#version 450

layout (location = 0) in vec3 aPos;
layout (location = 1) in vec2 aTexCoords;

out vec3 FragPos;
out vec2 TexCoords;
out vec3 Normal;

uniform mat4 model;
uniform mat4 view;
uniform mat4 projection;
uniform float uTime;

// Wave configuration constants
const float AMPLITUDE = 0.15;
const float FREQUENCY = 1.5;
const float SPEED = 2.0;

// Simple wave function that modifies elevation based on position and time
float calculateWave(vec3 pos, float time, vec2 direction) {
    return AMPLITUDE * sin(dot(pos.xz, direction) * FREQUENCY + time * SPEED);
}

// Derivative of the wave function to calculate accurate dynamic surface normals
vec3 calculateWaveNormal(vec3 pos, float time) {
    float dx = AMPLITUDE * FREQUENCY * cos(pos.x * FREQUENCY + time * SPEED);
    float dz = AMPLITUDE * FREQUENCY * cos(pos.z * FREQUENCY + time * SPEED);
    return normalize(vec3(-dx, 1.0, -dz));
}

void main() {
    vec3 displacedPos = aPos;

    // Combine two wave directions for a less predictable, more organic look
    displacedPos.y += calculateWave(aPos, uTime, vec2(1.0, 0.0));
    displacedPos.y += calculateWave(aPos, uTime * 1.2, vec2(0.5, 0.8));

    FragPos = vec3(model * vec4(displacedPos, 1.0));
    TexCoords = aTexCoords;

    // Pass transformed normals and position to the fragment shader
    Normal = mat3(transpose(inverse(model))) * calculateWaveNormal(displacedPos, uTime);

    gl_Position = projection * view * model * vec4(displacedPos, 1.0);
}