#version 430

in vec4 vPosition;
in vec4 vNormal;
in vec2 vCoords;

uniform mat4 World;
uniform vec3 SunPos = vec3(0,1000,7200);
uniform float elapsedTime;

uniform samplerCube skybox;

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

vec4 permute(vec4 x)
{
    return mod289(((x*34.0)+1.0)*x);
}

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

vec2 fade(vec2 t)
{
    return t * t * t * ( t * ( t * 6.0 - 15.0 ) + 10.0 );
}

float cnoise(vec2 P, vec2 rep)
{
    vec4 Pi = floor(P.xyxy) + vec4(0.0,0.0,1.0,1.0);
    vec4 Pf = fract(P.xyxy) - vec4(0.0,0.0,1.0,1.0);
    Pi = mod(Pi, rep.xyxy);  // To create noise with explicit period
    Pi = mod289(Pi);         // To avoid truncation effects in permutation
    vec4 ix = Pi.xzxz;
    vec4 iy = Pi.yyww;
    vec4 fx = Pf.xzxz;
    vec4 fy = Pf.yyww;

    vec4 i = permute( permute(ix) + iy );

    vec4 gx = fract(i * (1.0 / 41.0)) * 2.0 - 1.0;
    vec4 gy = abs(gx) - 0.5;
    vec4 tx = floor(gx + 0.5);
    gx = gx - tx;

    vec2 g00 = vec2(gx.x, gy.x);
    vec2 g10 = vec2(gx.y, gy.y);
    vec2 g01 = vec2(gx.z, gy.z);
    vec2 g11 = vec2(gx.w, gy.w);

    vec4 norm = taylorInvSqrt( vec4(dot(g00,g00), dot(g01,g01), dot(g10,g10), dot(g11,g11) ) );
    g00 *= norm.x;
    g01 *= norm.y;
    g10 *= norm.z;
    g11 *= norm.w;

    float n00 = dot(g00, vec2(fx.x, fy.x));
    float n10 = dot(g10, vec2(fx.y, fy.y));
    float n01 = dot(g01, vec2(fx.z, fy.z));
    float n11 = dot(g11, vec2(fx.w, fy.w));

    vec2 fade_xy = fade(Pf.xy);
    vec2 n_x = mix(vec2(n00,n01), vec2(n10, n11), fade_xy.x);
    float n_xy = mix(n_x.x, n_x.y, fade_xy.y);
    return 2.3 * n_xy;
}

float cnoise(vec2 P)
{
    vec4 Pi = floor(P.xyxy) + vec4(0.0,0.0,1.0,1.0);
    vec4 Pf = fract(P.xyxy) - vec4(0.0,0.0,1.0,1.0);
    Pi = mod289(Pi);         // To avoid truncation effects in permutation
    vec4 ix = Pi.xzxz;
    vec4 iy = Pi.yyww;
    vec4 fx = Pf.xzxz;
    vec4 fy = Pf.yyww;

    vec4 i = permute( permute(ix) + iy );

    vec4 gx = fract(i * (1.0 / 41.0)) * 2.0 - 1.0;
    vec4 gy = abs(gx) - 0.5;
    vec4 tx = floor(gx + 0.5);
    gx = gx - tx;

    vec2 g00 = vec2(gx.x, gy.x);
    vec2 g10 = vec2(gx.y, gy.y);
    vec2 g01 = vec2(gx.z, gy.z);
    vec2 g11 = vec2(gx.w, gy.w);

    vec4 norm = taylorInvSqrt( vec4(dot(g00,g00), dot(g01,g01), dot(g10,g10), dot(g11,g11) ) );
    g00 *= norm.x;
    g01 *= norm.y;
    g10 *= norm.z;
    g11 *= norm.w;

    float n00 = dot(g00, vec2(fx.x, fy.x));
    float n10 = dot(g10, vec2(fx.y, fy.y));
    float n01 = dot(g01, vec2(fx.z, fy.z));
    float n11 = dot(g11, vec2(fx.w, fy.w));

    vec2 fade_xy = fade(Pf.xy);
    vec2 n_x = mix(vec2(n00,n01), vec2(n10, n11), fade_xy.x);
    float n_xy = mix(n_x.x, n_x.y, fade_xy.y);
    return 2.3 * n_xy;
}

float fbm(vec2 P, float lacunarity, float gain)
{
    float sum = 0.0;
    float amp = 0.3;
    vec2 pp = P;
    const int octaves = 4;
    int i;

    for(i = 0; i < octaves; i+=1)
    {
        amp *= gain;
        sum += amp * cnoise(pp);
        pp *= lacunarity;
    }
    return sum;
}

float pattern( in vec2 p, out vec2 q, out vec2 r , in float time)
{
    float l = 4.3;
    float g = 0.4;

    q.x = fbm( p + vec2(time,time),l,g);
    q.y = fbm( p + vec2(5.2*time,1.3*time),l,g);

    r.x = fbm( p + 4.0*q + vec2(1.7,9.2),l,g);
    r.y = fbm( p + 4.0*q + vec2(8.3,2.8),l,g);


    // NOTE:: g pretty much controls the height/intensity of the
    // water - thus around environments that'd be great.
    //  - slow movement
    return fbm( q + 4.0*r,l,g);
}

float pattern2( in vec2 p, out vec2 q, out vec2 r , in float time)
{
    float l = 1.3;
    float g = 2.4;

    q.x = fbm( p + vec2(time,time),l,g);
    q.y = fbm( p + vec2(5.2*time,8.3*time),l,g);

    r.x = cnoise( p + 4.0*q + vec2(1.7,9.2));
    r.y = cnoise( p + 4.0*q + vec2(8.3,2.8));

    return fbm( q + 4.0*r,l,g);
}

void main()
{
    vec3 I = vec3(normalize(vPosition.xyz - World[3].xyz));
    vec3 R = vec3(reflect(I, normalize(vNormal.xyz)));

    vec2 qq = vec2(0), rep = vec2(0), p = (-vPosition.xz/100);

    float perlin = pattern(p,qq,rep,elapsedTime*0.25);
    vec4 greenyBlue = texture(skybox, R) * vec4(0.584313, 0.709, 0.709, 1);

    vec4 finalColour = (greenyBlue.rgb+texture(skybox,R).rgb) * perlin;
    finalColour.rgb += finalColour.rgb + (1 - perlin) * greenyBlue.rgb;
    finalColour.rgb += ((vec3(specularity)*vec3(1, 0.75, 0.65)));
    finalColour.a = 0.6;

    gl_FragColor = finalColour;
}