cmake_minimum_required(VERSION 3.11)
project(DownloadFile)

cmake_policy(SET CMP0140 NEW)
function(check_file_reachable url)
    file(DOWNLOAD "${url}"
        RANGE_END 10
        TIMEOUT 2
        INACTIVITY_TIMEOUT 1
        STATUS download_status)

    list(GET download_status 0 download_status_code)
    if("${download_status_code}" STREQUAL "0")
        set(file_reachable "1")
    else()
        set(file_reachable "0")
    endif()
    return(PROPAGATE file_reachable) # File is reachable
endfunction()

function(download_file_with_hash_check url dest)
    set(options REQUIRED)
    set(oneValueArgs URL DEST HASH_URL)
    cmake_parse_arguments(PARSE_ARGV 0 ARG "${options}" "${oneValueArgs}" "")

    if(ARG_URL)
        set(url "${ARG_URL}")
    endif()

    if(ARG_DEST)
        set(dest "${ARG_DEST}")
    endif()

    set(hash_url "${url}.hash")

    if(ARG_HASH_URL)
        set(hash_url "${ARG_HASH_URL}")
    endif()
    message(STATUS "${hash_url}")

    check_file_reachable("${url}")

    if("${file_reachable}" STREQUAL "0")
        if(ARG_REQUIRED)
            if(NOT EXISTS "${dest}")
                message(FATAL_ERROR "File ${dest} could not be downloaded and is not present, even though it was marked as REQUIRED.")
            endif()
        endif()
        return()
    endif()

    set(hash_file "${dest}.hash")
    set(hash_file_temp "${hash_file}.temp")

    # Download the hash file (if available)
    file(DOWNLOAD "${hash_url}" "${hash_file_temp}"
        STATUS download_status
        TIMEOUT 60)

    list(GET download_status 0 download_status_code)
    if(NOT "${download_status_code}" STREQUAL "0")
        file(REMOVE "${hash_file_temp}")
        # Hash file is not available, just check if the file exists
        if(EXISTS "${dest}")
            message(STATUS "File ${dest} already exists, no hash file found. Skipping download.")
            return()
        else()
            message(STATUS "File ${dest} not found, downloading without hash check.")
            file(DOWNLOAD "${url}" "${dest}" SHOW_PROGRESS TIMEOUT 60)
            return()
        endif()
    endif()

    file(READ "${hash_file_temp}" expected_hash)
    string(STRIP "${expected_hash}" expected_hash)
    if(NOT "${expected_hash}" STREQUAL "")
        file(RENAME "${hash_file_temp}" "${hash_file}")
    endif()

    # Hash file downloaded, now read the hash
    file(READ "${hash_file}" expected_hash)
    string(STRIP "${expected_hash}" expected_hash) # Remove whitespace around hash
    if(EXISTS "${dest}")
        file(SHA256 "${dest}" actual_hash)
        if("${expected_hash}" STREQUAL "${actual_hash}")
            message(STATUS "File ${dest} already matches the hash. Skipping download.")
            return()
        else()
            message(WARNING "Hash mismatch for ${dest}. Downloading the file again.")
        endif()
    else()
        message(STATUS "File ${dest} not found. Downloading.")
    endif()

    # Download the actual file
    file(DOWNLOAD "${url}" "${dest}" SHOW_PROGRESS TIMEOUT 60)

    # Recheck the hash after downloading
    file(SHA256 "${dest}" actual_hash)
    if(NOT "${expected_hash}" STREQUAL "${actual_hash}")
        message(FATAL_ERROR "Downloaded file ${dest} hash mismatch. Expected: ${expected_hash}, got: ${actual_hash}")
    else()
        message(STATUS "File ${dest} downloaded and verified successfully.")
    endif()
endfunction()

download_file_with_hash_check(URL "http://127.0.0.1:8080/random_file.bin" DEST "${CMAKE_BINARY_DIR}/random_file.bin" REQUIRED)