/* -*- Mode: C; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/*
 * This file is part of the LibreOffice project.
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */

#version 120

#define M_PI 3.1415926535897932384626433832795

attribute vec3 a_position;
attribute vec3 a_normal;

uniform mat4 u_projectionMatrix;
uniform mat4 u_modelViewMatrix;
uniform mat4 u_sceneTransformMatrix;
uniform mat4 u_primitiveTransformMatrix;
uniform mat4 u_operationsTransformMatrix;

varying vec2 v_texturePosition;
varying vec3 v_normal;

attribute vec3 center;
uniform float time;
uniform sampler2D permTexture;
varying float angle;

#if __VERSION__ < 140
mat4 inverse(mat4 m)
{
    float a00 = m[0][0], a01 = m[0][1], a02 = m[0][2], a03 = m[0][3];
    float a10 = m[1][0], a11 = m[1][1], a12 = m[1][2], a13 = m[1][3];
    float a20 = m[2][0], a21 = m[2][1], a22 = m[2][2], a23 = m[2][3];
    float a30 = m[3][0], a31 = m[3][1], a32 = m[3][2], a33 = m[3][3];

    float b00 = a00 * a11 - a01 * a10;
    float b01 = a00 * a12 - a02 * a10;
    float b02 = a00 * a13 - a03 * a10;
    float b03 = a01 * a12 - a02 * a11;
    float b04 = a01 * a13 - a03 * a11;
    float b05 = a02 * a13 - a03 * a12;
    float b06 = a20 * a31 - a21 * a30;
    float b07 = a20 * a32 - a22 * a30;
    float b08 = a20 * a33 - a23 * a30;
    float b09 = a21 * a32 - a22 * a31;
    float b10 = a21 * a33 - a23 * a31;
    float b11 = a22 * a33 - a23 * a32;

    float det = b00 * b11 - b01 * b10 + b02 * b09 + b03 * b08 - b04 * b07 + b05 * b06;

    return mat4(
        a11 * b11 - a12 * b10 + a13 * b09,
        a02 * b10 - a01 * b11 - a03 * b09,
        a31 * b05 - a32 * b04 + a33 * b03,
        a22 * b04 - a21 * b05 - a23 * b03,
        a12 * b08 - a10 * b11 - a13 * b07,
        a00 * b11 - a02 * b08 + a03 * b07,
        a32 * b02 - a30 * b05 - a33 * b01,
        a20 * b05 - a22 * b02 + a23 * b01,
        a10 * b10 - a11 * b08 + a13 * b06,
        a01 * b08 - a00 * b10 - a03 * b06,
        a30 * b04 - a31 * b02 + a33 * b00,
        a21 * b02 - a20 * b04 - a23 * b00,
        a11 * b07 - a10 * b09 - a12 * b06,
        a00 * b09 - a01 * b07 + a02 * b06,
        a31 * b01 - a30 * b03 - a32 * b00,
        a20 * b03 - a21 * b01 + a22 * b00) / det;
}
#endif

float snoise(vec2 p)
{
    return texture2D(permTexture, p).r;
}

mat4 translationMatrix(vec3 axis)
{
    return mat4(1.0,    0.0,    0.0,    0.0,
                0.0,    1.0,    0.0,    0.0,
                0.0,    0.0,    1.0,    0.0,
                axis.x, axis.y, axis.z, 1.0);
}

mat4 rotationMatrix(vec3 axis, float angle)
{
    axis = normalize(axis);
    float s = sin(angle);
    float c = cos(angle);
    float oc = 1.0 - c;

    return mat4(oc * axis.x * axis.x + c,           oc * axis.x * axis.y - axis.z * s,  oc * axis.z * axis.x + axis.y * s,  0.0,
                oc * axis.x * axis.y + axis.z * s,  oc * axis.y * axis.y + c,           oc * axis.y * axis.z - axis.x * s,  0.0,
                oc * axis.z * axis.x - axis.y * s,  oc * axis.y * axis.z + axis.x * s,  oc * axis.z * axis.z + c,           0.0,
                0.0,                                0.0,                                0.0,                                1.0);
}

void main( void )
{
    vec2 pos = (center.xy + 1.0) / 2.0;

    // 0..1 pseudo-random value used to randomize the tile’s start time.
    float fuzz = snoise(pos);

    float startTime = pos.x * 0.5 + fuzz * 0.25;
    float endTime = startTime + 0.25;

    // Scale the transition time to minimize the time a tile will stay black.
    float transitionTime = clamp((time - startTime) / (endTime - startTime), 0.0, 1.0);
    if (transitionTime < 0.5)
        transitionTime = transitionTime / 2.0;
    else
        transitionTime = (transitionTime / 2.0) + 0.5;
    angle = transitionTime * M_PI * 2.0;

    mat4 modelViewMatrix = u_modelViewMatrix * u_operationsTransformMatrix * u_sceneTransformMatrix * u_primitiveTransformMatrix;
    mat4 transformMatrix = translationMatrix(center) * rotationMatrix(vec3(0.0, 1.0, 0.0), angle) * translationMatrix(-center);

    mat3 normalMatrix = mat3(transpose(inverse(transformMatrix)));
    gl_Position = u_projectionMatrix * modelViewMatrix * transformMatrix * vec4(a_position, 1.0);
    v_texturePosition = vec2((a_position.x + 1.0) / 2.0, (1.0 - a_position.y) / 2.0);
    v_normal = normalize(normalMatrix * a_normal);
}

/* vim:set shiftwidth=4 softtabstop=4 expandtab: */