# Compiles src/shaders/scene.hlsl (which includes src/sceneShared.h) into a C header of SPIR-V, DXIL and MSL blobs with
# SDL_shadercross.  Run by the build as
#   cmake -DSHADERCROSS=<tool> -DSOURCE=<scene.hlsl> -DOUTPUT=<sceneShaders.h> -P shaderHeader.cmake
# so the header is generated into the build tree like the icon and the other embedded files.

# Invoked in script mode:  -DSHADERCROSS -DSOURCE=<file.hlsl> -DOUTPUT=<header> -DENTRIES=<name:stage;...>
# -DPREFIX=<lowerCamel prefix> -DTYPE=<struct name>.  ENTRIES, PREFIX and TYPE default to the scene's.
if(NOT ENTRIES)
	set(ENTRIES vertexStatic:vertex vertexSkinned:vertex fragmentMain:fragment depthMain:fragment depthCutoutMain:fragment particleVertex:vertex particleFragment:fragment lineVertex:vertex lineFragment:fragment postVertex:vertex postFragment:fragment skyFragment:fragment bloomDown:fragment bloomUp:fragment)
endif()
if(NOT PREFIX)
	set(PREFIX sceneShader)
endif()
if(NOT TYPE)
	set(TYPE SceneShaderT)
endif()
get_filename_component(sourceName ${SOURCE} NAME)
string(TOUPPER "${PREFIX}" guard)
string(REPLACE "SHADER" "_SHADERS_H" guard "${guard}")
set(entries ${ENTRIES})
set(formats SPIRV DXIL MSL)
get_filename_component(sourceDir ${SOURCE} DIRECTORY)
get_filename_component(includeDir ${sourceDir} DIRECTORY)
get_filename_component(outputDir ${OUTPUT} DIRECTORY)
set(work ${outputDir}/work)
file(MAKE_DIRECTORY ${work})

set(header "// Generated from ${sourceName} by cmake/shaderHeader.cmake with SDL_shadercross; do not edit.\n")
string(APPEND header "// SPIR-V for Vulkan, DXIL for Direct3D 12, MSL for Metal, one set per entry point.\n\n")
string(APPEND header "#ifndef ${guard}\n#define ${guard}\n\n#include <stddef.h>\n\n")
string(REGEX REPLACE "T$" "S" structName "${TYPE}")
string(APPEND header "typedef struct ${structName} {\n\tconst char          *entryPoint;\n\tconst unsigned char *spirv;\n\tsize_t               spirvSize;\n\tconst unsigned char *dxil;\n\tsize_t               dxilSize;\n\tconst unsigned char *msl;\n\tsize_t               mslSize;\n} ${TYPE};\n\n")
foreach(entry IN LISTS entries)
	string(REPLACE ":" ";" parts ${entry})
	list(GET parts 0 name)
	list(GET parts 1 stage)
	foreach(format IN LISTS formats)
		string(TOLOWER ${format} extension)
		set(blob ${work}/${name}.${extension})
		execute_process(COMMAND ${SHADERCROSS} ${SOURCE} -s HLSL -d ${format} -t ${stage} -e ${name} -I ${includeDir} -o ${blob} RESULT_VARIABLE code OUTPUT_VARIABLE out ERROR_VARIABLE err)
		if(NOT code EQUAL 0)
			message(FATAL_ERROR "Shader ${name} (${format}) failed to compile:\n${out}\n${err}")
		endif()
		file(READ ${blob} hex HEX)
		string(REGEX REPLACE "([0-9a-f][0-9a-f])" "0x\\1," bytes "${hex}")
		string(APPEND header "static const unsigned char _${name}${format}[] = {\n\t${bytes}\n};\n\n")
	endforeach()
	string(SUBSTRING ${name} 0 1 initial)
	string(SUBSTRING ${name} 1 -1 rest)
	string(TOUPPER ${initial} initial)
	string(APPEND header "static const ${TYPE} ${PREFIX}${initial}${rest} = { \"${name}\", _${name}SPIRV, sizeof(_${name}SPIRV), _${name}DXIL, sizeof(_${name}DXIL), _${name}MSL, sizeof(_${name}MSL) };\n\n")
endforeach()
string(APPEND header "#endif\n")
file(WRITE ${OUTPUT} "${header}")