#include <assert.h>
#include <stdio.h>
#include <string.h>
#include <math.h>
#include <limits.h>

#include "private.h"
#include "platform.h"

#define _MIN(x, y) (x < y) ? x : y

/* Lighting will not be calculated if the attenuation
 * multiplier ends up less than this value */
#define ATTENUATION_THRESHOLD 100.0f

static GLfloat SCENE_AMBIENT [] = {0.2f, 0.2f, 0.2f, 1.0f};
static GLboolean VIEWER_IN_EYE_COORDINATES = GL_TRUE;
static GLenum COLOR_CONTROL = GL_SINGLE_COLOR;

static GLenum COLOR_MATERIAL_MODE = GL_AMBIENT_AND_DIFFUSE;

#define AMBIENT_MASK 1
#define DIFFUSE_MASK 2
#define EMISSION_MASK 4
#define SPECULAR_MASK 8
#define SCENE_AMBIENT_MASK 16

static GLenum COLOR_MATERIAL_MASK = AMBIENT_MASK | DIFFUSE_MASK;

static LightSource LIGHTS[MAX_GLDC_LIGHTS];
static GLuint ENABLED_LIGHT_COUNT = 0;
static Material MATERIAL;

GL_FORCE_INLINE void _glPrecalcLightingValues(GLuint mask);

static void recalcEnabledLights() {
    GLubyte i;

    ENABLED_LIGHT_COUNT = 0;
    for(i = 0; i < MAX_GLDC_LIGHTS; ++i) {
        if(LIGHTS[i].isEnabled) {
            ENABLED_LIGHT_COUNT++;
        }
    }
}

void _glInitLights() {
    static GLfloat ONE [] = {1.0f, 1.0f, 1.0f, 1.0f};
    static GLfloat ZERO [] = {0.0f, 0.0f, 0.0f, 1.0f};
    static GLfloat PARTIAL [] = {0.2f, 0.2f, 0.2f, 1.0f};
    static GLfloat MOSTLY [] = {0.8f, 0.8f, 0.8f, 1.0f};

    memcpy(MATERIAL.ambient, PARTIAL, sizeof(GLfloat) * 4);
    memcpy(MATERIAL.diffuse, MOSTLY, sizeof(GLfloat) * 4);
    memcpy(MATERIAL.specular, ZERO, sizeof(GLfloat) * 4);
    memcpy(MATERIAL.emissive, ZERO, sizeof(GLfloat) * 4);
    MATERIAL.exponent = 0.0f;

    GLubyte i;
    for(i = 0; i < MAX_GLDC_LIGHTS; ++i) {
        memcpy(LIGHTS[i].ambient, ZERO, sizeof(GLfloat) * 4);
        memcpy(LIGHTS[i].diffuse, ONE, sizeof(GLfloat) * 4);
        memcpy(LIGHTS[i].specular, ONE, sizeof(GLfloat) * 4);

        if(i > 0) {
            memcpy(LIGHTS[i].diffuse, ZERO, sizeof(GLfloat) * 4);
            memcpy(LIGHTS[i].specular, ZERO, sizeof(GLfloat) * 4);
        }

        LIGHTS[i].position[0] = LIGHTS[i].position[1] = LIGHTS[i].position[3] = 0.0f;
        LIGHTS[i].position[2] = 1.0f;
        LIGHTS[i].isDirectional = GL_TRUE;
        LIGHTS[i].isEnabled = GL_FALSE;

        LIGHTS[i].spot_direction[0] = LIGHTS[i].spot_direction[1] = 0.0f;
        LIGHTS[i].spot_direction[2] = -1.0f;

        LIGHTS[i].spot_exponent = 0.0f;
        LIGHTS[i].spot_cutoff = 180.0f;

        LIGHTS[i].constant_attenuation = 1.0f;
        LIGHTS[i].linear_attenuation = 0.0f;
        LIGHTS[i].quadratic_attenuation = 0.0f;
    }

    _glPrecalcLightingValues(~0);
    recalcEnabledLights();
}

void _glEnableLight(GLubyte light, GLboolean value) {
    LIGHTS[light].isEnabled = value;
    recalcEnabledLights();
}

GL_FORCE_INLINE void _glPrecalcLightingValues(GLuint mask) {
    /* Pre-calculate lighting values */
    GLshort i;

    if(mask & AMBIENT_MASK) {
        for(i = 0; i < MAX_GLDC_LIGHTS; ++i) {
            LIGHTS[i].ambientMaterial[0] = LIGHTS[i].ambient[0] * MATERIAL.ambient[0];
            LIGHTS[i].ambientMaterial[1] = LIGHTS[i].ambient[1] * MATERIAL.ambient[1];
            LIGHTS[i].ambientMaterial[2] = LIGHTS[i].ambient[2] * MATERIAL.ambient[2];
            LIGHTS[i].ambientMaterial[3] = LIGHTS[i].ambient[3] * MATERIAL.ambient[3];
        }
    }

    if(mask & DIFFUSE_MASK) {
        for(i = 0; i < MAX_GLDC_LIGHTS; ++i) {
            LIGHTS[i].diffuseMaterial[0] = LIGHTS[i].diffuse[0] * MATERIAL.diffuse[0];
            LIGHTS[i].diffuseMaterial[1] = LIGHTS[i].diffuse[1] * MATERIAL.diffuse[1];
            LIGHTS[i].diffuseMaterial[2] = LIGHTS[i].diffuse[2] * MATERIAL.diffuse[2];
            LIGHTS[i].diffuseMaterial[3] = LIGHTS[i].diffuse[3] * MATERIAL.diffuse[3];
        }
    }

    if(mask & SPECULAR_MASK) {
        for(i = 0; i < MAX_GLDC_LIGHTS; ++i) {
            LIGHTS[i].specularMaterial[0] = LIGHTS[i].specular[0] * MATERIAL.specular[0];
            LIGHTS[i].specularMaterial[1] = LIGHTS[i].specular[1] * MATERIAL.specular[1];
            LIGHTS[i].specularMaterial[2] = LIGHTS[i].specular[2] * MATERIAL.specular[2];
            LIGHTS[i].specularMaterial[3] = LIGHTS[i].specular[3] * MATERIAL.specular[3];
        }
    }

    /* If ambient or emission are updated, we need to update
     * the base colour. */
    if((mask & AMBIENT_MASK) || (mask & EMISSION_MASK) || (mask & SCENE_AMBIENT_MASK)) {
        MATERIAL.baseColour[0] = MATH_fmac(SCENE_AMBIENT[0], MATERIAL.ambient[0], MATERIAL.emissive[0]);
        MATERIAL.baseColour[1] = MATH_fmac(SCENE_AMBIENT[1], MATERIAL.ambient[1], MATERIAL.emissive[1]);
        MATERIAL.baseColour[2] = MATH_fmac(SCENE_AMBIENT[2], MATERIAL.ambient[2], MATERIAL.emissive[2]);
        MATERIAL.baseColour[3] = MATH_fmac(SCENE_AMBIENT[3], MATERIAL.ambient[3], MATERIAL.emissive[3]);
    }
}

void APIENTRY glLightModelf(GLenum pname, const GLfloat param) {
    glLightModelfv(pname, &param);
}

void APIENTRY glLightModeli(GLenum pname, const GLint param) {
    glLightModeliv(pname, &param);
}

void APIENTRY glLightModelfv(GLenum pname, const GLfloat *params) {
    switch(pname) {
        case GL_LIGHT_MODEL_AMBIENT: {
            memcpy(SCENE_AMBIENT, params, sizeof(GLfloat) * 4);
            _glPrecalcLightingValues(SCENE_AMBIENT_MASK);
        } break;
        case GL_LIGHT_MODEL_LOCAL_VIEWER:
            VIEWER_IN_EYE_COORDINATES = (*params) ? GL_TRUE : GL_FALSE;
        break;
    case GL_LIGHT_MODEL_TWO_SIDE:
        /* Not implemented */
    default:
        _glKosThrowError(GL_INVALID_ENUM, __func__);
    }
}

void APIENTRY glLightModeliv(GLenum pname, const GLint* params) {
    switch(pname) {
        case GL_LIGHT_MODEL_COLOR_CONTROL:
            COLOR_CONTROL = *params;
        break;
        case GL_LIGHT_MODEL_LOCAL_VIEWER:
            VIEWER_IN_EYE_COORDINATES = (*params) ? GL_TRUE : GL_FALSE;
        break;
    default:
        _glKosThrowError(GL_INVALID_ENUM, __func__);
    }
}

void APIENTRY glLightfv(GLenum light, GLenum pname, const GLfloat *params) {
    GLubyte idx = light & 0xF;

    if(idx >= MAX_GLDC_LIGHTS) {
        return;
    }

    GLuint mask = (pname == GL_AMBIENT) ? AMBIENT_MASK :
                  (pname == GL_DIFFUSE) ? DIFFUSE_MASK :
                  (pname == GL_SPECULAR) ? SPECULAR_MASK : 0;

    switch(pname) {
        case GL_AMBIENT:
            memcpy(LIGHTS[idx].ambient, params, sizeof(GLfloat) * 4);
        break;
        case GL_DIFFUSE:
            memcpy(LIGHTS[idx].diffuse, params, sizeof(GLfloat) * 4);
        break;
        case GL_SPECULAR:
            memcpy(LIGHTS[idx].specular, params, sizeof(GLfloat) * 4);
        break;
        case GL_POSITION: {
            _glMatrixLoadModelView();
            memcpy(LIGHTS[idx].position, params, sizeof(GLfloat) * 4);

            LIGHTS[idx].isDirectional = params[3] == 0.0f;

            if(LIGHTS[idx].isDirectional) {
                //FIXME: Do we need to rotate directional lights?
            } else {
                TransformVec3(LIGHTS[idx].position);
            }
        }
        break;
        case GL_SPOT_DIRECTION: {
            LIGHTS[idx].spot_direction[0] = params[0];
            LIGHTS[idx].spot_direction[1] = params[1];
            LIGHTS[idx].spot_direction[2] = params[2];
        } break;
        case GL_CONSTANT_ATTENUATION:
        case GL_LINEAR_ATTENUATION:
        case GL_QUADRATIC_ATTENUATION:
        case GL_SPOT_CUTOFF:
        case GL_SPOT_EXPONENT:
            glLightf(light, pname, *params);
        break;
    default:
        _glKosThrowError(GL_INVALID_ENUM, __func__);
        return;
    }

    _glPrecalcLightingValues(mask);
}

void APIENTRY glLightf(GLenum light, GLenum pname, GLfloat param) {
    GLubyte idx = light & 0xF;

    if(idx >= MAX_GLDC_LIGHTS) {
        return;
    }

    switch(pname) {
        case GL_CONSTANT_ATTENUATION:
            LIGHTS[idx].constant_attenuation = param;
        break;
        case GL_LINEAR_ATTENUATION:
            LIGHTS[idx].linear_attenuation = param;
        break;
        case GL_QUADRATIC_ATTENUATION:
            LIGHTS[idx].quadratic_attenuation = param;
        break;
        case GL_SPOT_EXPONENT:
            LIGHTS[idx].spot_exponent = param;
        break;
        case GL_SPOT_CUTOFF:
            LIGHTS[idx].spot_cutoff = param;
        break;
    default:
        _glKosThrowError(GL_INVALID_ENUM, __func__);
    }
}

void APIENTRY glMaterialf(GLenum face, GLenum pname, const GLfloat param) {
    if(face == GL_BACK || pname != GL_SHININESS) {
        _glKosThrowError(GL_INVALID_ENUM, __func__);
        return;
    }

    MATERIAL.exponent = _MIN(param, 128);  /* 128 is the max according to the GL spec */
}

void APIENTRY glMateriali(GLenum face, GLenum pname, const GLint param) {
    glMaterialf(face, pname, param);
}

void APIENTRY glMaterialfv(GLenum face, GLenum pname, const GLfloat *params) {
    if(face == GL_BACK) {
        _glKosThrowError(GL_INVALID_ENUM, __func__);
        return;
    }

    switch(pname) {
        case GL_SHININESS:
            glMaterialf(face, pname, *params);
        break;
        case GL_AMBIENT:
            vec4cpy(MATERIAL.ambient, params);
        break;
        case GL_DIFFUSE:
            vec4cpy(MATERIAL.diffuse, params);
        break;
        case GL_SPECULAR:
            vec4cpy(MATERIAL.specular, params);
        break;
        case GL_EMISSION:
            vec4cpy(MATERIAL.emissive, params);
        break;
        case GL_AMBIENT_AND_DIFFUSE: {
            vec4cpy(MATERIAL.ambient, params);
            vec4cpy(MATERIAL.diffuse, params);
        } break;
        case GL_COLOR_INDEXES:
        default: {
            _glKosThrowError(GL_INVALID_ENUM, __func__);
            return;
        }
    }

    GLuint updateMask = (pname == GL_AMBIENT) ? AMBIENT_MASK:
                        (pname == GL_DIFFUSE) ? DIFFUSE_MASK:
                        (pname == GL_SPECULAR) ? SPECULAR_MASK:
                        (pname == GL_EMISSION) ? EMISSION_MASK:
                        (pname == GL_AMBIENT_AND_DIFFUSE) ? AMBIENT_MASK | DIFFUSE_MASK : 0;

    _glPrecalcLightingValues(updateMask);
}

void APIENTRY glColorMaterial(GLenum face, GLenum mode) {
    if(face != GL_FRONT_AND_BACK) {
        _glKosThrowError(GL_INVALID_ENUM, __func__);
        return;
    }

    GLint validModes[] = {GL_AMBIENT, GL_DIFFUSE, GL_AMBIENT_AND_DIFFUSE, GL_EMISSION, GL_SPECULAR, 0};

    if(_glCheckValidEnum(mode, validModes, __func__) != 0) {
        return;
    }

    COLOR_MATERIAL_MASK = (mode == GL_AMBIENT) ? AMBIENT_MASK:
                          (mode == GL_DIFFUSE) ? DIFFUSE_MASK:
                          (mode == GL_AMBIENT_AND_DIFFUSE) ? AMBIENT_MASK | DIFFUSE_MASK:
                          (mode == GL_EMISSION) ? EMISSION_MASK : SPECULAR_MASK;

    COLOR_MATERIAL_MODE = mode;
}

GL_FORCE_INLINE void bgra_to_float(const uint8_t* input, GLfloat* output) {
    static const float scale = 1.0f / 255.0f;

    output[0] = ((float) input[R8IDX]) * scale;
    output[1] = ((float) input[G8IDX]) * scale;
    output[2] = ((float) input[B8IDX]) * scale;
    output[3] = ((float) input[A8IDX]) * scale;
}

void _glUpdateColourMaterialA(const GLubyte* argb) {
    float colour[4];
    bgra_to_float(argb, colour);
    vec4cpy(MATERIAL.ambient, colour);
    _glPrecalcLightingValues(COLOR_MATERIAL_MASK);
}

void _glUpdateColourMaterialD(const GLubyte* argb) {
    float colour[4];
    bgra_to_float(argb, colour);
    vec4cpy(MATERIAL.diffuse, colour);
    _glPrecalcLightingValues(COLOR_MATERIAL_MASK);
}

void _glUpdateColourMaterialE(const GLubyte* argb) {
    float colour[4];
    bgra_to_float(argb, colour);
    vec4cpy(MATERIAL.emissive, colour);
    _glPrecalcLightingValues(COLOR_MATERIAL_MASK);
}

void _glUpdateColourMaterialAD(const GLubyte* argb) {
    float colour[4];
    bgra_to_float(argb, colour);
    vec4cpy(MATERIAL.ambient, colour);
    vec4cpy(MATERIAL.diffuse, colour);
    _glPrecalcLightingValues(COLOR_MATERIAL_MASK);
}

GL_FORCE_INLINE GLboolean isDiffuseColorMaterial() {
    return (COLOR_MATERIAL_MODE == GL_DIFFUSE || COLOR_MATERIAL_MODE == GL_AMBIENT_AND_DIFFUSE);
}

GL_FORCE_INLINE GLboolean isAmbientColorMaterial() {
    return (COLOR_MATERIAL_MODE == GL_AMBIENT || COLOR_MATERIAL_MODE == GL_AMBIENT_AND_DIFFUSE);
}

GL_FORCE_INLINE GLboolean isSpecularColorMaterial() {
    return (COLOR_MATERIAL_MODE == GL_SPECULAR);
}

/*
 * Implementation from here (MIT):
 * https://github.com/appleseedhq/appleseed/blob/master/src/appleseed/foundation/math/fastmath.h
 */
GL_FORCE_INLINE float faster_pow2(const float p) {
    // Underflow of exponential is common practice in numerical routines, so handle it here.
    const float clipp = p < -126.0f ? -126.0f : p;
    const union { uint32_t i; float f; } v =
    {
        (uint32_t) ((1 << 23) * (clipp + 126.94269504f))
    };

    return v.f;
}

GL_FORCE_INLINE float faster_log2(const float x) {
    assert(x >= 0.0f);

    const union { float f; uint32_t i; } vx = { x };
    const float y = (float) (vx.i) * 1.1920928955078125e-7f;

    return y - 126.94269504f;
}

GL_FORCE_INLINE float faster_pow(const float x, const float p) {
    return faster_pow2(p * faster_log2(x));
}

GL_FORCE_INLINE void _glLightVertexDirectional(
    float* final, uint8_t lid,
    float LdotN, float NdotH) {

    float FI = (MATERIAL.exponent) ?
        faster_pow((LdotN != 0.0f) * NdotH, MATERIAL.exponent) : 1.0f;

#define _PROCESS_COMPONENT(X) \
    final[X] += (LdotN * LIGHTS[lid].diffuseMaterial[X] + LIGHTS[lid].ambientMaterial[X]) \
        + (FI * LIGHTS[lid].specularMaterial[X]); \

    _PROCESS_COMPONENT(0);
    _PROCESS_COMPONENT(1);
    _PROCESS_COMPONENT(2);

#undef _PROCESS_COMPONENT
}

GL_FORCE_INLINE void _glLightVertexPoint(
    float* final, uint8_t lid,
    float LdotN, float NdotH, float att) {

    float FI = (MATERIAL.exponent) ?
        faster_pow((LdotN != 0.0f) * NdotH, MATERIAL.exponent) : 1.0f;

#define _PROCESS_COMPONENT(X) \
    final[X] += ((LdotN * LIGHTS[lid].diffuseMaterial[X] + LIGHTS[lid].ambientMaterial[X]) \
        + (FI * LIGHTS[lid].specularMaterial[X])) * att; \

    _PROCESS_COMPONENT(0);
    _PROCESS_COMPONENT(1);
    _PROCESS_COMPONENT(2);

#undef _PROCESS_COMPONENT
}

void _glPerformLighting(Vertex* vertices, EyeSpaceData* es, const uint32_t count) {
    GLubyte i;
    GLuint j;

    Vertex* vertex = vertices;
    EyeSpaceData* data = es;

    /* Calculate the colour material function once */
    void (*updateColourMaterial)(const GLubyte*) = NULL;

    if(_glIsColorMaterialEnabled()) {
        switch(COLOR_MATERIAL_MODE) {
            case GL_AMBIENT:
                updateColourMaterial = _glUpdateColourMaterialA;
            break;
            case GL_DIFFUSE:
                updateColourMaterial = _glUpdateColourMaterialD;
            break;
            case GL_EMISSION:
                updateColourMaterial = _glUpdateColourMaterialE;
            break;
            case GL_AMBIENT_AND_DIFFUSE:
                updateColourMaterial = _glUpdateColourMaterialAD;
            break;
        }
    }

    /* Calculate the ambient lighting and set up colour material */
    for(j = 0; j < count; ++j, ++vertex, ++data) {
        if(updateColourMaterial) {
            updateColourMaterial(vertex->bgra);
        }

        /* Copy the base colour across */
        vec4cpy(data->finalColour, MATERIAL.baseColour);
    }

    if(!ENABLED_LIGHT_COUNT) {
        return;
    }

    vertex = vertices;
    data = es;
    for(j = 0; j < count; ++j, ++vertex, ++data) {
        /* Direction to vertex in eye space */
        float Vx = -vertex->xyz[0];
        float Vy = -vertex->xyz[1];
        float Vz = -vertex->xyz[2];
        VEC3_NORMALIZE(Vx, Vy, Vz);

        const float Nx = data->n[0];
        const float Ny = data->n[1];
        const float Nz = data->n[2];

        for(i = 0; i < MAX_GLDC_LIGHTS; ++i) {
            if(!LIGHTS[i].isEnabled) {
                continue;
            }

            float Lx = LIGHTS[i].position[0] - vertex->xyz[0];
            float Ly = LIGHTS[i].position[1] - vertex->xyz[1];
            float Lz = LIGHTS[i].position[2] - vertex->xyz[2];

            if(LIGHTS[i].isDirectional) {
                float Hx = (Lx + 0);
                float Hy = (Ly + 0);
                float Hz = (Lz + 1);

                VEC3_NORMALIZE(Lx, Ly, Lz);
                VEC3_NORMALIZE(Hx, Hy, Hz);

                float LdotN, NdotH;
                VEC3_DOT(
                    Nx, Ny, Nz, Lx, Ly, Lz, LdotN
                );

                VEC3_DOT(
                    Nx, Ny, Nz, Hx, Hy, Hz, NdotH
                );

                if(LdotN < 0.0f) LdotN = 0.0f;
                if(NdotH < 0.0f) NdotH = 0.0f;

                _glLightVertexDirectional(
                    data->finalColour,
                    i, LdotN, NdotH
                );
            } else {
                float D;
                VEC3_LENGTH(Lx, Ly, Lz, D);

                float att = (
                    LIGHTS[i].constant_attenuation + (
                        LIGHTS[i].linear_attenuation * D
                    ) + (LIGHTS[i].quadratic_attenuation * D * D)
                );

                /* Anything over the attenuation threshold will
                 * be a tiny value after inversion (< 0.01f) so
                 * let's just skip the lighting at that point */
                if(att < ATTENUATION_THRESHOLD) {
                    att = MATH_Fast_Invert(att);

                    float Hx = (Lx + Vx);
                    float Hy = (Ly + Vy);
                    float Hz = (Lz + Vz);

                    VEC3_NORMALIZE(Lx, Ly, Lz);
                    VEC3_NORMALIZE(Hx, Hy, Hz);

                    float LdotN, NdotH;
                    VEC3_DOT(
                        Nx, Ny, Nz, Lx, Ly, Lz, LdotN
                    );

                    VEC3_DOT(
                        Nx, Ny, Nz, Hx, Hy, Hz, NdotH
                    );

                    if(LdotN < 0.0f) LdotN = 0.0f;
                    if(NdotH < 0.0f) NdotH = 0.0f;

                    _glLightVertexPoint(
                        data->finalColour,
                        i, LdotN, NdotH, att
                    );
                }
            }
        }

        vertex->bgra[R8IDX] = clamp(data->finalColour[0] * 255.0f, 0, 255);
        vertex->bgra[G8IDX] = clamp(data->finalColour[1] * 255.0f, 0, 255);
        vertex->bgra[B8IDX] = clamp(data->finalColour[2] * 255.0f, 0, 255);
        vertex->bgra[A8IDX] = clamp(data->finalColour[3] * 255.0f, 0, 255);
    }
}

#undef LIGHT_COMPONENT