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! Copyright (c) 2020 Jeffrey Armstrong <jeff@rainbow-100.com>
!
! Permission is hereby granted, free of charge, to any person obtaining a copy
! of this software and associated documentation files (the "Software"), to deal
! in the Software without restriction, including without limitation the rights
! to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
! copies of the Software, and to permit persons to whom the Software is
! furnished to do so, subject to the following conditions:
!
! The above copyright notice and this permission notice shall be included in
! all copies or substantial portions of the Software.
!
! The Software shall be used for Good, not Evil.
!
! THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
! IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
! FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
! AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
! LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
! OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
! SOFTWARE.

module history
implicit none

    type :: location
        character(1024)::url
        type(location), pointer::next
    end type
    
contains

    function last_location(first_location)
    implicit none
    
        type(location), pointer::first_location
        type(location), pointer::last_location

        if(.not. associated(first_location)) then
            last_location => null()
        else
            last_location => first_location
            
            do while(associated(last_location%next))
                
                last_location => last_location%next
                
            end do
        end if
        
    end function last_location

    function add_location(first_location, url) result(head)
    implicit none
    
        type(location), pointer::first_location
        type(location), pointer::head
        character(*), intent(in)::url
        
        type(location), pointer::last
        
        ! Check if it is our first location
        if(.not. associated(first_location)) then
        
            allocate(first_location)
            first_location%next => null()
            first_location%url = url
        
        else
        
            last => last_location(first_location)
            if(trim(last%url) /= trim(url)) then
            
                allocate(last%next)
                last => last%next
                last%next => null()
                last%url = url
                
            end if
            
        end if
        
        head => first_location

    end function add_location
    
    subroutine back_location(first_location, url)
    implicit none
    
        type(location), pointer::first_location
        character(*), intent(out)::url
        
        type(location), pointer::last, new_last
    
        url = " "
    
        last => last_location(first_location)
        if(associated(last)) then
            
            if(.not. associated(last, first_location)) then
                new_last => first_location
                do while(.not. associated(new_last%next, last))
                    new_last => new_last%next
                end do
                deallocate(last)
            else
                new_last => first_location
            end if
            
            new_last%next => null()
            url = new_last%url
            
        end if
        
    end subroutine back_location

end module history