option(XREPO_PACKAGE_DISABLE "Disable Xrepo Packages" OFF)
option(XREPO_PACKAGE_VERBOSE "Enable verbose output for Xrepo Packages" OFF)
option(XREPO_BOOTSTRAP_XMAKE "Bootstrap Xmake automatically" ON)

# Following options are for cross compilation, or when specifying a specific compiler.
set(XREPO_PLATFORM "" CACHE STRING "Xrepo package platform")
set(XREPO_ARCH "" CACHE STRING "Xrepo package architecture")
set(XREPO_TOOLCHAIN "" CACHE STRING "Xrepo package toolchain")
set(XREPO_XMAKEFILE "" CACHE STRING "Xmake script file of Xrepo package")

# xrepo_package:
#
# Parameters:
#      package_spec: required
#          The package name and version recognized by xrepo.
#      CONFIGS: optional
#          Run `xrepo info <package>` to see what configs are available.
#          There are two ways to specify configs:
#            1. String, for example "shared=true,ssl=openssl"
#            2. Path to a lua script. This is for fine control over package configs.
#               Refer to examples for how to use this.
#               Note:
#                 - Do not use ~ to refer to home directory. Non-absolute path
#                   will be treated as relative to the current CMakeLists.txt.
#                 - Only CONFIGS specified lua script modification time is checked
#                   to decide whether xrepo install can be skipped. If using "includes"
#                   in lua script, this is not reliable. Please touch the CONFIGS lua
#                   script manually to trigger run xrepo install in that case.
#      DEPS: optional
#          If specified, include all dependent libraries' settings in various
#          variables. Also add all dependent libraries' install dir to
#          CMAKE_PREFIX_PATH.
#      MODE: optional, debug|release
#          Pass `--mode` option to xrepo install command. If not specified,
#          `--mode` option is not passed.
#      OUTPUT: optional, verbose|diagnosis|quiet
#          Control output for xrepo install command.
#      DIRECTORY_SCOPE: optional
#          If specified, setup include and link directories for the package in
#          CMake directory scope. CMake code in `add_subdirectory` can also use
#          the package directly.
#
# Example:
#
#      xrepo_package(
#          "foo 1.2.3"
#          [CONFIGS feature1=true,feature2=false]
#          [CONFIGS path/to/script.lua]
#          [DEPS]
#          [MODE debug|release]
#          [OUTPUT verbose|diagnosis|quiet]
#          [DIRECTORY_SCOPE]
#      )
#
# `xrepo_package` does the following tasks for the above call:
#
# 1. Ensure specified package `foo` version 1.2.3 with given config is installed.
# 2. Set variable `foo_INCLUDE_DIRS` and `foo_LIBRARY_DIRS` to header and library
#     path.
#     - Use these variables in `target_include_directories` and
#       `target_link_directories` to use the package.
#     - User should figure out what library to use for `target_link_libraries`.
#     - If `DIRECTORY_SCOPE` is specified, execute following code so the package
#       can be used in cmake's direcotry scope:
#           include_directories(foo_INCLUDE_DIRS)
#           link_directories(foo_LIBRARY_DIRS)
# 3. Append package install directory to `CMAKE_PREFIX_PATH`.

function(_install_xmake_program)
    if (NOT XMAKE_RELEASE_LATEST)
        set(XMAKE_RELEASE_LATEST 2.7.6)
    endif()
    set(XMAKE_VERSION master)
    set(XMAKE_BINARY_DIR ${CMAKE_BINARY_DIR}/xmake)
    message(STATUS "xmake not found, Install it to ${XMAKE_BINARY_DIR} automatically!")
    if(EXISTS "${XMAKE_BINARY_DIR}")
        file(REMOVE_RECURSE ${XMAKE_BINARY_DIR})
    endif()

    # Download xmake archive file
    if(WIN32)
        set(XMAKE_ARCHIVE_FILE ${CMAKE_BINARY_DIR}/xmake-${XMAKE_VERSION}.win32.zip)
        set(XMAKE_ARCHIVE_URL https://github.com/xmake-io/xmake/releases/download/v${XMAKE_RELEASE_LATEST}/xmake-${XMAKE_VERSION}.win32.zip)
    else()
        set(XMAKE_ARCHIVE_FILE ${CMAKE_BINARY_DIR}/xmake-${XMAKE_VERSION}.tar.gz)
        set(XMAKE_ARCHIVE_URL https://github.com/xmake-io/xmake/releases/download/v${XMAKE_RELEASE_LATEST}/xmake-${XMAKE_VERSION}.tar.gz)
    endif()
    if(NOT EXISTS "${XMAKE_ARCHIVE_FILE}")
        message(STATUS "Downloading xmake from ${XMAKE_ARCHIVE_URL}")
        file(DOWNLOAD "${XMAKE_ARCHIVE_URL}"
                      "${XMAKE_ARCHIVE_FILE}"
                      TLS_VERIFY ON)
    endif()

    # Extract xmake archive file
    if(NOT EXISTS "${XMAKE_BINARY_DIR}")
        message(STATUS "Extracting ${XMAKE_ARCHIVE_FILE}")
        file(MAKE_DIRECTORY ${XMAKE_BINARY_DIR})
        execute_process(COMMAND ${CMAKE_COMMAND} -E tar xzf ${XMAKE_ARCHIVE_FILE}
            WORKING_DIRECTORY ${XMAKE_BINARY_DIR}
            RESULT_VARIABLE exit_code)
        if(NOT "${exit_code}" STREQUAL "0")
            message(FATAL_ERROR "unzip ${XMAKE_ARCHIVE_FILE} failed, exit code: ${exit_code}")
        endif()
    endif()

    # Install xmake
    if(WIN32)
        set(XMAKE_BINARY ${XMAKE_BINARY_DIR}/xmake/xmake.exe)
        if(EXISTS ${XMAKE_BINARY})
            set(XMAKE_CMD ${XMAKE_BINARY} PARENT_SCOPE)
        endif()
    else()
        set(XMAKE_SOURCE_DIR ${XMAKE_BINARY_DIR}/xmake-${XMAKE_RELEASE_LATEST})
        message(STATUS "Configuring xmake")
        execute_process(COMMAND ${CMAKE_COMMAND} -E env --unset=CC --unset=CXX --unset=LD ./configure
            WORKING_DIRECTORY ${XMAKE_SOURCE_DIR}
            RESULT_VARIABLE exit_code)
        if(NOT "${exit_code}" STREQUAL "0")
            message(FATAL_ERROR "Configure xmake failed, exit code: ${exit_code}")
        endif()

        message(STATUS "Building xmake")
        execute_process(COMMAND ${CMAKE_COMMAND} -E env --unset=CC --unset=CXX --unset=LD make -j4
            WORKING_DIRECTORY ${XMAKE_SOURCE_DIR}
            RESULT_VARIABLE exit_code)
        if(NOT "${exit_code}" STREQUAL "0")
            message(FATAL_ERROR "Build xmake failed, exit code: ${exit_code}")
        endif()

        message(STATUS "Installing xmake")
        execute_process(COMMAND make install PREFIX=${XMAKE_BINARY_DIR}/install
            WORKING_DIRECTORY ${XMAKE_SOURCE_DIR}
            RESULT_VARIABLE exit_code)
        if(NOT "${exit_code}" STREQUAL "0")
            message(FATAL_ERROR "Install xmake failed, exit code: ${exit_code}")
        endif()

        set(XMAKE_BINARY ${XMAKE_BINARY_DIR}/install/bin/xmake)
        if(EXISTS ${XMAKE_BINARY})
            set(XMAKE_CMD ${XMAKE_BINARY} PARENT_SCOPE)
        endif()
    endif()
endfunction()

macro(_detect_xmake_cmd)
    if(NOT XMAKE_CMD)
        # Note: if XMAKE_CMD is already defined, find_program does not search.
        # find_program makes XMAKE_CMD a cached variable. So find_program
        # searches only once for each cmake build directory.
        find_program(XMAKE_CMD xmake)
    endif()

    if(NOT XMAKE_CMD)
        if(WIN32)
            set(XMAKE_BINARY ${CMAKE_BINARY_DIR}/xmake/xmake/xmake.exe)
        else()
            set(XMAKE_BINARY ${CMAKE_BINARY_DIR}/xmake/install/bin/xmake)
        endif()
        if(EXISTS ${XMAKE_BINARY})
            set(XMAKE_CMD ${XMAKE_BINARY})
        endif()
    endif()
    if(NOT XMAKE_CMD AND XREPO_BOOTSTRAP_XMAKE)
        _install_xmake_program()
    endif()
    if(NOT XMAKE_CMD)
        message(FATAL_ERROR "xmake not found, Please install it first from https://xmake.io")
    endif()

    message(STATUS "xmake command: ${XMAKE_CMD}")
    set(XREPO_CMD ${XMAKE_CMD} lua private.xrepo)
endmacro()

function(_xrepo_detect_json_support)
    if(DEFINED XREPO_FETCH_JSON)
        return()
    endif()

    # Whether to use `xrepo fetch --json` to get package info.
    set(use_fetch_json ON)

    if(CMAKE_VERSION VERSION_LESS 3.19)
        message(WARNING "Please use CMake version >= 3.19 for JSON support. "
                        "Otherwise xrepo_package maybe unreliable to setup package variables.")
        set(use_fetch_json OFF)
    elseif(XREPO_CMD)
        execute_process(COMMAND ${XREPO_CMD} fetch --help
                        OUTPUT_VARIABLE help_output
                        RESULT_VARIABLE exit_code)
        if(NOT "${exit_code}" STREQUAL "0")
            message(FATAL_ERROR "xrepo fetch --help failed, exit code: ${exit_code}")
        endif()

        if(NOT "${help_output}" MATCHES "--json")
            message(WARNING "xrepo fetch does not support --json (please upgrade xrepo/xmake to the latest version), "
                            "xrepo_package maybe unreliable to setup package variables")
            set(use_fetch_json OFF)
        endif()
    endif()

    set(XREPO_FETCH_JSON ${use_fetch_json} CACHE BOOL "Use xrepo JSON output" FORCE)
endfunction()

function(_detect_toolchain)
    if(NOT "${XREPO_TOOLCHAIN}" STREQUAL "")
        return()
    endif()

    if(DEFINED CMAKE_C_COMPILER)
        get_filename_component(_compiler_name "${CMAKE_C_COMPILER}" NAME_WLE)
    elseif(DEFINED CMAKE_CXX_COMPILER)
        get_filename_component(_compiler_name "${CMAKE_CXX_COMPILER}" NAME_WLE)
        string(REPLACE "g++" "gcc" "${_compiler_name}" _compiler_name)
        string(REPLACE "clang++" "clang" "${_compiler_name}" _compiler_name)
    else()
        # Shouldn't reach here because cmake will try to detect compiler and set
        # corresponding variables.
        return()
    endif()

    if(("${_compiler_name}" MATCHES "^gcc")
            OR ("${_compiler_name}" MATCHES "^clang"))
        message(STATUS "xrepo: set(XREPO_TOOLCHAIN ${_compiler_name}) because CMAKE_C_COMPILER or CMAKE_CXX_COMPILER is set")
        set(XREPO_TOOLCHAIN "${_compiler_name}" PARENT_SCOPE)
    else()
        message(STATUS "xrepo: CMAKE_C_COMPILER=${CMAKE_C_COMPILER} CMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER} using system default toolchain.")
    endif()
endfunction()

if(NOT XREPO_PACKAGE_DISABLE)
    # Setup for xmake.
    _detect_xmake_cmd()

    # Some cmake find module code may use pkgconfig to find header, library, etc.
    # Refer to https://cmake.org/cmake/help/latest/manual/cmake-developer.7.html#a-sample-find-module
    # If CMAKE_MINIMUM_REQUIRED_VERSION is 3.1 or later, paths in CMAKE_PREFIX_PATH are added to pkg-config
    # search path. (https://cmake.org/cmake/help/latest/module/FindPkgConfig.html#variable:PKG_CONFIG_USE_CMAKE_PREFIX_PATH)
    if(CMAKE_MINIMUM_REQUIRED_VERSION VERSION_LESS 3.1)
        message(WARNING "xrepo: CMAKE_MINIMUM_REQUIRED_VERSION less than 3.1. "
                        "CMAKE_PREFIX_PATH are not included in pkg-config search. "
                        "Some find module code may fail or resolve to system installed libraries.")
    endif()

    _xrepo_detect_json_support()
    message(STATUS "xrepo: fetch --json: ${XREPO_FETCH_JSON}")
    _detect_toolchain()
    if((NOT "${XREPO_TOOLCHAIN}" STREQUAL "") AND ("${XREPO_PLATFORM}" STREQUAL ""))
        message(STATUS "xrepo: XREPO_TOOLCHAIN is set but XREPO_PLATFORM is not, this is experimental feature of xmake")
    endif()
endif()

function(xrepo_package package)
    if(XREPO_PACKAGE_DISABLE)
        return()
    endif()

    set(options "DIRECTORY_SCOPE;DEPS")
    set(one_value_args CONFIGS MODE OUTPUT ALIAS)
    cmake_parse_arguments(ARG "${options}" "${one_value_args}" "" ${ARGN})

    # Construct options to xrepo install and fetch command.
    if(DEFINED ARG_CONFIGS)
        if(ARG_CONFIGS MATCHES "\\.lua$")
            if(IS_ABSOLUTE "${ARG_CONFIGS}" AND EXISTS "${ARG_CONFIGS}")
                set(_config_lua_script "${ARG_CONFIGS}")
            elseif(EXISTS "${CMAKE_CURRENT_LIST_DIR}/${ARG_CONFIGS}")
                set(_config_lua_script "${CMAKE_CURRENT_LIST_DIR}/${ARG_CONFIGS}")
            else()
                message(WARNING "CONFIGS ${ARG_CONFIGS} ends with '.lua' but no file found, taken as normal config")
            endif()
        endif()

        if(DEFINED _config_lua_script)
            set(configs "${_config_lua_script}")
            # Trigger cmake configure when ${_config_lua_script} changes.
            set_property(
                DIRECTORY 
                APPEND 
                PROPERTY CMAKE_CONFIGURE_DEPENDS
                "${_config_lua_script}"
            )
        else()
            set(configs "--configs=${ARG_CONFIGS}")
        endif()
    endif()

    if(DEFINED ARG_MODE)
        set(mode "--mode=${ARG_MODE}")
    endif()

    if(XREPO_PACKAGE_VERBOSE)
        set(verbose "-vD")
    elseif(DEFINED ARG_OUTPUT)
        string(TOLOWER "${ARG_OUTPUT}" _output)
        if(_output STREQUAL "diagnosis")
            set(verbose "-vD")
        elseif(_output STREQUAL "verbose")
            set(verbose "-v")
        elseif(_output STREQUAL "quiet")
            set(verbose "-q")
        endif()
    endif()

    # Options for cross compilation and toolchain.
    if(NOT "${XREPO_PLATFORM}" STREQUAL "")
        set(platform "--plat=${XREPO_PLATFORM}")
    endif()
    if(NOT "${XREPO_ARCH}" STREQUAL "")
        set(arch "--arch=${XREPO_ARCH}")
    endif()
    if(NOT "${XREPO_TOOLCHAIN}" STREQUAL "")
        set(toolchain "--toolchain=${XREPO_TOOLCHAIN}")
    endif()
    if(NOT "${XREPO_XMAKEFILE}" STREQUAL "")
        set(includes "--includes=${XREPO_XMAKEFILE}")
    endif()

    # Get package_name that will be used as various variables' prefix.
    if(DEFINED ARG_ALIAS)
        _xrepo_package_name(${ARG_ALIAS})
    else()
        _xrepo_package_name(${package})
    endif()

    # Verbose option should not be passed to xrepo fetch.
    # Otherwise, the output would be invalid to parse.
    set(_xrepo_cmdargs ${platform} ${arch} ${toolchain} ${includes} ${mode} ${configs})
    if(NOT DEFINED _config_lua_script)
        list(APPEND _xrepo_cmdargs ${package})
    endif()

    # To speedup cmake re-configure, if xrepo command and args are the same as
    # cached value, load related variables from cache to avoid executing xrepo
    # command again.
    string(REGEX REPLACE ";" " " _xrepo_cmdargs_${package_name} "${XREPO_CMD} install ${_xrepo_cmdargs}")
    if(DEFINED _config_lua_script)
        file(TIMESTAMP ${_config_lua_script} _config_lua_script_modify_timestamp)
        set(_xrepo_cmdargs_${package_name} "${_xrepo_cmdargs_${package_name}} (mtime: ${_config_lua_script_modify_timestamp})")
    endif()

    if("${_cache_xrepo_cmdargs_${package_name}}" STREQUAL "${_xrepo_cmdargs_${package_name}}")
        message(STATUS "xrepo: ${package} already installed, using cached variables")

        foreach(var ${_cache_xrepo_vars_${package_name}})
            message(STATUS "xrepo: ${var} ${${var}}")
        endforeach()

        _xrepo_finish_package_setup(${package_name})
        return()
    endif()

    if(XREPO_BUILD_PARALLEL_JOBS)
        set(XREPO_BUILD_PARALLEL_JOBS_STR -j${XREPO_BUILD_PARALLEL_JOBS})
    endif()

    message(STATUS "xrepo: ${_xrepo_cmdargs_${package_name}}")
    execute_process(COMMAND ${CMAKE_COMMAND} -E env --unset=CC --unset=CXX --unset=LD ${XREPO_CMD} install --yes ${verbose} ${XREPO_BUILD_PARALLEL_JOBS_STR} ${_xrepo_cmdargs}
                    RESULT_VARIABLE exit_code)
    if(NOT "${exit_code}" STREQUAL "0")
        message(FATAL_ERROR "xrepo install ${package} failed, exit code: ${exit_code}")
    endif()

    if(XREPO_FETCH_JSON)
        _xrepo_fetch_json()
    else()
        _xrepo_fetch_cflags()
    endif()

    _xrepo_finish_package_setup(${package_name})

    # Store xrepo command and arguments for furture comparison.
    set(_cache_xrepo_cmdargs_${package_name} "${_xrepo_cmdargs_${package_name}}" CACHE INTERNAL "")
endfunction()

function(xrepo_target_packages target)
    if(XREPO_PACKAGE_DISABLE)
        return()
    endif()

    set(options NO_LINK_LIBRARIES PRIVATE PUBLIC INTERFACE)
    cmake_parse_arguments(ARG "${options}" "" "" ${ARGN})

    if(ARG_PRIVATE)
        set(_visibility "PRIVATE")
    elseif(ARG_PUBLIC)
        set(_visibility "PUBLIC")
    elseif(ARG_INTERFACE)
        set(_visibility "INTERFACE")
    endif()

    foreach(package_name IN LISTS ARG_UNPARSED_ARGUMENTS)
        if(DEFINED ${package_name}_INCLUDE_DIRS)
            message(STATUS "xrepo: target_include_directories(${target} ${_visibility} ${${package_name}_INCLUDE_DIRS})")
            target_include_directories(${target} ${_visibility} ${${package_name}_INCLUDE_DIRS})
        endif()
        if(DEFINED ${package_name}_LIBRARY_DIRS)
            message(STATUS "xrepo: target_link_directories(${target} ${_visibility} ${${package_name}_LIBRARY_DIRS})")
            target_link_directories(${target} ${_visibility} ${${package_name}_LIBRARY_DIRS})
        endif()
        if((DEFINED ${package_name}_LIBRARIES) AND (NOT ARG_NO_LINK_LIBRARIES))
            message(STATUS "xrepo: target_link_libraries(${target} ${_visibility} ${${package_name}_LIBRARIES})")
            target_link_libraries(${target} ${_visibility} ${${package_name}_LIBRARIES})
        endif()
        if(DEFINED ${package_name}_DEFINITIONS)
            message(STATUS "xrepo: target_compile_definitions(${target} ${_visibility} ${${package_name}_DEFINITIONS})")
            target_compile_definitions(${target} ${_visibility} ${${package_name}_DEFINITIONS})
        endif()
    endforeach()
endfunction()

# Append parent directorie of include directory to CMAKE_PREFIX_PATH.
macro(_xrepo_set_cmake_prefix_path package_name)
    # CMake looks for quite a few directories under each prefix directory for config-file.cmake.
    # Thus Using CMAKE_PREFIX_PATH is easier and more reliable for config-file packages to be found
    # than setting <package_name>_DIR.
    # Refer to https://cmake.org/cmake/help/latest/command/find_package.html#config-mode-search-procedure

    if(NOT DEFINED ${package_name}_INCLUDE_DIRS)
        return()
    endif()

    foreach(var ${${package_name}_INCLUDE_DIRS})
        get_filename_component(_install_dir "${var}" DIRECTORY)
        if(NOT "${var}" IN_LIST CMAKE_PREFIX_PATH)
            # Use prepend to make xrepo packages have high priority in search.
            list(PREPEND CMAKE_PREFIX_PATH "${_install_dir}")
            message(STATUS "xrepo: ${package_name} prepend to CMAKE_PREFIX_PATH: ${_install_dir}")
        endif()
        unset(_install_dir)
    endforeach()
endmacro()

function(_xrepo_directory_scope package_name)
    if(DEFINED ${package_name}_INCLUDE_DIRS)
        message(STATUS "xrepo: directory scope include_directories(${${package_name}_INCLUDE_DIRS})")
        include_directories(${${package_name}_INCLUDE_DIRS})
    endif()
    if(DEFINED ${package_name}_LIBRARY_DIRS)
        message(STATUS "xrepo: directory scope link_directories(${${package_name}_LIBRARY_DIRS})")
        link_directories(${${package_name}_LIBRARY_DIRS})
    endif()
endfunction()

macro(_xrepo_finish_package_setup package_name)
    _xrepo_set_cmake_prefix_path(${package_name})
    if(ARG_DIRECTORY_SCOPE)
        _xrepo_directory_scope(${package_name})
    endif()

    set(CMAKE_PREFIX_PATH ${CMAKE_PREFIX_PATH} PARENT_SCOPE)
endmacro()

function(_xrepo_package_name package)
    # For find_package(pkg) to work, we need to set variable <pkg>_DIR to the
    # cmake module directory provided by the package. Thus we need to extract
    # package name from package specification, which may also contain package
    # source and version.
    if(package MATCHES "^conan::.*")
        string(REGEX REPLACE "conan::([^/]+).*" "\\1" package_name ${package})
    elseif(package MATCHES "^conda::.*")
        string(REGEX REPLACE "conda::([^ ]+).*" "\\1" package_name ${package})
    elseif(package MATCHES "^vcpkg::.*")
        string(REGEX REPLACE "vcpkg::(.*)" "\\1" package_name ${package})
    elseif(package MATCHES "^brew::.*")
        string(REGEX REPLACE "brew::([^/]+).*" "\\1" package_name ${package})
    else()
        string(REGEX REPLACE "([^ ]+).*" "\\1" package_name ${package})
    endif()

    set(package_name ${package_name} PARENT_SCOPE)
endfunction()

macro(_xrepo_fetch_json)
    if(ARG_DEPS)
        set(_deps "--deps")
    endif()

    execute_process(COMMAND ${XREPO_CMD} fetch ${_deps} --json ${_xrepo_cmdargs}
                    OUTPUT_VARIABLE json_output
                    ERROR_VARIABLE json_error_output
                    RESULT_VARIABLE exit_code)
    if(NOT "${exit_code}" STREQUAL "0")
        message(STATUS "xrepo fetch --json:")
        message(STATUS "STDOUT:\n${json_output}")
        message(STATUS "STDERR:\n${json_error_output}")
        message(FATAL_ERROR "xrepo fetch --json failed, exit code: ${exit_code}")
    endif()

    # Loop over out most array for the json object.
    # The following code supports parsing the output of `xrepo fetch --deps`.
    # But pulling in the output of `--deps` is problematic because the dependent
    # libraries maybe using different configs.
    # For example, glog depends on gflags. But the gflags library pulled in by glog is with
    # default configs {mt=false,shared=false}, while the user maybe requiring gflags with
    # configs {mt=true,shared=true}.
    # It's error-prone so we don't support it for now.
    #message(STATUS "xrepo DEBUG: json output: ${json_output}")
    string(JSON len ERROR_VARIABLE json_error LENGTH ${json_output})
    if(NOT "${json_error}" STREQUAL "NOTFOUND")
        message(STATUS "xrepo fetch --json:")
        message(STATUS "STDOUT:\n${json_output}")
        message(STATUS "location:\n${len}")
        message(FATAL_ERROR "xrepo fetch --json: fail to parse output, error: ${json_error}")
    endif()
    math(EXPR len_end "${len} - 1")
    foreach(idx RANGE 0 ${len_end})
        # Loop over includedirs.
        string(JSON includedirs_len ERROR_VARIABLE includedirs_error LENGTH ${json_output} ${idx} "includedirs")
        if("${includedirs_error}" STREQUAL "NOTFOUND")
            math(EXPR includedirs_end "${includedirs_len} - 1")
            foreach(includedirs_idx RANGE 0 ${includedirs_end})
                string(JSON dir GET ${json_output} ${idx} includedirs ${includedirs_idx})
                # It's difficult to know package name while looping over all packages.
                # Thus we use list to collect all include and link dirs.
                list(APPEND includedirs ${dir})
                #message(STATUS "xrepo DEBUG: includedirs ${idx} ${includedirs_idx} ${dir}")
            endforeach()
        endif()

        # Loop over linkdirs.
        string(JSON linkdirs_len ERROR_VARIABLE linkdirs_error LENGTH ${json_output} ${idx} "linkdirs")
        if("${linkdirs_error}" STREQUAL "NOTFOUND")
            math(EXPR linkdirs_end "${linkdirs_len} - 1")
            foreach(linkdirs_idx RANGE 0 ${linkdirs_end})
                string(JSON dir GET ${json_output} ${idx} linkdirs ${linkdirs_idx})
                list(APPEND linkdirs ${dir})
                #message(STATUS "xrepo DEBUG: linkdirs ${idx} ${linkdirs_idx} ${dir}")
            endforeach()
        endif()

        # Loop over links.
        string(JSON links_len ERROR_VARIABLE links_error LENGTH ${json_output} ${idx} "links")
        if("${links_error}" STREQUAL "NOTFOUND")
            math(EXPR links_end "${links_len} - 1")
            foreach(links_idx RANGE 0 ${links_end})
                string(JSON dir GET ${json_output} ${idx} links ${links_idx})
                list(APPEND links ${dir})
                #message(STATUS "xrepo DEBUG: links ${idx} ${links_idx} ${dir}")
            endforeach()
        endif()

        # Loop over syslinks.
        string(JSON syslinks_len ERROR_VARIABLE syslinks_error LENGTH ${json_output} ${idx} "syslinks")
        if("${syslinks_error}" STREQUAL "NOTFOUND")
            math(EXPR syslinks_end "${syslinks_len} - 1")
            foreach(syslinks_idx RANGE 0 ${syslinks_end})
                string(JSON dir GET ${json_output} ${idx} syslinks ${syslinks_idx})
                list(APPEND syslinks ${dir})
                #message(STATUS "xrepo DEBUG: syslinks ${idx} ${syslinks_idx} ${dir}")
            endforeach()
        endif()

        # Loop over defines.
        string(JSON defines_len ERROR_VARIABLE defines_error LENGTH ${json_output} ${idx} "defines")
        if("${defines_error}" STREQUAL "NOTFOUND")
            math(EXPR defines_end "${defines_len} - 1")
            foreach(defines_idx RANGE 0 ${defines_end})
                string(JSON dir GET ${json_output} ${idx} defines ${defines_idx})
                list(APPEND defines ${dir})
                #message(STATUS "xrepo DEBUG: defines ${idx} ${defines_idx} ${dir}")
            endforeach()
        endif()
    endforeach()

    if(DEFINED includedirs)
        set(${package_name}_INCLUDE_DIRS "${includedirs}" CACHE INTERNAL "")
        set(${package_name}_INCLUDE_DIR "${includedirs}" CACHE INTERNAL "") # Keep compatibility, remove in the future.
        list(APPEND xrepo_vars_${package_name} ${package_name}_INCLUDE_DIRS)
        message(STATUS "xrepo: ${package_name}_INCLUDE_DIRS ${${package_name}_INCLUDE_DIRS}")
    else()
        message(STATUS "xrepo fetch --json: ${package_name} includedirs not found")
    endif()

    if(DEFINED linkdirs)
        set(${package_name}_LIBRARY_DIRS "${linkdirs}" CACHE INTERNAL "")
        set(${package_name}_LINK_DIR "${includedirs}" CACHE INTERNAL "") # Keep compatibility, remove in the future.
        list(APPEND xrepo_vars_${package_name} ${package_name}_LIBRARY_DIRS)
        message(STATUS "xrepo: ${package_name}_LIBRARY_DIRS ${${package_name}_LIBRARY_DIRS}")
    else()
        message(STATUS "xrepo fetch --json: ${package_name} linkdirs not found")
    endif()

    if(DEFINED links)
        set(${package_name}_LIBRARIES "${links}" CACHE INTERNAL "")
        set(${package_name}_LINK_LIBRARIES "${links}" CACHE INTERNAL "") # Keep compatibility, remove in the future.
        list(APPEND xrepo_vars_${package_name} ${package_name}_LIBRARIES)
        message(STATUS "xrepo: ${package_name}_LIBRARIES ${${package_name}_LIBRARIES}")
    else()
        message(STATUS "xrepo fetch --json: ${package_name} links not found")
    endif()

    if(DEFINED syslinks)
        set(${package_name}_LIBRARIES "${syslinks}" CACHE INTERNAL "")
        list(APPEND xrepo_vars_${package_name} ${package_name}_LIBRARIES)
        message(STATUS "xrepo: ${package_name}_LIBRARIES ${${package_name}_LIBRARIES}")
    endif()

    if(DEFINED defines)
        set(${package_name}_DEFINITIONS "${defines}" CACHE INTERNAL "")
        list(APPEND xrepo_vars_${package_name} ${package_name}_DEFINITIONS)
        message(STATUS "xrepo: ${package_name}_DEFINITIONS ${${package_name}_DEFINITIONS}")
    endif()

    set(_cache_xrepo_vars_${package_name} "${xrepo_vars_${package_name}}" CACHE INTERNAL "")
endmacro()

macro(_xrepo_fetch_cflags)
    # Use cflags to get include path. Then we look for lib and cmake dir relative to include path.
    execute_process(COMMAND ${XREPO_CMD} fetch --cflags ${_xrepo_cmdargs}
                    OUTPUT_VARIABLE cflags_output
                    ERROR_VARIABLE cflags_error_output
                    RESULT_VARIABLE exit_code)
    if(NOT "${exit_code}" STREQUAL "0")
        message(STATUS "xrepo fetch --cflags:")
        message(STATUS "STDOUT:\n${cflags_output}")
        message(STATUS "STDERR:\n${cflags_error_output}")
        message(FATAL_ERROR "xrepo fetch --cflags failed, exit code: ${exit_code}")
    endif()

    string(REGEX REPLACE "-I(.*)/include.*" "\\1" install_dir ${cflags_output})

    set(${package_name}_INCLUDE_DIRS "${install_dir}/include" CACHE INTERNAL "")
    list(APPEND xrepo_vars_${package_name} ${package_name}_INCLUDE_DIRS)
    message(STATUS "xrepo: ${package_name}_INCLUDE_DIRS ${${package_name}_INCLUDE_DIRS}")

    if(EXISTS "${install_dir}/lib")
        set(${package_name}_LIBRARY_DIRS "${install_dir}/lib" CACHE INTERNAL "")
        list(APPEND xrepo_vars_${package_name} ${package_name}_LIBRARY_DIRS)
        message(STATUS "xrepo: ${package_name}_LIBRARY_DIRS ${${package_name}_LIBRARY_DIRS}")
    endif()
    if(EXISTS "${install_dir}/lib/cmake/${package_name}")
        set(${package_name}_DIR "${install_dir}/lib/cmake/${package_name}" CACHE INTERNAL "")
        list(APPEND xrepo_vars_${package_name} ${package_name}_DIR)
        message(STATUS "xrepo: ${package_name}_DIR ${${package_name}_DIR}")
    endif()

    set(_cache_xrepo_vars_${package_name} "${xrepo_vars_${package_name}}" CACHE INTERNAL "")
endmacro()