(*
    BSD 2-Clause License

    Copyright (c) 2018, 2019, Anton Krotov
    All rights reserved.
*)

MODULE SCAN;

IMPORT TXT := TEXTDRV, AVL := AVLTREES, ARITH, S := STRINGS;


CONST

    LEXLEN = 1024;

    lxUNDEF*   =  0;  lxIDENT*   =  1;  lxINTEGER*   =  2;  lxHEX*     =  3;
    lxCHAR*    =  4;  lxFLOAT*   =  5;  lxSTRING*    =  6;  lxCOMMENT* =  7;
    lxEOF*     =  8;

    lxPLUS*    = 21;  lxMINUS*   = 22;  lxMUL*       = 23;  lxSLASH*   = 24;
    lxNOT*     = 25;  lxAND*     = 26;  lxPOINT*     = 27;  lxCOMMA*   = 28;
    lxSEMI*    = 29;  lxBAR*     = 30;  lxLROUND*    = 31;  lxLSQUARE* = 32;
    lxLCURLY*  = 33;  lxCARET*   = 34;  lxEQ*        = 35;  lxNE*      = 36;
    lxLT*      = 37;  lxGT*      = 38;  lxCOLON*     = 39;  lxRROUND*  = 40;
    lxRSQUARE* = 41;  lxRCURLY*  = 42;  lxLE*        = 43;  lxGE*      = 44;
    lxASSIGN*  = 45;  lxRANGE*   = 46;

    lxKW       = 51;

    lxARRAY*   = 51;  lxBEGIN*   = 52;  lxBY*        = 53;  lxCASE*    = 54;
    lxCONST*   = 55;  lxDIV*     = 56;  lxDO*        = 57;  lxELSE*    = 58;
    lxELSIF*   = 59;  lxEND*     = 60;  lxFALSE*     = 61;  lxFOR*     = 62;
    lxIF*      = 63;  lxIMPORT*  = 64;  lxIN*        = 65;  lxIS*      = 66;
    lxMOD*     = 67;  lxMODULE*  = 68;  lxNIL*       = 69;  lxOF*      = 70;
    lxOR*      = 71;  lxPOINTER* = 72;  lxPROCEDURE* = 73;  lxRECORD*  = 74;
    lxREPEAT*  = 75;  lxRETURN*  = 76;  lxTHEN*      = 77;  lxTO*      = 78;
    lxTRUE*    = 79;  lxTYPE*    = 80;  lxUNTIL*     = 81;  lxVAR*     = 82;
    lxWHILE*   = 83;

    lxERROR01* =  -1;  lxERROR02* =  -2;  lxERROR03* =  -3;  lxERROR04* =  -4;
    lxERROR05* =  -5;  lxERROR06* =  -6;  lxERROR07* =  -7;  lxERROR08* =  -8;
    lxERROR09* =  -9;  lxERROR10* = -10;  lxERROR11* = -11;  lxERROR12* = -12;
    lxERROR13* = -13;


TYPE

    LEXSTR* = ARRAY LEXLEN OF CHAR;

    IDENT* = POINTER TO RECORD (AVL.DATA)

        s*: LEXSTR;
        offset*, offsetW*: INTEGER

    END;

    POSITION* = RECORD

        line*, col*: INTEGER

    END;

    LEX* = RECORD

        s*:         LEXSTR;
        length*:    INTEGER;
        sym*:       INTEGER;
        pos*:       POSITION;
        ident*:     IDENT;
        string*:    IDENT;
        value*:     ARITH.VALUE;
        error*:     INTEGER;

        over:       BOOLEAN

    END;

    SCANNER* = TXT.TEXT;

    KEYWORD = ARRAY 10 OF CHAR;


VAR

    vocabulary: RECORD

        KW:         ARRAY 33 OF KEYWORD;
        delimiters: ARRAY 256 OF BOOLEAN;
        idents:     AVL.NODE;
        ident:      IDENT

    END;

    upto: BOOLEAN;


PROCEDURE nodecmp (a, b: AVL.DATA): INTEGER;
    RETURN ORD(a(IDENT).s > b(IDENT).s) - ORD(a(IDENT).s < b(IDENT).s)
END nodecmp;


PROCEDURE key (VAR lex: LEX);
VAR
    L, R, M: INTEGER;
    found: BOOLEAN;

BEGIN
    L := 0;
    R := LEN(vocabulary.KW) - 1;
    found := FALSE;

    REPEAT
        M := (L + R) DIV 2;

        IF lex.s # vocabulary.KW[M] THEN
            IF lex.s > vocabulary.KW[M] THEN
                L := M + 1
            ELSE
                R := M - 1
            END
        ELSE
            found := TRUE;
            lex.sym := lxKW + M
        END
    UNTIL found OR (L > R)
END key;


PROCEDURE enterid* (s: LEXSTR): IDENT;
VAR
    newnode: BOOLEAN;
    node:    AVL.NODE;

BEGIN
    vocabulary.ident.s := s;
    vocabulary.idents := AVL.insert(vocabulary.idents, vocabulary.ident, nodecmp, newnode, node);

    IF newnode THEN
        NEW(vocabulary.ident);
        vocabulary.ident.offset  := -1;
        vocabulary.ident.offsetW := -1
    END

    RETURN node.data(IDENT)
END enterid;


PROCEDURE putchar (VAR lex: LEX; c: CHAR);
BEGIN
    IF lex.length < LEXLEN - 1 THEN
        lex.s[lex.length] := c;
        INC(lex.length);
        lex.s[lex.length] := 0X
    ELSE
        lex.over := TRUE
    END
END putchar;


PROCEDURE nextc (text: TXT.TEXT): CHAR;
BEGIN
    TXT.next(text)
    RETURN text.peak
END nextc;


PROCEDURE ident (text: TXT.TEXT; VAR lex: LEX);
VAR
    c: CHAR;

BEGIN
    c := text.peak;
    ASSERT(S.letter(c));

    WHILE S.letter(c) OR S.digit(c) DO
        putchar(lex, c);
        c := nextc(text)
    END;

    IF lex.over THEN
        lex.sym := lxERROR06
    ELSE
        lex.sym := lxIDENT;
        key(lex)
    END;

    IF lex.sym = lxIDENT THEN
        lex.ident := enterid(lex.s)
    END

END ident;


PROCEDURE number (text: TXT.TEXT; VAR lex: LEX);
VAR
    c: CHAR;
    hex: BOOLEAN;
    error: INTEGER;

BEGIN
    c := text.peak;
    ASSERT(S.digit(c));

    error := 0;

    lex.sym := lxINTEGER;
    hex := FALSE;

    WHILE S.digit(c) DO
        putchar(lex, c);
        c := nextc(text)
    END;

    WHILE S.hexdigit(c) DO
        putchar(lex, c);
        c := nextc(text);
        hex := TRUE
    END;

    IF c = "H" THEN
        putchar(lex, c);
        TXT.next(text);
        lex.sym := lxHEX

    ELSIF c = "X" THEN
        putchar(lex, c);
        TXT.next(text);
        lex.sym := lxCHAR

    ELSIF c = "." THEN

        IF hex THEN
            lex.sym := lxERROR01
        ELSE

            c := nextc(text);

            IF c # "." THEN
                putchar(lex, ".");
                lex.sym := lxFLOAT
            ELSE
                lex.sym := lxINTEGER;
                text.peak := 7FX;
                upto := TRUE
            END;

            WHILE S.digit(c) DO
                putchar(lex, c);
                c := nextc(text)
            END;

            IF c = "E" THEN

                putchar(lex, c);
                c := nextc(text);
                IF (c = "+") OR (c = "-") THEN
                    putchar(lex, c);
                    c := nextc(text)
                END;

                IF S.digit(c) THEN
                    WHILE S.digit(c) DO
                        putchar(lex, c);
                        c := nextc(text)
                    END
                ELSE
                    lex.sym := lxERROR02
                END

            END

        END

    ELSIF hex THEN
        lex.sym := lxERROR01

    END;

    IF lex.over & (lex.sym >= 0) THEN
        lex.sym := lxERROR07
    END;

    IF lex.sym = lxINTEGER THEN
        ARITH.iconv(lex.s, lex.value, error)
    ELSIF (lex.sym = lxHEX) OR (lex.sym = lxCHAR) THEN
        ARITH.hconv(lex.s, lex.value, error)
    ELSIF lex.sym = lxFLOAT THEN
        ARITH.fconv(lex.s, lex.value, error)
    END;

    CASE error OF
    |0:
    |1: lex.sym := lxERROR08
    |2: lex.sym := lxERROR09
    |3: lex.sym := lxERROR10
    |4: lex.sym := lxERROR11
    |5: lex.sym := lxERROR12
    END

END number;


PROCEDURE string (text: TXT.TEXT; VAR lex: LEX; quot: CHAR);
VAR
    c: CHAR;
    n: INTEGER;

BEGIN
    c  := nextc(text);
    n  := 0;

    WHILE (c # quot) & (c # 0X) & ~text.eol & ~text.eof DO
        putchar(lex, c);
        c := nextc(text);
        INC(n)
    END;

    IF c = quot THEN
        TXT.next(text);
        IF lex.over THEN
            lex.sym := lxERROR05
        ELSE
            IF n # 1 THEN
                lex.sym := lxSTRING
            ELSE
                lex.sym := lxCHAR;
                ARITH.setChar(lex.value, ORD(lex.s[0]))
            END
        END
    ELSE
        lex.sym := lxERROR03
    END;

    IF lex.sym = lxSTRING THEN
        lex.string := enterid(lex.s);
        lex.value.typ := ARITH.tSTRING;
        lex.value.string := lex.string
    END

END string;


PROCEDURE comment (text: TXT.TEXT);
VAR
    c: CHAR;
    cond, depth: INTEGER;

BEGIN
    cond  := 0;
    depth := 1;

    REPEAT

        c := text.peak;
        TXT.next(text);

        IF c = "*" THEN
            IF cond = 1 THEN
                cond := 0;
                INC(depth)
            ELSE
               cond := 2
            END
        ELSIF c = ")" THEN
            IF cond = 2 THEN
                DEC(depth)
            END;
            cond := 0
        ELSIF c = "(" THEN
            cond := 1
        ELSE
            cond := 0
        END

    UNTIL (depth = 0) OR text.eof

END comment;


PROCEDURE delimiter (text: TXT.TEXT; VAR lex: LEX; c: CHAR);
BEGIN
    putchar(lex, c);
    c := nextc(text);

    CASE lex.s[0] OF
    |"+":
        lex.sym := lxPLUS

    |"-":
        lex.sym := lxMINUS

    |"*":
        lex.sym := lxMUL

    |"/":
        lex.sym := lxSLASH;

        IF c = "/" THEN
            lex.sym := lxCOMMENT;
            REPEAT
                TXT.next(text)
            UNTIL text.eol OR text.eof
        END

    |"~":
        lex.sym := lxNOT

    |"&":
        lex.sym := lxAND

    |".":
        lex.sym := lxPOINT;

        IF c = "." THEN
            lex.sym := lxRANGE;
            putchar(lex, c);
            TXT.next(text)
        END

    |",":
        lex.sym := lxCOMMA

    |";":
        lex.sym := lxSEMI

    |"|":
        lex.sym := lxBAR

    |"(":
        lex.sym := lxLROUND;

        IF c = "*" THEN
            lex.sym := lxCOMMENT;
            TXT.next(text);
            comment(text)
        END

    |"[":
        lex.sym := lxLSQUARE

    |"{":
        lex.sym := lxLCURLY

    |"^":
        lex.sym := lxCARET

    |"=":
        lex.sym := lxEQ

    |"#":
        lex.sym := lxNE

    |"<":
        lex.sym := lxLT;

        IF c = "=" THEN
            lex.sym := lxLE;
            putchar(lex, c);
            TXT.next(text)
        END

    |">":
        lex.sym := lxGT;

        IF c = "=" THEN
            lex.sym := lxGE;
            putchar(lex, c);
            TXT.next(text)
        END

    |":":
        lex.sym := lxCOLON;

        IF c = "=" THEN
            lex.sym := lxASSIGN;
            putchar(lex, c);
            TXT.next(text)
        END

    |")":
        lex.sym := lxRROUND

    |"]":
        lex.sym := lxRSQUARE

    |"}":
        lex.sym := lxRCURLY

    END

END delimiter;


PROCEDURE Next* (text: SCANNER; VAR lex: LEX);
VAR
    c: CHAR;

BEGIN

    REPEAT
        c := text.peak;

        WHILE S.space(c) DO
            c := nextc(text)
        END;

        lex.s[0]     := 0X;
        lex.length   := 0;
        lex.pos.line := text.line;
        lex.pos.col  := text.col;
        lex.ident    := NIL;
        lex.over     := FALSE;

        IF S.letter(c) THEN
            ident(text, lex)
        ELSIF S.digit(c) THEN
            number(text, lex)
        ELSIF (c = '"') OR (c = "'") THEN
            string(text, lex, c)
        ELSIF vocabulary.delimiters[ORD(c)] THEN
            delimiter(text, lex, c)
        ELSIF c = 0X THEN
            lex.sym := lxEOF;
            IF text.eof THEN
                INC(lex.pos.col)
            END
        ELSIF (c = 7FX) & upto THEN
            upto := FALSE;
            lex.sym := lxRANGE;
            putchar(lex, ".");
            putchar(lex, ".");
            DEC(lex.pos.col);
            TXT.next(text)
        ELSE
            putchar(lex, c);
            TXT.next(text);
            lex.sym := lxERROR04
        END;

        IF lex.sym < 0 THEN
            lex.error := -lex.sym
        ELSE
            lex.error := 0
        END

    UNTIL lex.sym # lxCOMMENT

END Next;


PROCEDURE open* (name: ARRAY OF CHAR): SCANNER;
    RETURN TXT.open(name)
END open;


PROCEDURE close* (VAR scanner: SCANNER);
BEGIN
    TXT.close(scanner)
END close;


PROCEDURE init;
VAR
    i: INTEGER;
    delim: ARRAY 23 OF CHAR;


    PROCEDURE enterkw (VAR i: INTEGER; kw: KEYWORD);
    BEGIN
        vocabulary.KW[i] := kw;
        INC(i)
    END enterkw;


BEGIN
    upto := FALSE;

    FOR i := 0 TO 255 DO
        vocabulary.delimiters[i] := FALSE
    END;

    delim := "+-*/~&.,;|([{^=#<>:)]}";

    FOR i := 0 TO LEN(delim) - 2 DO
        vocabulary.delimiters[ORD(delim[i])] := TRUE
    END;

    i := 0;
    enterkw(i, "ARRAY");
    enterkw(i, "BEGIN");
    enterkw(i, "BY");
    enterkw(i, "CASE");
    enterkw(i, "CONST");
    enterkw(i, "DIV");
    enterkw(i, "DO");
    enterkw(i, "ELSE");
    enterkw(i, "ELSIF");
    enterkw(i, "END");
    enterkw(i, "FALSE");
    enterkw(i, "FOR");
    enterkw(i, "IF");
    enterkw(i, "IMPORT");
    enterkw(i, "IN");
    enterkw(i, "IS");
    enterkw(i, "MOD");
    enterkw(i, "MODULE");
    enterkw(i, "NIL");
    enterkw(i, "OF");
    enterkw(i, "OR");
    enterkw(i, "POINTER");
    enterkw(i, "PROCEDURE");
    enterkw(i, "RECORD");
    enterkw(i, "REPEAT");
    enterkw(i, "RETURN");
    enterkw(i, "THEN");
    enterkw(i, "TO");
    enterkw(i, "TRUE");
    enterkw(i, "TYPE");
    enterkw(i, "UNTIL");
    enterkw(i, "VAR");
    enterkw(i, "WHILE");

    NEW(vocabulary.ident);
    vocabulary.ident.s       := "";
    vocabulary.ident.offset  := -1;
    vocabulary.ident.offsetW := -1;
    vocabulary.idents := NIL
END init;


BEGIN
    init
END SCAN.