//
// Copyright 2018 The ANGLE Project Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
//

// GLES1Shaders.inc: Defines GLES1 emulation shader.
//
// According to the GLES1 specification:
//
// We require simply that numbers' floating point parts contain enough bits and that their exponent
// fields are large enough so that individual results of floating-point operations are accurate to
// about 1 part in 10^5.  The maximum representable magnitude of a floating-point number used to
// represent positional or normal coordinates must be at least 2^32; the maximum representable
// magnitude for colors or texture coordinates must be at least 2^10.  The maximum representable
// magnitude for all other floating-point values must be at least 2^32 .
//
// Internal computations can use either fixed-point or floating-point arithmetic.  Fixed-point
// computations must be accurate to within ±2^-15.  The maximum representable magnitude for a
// fixed-point number used to represent positional or normal coordinates must be at least 2^15; the
// maximum representable magnitude for colors or texture coordinates must be at least 2^10.  The
// maximum representable magnitude for all other fixed-point values must be at least 2^15
//
// Accordingly, ANGLE uses highp floats for position and normal data, mediump for color and texture
// coordinates, and highp for everything else.

// The following variables are added in GLES1Renderer::initializeRendererProgram
// #define kTexUnits
// bool clip_plane_enables
// bool enable_alpha_test
// bool enable_clip_planes
// bool enable_color_material
// bool enable_draw_texture
// bool enable_fog
// bool enable_lighting
// bool enable_normalize
// bool enable_rescale_normal
// bool enable_texture_2d[kMaxTexUnits]
// bool enable_texture_cube_map[kMaxTexUnits]
// bool light_enables[kMaxLights]
// bool light_model_two_sided
// bool point_rasterization
// bool point_sprite_coord_replace
// bool point_sprite_enabled
// bool shade_model_flat
// uint texture_format[kMaxTexUnits];
// uint texture_env_mode[kMaxTexUnits];
// uint combine_rgb[kMaxTexUnits];
// uint combine_alpha[kMaxTexUnits];
// uint src0_rgb[kMaxTexUnits];
// uint src0_alpha[kMaxTexUnits];
// uint src1_rgb[kMaxTexUnits];
// uint src1_alpha[kMaxTexUnits];
// uint src2_rgb[kMaxTexUnits];
// uint src2_alpha[kMaxTexUnits];
// uint op0_rgb[kMaxTexUnits];
// uint op0_alpha[kMaxTexUnits];
// uint op1_rgb[kMaxTexUnits];
// uint op1_alpha[kMaxTexUnits];
// uint op2_rgb[kMaxTexUnits];
// uint op2_alpha[kMaxTexUnits];
// uint alpha_func;
// uint fog_mode;

constexpr char kGLES1TexUnitsDefine[] = R"(#define kTexUnits )";

constexpr char kGLES1DrawVShaderHeader[] = R"(#version 300 es
precision highp float;

#define kMaxTexUnits 4u
#define kMaxLights   8u
)";

constexpr char kGLES1DrawVShader[] = R"(

in vec4 pos;
in vec3 normal;
in mediump vec4 color;
in float pointsize;
#if kTexUnits >= 1u
in mediump vec4 texcoord0;
#endif
#if kTexUnits >= 2u
in mediump vec4 texcoord1;
#endif
#if kTexUnits >= 3u
in mediump vec4 texcoord2;
#endif
#if kTexUnits >= 4u
in mediump vec4 texcoord3;
#endif

uniform mat4 projection;
uniform mat4 modelview;
uniform mat4 modelview_invtr;
uniform mat4 texture_matrix[kMaxTexUnits];

// Point rasterization//////////////////////////////////////////////////////////

uniform float point_size_min;
uniform float point_size_max;
uniform vec3 point_distance_attenuation;

// Shading: flat shading, lighting, and materials///////////////////////////////

uniform mediump vec4 material_ambient;
uniform mediump vec4 material_diffuse;
uniform mediump vec4 material_specular;
uniform mediump vec4 material_emissive;
uniform float material_specular_exponent;

uniform mediump vec4 light_model_scene_ambient;

uniform mediump vec4 light_ambients[kMaxLights];
uniform mediump vec4 light_diffuses[kMaxLights];
uniform mediump vec4 light_speculars[kMaxLights];
uniform vec4 light_positions[kMaxLights];
uniform vec3 light_directions[kMaxLights];
uniform float light_spotlight_exponents[kMaxLights];
uniform float light_spotlight_cutoff_angles[kMaxLights];
uniform float light_attenuation_consts[kMaxLights];
uniform float light_attenuation_linears[kMaxLights];
uniform float light_attenuation_quadratics[kMaxLights];

// GL_OES_draw_texture uniforms/////////////////////////////////////////////////

uniform vec4 draw_texture_coords;
uniform vec2 draw_texture_dims;
uniform mediump vec4 draw_texture_normalized_crop_rect[kMaxTexUnits];

// Varyings/////////////////////////////////////////////////////////////////////

out vec4 pos_varying;
out vec3 normal_varying;
out mediump vec4 color_varying;
flat out mediump vec4 color_varying_flat;
#if kTexUnits >= 1u
out mediump vec3 texcoord0_varying;
#endif
#if kTexUnits >= 2u
out mediump vec3 texcoord1_varying;
#endif
#if kTexUnits >= 3u
out mediump vec3 texcoord2_varying;
#endif
#if kTexUnits >= 4u
out mediump vec3 texcoord3_varying;
#endif

float posDot(vec3 a, vec3 b)
{
    return max(dot(a, b), 0.0);
}

mediump vec4 doLighting(mediump vec4 vertexColor)
{
    mediump vec4 materialAmbientActual = material_ambient;
    mediump vec4 materialDiffuseActual = material_diffuse;

    if (enable_color_material)
    {
        materialAmbientActual = vertexColor;
        materialDiffuseActual = vertexColor;
    }

    mediump vec4 lightingResult = material_emissive + materialAmbientActual * light_model_scene_ambient;

    for (uint i = 0u; i < kMaxLights; i++)
    {

        if (!light_enables[i])
            continue;

        mediump vec4 lightAmbient  = light_ambients[i];
        mediump vec4 lightDiffuse  = light_diffuses[i];
        mediump vec4 lightSpecular = light_speculars[i];
        vec4 lightPos      = light_positions[i];
        vec3 lightDir      = light_directions[i];
        float attConst     = light_attenuation_consts[i];
        float attLinear    = light_attenuation_linears[i];
        float attQuadratic = light_attenuation_quadratics[i];
        float spotAngle    = light_spotlight_cutoff_angles[i];
        float spotExponent = light_spotlight_exponents[i];

        vec3 toLight;
        if (lightPos.w == 0.0)
        {
            toLight = lightPos.xyz;
        }
        else
        {
            toLight = (lightPos.xyz / lightPos.w - pos_varying.xyz);
        }

        float lightDist = length(toLight);
        vec3 toLightNormalized = normalize(toLight);
        vec3 h                 = toLightNormalized + vec3(0.0, 0.0, 1.0);
        float ndotL            = posDot(normal_varying, toLightNormalized);
        float ndoth            = posDot(normal_varying, normalize(h));

        float specAtt;

        if (ndotL != 0.0)
        {
            specAtt = 1.0;
        }
        else
        {
            specAtt = 0.0;
        }

        float att;

        if (lightPos.w != 0.0)
        {
            float attDenom =
                (attConst + attLinear * lightDist + attQuadratic * lightDist * lightDist);
            att = 1.0 / attDenom;
        }
        else
        {
            att = 1.0;
        }

        mediump float spot;

        mediump float spotAngleCos = cos(radians(spotAngle));
        vec3 toSurfaceDir  = -toLightNormalized;
        mediump float spotDot      = posDot(toSurfaceDir, normalize(lightDir));

        if (spotAngle == 180.0 || lightPos.w == 0.0)
        {
            spot = 1.0;
        }
        else
        {
            if (spotDot < spotAngleCos)
            {
                spot = 0.0;
            }
            else
            {
                spot = pow(spotDot, spotExponent);
            }
        }

        mediump vec4 contrib = materialAmbientActual * lightAmbient;
        contrib += ndotL * materialDiffuseActual * lightDiffuse;
        if (ndoth > 0.0 && material_specular_exponent > 0.0)
        {
            contrib += specAtt * pow(ndoth, material_specular_exponent) * material_specular *
                       lightSpecular;
        }
        else
        {
            if (ndoth > 0.0)
            {
                contrib += specAtt * material_specular * lightSpecular;
            }
        }
        contrib *= att * spot;
        lightingResult += contrib;
    }

    return lightingResult;
}

const mediump vec4 drawTextureVertices[6] = vec4[](
    vec4(0.0, 0.0, 0.0, 1.0),
    vec4(1.0, 0.0, 0.0, 1.0),
    vec4(1.0, 1.0, 0.0, 1.0),
    vec4(0.0, 0.0, 0.0, 1.0),
    vec4(1.0, 1.0, 0.0, 1.0),
    vec4(0.0, 1.0, 0.0, 1.0));

mediump vec4 drawTexturePosition(int vertexId)
{
    // The texture is drawn in the XY plane, so Z is constant.
    vec2 positionXY = draw_texture_coords.xy + drawTextureVertices[vertexId].xy * draw_texture_dims;
    return vec4(positionXY, draw_texture_coords.z, 1.0);
}

mediump vec3 drawTextureTexCoord(int vertexId, uint textureUnit)
{
    // The texture is drawn in the XY plane, so Z is 0.
    mediump vec2 texCropPos = draw_texture_normalized_crop_rect[textureUnit].xy;
    mediump vec2 texCropDim = draw_texture_normalized_crop_rect[textureUnit].zw;
    mediump vec2 texCoords  = texCropPos + drawTextureVertices[vertexId].xy * texCropDim;

    return vec3(texCoords, 0.0);
}

vec4 calcWorldPosition(vec4 posInput)
{
    return modelview * posInput;
}

vec4 calcNdcFromWorldPosition(vec4 worldPos)
{
    return projection * worldPos;
}

float calcPointSize(vec4 ndcPos)
{
    float dist         = length(ndcPos.z);
    float attConst     = point_distance_attenuation[0];
    float attLinear    = point_distance_attenuation[1];
    float attQuad      = point_distance_attenuation[2];
    float attPart      = attConst + attLinear * dist + attQuad * dist * dist;
    float attPointSize = pointsize / pow(attPart, 0.5);

    return clamp(attPointSize, point_size_min, point_size_max);
}

vec3 calcNormal(vec3 normalInput)
{
    mat3 mvInvTr3 = mat3(modelview_invtr);
    vec3 result   = mvInvTr3 * normalInput;

    if (enable_rescale_normal)
    {
        float rescale   = 1.0;
        vec3 rescaleVec = vec3(mvInvTr3[2]);
        float len       = length(rescaleVec);
        if (len > 0.0)
        {
            rescale = 1.0 / len;
        }
        result *= rescale;
    }

    if (enable_normalize)
    {
        result = normalize(result);
    }

    return result;
}

void main()
{
    if (enable_draw_texture)
    {
        int vertexId        = gl_VertexID;
        mediump vec4 posDrawTexture = drawTexturePosition(vertexId);

        gl_Position = posDrawTexture;
        pos_varying = posDrawTexture;

        normal_varying = normal;

        gl_PointSize = pointsize;

#if kTexUnits >= 1u
        texcoord0_varying = drawTextureTexCoord(vertexId, 0u);
#endif
#if kTexUnits >= 2u
        texcoord1_varying = drawTextureTexCoord(vertexId, 1u);
#endif
#if kTexUnits >= 3u
        texcoord2_varying = drawTextureTexCoord(vertexId, 2u);
#endif
#if kTexUnits >= 4u
        texcoord3_varying = drawTextureTexCoord(vertexId, 3u);
#endif
    }
    else
    {
        vec4 worldPos = calcWorldPosition(pos);
        vec4 ndcPos   = calcNdcFromWorldPosition(worldPos);

        gl_Position = ndcPos;
        pos_varying = worldPos;

        normal_varying = calcNormal(normal);

        // Avoid calculating point size stuff
        // if we are not rendering points.
        if (point_rasterization)
        {
            gl_PointSize = calcPointSize(ndcPos);
        }
        else
        {
            gl_PointSize = pointsize;
        }

#if kTexUnits >= 1u
        texcoord0_varying = (texture_matrix[0] * texcoord0).xyz;
#endif
#if kTexUnits >= 2u
        texcoord1_varying = (texture_matrix[1] * texcoord1).xyz;
#endif
#if kTexUnits >= 3u
        texcoord2_varying = (texture_matrix[2] * texcoord2).xyz;
#endif
#if kTexUnits >= 4u
        texcoord3_varying = (texture_matrix[3] * texcoord3).xyz;
#endif
    }

    mediump vec4 vertex_color = color;

    if (enable_lighting)
    {
        vertex_color = doLighting(color);
    }

    vertex_color = clamp(vertex_color, vec4(0), vec4(1));

    color_varying      = vertex_color;
    color_varying_flat = vertex_color;
}
)";

constexpr char kGLES1DrawFShaderVersion[] = R"(#version 300 es
)";

constexpr char kGLES1DrawFShaderHeader[] = R"(precision highp float;

// Defines for GL constants
#define kMaxTexUnits                         4u
#define kMaxClipPlanes                       6u

#define kModulate                       0x2100u
#define kDecal                          0x2101u
#define kCombine                        0x8570u
#define kReplace                        0x1E01u
#define kBlend                          0x0BE2u
#define kAdd                            0x0104u

#define kAddSigned                      0x8574u
#define kInterpolate                    0x8575u
#define kSubtract                       0x84E7u
#define kDot3Rgb                        0x86AEu
#define kDot3Rgba                       0x86AFu

#define kAlpha                          0x1906u
#define kRGB                            0x1907u
#define kRGBA                           0x1908u
#define kLuminance                      0x1909u
#define kLuminanceAlpha                 0x190Au

#define kTexture                        0x1702u
#define kConstant                       0x8576u
#define kPrimaryColor                   0x8577u
#define kPrevious                       0x8578u

#define kSrcColor                       0x0300u
#define kOneMinusSrcColor               0x0301u
#define kSrcAlpha                       0x0302u
#define kOneMinusSrcAlpha               0x0303u

#define kLinear                         0x2601u
#define kExp                            0x0800u
#define kExp2                           0x0801u

#define kNever                          0x0200u
#define kLess                           0x0201u
#define kEqual                          0x0202u
#define kLequal                         0x0203u
#define kGreater                        0x0204u
#define kNotequal                       0x0205u
#define kGequal                         0x0206u
#define kAlways                         0x0207u
#define kZero                              0x0u
#define kOne                               0x1u

#define kAnd                            0u
#define kAndInverted                    1u
#define kAndReverse                     2u
#define kClear                          3u
#define kCopy                           4u
#define kCopyInverted                   5u
#define kEquiv                          6u
#define kInvert                         7u
#define kNand                           8u
#define kNoop                           9u
#define kNor                            10u
#define kOr                             11u
#define kOrInverted                     12u
#define kOrReverse                      13u
#define kSet                            14u
#define kXor                            15u
)";

constexpr char kGLES1DrawFShaderUniformDefs[] = R"(

// Texture units ///////////////////////////////////////////////////////////////

// These are not arrays because hw support for arrays
// of samplers is rather lacking.

uniform mediump sampler2D tex_sampler0;
uniform mediump samplerCube tex_cube_sampler0;

uniform mediump sampler2D tex_sampler1;
uniform mediump samplerCube tex_cube_sampler1;

uniform mediump sampler2D tex_sampler2;
uniform mediump samplerCube tex_cube_sampler2;

uniform mediump sampler2D tex_sampler3;
uniform mediump samplerCube tex_cube_sampler3;

uniform mediump vec4 texture_env_color[kMaxTexUnits];
uniform mediump float texture_env_rgb_scale[kMaxTexUnits];
uniform mediump float texture_env_alpha_scale[kMaxTexUnits];

// Vertex attributes////////////////////////////////////////////////////////////

in vec4 pos_varying;
in vec3 normal_varying;
in mediump vec4 color_varying;
flat in mediump vec4 color_varying_flat;
#if kTexUnits >= 1u
in mediump vec3 texcoord0_varying;
#endif
#if kTexUnits >= 2u
in mediump vec3 texcoord1_varying;
#endif
#if kTexUnits >= 3u
in mediump vec3 texcoord2_varying;
#endif
#if kTexUnits >= 4u
in mediump vec3 texcoord3_varying;
#endif

// Alpha test///////////////////////////////////////////////////////////////////

uniform mediump float alpha_test_ref;

// Fog /////////////////////////////////////////////////////////////////////////

uniform float fog_density;
uniform float fog_start;
uniform float fog_end;
uniform mediump vec4 fog_color;

// User clip plane /////////////////////////////////////////////////////////////

uniform vec4 clip_planes[kMaxClipPlanes];

// Logic Op ////////////////////////////////////////////////////////////////////

// Format is:
// - 4x4 bits depicting the bit width of each channel of color output
// - 4 bits for the op based on LogicalOperation's packing
uniform highp uint logic_op;

// Point rasterization//////////////////////////////////////////////////////////

// GL_OES_draw_texture//////////////////////////////////////////////////////////
)";

constexpr char kGLES1DrawFShaderOutputDef[] = R"(
out mediump vec4 frag_color;
)";

constexpr char kGLES1DrawFShaderFramebufferFetchOutputDef[] = R"(
inout mediump vec4 frag_color;
)";

constexpr char kGLES1DrawFShaderFramebufferFetchNonCoherentOutputDef[] = R"(
layout(noncoherent) inout mediump vec4 frag_color;
)";

constexpr char kGLES1DrawFShaderFunctions[] = R"(

bool doAlphaTest(mediump vec4 currentFragment)
{
    bool shouldPassAlpha   = false;
    mediump float incAlpha = currentFragment.a;

    switch (alpha_func)
    {
        case kNever:
            shouldPassAlpha = false;
            break;
        case kLess:
            shouldPassAlpha = incAlpha < alpha_test_ref;
            break;
        case kLequal:
            shouldPassAlpha = incAlpha <= alpha_test_ref;
            break;
        case kEqual:
            shouldPassAlpha = incAlpha == alpha_test_ref;
            break;
        case kGequal:
            shouldPassAlpha = incAlpha >= alpha_test_ref;
            break;
        case kGreater:
            shouldPassAlpha = incAlpha > alpha_test_ref;
            break;
        case kNotequal:
            shouldPassAlpha = incAlpha != alpha_test_ref;
            break;
        case kAlways:
        default:
            shouldPassAlpha = true;
            break;
    }

    return shouldPassAlpha;
}

bool doClipPlaneTest()
{
    bool res = true;

    for (uint i = 0u; i < kMaxClipPlanes; i++)
    {
        if (clip_plane_enables[i])
        {
            float dist = dot(clip_planes[i].xyz, pos_varying.xyz) + clip_planes[i].w * pos_varying.w;
            res        = res && (dist >= 0.0);
        }
    }

    return res;
}

mediump vec4 doFog(mediump vec4 currentFragment)
{

    float eyeDist = -pos_varying.z / pos_varying.w;
    float f       = 1.0;
    switch (fog_mode)
    {
        case kExp:
            f = exp(-fog_density * eyeDist);
            break;
        case kExp2:
            f = exp(-(pow(fog_density * eyeDist, 2.0)));
            break;
        case kLinear:
            f = (fog_end - eyeDist) / (fog_end - fog_start);
            break;
        default:
            break;
    }

    f = clamp(f, 0.0, 1.0);
    mediump vec4 result = vec4(f * currentFragment.rgb + (1.0 - f) * fog_color.rgb, currentFragment.a);
    return result;
}
)";

constexpr char kGLES1DrawFShaderLogicOpFramebufferFetchDisabled[] = R"(
mediump vec4 applyLogicOp(mediump vec4 currentFragment)
{
    return currentFragment;
}
)";

// applyLogicOp takes logic-op information from a packed uniform and applies it to the color
// attachment using framebuffer fetch.  See the description of logic_op above for the format of the
// uniform.
//
// In particular, 4 bits in logic_op (at offset 16) contain the packed logical operation (of
// LogicalOperation type).  Based on the selected operation, the formula specified in the spec is
// applied (applied as bitwise operations on unorm values).
constexpr char kGLES1DrawFShaderLogicOpFramebufferFetchEnabled[] = R"(
mediump vec4 applyLogicOp(mediump vec4 currentFragment)
{
    mediump vec4 previousFragment = frag_color;

    mediump uvec4 channelWidths = uvec4(logic_op & 0xFu,
                                        logic_op >> 4u & 0xFu,
                                        logic_op >> 8u & 0xFu,
                                        logic_op >> 12u & 0xFu);

    mediump uvec4 channelMasks = (uvec4(1) << channelWidths) - 1u;

    mediump uvec4 src = uvec4(round(currentFragment * vec4(channelMasks)));
    mediump uvec4 dst = uvec4(round(previousFragment * vec4(channelMasks)));
    mediump uvec4 result;

    switch (logic_op >> 16u & 0xFu)
    {
        case kAnd:
            result = src & dst;
            break;
        case kAndInverted:
            result = ~src & dst;
            break;
        case kAndReverse:
            result = src & ~dst;
            break;
        case kClear:
            result = uvec4(0);
            break;
        case kCopy:
            result = src;
            break;
        case kCopyInverted:
            result = ~src;
            break;
        case kEquiv:
            result = ~(src ^ dst);
            break;
        case kInvert:
            result = ~dst;
            break;
        case kNand:
            result = ~(src & dst);
            break;
        case kNoop:
            result = dst;
            break;
        case kNor:
            result = ~(src | dst);
            break;
        case kOr:
            result = src | dst;
            break;
        case kOrInverted:
            result = ~src | dst;
            break;
        case kOrReverse:
            result = src | ~dst;
            break;
        case kSet:
            result = channelMasks;
            break;
        case kXor:
            result = src ^ dst;
            break;
    }

    result &= channelMasks;

    // Avoid division by zero for formats without alpha
    channelMasks.a = max(channelMasks.a, 1u);

    return vec4(result) / vec4(channelMasks);
}
)";

constexpr char kGLES1DrawFShaderMultitexturing[] = R"(

bool isTextureUnitEnabled(uint unit)
{
    return enable_texture_2d[unit] || enable_texture_cube_map[unit];
}

mediump vec4 getTextureColor(uint unit)
{
    mediump vec4 res;

    switch (unit)
    {
#if kTexUnits >= 1u
        case 0u:
            if (enable_texture_2d[0])
            {
                res = texture(tex_sampler0, texcoord0_varying.xy);
            }
            else if (enable_texture_cube_map[0])
            {
                res = texture(tex_cube_sampler0, texcoord0_varying);
            }
            break;
#endif
#if kTexUnits >= 2u
        case 1u:
            if (enable_texture_2d[1])
            {
                res = texture(tex_sampler1, texcoord1_varying.xy);
            }
            else if (enable_texture_cube_map[1])
            {
                res = texture(tex_cube_sampler1, texcoord1_varying);
            }
            break;
#endif
#if kTexUnits >= 3u
        case 2u:
            if (enable_texture_2d[2])
            {
                res = texture(tex_sampler2, texcoord2_varying.xy);
            }
            else if (enable_texture_cube_map[2])
            {
                res = texture(tex_cube_sampler2, texcoord2_varying);
            }
            break;
#endif
#if kTexUnits >= 4u
        case 3u:
            if (enable_texture_2d[3])
            {
                res = texture(tex_sampler3, texcoord3_varying.xy);
            }
            else if (enable_texture_cube_map[3])
            {
                // TODO: Weird stuff happens
                // res = texture(tex_cube_sampler3, texcoord3_varying);
            }
            break;
#endif
        default:
            break;
    }

    return res;
}

mediump vec4 getPointSpriteTextureColor(uint unit)
{
    mediump vec4 res;

    switch (unit)
    {
        case 0u:
            if (enable_texture_2d[0])
            {
                res = texture(tex_sampler0, gl_PointCoord.xy);
            }
            break;
        case 1u:
            if (enable_texture_2d[1])
            {
                res = texture(tex_sampler1, gl_PointCoord.xy);
            }
            break;
        case 2u:
            if (enable_texture_2d[2])
            {
                res = texture(tex_sampler2, gl_PointCoord.xy);
            }
            break;
        case 3u:
            if (enable_texture_2d[3])
            {
                res = texture(tex_sampler3, gl_PointCoord.xy);
            }
            break;
        default:
            break;
    }

    return res;
}

mediump vec3 textureCombineSrcnOpnRgb(uint srcnRgb,
                                      uint opnRgb,
                                      mediump vec4 textureEnvColor,
                                      mediump vec4 vertexColor,
                                      mediump vec4 texturePrevColor,
                                      mediump vec4 textureColor)
{
    mediump vec3 res;
    mediump vec4 op;

    switch (srcnRgb)
    {
        case kTexture:
            op = textureColor;
            break;
        case kConstant:
            op = textureEnvColor;
            break;
        case kPrimaryColor:
            op = vertexColor;
            break;
        case kPrevious:
            op = texturePrevColor;
            break;
        default:
            op = texturePrevColor;
            break;
    }

    switch (opnRgb)
    {
        case kSrcColor:
            res = op.rgb;
            break;
        case kOneMinusSrcColor:
            res = 1.0 - op.rgb;
            break;
        case kSrcAlpha:
            res = vec3(op.a, op.a, op.a);
            break;
        case kOneMinusSrcAlpha:
            res = vec3(1.0 - op.a, 1.0 - op.a, 1.0 - op.a);
            break;
        default:
            break;
    }

    return res;
}

mediump float textureCombineSrcnOpnAlpha(uint srcn,
                                         uint opn,
                                         mediump vec4 textureEnvColor,
                                         mediump vec4 vertexColor,
                                         mediump vec4 texturePrevColor,
                                         mediump vec4 textureColor)
{
    mediump float res;
    mediump vec4 op;

    switch (srcn)
    {
        case kTexture:
            op = textureColor;
            break;
        case kConstant:
            op = textureEnvColor;
            break;
        case kPrimaryColor:
            op = vertexColor;
            break;
        case kPrevious:
            op = texturePrevColor;
            break;
        default:
            op = texturePrevColor;
            break;
    }

    switch (opn)
    {
        case kSrcAlpha:
            res = op.a;
            break;
        case kOneMinusSrcAlpha:
            res = 1.0 - op.a;
            break;
        default:
            break;
    }

    return res;
}

mediump vec4 textureCombine(uint combineRgb,
                            uint combineAlpha,
                            uint src0Rgb,
                            uint src0Alpha,
                            uint src1Rgb,
                            uint src1Alpha,
                            uint src2Rgb,
                            uint src2Alpha,
                            uint op0Rgb,
                            uint op0Alpha,
                            uint op1Rgb,
                            uint op1Alpha,
                            uint op2Rgb,
                            uint op2Alpha,
                            mediump vec4 textureEnvColor,
                            mediump float rgbScale,
                            mediump float alphaScale,
                            mediump vec4 vertexColor,
                            mediump vec4 texturePrevColor,
                            mediump vec4 textureColor)
{

    mediump vec3 resRgb;
    mediump float resAlpha;

    mediump vec3 arg0Rgb;
    mediump float arg0Alpha;
    mediump vec3 arg1Rgb;
    mediump float arg1Alpha;
    mediump vec3 arg2Rgb;
    mediump float arg2Alpha;
    mediump float dotVal;

    arg0Rgb   = textureCombineSrcnOpnRgb(src0Rgb, op0Rgb, textureEnvColor, vertexColor,
                                       texturePrevColor, textureColor);
    arg0Alpha = textureCombineSrcnOpnAlpha(src0Alpha, op0Alpha, textureEnvColor, vertexColor,
                                           texturePrevColor, textureColor);

    if (combineRgb != kReplace)
    {
        arg1Rgb = textureCombineSrcnOpnRgb(src1Rgb, op1Rgb, textureEnvColor, vertexColor,
                                           texturePrevColor, textureColor);
    }

    if (combineAlpha != kReplace)
    {
        arg1Alpha = textureCombineSrcnOpnAlpha(src1Alpha, op1Alpha, textureEnvColor, vertexColor,
                                               texturePrevColor, textureColor);
    }

    if (combineRgb == kInterpolate)
    {
        arg2Rgb = textureCombineSrcnOpnRgb(src2Rgb, op2Rgb, textureEnvColor, vertexColor,
                                           texturePrevColor, textureColor);
    }

    if (combineAlpha == kInterpolate)
    {
        arg2Alpha = textureCombineSrcnOpnAlpha(src2Alpha, op2Alpha, textureEnvColor, vertexColor,
                                               texturePrevColor, textureColor);
    }

    switch (combineRgb)
    {
        case kReplace:
            resRgb = arg0Rgb;
            break;
        case kModulate:
            resRgb = arg0Rgb * arg1Rgb;
            break;
        case kAdd:
            resRgb = arg0Rgb + arg1Rgb;
            break;
        case kAddSigned:
            resRgb = arg0Rgb + arg1Rgb - 0.5;
            break;
        case kInterpolate:
            resRgb = arg0Rgb * arg2Rgb + arg1Rgb * (1.0 - arg2Rgb);
            break;
        case kSubtract:
            resRgb = arg0Rgb - arg1Rgb;
            break;
        default:
            break;
    }

    switch (combineAlpha)
    {
        case kReplace:
            resAlpha = arg0Alpha;
            break;
        case kModulate:
            resAlpha = arg0Alpha * arg1Alpha;
            break;
        case kAdd:
            resAlpha = arg0Alpha + arg1Alpha;
            break;
        case kAddSigned:
            resAlpha = arg0Alpha + arg1Alpha - 0.5;
            break;
        case kInterpolate:
            resAlpha = arg0Alpha * arg2Alpha + arg1Alpha * (1.0 - arg2Alpha);
            break;
        case kSubtract:
            resAlpha = arg0Alpha - arg1Alpha;
            break;
        default:
            break;
    }

    if (combineRgb == kDot3Rgb || combineRgb == kDot3Rgba)
    {
        dotVal = 4.0 * dot(arg0Rgb - 0.5, arg1Rgb - 0.5);

        if (combineRgb == kDot3Rgb)
        {
            return vec4(dotVal, dotVal, dotVal, resAlpha);
        }
        else
        {
            return vec4(dotVal, dotVal, dotVal, dotVal);
        }
    }
    else
    {
        return vec4(resRgb, resAlpha);
    }
}

mediump vec4 textureFunction(uint unit,
                             uint texFormat,
                             uint envMode,
                             uint combineRgb,
                             uint combineAlpha,
                             uint src0Rgb,
                             uint src0Alpha,
                             uint src1Rgb,
                             uint src1Alpha,
                             uint src2Rgb,
                             uint src2Alpha,
                             uint op0Rgb,
                             uint op0Alpha,
                             uint op1Rgb,
                             uint op1Alpha,
                             uint op2Rgb,
                             uint op2Alpha,
                             mediump vec4 textureEnvColor,
                             mediump float rgbScale,
                             mediump float alphaScale,
                             mediump vec4 vertexColor,
                             mediump vec4 texturePrevColor,
                             mediump vec4 textureColor)
{

    if (!isTextureUnitEnabled(unit))
    {
        return texturePrevColor;
    }

    mediump vec4 res;

    switch (envMode)
    {
        case kReplace:
            switch (texFormat)
            {
                case kAlpha:
                    res.rgb = texturePrevColor.rgb;
                    res.a   = textureColor.a;
                    break;
                case kRGBA:
                case kLuminanceAlpha:
                    res.rgba = textureColor.rgba;
                    break;
                case kRGB:
                case kLuminance:
                default:
                    res.rgb = textureColor.rgb;
                    res.a   = texturePrevColor.a;
                    break;
            }
            break;
        case kModulate:
            switch (texFormat)
            {
                case kAlpha:
                    res.rgb = texturePrevColor.rgb;
                    res.a   = texturePrevColor.a * textureColor.a;
                    break;
                case kRGBA:
                case kLuminanceAlpha:
                    res.rgba = texturePrevColor.rgba * textureColor.rgba;
                    break;
                case kRGB:
                case kLuminance:
                default:
                    res.rgb = texturePrevColor.rgb * textureColor.rgb;
                    res.a   = texturePrevColor.a;
                    break;
            }
            break;
        case kDecal:
            switch (texFormat)
            {
                case kRGB:
                    res.rgb = textureColor.rgb;
                    res.a   = texturePrevColor.a;
                    break;
                case kRGBA:
                    res.rgb = texturePrevColor.rgb * (1.0 - textureColor.a) +
                              textureColor.rgb * textureColor.a;
                    res.a = texturePrevColor.a;
                    break;
                case kAlpha:
                case kLuminance:
                case kLuminanceAlpha:
                default:
                    res.rgb = texturePrevColor.rgb * textureColor.rgb;
                    res.a   = texturePrevColor.a;
                    break;
            }
            break;
        case kBlend:
            switch (texFormat)
            {
                case kAlpha:
                    res.rgb = texturePrevColor.rgb;
                    res.a   = textureColor.a * texturePrevColor.a;
                    break;
                case kLuminance:
                case kRGB:
                    res.rgb = texturePrevColor.rgb * (1.0 - textureColor.rgb) +
                              textureEnvColor.rgb * textureColor.rgb;
                    res.a = texturePrevColor.a;
                    break;
                case kLuminanceAlpha:
                case kRGBA:
                default:
                    res.rgb = texturePrevColor.rgb * (1.0 - textureColor.rgb) +
                              textureEnvColor.rgb * textureColor.rgb;
                    res.a = textureColor.a * texturePrevColor.a;
                    break;
            }
            break;
        case kAdd:
            switch (texFormat)
            {
                case kAlpha:
                    res.rgb = texturePrevColor.rgb;
                    res.a   = textureColor.a * texturePrevColor.a;
                    break;
                case kLuminance:
                case kRGB:
                    res.rgb = texturePrevColor.rgb + textureColor.rgb;
                    res.a   = texturePrevColor.a;
                    break;
                case kLuminanceAlpha:
                case kRGBA:
                default:
                    res.rgb = texturePrevColor.rgb + textureColor.rgb;
                    res.a   = textureColor.a * texturePrevColor.a;
                    break;
            }
            break;
        case kCombine:
            res = textureCombine(combineRgb, combineAlpha, src0Rgb, src0Alpha, src1Rgb, src1Alpha,
                                 src2Rgb, src2Alpha, op0Rgb, op0Alpha, op1Rgb, op1Alpha, op2Rgb,
                                 op2Alpha, textureEnvColor, rgbScale, alphaScale, vertexColor,
                                 texturePrevColor, textureColor);
            res.rgb *= rgbScale;
            res.a *= alphaScale;
            break;
        default:
            break;
    }

    return clamp(res, 0.0, 1.0);
}
)";

constexpr char kGLES1DrawFShaderMain[] = R"(
void main()
{
    if (enable_clip_planes && !enable_draw_texture)
    {
        if (!doClipPlaneTest())
        {
            discard;
        }
    }

    mediump vec4 vertex_color;

    if (shade_model_flat)
    {
        vertex_color = color_varying_flat;
    }
    else
    {
        vertex_color = color_varying;
    }

    mediump vec4 currentFragment = vertex_color;

    mediump vec4 texturePrevColor = currentFragment;

    for (uint i = 0u; i < kTexUnits; i++)
    {
        mediump vec4 textureColor;

        if (point_rasterization && point_sprite_enabled &&
            point_sprite_coord_replace[i]) {
            textureColor = getPointSpriteTextureColor(i);
        } else {
            textureColor = getTextureColor(i);
        }

        currentFragment = textureFunction(
            i, texture_format[i], texture_env_mode[i], combine_rgb[i], combine_alpha[i],
            src0_rgb[i], src0_alpha[i], src1_rgb[i], src1_alpha[i], src2_rgb[i], src2_alpha[i],
            op0_rgb[i], op0_alpha[i], op1_rgb[i], op1_alpha[i], op2_rgb[i], op2_alpha[i],
            texture_env_color[i], texture_env_rgb_scale[i], texture_env_alpha_scale[i],
            vertex_color, texturePrevColor, textureColor);

        texturePrevColor = currentFragment;
    }

    if (enable_fog)
    {
        currentFragment = doFog(currentFragment);
    }

    if (enable_alpha_test && !doAlphaTest(currentFragment))
    {
        discard;
    }

    frag_color = applyLogicOp(currentFragment);
}
)";