--
-- Author:  Robert C. Shock,  Dept of CS & CEG   Wright State University
-- In cooperation with:  WRDC/ELED WPAFB   Dayton, OH
--
--
-- Purpose
-- The procedure vhdl_scroll_set_style preserves the shape style of vhdl source, while scrolling the vhdl code to the screen in a fixed number of rows per screen. No lexical unit except the comment line is separated. 
-- The scroll style of an vhdl source code consist of these specifications:  the_column_width, the_indent_margin, the_tab_set, the_wrap_indent_length, the_comment_ragged_indent, and the_comment_wrap_string ( length exactly 4 characters ), the_rows_per_screen, the_prompt_message;
-- The purpose of the procedure vhdl_scroll_set_style is to provide a mechanism that assigns values to the shape specifications without recompiling code. 

 
-- Assumptions and process overview
-- Input:  device = text_io.standard_input;
--         data = vhdl_lexicon_shape_style.specifciation + rows_per_screen 
--                 + prompt_message + vhdl (syntax) source code
-- Output: device = text_io.standard_output
--         data = text format with these specifications below 
--
-- Process: see purpose; below are the default values of the scroll specifications
--         the_column_width = 80, 
--         the_indent_margin = 48, 
--         the_tab_set = 3, 
--         the_wrap_indent_length = 1, 
--         the_comment_ragged_indent = 14, 
--         the_comment_wrap_string = "--  ", 
--         the_rows_per_screen = 23,
--         the_prompt_message = string = ""
-- CONSTRAINT: the values must satisfy these equations
--     the_wrap_indent_length <= the_tab_set and 
--     the_tab_set <= the_indent_margin and 
--     the_indent_margin < 3 + the_column_width - the_comment_wrap_string'length 
-- NOTE: A violation of the above constraint outputs an empty file.


-- Design decision and organizations
-- Used the construct, passive iterator with parameters, located in the package vhdl_lexicon_shape_style.

with vhdl_lexicon;
with vhdl_lexicon_shape_style;
with vhdl_lexicon_scroll_style;
with text_io;


procedure vhdl_scroll_set_style is

package positive_io is new text_io.integer_io ( positive );

function next_string_value_is return string is
the_string: string ( 1 .. 1 ) := ( others => ' ' );
begin
if text_io.end_of_line then
text_io.skip_line;
return "";
else
text_io.get ( the_string ( 1 ) );
return the_string & next_string_value_is;
end if;
end next_string_value_is;

function the_rows_per_screen_is return natural is
the_rows_per_screen: natural := 23; 
begin
positive_io.get ( the_rows_per_screen ); 
text_io.skip_line;
return the_rows_per_screen;
end the_rows_per_screen_is;


begin
-- the order of input is fixed and must be followed
vhdl_lexicon_scroll_style.iterate_to_standard_output 
(
with_the_shape_specification => vhdl_lexicon_shape_style.is_initializing ( text_io.standard_input ),
with_the_rows_per_screen => the_rows_per_screen_is,
the_prompt_message => next_string_value_is,
the_file_name => next_string_value_is
);


exception 
when others =>
vhdl_lexicon.put ( "Error does the file exist ?  " &  ( 1 => vhdl_lexicon.the_end_line_character ) );

end vhdl_scroll_set_style;