## # vcpkg_download_distfile
##
## Download and cache a file needed for this port.
##
## This helper should always be used instead of CMake's built-in `file(DOWNLOAD)` command.
##
## ## Usage
## ```cmake
## vcpkg_download_distfile(
##     <OUT_VARIABLE>
##     URLS <http://mainUrl> <http://mirror1>...
##     FILENAME <output.zip>
##     SHA512 <5981de...>
## )
## ```
## ## Parameters
## ### OUT_VARIABLE
## This variable will be set to the full path to the downloaded file. This can then immediately be passed in to [`vcpkg_extract_source_archive`](vcpkg_extract_source_archive.md) for sources.
##
## ### URLS
## A list of URLs to be consulted. They will be tried in order until one of the downloaded files successfully matches the SHA512 given.
##
## ### FILENAME
## The local name for the file. Files are shared between ports, so the file may need to be renamed to make it clearly attributed to this port and avoid conflicts.
##
## ### SHA512
## The expected hash for the file.
##
## If this doesn't match the downloaded version, the build will be terminated with a message describing the mismatch.
##
## ### SKIP_SHA512
## Skip SHA512 hash check for file.
##
## This switch is only valid when building with the `--head` command line flag.
##
## ## Notes
## The helper [`vcpkg_from_github`](vcpkg_from_github.md) should be used for downloading from GitHub projects.
##
## ## Examples
##
## * [apr](https://github.com/Microsoft/vcpkg/blob/master/ports/apr/portfile.cmake)
## * [fontconfig](https://github.com/Microsoft/vcpkg/blob/master/ports/fontconfig/portfile.cmake)
## * [openssl](https://github.com/Microsoft/vcpkg/blob/master/ports/openssl/portfile.cmake)
function(vcpkg_download_distfile VAR)
    set(options SKIP_SHA512)
    set(oneValueArgs FILENAME SHA512)
    set(multipleValuesArgs URLS)
    cmake_parse_arguments(vcpkg_download_distfile "${options}" "${oneValueArgs}" "${multipleValuesArgs}" ${ARGN})

    if(NOT DEFINED vcpkg_download_distfile_URLS)
        message(FATAL_ERROR "vcpkg_download_distfile requires a URLS argument.")
    endif()
    if(NOT DEFINED vcpkg_download_distfile_FILENAME)
        message(FATAL_ERROR "vcpkg_download_distfile requires a FILENAME argument.")
    endif()
    if(NOT _VCPKG_INTERNAL_NO_HASH_CHECK)
        if(vcpkg_download_distfile_SKIP_SHA512 AND NOT VCPKG_USE_HEAD_VERSION)
            message(FATAL_ERROR "vcpkg_download_distfile only allows SKIP_SHA512 when building with --head")
        endif()
        if(NOT vcpkg_download_distfile_SKIP_SHA512 AND NOT DEFINED vcpkg_download_distfile_SHA512)
            message(FATAL_ERROR "vcpkg_download_distfile requires a SHA512 argument. If you do not know the SHA512, add it as 'SHA512 0' and re-run this command.")
        endif()
        if(vcpkg_download_distfile_SKIP_SHA512 AND DEFINED vcpkg_download_distfile_SHA512)
            message(FATAL_ERROR "vcpkg_download_distfile must not be passed both SHA512 and SKIP_SHA512.")
        endif()
    endif()

    set(downloaded_file_path ${DOWNLOADS}/${vcpkg_download_distfile_FILENAME})
    set(download_file_path_part "${DOWNLOADS}/temp/${vcpkg_download_distfile_FILENAME}")

    file(REMOVE_RECURSE "${DOWNLOADS}/temp")
    file(MAKE_DIRECTORY "${DOWNLOADS}/temp")

    function(test_hash FILE_KIND CUSTOM_ERROR_ADVICE)
        if(_VCPKG_INTERNAL_NO_HASH_CHECK)
            # When using the internal hash skip, do not output an explicit message.
            return()
        endif()
        if(vcpkg_download_distfile_SKIP_SHA512)
            message(STATUS "Skipping hash check for ${downloaded_file_path}.")
            return()
        endif()

        message(STATUS "Testing integrity of ${FILE_KIND}...")
        file(SHA512 ${downloaded_file_path} FILE_HASH)
        if(NOT "${FILE_HASH}" STREQUAL "${vcpkg_download_distfile_SHA512}")
            message(FATAL_ERROR
                "\nFile does not have expected hash:\n"
                "        File path: [ ${downloaded_file_path} ]\n"
                "    Expected hash: [ ${vcpkg_download_distfile_SHA512} ]\n"
                "      Actual hash: [ ${FILE_HASH} ]\n"
                "${CUSTOM_ERROR_ADVICE}\n")
        endif()
        message(STATUS "Testing integrity of ${FILE_KIND}... OK")
    endfunction()

    if(EXISTS ${downloaded_file_path})
        message(STATUS "Using cached ${downloaded_file_path}")
        test_hash("cached file" "Please delete the file and retry if this file should be downloaded again.")
    else()
        if(_VCPKG_NO_DOWNLOADS)
            message(FATAL_ERROR "Downloads are disabled, but '${downloaded_file_path}' does not exist.")
        endif()

        # Tries to download the file.
        foreach(url IN LISTS vcpkg_download_distfile_URLS)
            message(STATUS "Downloading ${url}...")
            file(DOWNLOAD ${url} "${download_file_path_part}" STATUS download_status)
            list(GET download_status 0 status_code)
            if (NOT "${status_code}" STREQUAL "0")
                message(STATUS "Downloading ${url}... Failed. Status: ${download_status}")
                set(download_success 0)
            else()
                get_filename_component(downloaded_file_dir "${downloaded_file_path}" DIRECTORY)
                file(MAKE_DIRECTORY "${downloaded_file_dir}")
                file(RENAME ${download_file_path_part} ${downloaded_file_path})
                message(STATUS "Downloading ${url}... OK")
                set(download_success 1)
                break()
            endif()
        endforeach(url)

        if (NOT download_success)
            message(FATAL_ERROR
            "\n"
            "    Failed to download file.\n"
            "    Add mirrors or submit an issue at https://github.com/Microsoft/vcpkg/issues\n")
        else()
            test_hash("downloaded file" "The file may have been corrupted in transit.")
        endif()
    endif()
    set(${VAR} ${downloaded_file_path} PARENT_SCOPE)
endfunction()