0.0,1.0);mainImage( color, gl_FragCoord.xy );color.w = 1.0; FragColor = color;}  
