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

import static org.openstreetmap.josm.tools.I18n.marktr;
import static org.openstreetmap.josm.tools.I18n.tr;

import java.io.IOException;
import java.io.Reader;
import java.util.Arrays;
import java.util.List;

import org.openstreetmap.josm.actions.search.SearchCompiler.ParseError;

public class PushbackTokenizer {

    public class Range {
        private final long start;
        private final long end;

        public Range(long start, long end) {
            this.start = start;
            this.end = end;
        }

        public long getStart() {
            return start;
        }

        public long getEnd() {
            return end;
        }
    }

    private final Reader search;

    private Token currentToken;
    private String currentText;
    private Long currentNumber;
    private Long currentRange;
    private int c;

    public PushbackTokenizer(Reader search) {
        this.search = search;
        getChar();
    }

    public enum Token {
        NOT(marktr("<not>")), OR(marktr("<or>")), LEFT_PARENT(marktr("<left parent>")),
        RIGHT_PARENT(marktr("<right parent>")), COLON(marktr("<colon>")), EQUALS(marktr("<equals>")),
        KEY(marktr("<key>")), QUESTION_MARK(marktr("<question mark>")),
        EOF(marktr("<end-of-file>"));

        private Token(String name) {
            this.name = name;
        }

        private final String name;

        @Override
        public String toString() {
            return tr(name);
        }
    }


    private void getChar() {
        try {
            c = search.read();
        } catch (IOException e) {
            throw new RuntimeException(e.getMessage(), e);
        }
    }

    private long getNumber() {
        long result = 0;
        while (Character.isDigit(c)) {
            result = result * 10 + (c - '0');
            getChar();
        }
        return result;
    }

    private static final List<Character> specialChars = Arrays.asList(new Character[] {'"', ':', '(', ')', '|', '=', '?'});
    private static final List<Character> specialCharsQuoted = Arrays.asList(new Character[] {'"'});

    private String getString(boolean quoted) {
        List<Character> sChars = quoted ? specialCharsQuoted : specialChars;
        StringBuilder s = new StringBuilder();
        boolean escape = false;
        while (c != -1 && (escape || (!sChars.contains(c) && (quoted || !Character.isWhitespace(c))))) {
            if (c == '\\' && !escape) {
                escape = true;
            } else {
                s.append((char)c);
                escape = false;
            }
            getChar();
        }
        return s.toString();
    }

    private String getString() {
        return getString(false);
    }

    /**
     * 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 Token nextToken() {
        if (currentToken != null) {
            Token result = currentToken;
            currentToken = null;
            return result;
        }

        while (Character.isWhitespace(c)) {
            getChar();
        }
        switch (c) {
        case -1:
            getChar();
            return Token.EOF;
        case ':':
            getChar();
            return Token.COLON;
        case '=':
            getChar();
            return Token.EQUALS;
        case '(':
            getChar();
            return Token.LEFT_PARENT;
        case ')':
            getChar();
            return Token.RIGHT_PARENT;
        case '|':
            getChar();
            return Token.OR;
        case '?':
            getChar();
            return Token.QUESTION_MARK;
        case '"':
            getChar();
            currentText = getString(true);
            getChar();
            return Token.KEY;
        default:
            String prefix = "";
            if (c == '-') {
                getChar();
                if (!Character.isDigit(c))
                    return Token.NOT;
                prefix = "-";
            }
            currentText = prefix + getString();
            if ("or".equals(currentText))
                return Token.OR;
            try {
                currentNumber = Long.parseLong(currentText);
            } catch (NumberFormatException e) {
                currentNumber = null;
            }
            int pos = currentText.indexOf('-', 1);
            if (pos > 0) {
                try {
                    currentNumber = Long.parseLong(currentText.substring(0, pos));
                    currentRange = Long.parseLong(currentText.substring(pos + 1));
                } catch (NumberFormatException e) {
                    currentNumber = null;
                    currentRange = null;
                }
            }
            return Token.KEY;
        }
    }

    public boolean readIfEqual(Token token) {
        Token nextTok = nextToken();
        if (nextTok == null ? token == null : nextTok == token)
            return true;
        currentToken = nextTok;
        return false;
    }

    public String readTextOrNumber() {
        Token nextTok = nextToken();
        if (nextTok == Token.KEY)
            return currentText;
        currentToken = nextTok;
        return null;
    }

    public long readNumber(String errorMessage) throws ParseError {
        if ((nextToken() == Token.KEY) && (currentNumber != null))
            return currentNumber;
        else
            throw new ParseError(errorMessage);
    }

    public long getReadNumber() {
        return (currentNumber != null) ? currentNumber : 0;
    }

    public Range readRange(String errorMessage) throws ParseError {
        if ((nextToken() == Token.KEY) && (currentNumber != null)) {
            if (currentRange == null)
                return new Range(currentNumber, currentNumber);
            else
                return new Range(currentNumber, currentRange);
        } else
            throw new ParseError(errorMessage);
    }

    public String getText() {
        return currentText;
    }
}