cmake_minimum_required(VERSION 3.10)

get_filename_component(TARGET_NAME ${CMAKE_CURRENT_SOURCE_DIR} NAME)
string(TOUPPER ${TARGET_NAME} TARGET_NAME_UPPER)

# ─── Test / Standalone 选项 ───────────────────────────────────────────
if(BUILD_${TARGET_NAME_UPPER}_HAS_TEST)
    option(BUILD_${TARGET_NAME_UPPER}_STANDALONE
        "Build ${TARGET_NAME_UPPER} as a standalone executable" OFF)
endif()

# ─── 判断顶层独立构建 vs 子模块嵌入 ─────────────────────────────────
if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
    set(IS_TOP_LEVEL TRUE)
    message(STATUS "[${TARGET_NAME}] Top-level project — enabling recursive flatten build.")
    set(NEED_FLATTEN TRUE)
else()
    set(IS_TOP_LEVEL FALSE)
    set(NEED_FLATTEN FALSE)
endif()

# ─── 收集源文件 ──────────────────────────────────────────────────────
if(NOT NEED_FLATTEN)
    file(GLOB_RECURSE MODULE_SRCS CONFIGURE_DEPENDS "${CMAKE_CURRENT_SOURCE_DIR}/*.c")
    # 过滤编辑器临时文件
    list(FILTER MODULE_SRCS EXCLUDE REGEX ".*[~]$|.*\\.bak$|.*\\.swp$")
endif()

# ─── 顶层构建: 扁平化拷贝所有源文件 ─────────────────────────────────
if(NEED_FLATTEN)
    set(FLAT_SRC_DIR "${CMAKE_BINARY_DIR}/flat_sources/${TARGET_NAME}")

    file(GLOB_RECURSE ALL_SOURCE_FILES CONFIGURE_DEPENDS
        "${CMAKE_CURRENT_SOURCE_DIR}/*.c"
        "${CMAKE_CURRENT_SOURCE_DIR}/*.h"
    )

    # 过滤: 构建目录 / CMake 内部文件 / 编辑器临时文件
    set(FILTERED_FILES "")
    foreach(SRC_FILE ${ALL_SOURCE_FILES})
        get_filename_component(ABS_FILE ${SRC_FILE} ABSOLUTE)
        get_filename_component(FILE_NAME ${SRC_FILE} NAME)

        if(ABS_FILE MATCHES "^${CMAKE_BINARY_DIR}")
            continue()
        endif()
        if(FILE_NAME MATCHES "CMakeCCompilerId\\.c$|CMakeTmp")
            continue()
        endif()
        if(FILE_NAME MATCHES "[~]$|\\.bak$|\\.swp$")
            continue()
        endif()

        list(APPEND FILTERED_FILES ${SRC_FILE})
    endforeach()

    list(LENGTH FILTERED_FILES FILE_COUNT)
    message(STATUS "[${TARGET_NAME}] Found ${FILE_COUNT} valid files after filtering.")
    if(NOT FILTERED_FILES)
        message(FATAL_ERROR "[${TARGET_NAME}] No valid source files found.")
    endif()

    # 将所有文件拷贝到 flat 目录（避免同名冲突）
    set(FLAT_SRCS "")
    set(COPY_COMMANDS "")
    foreach(SRC_FILE ${FILTERED_FILES})
        get_filename_component(FILE_NAME ${SRC_FILE} NAME)
        get_filename_component(FILE_EXT  ${SRC_FILE} EXT)
        set(DEST_FILE "${FLAT_SRC_DIR}/${FILE_NAME}")

        if(EXISTS "${DEST_FILE}")
            message(WARNING "[${TARGET_NAME}] Filename conflict: '${FILE_NAME}', skipping ${SRC_FILE}")
            continue()
        endif()

        list(APPEND COPY_COMMANDS
            COMMAND ${CMAKE_COMMAND} -E copy_if_different ${SRC_FILE} ${DEST_FILE}
        )
        if(FILE_EXT STREQUAL ".c")
            list(APPEND FLAT_SRCS ${DEST_FILE})
        endif()
    endforeach()

    if(NOT FLAT_SRCS)
        message(FATAL_ERROR "[${TARGET_NAME}] No .c files to compile!")
    endif()

    add_custom_target(${TARGET_NAME}_flatten_sources
        ${COPY_COMMANDS}
        COMMENT "[${TARGET_NAME}] Flattening sources..."
        BYPRODUCTS ${FLAT_SRC_DIR}
    )
    set_directory_properties(PROPERTIES ADDITIONAL_MAKE_CLEAN_FILES "${FLAT_SRC_DIR}")

    set(MODULE_SRCS ${FLAT_SRCS})
    set_source_files_properties(${MODULE_SRCS} PROPERTIES GENERATED TRUE)
endif()

# ─── 无源文件时创建 header-only INTERFACE 库 ────────────────────────
if(NOT MODULE_SRCS AND NOT IS_TOP_LEVEL)
    message(STATUS "[${TARGET_NAME}] No source files — creating INTERFACE (header-only) library.")
    add_library(${TARGET_NAME} INTERFACE)

    set(INTERFACE_INCLUDES "")
    foreach(inc
        "${CMAKE_CURRENT_SOURCE_DIR}/include"
        "${PROJECT_SOURCE_DIR}/include/${TARGET_NAME}"
        "${PROJECT_SOURCE_DIR}/include"
    )
        if(EXISTS "${inc}")
            list(APPEND INTERFACE_INCLUDES "${inc}")
        endif()
    endforeach()
    target_include_directories(${TARGET_NAME} INTERFACE ${INTERFACE_INCLUDES})
    message(STATUS "[${TARGET_NAME}] INTERFACE includes: ${INTERFACE_INCLUDES}")
    return()
endif()

# ─── 判断是否构建独立可执行文件 ─────────────────────────────────────
set(SHOULD_BUILD_EXECUTABLE FALSE)
if(BUILD_${TARGET_NAME_UPPER}_STANDALONE)
    set(SHOULD_BUILD_EXECUTABLE TRUE)
elseif(IS_TOP_LEVEL AND MAIN)
    set(SHOULD_BUILD_EXECUTABLE TRUE)
endif()

# ─── 创建目标 ────────────────────────────────────────────────────────
if(SHOULD_BUILD_EXECUTABLE)
    add_executable(${TARGET_NAME} ${MODULE_SRCS})
    target_compile_definitions(${TARGET_NAME} PRIVATE MAIN STANDALONE_BUILD)
    set_target_properties(${TARGET_NAME} PROPERTIES
        RUNTIME_OUTPUT_DIRECTORY ${PROJECT_SOURCE_DIR}/output
    )
else()
    if(MY_BUILD_STATIC)
        add_library(${TARGET_NAME} STATIC ${MODULE_SRCS})
    elseif(MY_BUILD_SHARED_LIBS)
        add_library(${TARGET_NAME} SHARED ${MODULE_SRCS})
    else()
        add_library(${TARGET_NAME} OBJECT ${MODULE_SRCS})
    endif()
    set_target_properties(${TARGET_NAME} PROPERTIES
        ARCHIVE_OUTPUT_DIRECTORY ${PROJECT_SOURCE_DIR}/output
        LIBRARY_OUTPUT_DIRECTORY ${PROJECT_SOURCE_DIR}/output
    )
endif()

message(STATUS "[${TARGET_NAME}] Configured target: ${TARGET_NAME} (Sources: ${MODULE_SRCS})")

# ─── Flatten 依赖 ────────────────────────────────────────────────────
if(NEED_FLATTEN)
    add_dependencies(${TARGET_NAME} ${TARGET_NAME}_flatten_sources)
    target_include_directories(${TARGET_NAME} PRIVATE ${FLAT_SRC_DIR})
endif()

# ─── 编译宏定义 ─────────────────────────────────────────────────────
target_compile_definitions(${TARGET_NAME}
    PRIVATE ${GLOBAL_ENABLED_MACROS}
    $<$<CONFIG:Debug>:DEBUG>
)

# ─── Include 目录 ────────────────────────────────────────────────────
set(MY_PUBLIC_INCLUDES "")
foreach(inc
    "${CMAKE_CURRENT_SOURCE_DIR}/include"
    "${PROJECT_SOURCE_DIR}/include/${TARGET_NAME}"
    "${PROJECT_SOURCE_DIR}/include"
)
    if(EXISTS "${inc}")
        list(APPEND MY_PUBLIC_INCLUDES "${inc}")
        message(STATUS "[${TARGET_NAME}] Found include: ${inc}")
    endif()
endforeach()

if(NOT MY_PUBLIC_INCLUDES)
    list(APPEND MY_PUBLIC_INCLUDES "${CMAKE_CURRENT_SOURCE_DIR}")
    message(STATUS "[${TARGET_NAME}] Fallback include: source dir")
endif()

target_include_directories(${TARGET_NAME}
    PUBLIC  ${MY_PUBLIC_INCLUDES}
    PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}
)

# ─── 链接依赖 ────────────────────────────────────────────────────────
target_link_libraries(${TARGET_NAME} PRIVATE m)

string(TOLOWER "${CMAKE_SYSTEM_NAME}" SYSTEM_NAME_LOWER)
if(CMAKE_CROSSCOMPILING AND NOT SYSTEM_NAME_LOWER MATCHES "linux|windows|darwin|android")
    message(STATUS ">>> 裸机/RTOS 环境 (${CMAKE_SYSTEM_NAME})，屏蔽 pthread")
else()
    find_package(Threads REQUIRED)
    target_link_libraries(${TARGET_NAME}
        PUBLIC  Threads::Threads
        PRIVATE ${CMAKE_DL_LIBS}
    )
    if(CMAKE_SYSTEM_NAME STREQUAL "Linux")
        target_link_libraries(${TARGET_NAME} PRIVATE rt)
    endif()
endif()

# ─── 编译选项 ────────────────────────────────────────────────────────
target_compile_options(${TARGET_NAME} PRIVATE
    -Wall -Werror
    -ffunction-sections -fdata-sections
    -Wno-unused-function
    $<$<CONFIG:Debug>:-g -O0>
    $<$<CONFIG:Release>:-O2>
)

target_link_options(${TARGET_NAME} PRIVATE
    -Wl,--gc-sections
    $<$<CONFIG:Release>:-s>
)