cmake_minimum_required(VERSION 3.10)
project(ksOSKernel LANGUAGES ASM C)

# --- Locate Swift toolchain with Embedded Swift stdlib ---
# Priority: cmake var > env var > auto-detect
if(NOT SWIFT_TOOLCHAIN AND DEFINED ENV{SWIFT_TOOLCHAIN})
    set(SWIFT_TOOLCHAIN "$ENV{SWIFT_TOOLCHAIN}")
endif()

if(SWIFT_TOOLCHAIN)
    set(SWIFTC             "${SWIFT_TOOLCHAIN}/usr/bin/swiftc")
    set(SWIFT_RESOURCE_DIR "${SWIFT_TOOLCHAIN}/usr/lib/swift")
elseif(CMAKE_HOST_SYSTEM_NAME STREQUAL "Darwin")
    # Scan for a swift.org toolchain that ships the embedded stdlib.
    # APPLE is false here (target is Generic), so we check the HOST OS.
    file(GLOB _tc_candidates
        "$ENV{HOME}/Library/Developer/Toolchains/*.xctoolchain"
        "/Library/Developer/Toolchains/*.xctoolchain"
    )
    foreach(_tc ${_tc_candidates})
        if(EXISTS "${_tc}/usr/lib/swift/embedded")
            set(SWIFTC             "${_tc}/usr/bin/swiftc")
            set(SWIFT_RESOURCE_DIR "${_tc}/usr/lib/swift")
            break()
        endif()
    endforeach()
else()
    # Linux: find swiftc in PATH
    find_program(_SWIFTC_EXE swiftc)
    if(_SWIFTC_EXE)
        get_filename_component(_SWIFTC_BIN "${_SWIFTC_EXE}" DIRECTORY)
        get_filename_component(_SWIFTC_USR "${_SWIFTC_BIN}" DIRECTORY)
        
        if(EXISTS "${_SWIFTC_USR}/lib/swift/embedded")
            set(SWIFTC             "${_SWIFTC_EXE}")
            set(SWIFT_RESOURCE_DIR "${_SWIFTC_USR}/lib/swift")
        elseif(EXISTS "${_SWIFTC_USR}/lib/swift/lib/swift/embedded")
            set(SWIFTC             "${_SWIFTC_EXE}")
            set(SWIFT_RESOURCE_DIR "${_SWIFTC_USR}/lib/swift/lib/swift")
        endif()
    endif()
endif()

if(NOT SWIFTC OR NOT EXISTS "${SWIFT_RESOURCE_DIR}/embedded")
    message(FATAL_ERROR
        "Swift toolchain with Embedded Swift not found.\n"
        "Install a swift.org toolchain and pass -DSWIFT_TOOLCHAIN=<root> "
        "or set the SWIFT_TOOLCHAIN env var.")
endif()

message(STATUS "Swift: ${SWIFTC}")
message(STATUS "Swift resource dir: ${SWIFT_RESOURCE_DIR}")

# --- Build ---
add_compile_options(-ffreestanding -nostdlib -O0 -g)

set(LINKER_SCRIPT ${CMAKE_CURRENT_SOURCE_DIR}/linker.ld)
add_link_options(
    -fuse-ld=lld
    -nostdlib
    -static
    -Wl,-T,${LINKER_SCRIPT}
)

set(SWIFT_SOURCES ${CMAKE_CURRENT_SOURCE_DIR}/Source/kernel.swift)
set(SWIFT_OBJ     ${CMAKE_CURRENT_BINARY_DIR}/kernel_swift.o)

add_custom_command(
    OUTPUT ${SWIFT_OBJ}
    COMMAND ${SWIFTC}
        -target aarch64-none-none-elf
        -enable-experimental-feature Embedded
        -parse-as-library
        -wmo
        -O
        -Xcc -fno-stack-protector
        -resource-dir ${SWIFT_RESOURCE_DIR}
        -c ${SWIFT_SOURCES}
        -o ${SWIFT_OBJ}
    COMMAND ${LLVM_OBJCOPY} --remove-section=.swift_modhash ${SWIFT_OBJ}
    DEPENDS ${SWIFT_SOURCES}
    COMMENT "Compiling Swift kernel"
)

set_source_files_properties(${SWIFT_OBJ} PROPERTIES
    EXTERNAL_OBJECT TRUE
    GENERATED TRUE
)

add_executable(kernel.elf Source/entry.S Source/stubs.c ${SWIFT_OBJ})

add_custom_command(TARGET kernel.elf POST_BUILD
    COMMAND ${LLVM_OBJCOPY} -O binary kernel.elf kernel.bin
    COMMENT "kernel.elf -> kernel.bin"
)