import std._io.stdio_reader;

fn in_range(char c, char lo, char hi) -> bool {
    ret lo <= c && c <= hi;
}

fn is_alpha(char c) -> bool {
    ret in_range(c, 'a', 'z') ||
        in_range(c, 'A', 'Z');
}

fn is_dec_digit(char c) -> bool {
    ret in_range(c, '0', '9');
}

fn is_hex_digit(char c) -> bool {
    ret in_range(c, '0', '9') ||
        in_range(c, 'a', 'f') ||
        in_range(c, 'A', 'F');
}

fn is_bin_digit(char c) -> bool {
    ret c == '0' || c == '1';
}

fn is_whitespace(char c) -> bool {
    ret c == ' ' || c == '\t' || c == '\r' || c == '\n';
}

fn consume_any_whitespace(stdio_reader rdr, char c) -> char {
    auto c1 = c;
    while (is_whitespace(c1)) {
        c1 = rdr.getc() as char;
    }
    be consume_any_line_comment(rdr, c1);
}

fn consume_any_line_comment(stdio_reader rdr, char c) -> char {
    auto c1 = c;
    if (c1 == '/') {
        auto c2 = rdr.getc() as char;
        if (c2 == '/') {
            while (c1 != '\n') {
                c1 = rdr.getc() as char;
            }
            // Restart whitespace munch.
            be consume_any_whitespace(rdr, c1);
        }
    }
    ret c;
}

fn next_token(stdio_reader rdr) -> token.token {
    auto eof = (-1) as char;
    auto c = rdr.getc() as char;
    auto accum_str = "";
    auto accum_int = 0;

    fn next(stdio_reader rdr) -> char {
        ret rdr.getc() as char;
    }

    fn forget(stdio_reader rdr, char c) {
        rdr.ungetc(c as int);
    }

    c = consume_any_whitespace(rdr, c);

    if (c == eof) { ret token.EOF(); }

    if (is_alpha(c)) {
        while (is_alpha(c)) {
            accum_str += (c as u8);
            c = next(rdr);
        }
        forget(rdr, c);
        ret token.IDENT(accum_str);
    }

    if (is_dec_digit(c)) {
        if (c == '0') {
        } else {
            while (is_dec_digit(c)) {
                accum_int *= 10;
                accum_int += (c as int) - ('0' as int);
                c = next(rdr);
            }
            forget(rdr, c);
            ret token.LIT_INT(accum_int);
        }
    }


    fn op_or_opeq(stdio_reader rdr, char c2,
                  token.op op) -> token.token {
        if (c2 == '=') {
            ret token.OPEQ(op);
        } else {
            forget(rdr, c2);
            ret token.OP(op);
        }
    }

    alt (c) {
        // One-byte tokens.
        case (';') { ret token.SEMI(); }
        case (',') { ret token.COMMA(); }
        case ('.') { ret token.DOT(); }
        case ('(') { ret token.LPAREN(); }
        case (')') { ret token.RPAREN(); }
        case ('{') { ret token.LBRACE(); }
        case ('}') { ret token.RBRACE(); }
        case ('[') { ret token.LBRACKET(); }
        case (']') { ret token.RBRACKET(); }
        case ('@') { ret token.AT(); }
        case ('#') { ret token.POUND(); }

        // Multi-byte tokens.
        case ('=') {
            auto c2 = next(rdr);
            if (c2 == '=') {
                ret token.OP(token.EQEQ());
            } else {
                forget(rdr, c2);
                ret token.OP(token.EQ());
            }
        }

        case ('-') {
            auto c2 = next(rdr);
            if (c2 == '>') {
                ret token.RARROW();
            } else {
                ret op_or_opeq(rdr, c2, token.MINUS());
            }
        }

        case ('&') {
            auto c2 = next(rdr);
            if (c2 == '&') {
                ret token.OP(token.ANDAND());
            } else {
                ret op_or_opeq(rdr, c2, token.AND());
            }
        }

        case ('+') {
            ret op_or_opeq(rdr, next(rdr), token.PLUS());
        }

        case ('*') {
            ret op_or_opeq(rdr, next(rdr), token.STAR());
        }

        case ('/') {
            ret op_or_opeq(rdr, next(rdr), token.STAR());
        }

        case ('!') {
            ret op_or_opeq(rdr, next(rdr), token.NOT());
        }

        case ('^') {
            ret op_or_opeq(rdr, next(rdr), token.CARET());
        }

        case ('%') {
            ret op_or_opeq(rdr, next(rdr), token.PERCENT());
        }

    }

    log "lexer stopping at ";
    log c;
    ret token.EOF();
}


//
// Local Variables:
// mode: rust
// fill-column: 78;
// indent-tabs-mode: nil
// c-basic-offset: 4
// buffer-file-coding-system: utf-8-unix
// compile-command: "make -k -C ../.. 2>&1 | sed -e 's/\\/x\\//x:\\//g'";
// End:
//