MODULE editor;

(* based on the kilo editor building course*)

(* Step 24 *)

(*** IMPORTS ***)

IMPORT IO, termios, FIO, libc, CharClass, NumberIO, ASCII ;
IMPORT STextIO, Strings, SYSTEM;

(*** data ***)

CONST
    clearScreenStrLen       = 4;
    cursorHomeStrLen        = 3;

VAR 
    c           : CHAR;
    theTermios  : termios.TERMIOS;
    TCSAFLUSH   : INTEGER;
    i           : CARDINAL;
    (* escape sequences *)
    clearScreenStr      : ARRAY[0..3] OF CHAR;
    cursorHomeStr       : ARRAY[0..2] OF CHAR;

    (* escape sequences length *)


(*** Terminal ***)

    PROCEDURE CtrlKey(c: CHAR) : CARDINAL;

        VAR
            n : BITSET;

    BEGIN
        n := BITSET(ORD(c));
        n := n * BITSET(1FH);
        RETURN CARDINAL(n)
    END CtrlKey;

    PROCEDURE die (s : ARRAY OF CHAR);
    BEGIN
        libc.write(FIO.StdOut,SYSTEM.ADR(cursorHomeStr), cursorHomeStrLen);
        libc.write(FIO.StdOut,SYSTEM.ADR(clearScreenStr), clearScreenStrLen);
        libc.perror(s);
        FOR i := 0 TO Strings.Length(s) DO
            IO.Write(s[i])
        END;
        HALT
    END die;

    PROCEDURE disablerawMode() : INTEGER;

        VAR
            result : INTEGER;
    BEGIN
        IO.BufferedMode(0,TRUE);
        IO.BufferedMode(1,TRUE);
        result := termios.tcsetattr(FIO.StdIn, TCSAFLUSH, theTermios);
        IF result = -1 THEN
            theTermios := termios.KillTermios(theTermios);
            die("tcsetattr")
        ELSE 
            RETURN result
        END;
    END disablerawMode;

    PROCEDURE enablerawMode;
    BEGIN
        libc.atexit(disablerawMode);
        theTermios := termios.InitTermios();
        IF termios.tcgetattr(FIO.StdIn, theTermios) = -1 THEN
            die("tcgetattr")
        END;

        IO.UnBufferedMode(0,TRUE);
        IO.UnBufferedMode(1,TRUE);
    END enablerawMode;

    PROCEDURE  editorReadKey() : CHAR;
        VAR
            c : CHAR;
    BEGIN
        IO.Read(c);
        RETURN c
    END editorReadKey; 
    
  PROCEDURE editorProcessKeypress;
        VAR
            c       : CHAR;
    BEGIN
        c := editorReadKey();
        CASE ORD(c) OF
          17 :  libc.write(FIO.StdOut,SYSTEM.ADR(cursorHomeStr), cursorHomeStrLen);
                libc.write(FIO.StdOut,SYSTEM.ADR(clearScreenStr), clearScreenStrLen);
                HALT; 
        END
    END editorProcessKeypress;

(*** Output ***)
    
PROCEDURE editorRefreshScreen;
BEGIN
    libc.write(FIO.StdOut,SYSTEM.ADR(cursorHomeStr), cursorHomeStrLen);
    libc.write(FIO.StdOut,SYSTEM.ADR(clearScreenStr), clearScreenStrLen);
END editorRefreshScreen;

(*** Input ***)



(*** Init ***)

PROCEDURE InitScreenEscapes;

    VAR temp : ARRAY[0..10] OF CHAR;
    BEGIN
        cursorHomeStr := "";
        Strings.Concat(cursorHomeStr,ASCII.esc,cursorHomeStr);
        Strings.Concat(cursorHomeStr,"[H",cursorHomeStr);

        clearScreenStr := "";
        Strings.Concat(clearScreenStr,ASCII.esc,clearScreenStr);
        Strings.Concat(clearScreenStr,"[2J",clearScreenStr);
    END InitScreenEscapes;


BEGIN
    InitScreenEscapes;
    TCSAFLUSH := termios.tcsflush (); 
    enablerawMode;
    editorRefreshScreen;
    LOOP
       editorProcessKeypress;
       editorRefreshScreen;
    END;
END editor.