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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 render
implicit none

    integer, parameter::render_action_none   = 1
    integer, parameter::render_action_goto   = 2
    integer, parameter::render_action_layout = 3
    integer, parameter::render_action_back   = 4
    integer, parameter::render_action_quit   = 5

    character(11), dimension(2)::base_supported_types = &
        ["text/plain ", &
         "text/gemini" ]

    character(*), parameter::idle_status = "LR-87 Ready"

    type, abstract :: renderer
    
        integer::y
        integer::max_width
        
        contains
        
        procedure::render_proportional
        procedure::type_supported
        procedure::status_ready
        
        procedure(initialize), deferred::initialize
        procedure(prepare_for_layout), deferred::prepare_for_layout
        procedure(new_page), deferred::new_page
        
        procedure(calculate_width), deferred::text_width
        procedure(calculate_height), deferred::text_height
        procedure(calculate_visibility), deferred::is_text_visible
        procedure(draw_text), deferred::draw_porportional

        procedure(calculate_simple_width), deferred::preformatted_width
        procedure(calculate_simple_height), deferred::preformatted_height
        procedure(calculate_visibility), deferred::is_preformatted_visible
        procedure(draw_simple_text), deferred::draw_preformatted
        
        procedure(calculate_simple_width), deferred::link_width
        procedure(calculate_simple_height), deferred::link_height
        procedure(calculate_visibility), deferred::is_link_visible
        procedure(draw_link), deferred::draw_link
        
        procedure(request_input), deferred::request_input
        
        procedure(draw_simple_text), deferred::draw_error
        
        procedure(draw_simple_text), deferred::report_status

        procedure(request_action), deferred::request_action
        
        procedure(draw_simple_text), deferred::report_displayed_page

    end type renderer

    abstract interface
        subroutine initialize(self)
        import::renderer
        class(renderer)::self
        end subroutine initialize
    end interface
    
    abstract interface
        subroutine new_page(self)
        import::renderer
        class(renderer)::self
        end subroutine new_page
    end interface

    abstract interface
        subroutine prepare_for_layout(self)
        import::renderer
        class(renderer)::self
        end subroutine prepare_for_layout
    end interface

    abstract interface
        function calculate_width(self, text, heading, list_item)
        import::renderer
        class(renderer)::self
        character(*), intent(in)::text
        integer, intent(in), optional::heading
        logical, intent(in), optional::list_item
        integer::calculate_width
        end function calculate_width
    end interface
    
    abstract interface
        function calculate_height(self, text, heading, list_item)
        import::renderer
        class(renderer)::self
        character(*), intent(in)::text
        integer, intent(in), optional::heading
        logical, intent(in), optional::list_item
        integer::calculate_height
        end function calculate_height
    end interface
    
    abstract interface
        subroutine draw_text(self, text, heading, list_item)
        import::renderer
        class(renderer)::self
        character(*), intent(in)::text
        integer, intent(in), optional::heading
        logical, intent(in), optional::list_item
        end subroutine draw_text
    end interface
    
    abstract interface
        function calculate_simple_width(self, text)
        import::renderer
        class(renderer)::self
        character(*), intent(in)::text
        integer::calculate_simple_width
        end function calculate_simple_width
    end interface
    
    abstract interface
        function calculate_simple_height(self, text)
        import::renderer
        class(renderer)::self
        character(*), intent(in)::text
        integer::calculate_simple_height
        end function calculate_simple_height
    end interface
    
    abstract interface
        subroutine draw_simple_text(self, text)
        import::renderer
        class(renderer)::self
        character(*), intent(in)::text
        end subroutine draw_simple_text
    end interface
    
    abstract interface
        function calculate_visibility(self, text)
        import::renderer
        class(renderer)::self
        character(*), intent(in)::text
        logical::calculate_visibility
        end function calculate_visibility
    end interface
    
    abstract interface
        subroutine draw_link(self, text, url)
        import::renderer
        class(renderer)::self
        character(*), intent(in)::text, url
        end subroutine draw_link
    end interface
    
    abstract interface
        function request_input(self, question, answer)
        import::renderer
        class(renderer)::self
        character(*), intent(in)::question
        character(*), intent(out)::answer
        logical::request_input
        end function request_input
    end interface
    
    abstract interface
        function request_action(self, text)
        import::renderer
        class(renderer)::self
        character(*), intent(out)::text
        integer::request_action
        end function request_action
    end interface
    
    abstract interface
        function request_save_filename(self, url, mimetype, filename)
        import::renderer
        class(renderer)::self
        character(*), intent(in)::url
        character(*), intent(in)::mimetype
        character(*), intent(out)::filename
        logical::request_save_filename
        end function request_save_filename
    end interface
    
contains
 
    function type_supported(self, mimetype)
    implicit none
    
        class(renderer)::self
        character(*), intent(in)::mimetype
        logical::type_supported
        integer::i

        integer::istop

        istop = index(mimetype, ";") - 1
        if(istop < 1) then
            istop = len_trim(mimetype)
        end if

        type_supported = .false.
        do i = 1, size(base_supported_types)
            if(mimetype(1:istop) == trim(base_supported_types(i))) then
                type_supported = .true.
                exit
            end if
        end do
        
    end function type_supported
 
    subroutine status_ready(self)
    implicit none
        
        class(renderer)::self
 
        call self%report_status(idle_status)
        
    end subroutine status_ready
    
    function width_of_line(r, text, startpos, endpos, heading_level, list_item)
    implicit none
    
        class(renderer)::r
        character(*), intent(in)::text
        integer, intent(in)::startpos, endpos
        integer, intent(in)::heading_level
        logical, intent(in)::list_item
        integer::width_of_line
        
        integer::my_start, my_end
        
        my_end = endpos
        if(endpos <= 0) then
            my_end = len_trim(text)
        end if
        
        my_start = startpos
        if(startpos <= 0) then
            my_start = 1
        end if
        
        if(my_end <= my_start) then
            width_of_line = 0
        else
            width_of_line = r%text_width(text(my_start:my_end), &
                                         heading=heading_level, &
                                         list_item=list_item)
        end if
    
    end function width_of_line

    function wrap_line(r, text, startpos, heading_level, list_item) result(endpos)
    implicit none

        class(renderer)::r
        character(*), intent(in)::text
        integer, intent(in)::startpos
        integer, intent(in)::heading_level
        logical, intent(in)::list_item
        integer::endpos
        integer::my_start
        integer::w
        
        my_start = startpos
        if(startpos == 0) then
            my_start = 1
        end if
        
        endpos = len_trim(text)
        w = width_of_line(r, text, my_start, endpos, heading_level, list_item)
        do while(w > r%max_width)
        
            endpos = endpos - 1
            do while(text(endpos:endpos) /= ' ' .and. text(endpos:endpos) /= '-' .and. endpos > my_start)
                endpos = endpos - 1
            end do
            
            w = width_of_line(r, text, my_start, endpos, heading_level, list_item)
        end do
        
    end function wrap_line
    
    subroutine render_proportional(r, text)
    implicit none
    
        class(renderer)::r
        character(*)::text
        
        integer::startpos, endpos
        integer::heading_level
        logical::list_item
        
        if(len_trim(text) == 0) then 
        
            if(r%is_text_visible(" ")) then
                call r%draw_porportional("")
            end if
            r%y = r%y + r%text_height(" ")
            
        else
        
            startpos = 1
            
            ! Check for headings first
            heading_level = 0
            do while(text(startpos:startpos) == '#') 
                heading_level = heading_level + 1
                startpos = startpos + 1
            end do
            
            ! Or a list item
            list_item = .FALSE.
            if(heading_level == 0) then
                list_item = (text(1:1) == '*') 
                if(list_item) then
                    startpos = startpos + 1
                end if
            end if
            
            ! If either occurred, advance past whitespace
            if(heading_level > 0 .or. list_item) then
                do while(text(startpos:startpos) == ' ' .or. text(startpos:startpos) == char(9))
                    startpos = startpos + 1
                end do
            end if
            
            endpos = wrap_line(r, text, startpos, heading_level, list_item)
            do while(endpos > startpos)
                if(r%is_text_visible(text(startpos:endpos))) then
                    call r%draw_porportional(text(startpos:endpos), &
                                             heading=heading_level, &
                                             list_item=list_item)
                end if
                r%y = r%y + r%text_height(text(startpos:endpos), &
                                          heading=heading_level, &
                                          list_item=list_item)
                
                ! Advance string positions
                startpos = endpos+1
                do while(text(startpos:startpos) == ' ')
                    startpos = startpos + 1
                end do
                
                ! Do not mark as a list item for subsequent lines
                list_item = .FALSE.
                
                endpos = wrap_line(r, text, startpos, heading_level, list_item)
            end do
        end if
    
    end subroutine render_proportional
    
    subroutine render_preformatted(r, text)
    implicit none
    
        class(renderer)::r
        character(*)::text
        
        if(r%is_preformatted_visible(text)) then
            call r%draw_preformatted(text)
        end if
        r%y = r%y + r%preformatted_height(text)
    
    end subroutine render_preformatted
    
    subroutine render_link(r, text)
    implicit none
    
        class(renderer)::r
        character(*)::text
        integer::i_whitespace, d_length, i_start_display
        
        character(len=:), allocatable::url, display
        
        ! Find the url first - just allocate the same 
        ! size as the text, good enough...
        allocate(character(len=len_trim(text)) :: url)
        url = adjustl(text)
        
        ! The display text occurs after the first whitespace
        ! in url now
        i_whitespace = index(trim(url)," ")
        if(index(trim(url), CHAR(9)) > 0) then
            if(i_whitespace == 0 .OR. index(trim(url), CHAR(9)) < i_whitespace) then
                i_whitespace = index(trim(url), CHAR(9))
            end if
        end if
        
        if(i_whitespace == 0) then
            allocate(character(len=len_trim(url)) :: display)
            display = url
        else
            d_length = len_trim(url) - i_whitespace + 1
            allocate(character(len=d_length) :: display)
            
            ! Adjustl doesn't handle tabs, so we need to do this manually...
            i_start_display = i_whitespace
            do while(any([" ", char(9)] == url(i_start_display:i_start_display)))
                i_start_display = i_start_display + 1
            end do
            display = url(i_start_display:len_trim(url))
            url = url(1:(i_whitespace-1))
        end if
        
        if(r%is_link_visible(display)) then
            call r%draw_link(display, url)
        end if
        r%y = r%y + r%link_height(display)
        
        deallocate(url)
        deallocate(display)
        
    end subroutine render_link
    
    function handle_input(r, url, unit_number)
    use escaper
    implicit none
    
        class(renderer)::r
        character(*), intent(inout)::url
        integer, intent(in)::unit_number
        
        logical::handle_input
        
        character(1024)::response_line
        character(256)::answer
        integer::question_index
        
        rewind(unit_number)
        
        read(unit_number, '(A1024)') response_line
        question_index = 3
        do while(response_line(question_index:question_index) == " " .or. &
                 response_line(question_index:question_index) == char(9))
            
            question_index = question_index + 1
            
        end do
        
        handle_input = r%request_input(response_line(question_index:len_trim(response_line)), &
                                       answer)
        
        if(handle_input) then
            question_index = index(url, "?")
            if(question_index < 1) then
                url = trim(url)//"?"
                question_index = len_trim(url)
            end if
            
            call escape_string(answer)
            
            url = url(1:question_index)//answer
        end if
        
    end function handle_input
    
end module render