/* SPDX-License-Identifier: GPL-2.0-or-later */

/* Common Metal header to be included in all compiled Metal shaders.
 * Both native MSL shaders and GLSL shaders. */

using namespace metal;

/* Should match GPUVertFetchMode. */
typedef enum {
  GPU_FETCH_FLOAT = 0,
  GPU_FETCH_INT,
  GPU_FETCH_INT_TO_FLOAT_UNIT,
  GPU_FETCH_INT_TO_FLOAT,
} GPUVertFetchMode;

/* Consant to flag base binding index of uniform buffers. */
constant int MTL_uniform_buffer_base_index [[function_constant(0)]];

/* Default Point Size.
 * Unused if function constant not set. */
constant float MTL_global_pointsize [[function_constant(1)]];

/* Attribute conversions flags (Up to 16 attributes supported in Blender). */
constant int MTL_AttributeConvert0 [[function_constant(2)]];
constant int MTL_AttributeConvert1 [[function_constant(3)]];
constant int MTL_AttributeConvert2 [[function_constant(4)]];
constant int MTL_AttributeConvert3 [[function_constant(5)]];
constant int MTL_AttributeConvert4 [[function_constant(6)]];
constant int MTL_AttributeConvert5 [[function_constant(7)]];
constant int MTL_AttributeConvert6 [[function_constant(8)]];
constant int MTL_AttributeConvert7 [[function_constant(9)]];
constant int MTL_AttributeConvert8 [[function_constant(10)]];
constant int MTL_AttributeConvert9 [[function_constant(11)]];
constant int MTL_AttributeConvert10 [[function_constant(12)]];
constant int MTL_AttributeConvert11 [[function_constant(13)]];
constant int MTL_AttributeConvert12 [[function_constant(14)]];
constant int MTL_AttributeConvert13 [[function_constant(15)]];
constant int MTL_AttributeConvert14 [[function_constant(16)]];
constant int MTL_AttributeConvert15 [[function_constant(17)]];

/* Consant to flag binding index of transform feedback buffer.
 * Unused if function constant not set. */
constant int MTL_transform_feedback_buffer_index [[function_constant(18)]];

/** Clip distance enablement. */
/* General toggle to control whether any clipping distanes are written at all.
 * This is an optimization to avoid having the clipping distance shader output
 * paramter if it is not needed. */
constant int MTL_clip_distances_enabled [[function_constant(19)]];

/* If clipping planes are enabled at all, then we require an enablement
 * flag per clipping plane. If enabled, then gl_ClipDistances[N] will
 * control clipping for a given plane, otherwise the value is ignored. */
constant int MTL_clip_distance_enabled0 [[function_constant(20)]];
constant int MTL_clip_distance_enabled1 [[function_constant(21)]];
constant int MTL_clip_distance_enabled2 [[function_constant(22)]];
constant int MTL_clip_distance_enabled3 [[function_constant(23)]];
constant int MTL_clip_distance_enabled4 [[function_constant(24)]];
constant int MTL_clip_distance_enabled5 [[function_constant(25)]];

/* Compute and SSBOs. */
constant int MTL_storage_buffer_base_index [[function_constant(26)]];

/** Internal attribute conversion functionality. */
/* Following descriptions in mtl_shader.hh, Metal only supports some implicit
 * attribute type conversions. These conversions occur when there is a difference
 * between the type specified in the vertex descriptor (In the input vertex buffers),
 * and the attribute type in the shader's VertexIn struct (ShaderInterface).
 *
 * The supported implicit conversions are described here:
 * https://developer.apple.com/documentation/metal/mtlvertexattributedescriptor/1516081-format?language=objc
 *
 * For unsupported conversions, the mtl_shader_generator will create an attribute reading function
 * which performs this conversion manually upon read, depending on the requested fetchmode.
 *
 * These conversions use the function constants above, so any branching is optimized out during
 * backend shader compilation (PSO creation).
 *
 * NOTE: Not all possibilities have been covered here, any additional conversion routines should
 * be added as needed, and mtl_shader_generator should also be updated with any newly required
 * read functions.
 *
 * These paths are only needed for cases where implicit conversion will not happen, in which
 * case the value will be read as the type in the shader.
 */
#define internal_vertex_attribute_convert_read_float(ATTR, v_in, v_out) \
  if (ATTR == GPU_FETCH_INT_TO_FLOAT) { \
    v_out = float(as_type<int>(v_in)); \
  } \
  else if (ATTR == GPU_FETCH_INT_TO_FLOAT_UNIT) { \
    v_out = float(as_type<int>(v_in)) / float(__INT_MAX__); \
  } \
  else { \
    v_out = v_in; \
  }

#define internal_vertex_attribute_convert_read_float2(ATTR, v_in, v_out) \
  if (ATTR == GPU_FETCH_INT_TO_FLOAT) { \
    v_out = float2(as_type<int2>(v_in)); \
  } \
  else if (ATTR == GPU_FETCH_INT_TO_FLOAT_UNIT) { \
    v_out = float2(as_type<int2>(v_in)) / float2(__INT_MAX__); \
  } \
  else { \
    v_out = v_in; \
  }

#define internal_vertex_attribute_convert_read_float3(ATTR, v_in, v_out) \
  if (ATTR == GPU_FETCH_INT_TO_FLOAT) { \
    v_out = float3(as_type<int3>(v_in)); \
  } \
  else if (ATTR == GPU_FETCH_INT_TO_FLOAT_UNIT) { \
    v_out = float3(as_type<int3>(v_in)) / float3(__INT_MAX__); \
  } \
  else { \
    v_out = v_in; \
  }

#define internal_vertex_attribute_convert_read_float4(ATTR, v_in, v_out) \
  if (ATTR == GPU_FETCH_INT_TO_FLOAT) { \
    v_out = float4(as_type<int4>(v_in)); \
  } \
  else if (ATTR == GPU_FETCH_INT_TO_FLOAT_UNIT) { \
    v_out = float4(as_type<int4>(v_in)) / float4(__INT_MAX__); \
  } \
  else { \
    v_out = v_in; \
  }