代理模式

正文：https://refactoringguru.cn/design-patterns/proxy

Go代码：https://refactoringguru.cn/design-patterns/proxy/go/example

module proxy_module

    use, intrinsic :: iso_fortran_env, only: int16
    implicit none
    private

    public :: nginx_type, new_nginx_server

    type, abstract :: server_type
    contains
        procedure(server_type_handle_request), deferred :: handle_request
    end type server_type

    abstract interface
        subroutine server_type_handle_request(self, url, method, code, msg)
            import server_type, int16
            class(server_type), intent(inout) :: self
            character(*), intent(in) :: url, method
            integer(int16), intent(out) :: code
            character(:), intent(out), allocatable :: msg
        end subroutine server_type_handle_request
    end interface

    type map_type
        character(:), allocatable :: url
        integer(int16) :: rate_limiter
    end type map_type

    type, extends(server_type) :: nginx_type
        type(application_type), allocatable :: application
        integer(int16) :: max_allowed_request
        type(map_type), allocatable :: map(:)
        ! TODO:
    contains
        procedure :: handle_request => nginx_t_handle_request
        procedure :: check_rate_limiting => nginx_t_check_rate_limiting
    end type nginx_type

    type, extends(server_type) :: application_type
    contains
        procedure :: handle_request => application_t_handle_request
    end type application_type

contains

    type(nginx_type) function new_nginx_server() result(nginx)
        type(map_type), allocatable :: map_(:)
        ! TODO:
        allocate (map_(2))
        map_(1) = map_type(url="/app/status", rate_limiter=0_int16)
        map_(2) = map_type(url="/create/user", rate_limiter=0_int16)

        nginx = nginx_type(application=application_type(), max_allowed_request=2, map=map_) ! TODO:
    end function new_nginx_server

    subroutine nginx_t_handle_request(self, url, method, code, msg)
        class(nginx_type), intent(inout) :: self
        character(*), intent(in) :: url, method
        integer(int16), intent(out) :: code
        character(:), intent(out), allocatable :: msg

        logical :: allowed

        allowed = self%check_rate_limiting(url)

        if (.not. allowed) then
            code = 403_int16
            msg = "Not Allowed"
            return
        end if

        call self%application%handle_request(url, method, code, msg)

    end subroutine nginx_t_handle_request

    logical function nginx_t_check_rate_limiting(self, url) result(allowed)
        class(nginx_type), intent(inout) :: self
        character(*), intent(in) :: url

        integer(int16) :: i

        do i = 1_int16, size(self%map, kind=int16)
            if (self%map(i)%url == url) exit
        end do

        ! i = i - 1_int16

        if (self%map(i)%rate_limiter == 0_int16) then
            self%map(i)%rate_limiter = 1_int16
        end if

        if (self%map(i)%rate_limiter > self%max_allowed_request) then
            allowed = .false.
            return
        end if

        allowed = .true.
        self%map(i)%rate_limiter = self%map(i)%rate_limiter + 1_int16

    end function nginx_t_check_rate_limiting

    subroutine application_t_handle_request(self, url, method, code, msg)
        class(application_type), intent(inout) :: self
        character(*), intent(in) :: url, method
        integer(int16), intent(out) :: code
        character(:), intent(out), allocatable :: msg

        if (url == "/app/status" .and. method == "GET") then
            code = 200_int16
            msg = "Ok"
            return
        end if

        if (url == "/create/user" .and. method == "POST") then
            code = 201_int16
            msg = "User Created"
            return
        end if

        code = 404_int16
        msg = "Not Ok"

    end subroutine application_t_handle_request

end module proxy_module

program proxy_main

    use, intrinsic :: iso_fortran_env, only: int16
    use proxy_module, only: nginx_type, new_nginx_server

    type(nginx_type) :: nginx_server
    character(*), parameter :: app_status_url = "/app/status", create_user_url = "/create/user"
    integer(int16) :: code
    character(:), allocatable :: body

    nginx_server = new_nginx_server()

    call nginx_server%handle_request(app_status_url, "GET", code, body)
    print *, "Url: ", app_status_url, new_line(""), &
        "Http code: ", code, new_line(""), &
        "Body: ", body

    call nginx_server%handle_request(app_status_url, "GET", code, body)
    print *, "Url: ", app_status_url, new_line(""), &
        "Http code: ", code, new_line(""), &
        "Body: ", body

    call nginx_server%handle_request(app_status_url, "GET", code, body)
    print *, "Url: ", app_status_url, new_line(""), &
        "Http code: ", code, new_line(""), &
        "Body: ", body

    call nginx_server%handle_request(create_user_url, "POST", code, body)
    print *, "Url: ", create_user_url, new_line(""), &
        "Http code: ", code, new_line(""), &
        "Body: ", body

    call nginx_server%handle_request(create_user_url, "GET", code, body)
    print *, "Url: ", create_user_url, new_line(""), &
        "Http code: ", code, new_line(""), &
        "Body: ", body

end program proxy_main

!> Results shall be:

!  Url: /app/status
!  Http code:     200
!  Body: Ok
!  Url: /app/status
!  Http code:     200
!  Body: Ok
!  Url: /app/status
!  Http code:     403
!  Body: Not Allowed
!  Url: /create/user
!  Http code:     201
!  Body: User Created
!  Url: /create/user
!  Http code:     404
!  Body: Not Ok