#include "water_frag.h"

const char* shader_water_frag = "precision highp float; \n"
" \n"
"varying vec3 vWorldPos; \n"
"varying vec3 vNormal; \n"
" \n"
"uniform vec3 cameraPos; \n"
"uniform vec3 sunDir;      // normalized direction from the water toward the sun \n"
"uniform vec3 sunColor; \n"
"uniform float time; \n"
" \n"
"float hash(vec2 p) { \n"
"    p = fract(p * vec2(123.34, 456.21)); \n"
"    p += dot(p, p + 45.32); \n"
"    return fract(p.x * p.y); \n"
"} \n"
" \n"
"float valueNoise(vec2 p) { \n"
"    vec2 i = floor(p); \n"
"    vec2 f = fract(p); \n"
"    float a = hash(i); \n"
"    float b = hash(i + vec2(1.0, 0.0)); \n"
"    float c = hash(i + vec2(0.0, 1.0)); \n"
"    float d = hash(i + vec2(1.0, 1.0)); \n"
"    vec2 u = f * f * (3.0 - 2.0 * f); \n"
"    return mix(mix(a, b, u.x), mix(c, d, u.x), u.y); \n"
"} \n"
" \n"
"void main() { \n"
"    vec3 N = normalize(vNormal); \n"
"    vec3 V = normalize(cameraPos - vWorldPos); \n"
" \n"
"    // Fresnel (Schlick). \n"
"    float f0 = 0.02; \n"
"    float fres = f0 + (1.0 - f0) * pow(1.0 - max(dot(N, V), 0.0), 5.0); \n"
" \n"
"    // Refraction: depth-tinted water body, wobbled by the surface normal. \n"
"    float depth01 = clamp((vWorldPos.z + 350.0) / 400.0, 0.0, 1.0); \n"
"    float wob = (N.x + N.z) * 0.5; \n"
"    vec3 shallow = vec3(0.10, 0.55, 0.60); \n"
"    vec3 deep    = vec3(0.02, 0.14, 0.28); \n"
"    vec3 refractCol = mix(shallow, deep, clamp(depth01 + wob * 0.15, 0.0, 1.0)); \n"
" \n"
"    // Reflection: sky gradient + reflected sun glow + broken-up specular glitter. \n"
"    vec3 R = reflect(-V, N); \n"
"    vec3 skyHorizon = vec3(0.80, 0.88, 0.98); \n"
"    vec3 skyTop     = vec3(0.30, 0.55, 0.95); \n"
"    float skyT = clamp(R.y * 2.0, 0.0, 1.0); \n"
"    vec3 reflectCol = mix(skyHorizon, skyTop, skyT); \n"
" \n"
"    float sunAmt = max(dot(R, sunDir), 0.0); \n"
"    reflectCol += sunColor * pow(sunAmt, 8.0) * 0.6; \n"
"    float sparkle = valueNoise(vWorldPos.xz * 0.5 + vec2(time * 1.3, time * 0.7)); \n"
"    float spec = pow(sunAmt, 200.0) * smoothstep(0.55, 0.9, sparkle); \n"
"    reflectCol += sunColor * spec * 4.0; \n"
" \n"
"    vec3 color = mix(refractCol, reflectCol, fres); \n"
" \n"
"    // Horizon haze: hide the far straight edge of the plane by fading to sky. \n"
"    float horizonFade = clamp((vWorldPos.z + 350.0) / 90.0, 0.0, 1.0); \n"
"    color = mix(skyHorizon, color, horizonFade); \n"
" \n"
"    gl_FragColor = vec4(color, 1.0);   // opaque -> occludes the sun below the waterline \n"
"} \n"
" \n";