# Ref.: https://stackoverflow.com/questions/67040258/cmake-compile-glsl-shaders
# Ref.: https://cmake.org/cmake/help/latest/command/add_custom_command.html

set(SHADER_SOURCE_DIR ${PROJECT_SOURCE_DIR}/shaders)
set(SHADER_BIN_DIR ${PROJECT_SOURCE_DIR}/assets/shaders)
file(GLOB VERTEX_SHADERS ${SHADER_SOURCE_DIR}/vs_*.sc)
file(GLOB FRAGMENT_SHADERS ${SHADER_SOURCE_DIR}/fs_*.sc)
file(GLOB COMPUTE_SHADERS ${SHADER_SOURCE_DIR}/cs_*.sc)

# vertex shaders
foreach(SHADER_IN IN LISTS VERTEX_SHADERS)
    cmake_path(GET SHADER_IN FILENAME SHADER_NAME) # ex. SHADER_NAME==vs_cubes.sc

    # output file
    string(REPLACE ".sc" ".spv" SHADER_OUT ${SHADER_NAME})
    set(SHADER_OUT ${SHADER_BIN_DIR}/${SHADER_OUT})

    # varying file 
    string(REPLACE "vs" "varying" SHADER_VARYING ${SHADER_IN})

    # message("SHADER_IN: " ${SHADER_IN} " - SHADER_VARYING: " ${SHADER_VARYING} " - SHADER_OUT: " ${SHADER_OUT})

    _bgfx_shaderc_parse(CLI
      FILE ${SHADER_IN}
      OUTPUT ${SHADER_OUT}
      VERTEX
      LINUX
      PROFILE spirv
      VARYINGDEF ${SHADER_VARYING}
      INCLUDES ${SHADER_BIN_DIR}
    )

    add_custom_command(
        OUTPUT ${SHADER_OUT}
        COMMAND ${SHADERC} ${CLI}
        DEPENDS ${SHADER_IN}
        COMMENT "Compiling shader ${SHADER_NAME}"
    )

    list(APPEND SPV_SHADERS ${SHADER_OUT})
endforeach()

# fragment shaders
foreach(SHADER_IN IN LISTS FRAGMENT_SHADERS)
    cmake_path(GET SHADER_IN FILENAME SHADER_NAME) # ex. SHADER_NAME==vs_cubes.sc

    # output file
    string(REPLACE ".sc" ".spv" SHADER_OUT ${SHADER_NAME})
    set(SHADER_OUT ${SHADER_BIN_DIR}/${SHADER_OUT})

    # varying file 
    string(REPLACE "fs" "varying" SHADER_VARYING ${SHADER_IN})

    # message("SHADER_IN: " ${SHADER_IN} " - SHADER_VARYING: " ${SHADER_VARYING} " - SHADER_OUT: " ${SHADER_OUT})

    _bgfx_shaderc_parse(CLI
      FILE ${SHADER_IN}
      OUTPUT ${SHADER_OUT}
      FRAGMENT
      LINUX
      PROFILE spirv
      VARYINGDEF ${SHADER_VARYING}
      INCLUDES ${SHADER_BIN_DIR}
    )

    add_custom_command(
        OUTPUT ${SHADER_OUT}
        COMMAND ${SHADERC} ${CLI}
        DEPENDS ${SHADER_IN}
        COMMENT "Compiling shader ${SHADER_NAME}"
    )

    list(APPEND SPV_SHADERS ${SHADER_OUT})
endforeach()

# compute shaders
foreach(SHADER_IN IN LISTS COMPUTE_SHADERS)
    cmake_path(GET SHADER_IN FILENAME SHADER_NAME) # ex. SHADER_NAME==vs_cubes.sc

    # output file
    string(REPLACE ".sc" ".spv" SHADER_OUT ${SHADER_NAME})
    set(SHADER_OUT ${SHADER_BIN_DIR}/${SHADER_OUT})

    # message("SHADER_IN: " ${SHADER_IN} " - "SHADER_OUT: " ${SHADER_OUT})

    _bgfx_shaderc_parse(CLI
      FILE ${SHADER_IN}
      OUTPUT ${SHADER_OUT}
      COMPUTE
      LINUX
      PROFILE spirv
      INCLUDES ${SHADER_BIN_DIR}
    )

    add_custom_command(
        OUTPUT ${SHADER_OUT}
        COMMAND ${SHADERC} ${CLI}
        DEPENDS ${SHADER_IN}
        COMMENT "Compiling shader ${SHADER_NAME}"
    )

    list(APPEND SPV_SHADERS ${SHADER_OUT})
endforeach()

add_custom_target(shaders ALL DEPENDS ${SPV_SHADERS})