#include "glslUtil.h"

void guMatrixLoadIdentity(guMatrix4x4 *m)
{
    for (int i = 0; i < 4; i++)
    {
        for (int j = 0; j < 4; j++)
        {
            m[i][j] = (i == j) ? 1.0 : 0.0;
        }
    }
}

void guMatrixMult(guMatrix4x4 *m, guMatrix4x4 *a, guMatrix4x4 *b)
{
    for (int i = 0; i < 4; i++)
    {
        for (int j = 0; j < 4; j++)
        {
            float v = 0.0;
            for (int p = 0; p < 4; p++)
            {
                v += a[i][p] * b[p][j];
            }
            m[i][j] = v;
        }
    }
}

void guMatrixTranslate(guMatrix4x4 *m, float x, float y, float z)
{
    for (int i = 0; i < 4; i++)
    {
        m[i][3] += m[i][0] * x + m[i][1] * y + m[i][2] * z;
    }
}

void guMatrixFrustum(guMatrix4x4 *m,
        float left, float right,
        float bottom, float top,
        float near, float far)
{
    guMatrix4x4 mult;
    for (int i = 0; i < 4; i++)
    {
        for (int j = 0; j < 4; j++)
        {
            mult[i][j] = 0.0;
        }
    }
    mult[0][0] = 2 * near / (right - left);
    mult[0][2] = (right + left) / (right - left);
    mult[1][1] = 2 * near / (top - bottom);
    mult[1][2] = (top + bottom) / (top - bottom);
    mult[2][2] = - (far + near) / (far - near);
    mult[2][3] = - 2 * far * near / (far - near);
    mult[3][2] = -1.0;
    guMatrixMult(m, &mult);
}