#include <libultraship.h>

void guLookAtF(float mf[4][4], float xEye, float yEye, float zEye, float xAt, float yAt, float zAt, float xUp,
               float yUp, float zUp) {
    float len;
    float xLook;
    float yLook;
    float zLook;
    float xRight;
    float yRight;
    float zRight;

    guMtxIdentF(mf);

    xLook = xAt - xEye;
    yLook = yAt - yEye;
    zLook = zAt - zEye;

    /* Negate because positive Z is behind us: */
    len = -1.0 / guSqrtf(xLook * xLook + yLook * yLook + zLook * zLook);
    xLook *= len;
    yLook *= len;
    zLook *= len;

    /* Right = Up x Look */

    xRight = yUp * zLook - zUp * yLook;
    yRight = zUp * xLook - xUp * zLook;
    zRight = xUp * yLook - yUp * xLook;
    len = 1.0 / guSqrtf(xRight * xRight + yRight * yRight + zRight * zRight);
    xRight *= len;
    yRight *= len;
    zRight *= len;

    /* Up = Look x Right */

    xUp = yLook * zRight - zLook * yRight;
    yUp = zLook * xRight - xLook * zRight;
    zUp = xLook * yRight - yLook * xRight;
    len = 1.0 / guSqrtf(xUp * xUp + yUp * yUp + zUp * zUp);
    xUp *= len;
    yUp *= len;
    zUp *= len;

    mf[0][0] = xRight;
    mf[1][0] = yRight;
    mf[2][0] = zRight;
    mf[3][0] = -(xEye * xRight + yEye * yRight + zEye * zRight);

    mf[0][1] = xUp;
    mf[1][1] = yUp;
    mf[2][1] = zUp;
    mf[3][1] = -(xEye * xUp + yEye * yUp + zEye * zUp);

    mf[0][2] = xLook;
    mf[1][2] = yLook;
    mf[2][2] = zLook;
    mf[3][2] = -(xEye * xLook + yEye * yLook + zEye * zLook);

    mf[0][3] = 0;
    mf[1][3] = 0;
    mf[2][3] = 0;
    mf[3][3] = 1;
}

void guLookAt(Mtx* m, float xEye, float yEye, float zEye, float xAt, float yAt, float zAt, float xUp, float yUp,
              float zUp) {
    float mf[4][4];

    guLookAtF(mf, xEye, yEye, zEye, xAt, yAt, zAt, xUp, yUp, zUp);

    guMtxF2L(mf, m);
}