source: josm/trunk/src/org/openstreetmap/josm/actions/search/PushbackTokenizer.java@ 627

// License: GPL. Copyright 2007 by Immanuel Scholz and others
package org.openstreetmap.josm.actions.search;

import java.io.IOException;
import java.io.PushbackReader;
import java.util.LinkedList;

public class PushbackTokenizer {
        private PushbackReader search;

        private LinkedList<String> pushBackBuf = new LinkedList<String>();

        public PushbackTokenizer(PushbackReader search) {
                this.search = search;
        }

        /**
         * The token returned is <code>null</code> or starts with an identifier character:
         * - for an '-'. This will be the only character
         * : for an key. The value is the next token
         * | for "OR"
         * ' ' for anything else.
         * @return The next token in the stream.
         */
        public String nextToken() {
                if (!pushBackBuf.isEmpty()) {
                        return pushBackBuf.removeLast();
                }

                try {
                        int next;
                        char c = ' ';
                        while (c == ' ' || c == '\t' || c == '\n') {
                                next = search.read();
                                if (next == -1)
                                        return null;
                                c = (char)next;
                        }
                        StringBuilder s;
                        switch (c) {
                        case ':':
                                next = search.read();
                                c = (char) next;
                                if (next == -1 || c == ' ' || c == '\t') {
                                        pushBack(" ");
                                } else {
                                        search.unread(next);
                                }
                                return ":";
                        case '-':
                                return "-";
                        case '(':
                                return "(";
                        case ')':
                                return ")";
                        case '"':
                                s = new StringBuilder(" ");
                                for (int nc = search.read(); nc != -1 && nc != '"'; nc = search.read())
                                        s.append((char)nc);
                                return s.toString();
                        default:
                                s = new StringBuilder();
                        for (;;) {
                                s.append(c);
                                next = search.read();
                                if (next == -1) {
                                        if (s.toString().equals("OR"))
                                                return "|";
                                        return " "+s.toString();
                                }
                                c = (char)next;
                                if (c == ' ' || c == '\t' || c == '"' || c == ':' || c == '(' || c == ')') {
                                        search.unread(next);
                                        if (s.toString().equals("OR"))
                                                return "|";
                                        return " "+s.toString();
                                }
                        }
                        }
                } catch (IOException e) {
                        throw new RuntimeException(e.getMessage(), e);
                }               
        }

        public boolean readIfEqual(String tok) {
                String nextTok = nextToken();
                if (nextTok == null ? tok == null : nextTok.equals(tok)) 
                        return true;
                pushBack(nextTok);
                return false;
        }

        public String readText() {
                String nextTok = nextToken();
                if (nextTok != null && nextTok.startsWith(" "))
                        return nextTok.substring(1);
                pushBack(nextTok);
                return null;
        }

        public void pushBack(String tok) {
                pushBackBuf.addLast(tok);
        }
}