DMDirc-Parser/common/src/main/java/com/dmdirc/parser/common/IgnoreList.java

/*
 * Copyright (c) 2006-2017 DMDirc Developers
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

package com.dmdirc.parser.common;

import java.util.ArrayList;
import java.util.List;
import java.util.regex.PatternSyntaxException;
import java.util.stream.Collectors;

/**
 * Parser Ignore list.
 */
public class IgnoreList {

    /** Arraylist storing ignore patterns. */
    protected final List<String> ignoreInfo = new ArrayList<>();

    /**
     * Creates a new instance of RegexStringList.
     */
    public IgnoreList() {
        // Do nothing
    }

    /**
     * Creates a new instance of RegexStringList, with the specified items.
     *
     * @param items Items to add to this RegexStringList
     */
    public IgnoreList(final Iterable<String> items) {
        addAll(items);
    }

    /**
     * Add a new ignore pattern to the ignore list.
     *
     * @param pattern Regex syntax for the ignore (Pattern is matched case-insensitively as ^pattern$)
     */
    public void add(final String pattern) {
        for (String target : ignoreInfo) {
            if (pattern.equalsIgnoreCase(target)) {
                return;
            }
        }

        ignoreInfo.add(pattern);
    }

    /**
     * Adds a set of patterns to the list.
     *
     * @param patterns A list of patterns to be added
     */
    public void addAll(final Iterable<String> patterns) {
        for (String pattern : patterns) {
            add(pattern);
        }
    }

    /**
     * Delete an ignore from the list.
     *
     * @param position Position in the list to remove
     */
    public void remove(final int position) {
        if (position < count()) {
            ignoreInfo.remove(position);
        }
    }

    /**
     * Clear the ignore list.
     */
    public void clear() {
        ignoreInfo.clear();
    }

    /**
     * Check if a string matches any of the ignores in the list.
     *
     * @param check String to check (Patterns are matched case-insensitively as ^pattern$)
     * @return integer showing the position of the first match in the ignore list (-1 if none)
     * @throws PatternSyntaxException if one of the items in the list is an invalid regex
     */
    public int matches(final String check) throws PatternSyntaxException {
        for (int i = 0; i < count(); i++) {
            if (check.matches("(?i)" + get(i))) {
                return i;
            }
        }
        return -1;
    }

    /**
     * Check if a string matches a specific ignore in the list.
     *
     * @param position Position to check
     * @param check String to check (Patterns are matched case-insensitively as ^pattern$)
     * @return boolean true/false
     * @throws PatternSyntaxException if the item is an invalid regex
     */
    public boolean matches(final int position, final String check) throws
            PatternSyntaxException {
        return position < count() && check.matches("(?i)" + get(position));
    }

    /**
     * Get the ignore pattern in a given position in the list.
     *
     * @param position Position to check
     * @return String showing the pattern. ("" if position isn't valid)
     */
    public String get(final int position) {
        if (position < count()) {
            return ignoreInfo.get(position);
        } else {
            return "";
        }
    }

    /**
     * Change the ignore pattern in a given position in the list.
     *
     * @param position Position to change
     * @param pattern New pattern
     */
    public void set(final int position, final String pattern) {
        if (position < count()) {
            ignoreInfo.set(position, pattern);
        }
    }

    /**
     * Get the amount of ignores in the list.
     *
     * @return int showing the number of ignores
     */
    public int count() {
        return ignoreInfo.size();
    }

    /**
     * Adds the specified simple pattern to this ignore list.
     *
     * @param pattern The simple pattern to be added
     */
    public void addSimple(final String pattern) {
        add(simpleToRegex(pattern));
    }

    /**
     * Determines if this list can be converted to a simple list.
     *
     * @return True if this list can be converted, false otherwise.
     */
    public boolean canConvert() {
        try {
            getSimpleList();
            return true;
        } catch (UnsupportedOperationException ex) {
            return false;
        }
    }

    /**
     * Retrieves a list of regular expressions in this ignore list.
     *
     * @return All expressions in this ignore list
     */
    public List<String> getRegexList() {
        return new ArrayList<>(ignoreInfo);
    }

    /**
     * Retrieves a list of simple expressions in this ignore list.
     *
     * @return All expressions in this ignore list, converted to simple expressions
     * @throws UnsupportedOperationException if an expression can't be converted
     */
    public List<String> getSimpleList() throws UnsupportedOperationException {
        return ignoreInfo.stream().map(IgnoreList::regexToSimple).collect(Collectors.toList());
    }

    /**
     * Converts a regular expression into a simple expression.
     *
     * @param regex The regular expression to be converted
     * @return A simple expression corresponding to the regex
     * @throws UnsupportedOperationException if the regex cannot be converted
     */
    protected static String regexToSimple(final String regex)
            throws UnsupportedOperationException {
        final StringBuilder res = new StringBuilder(regex.length());
        final ConversionState state = new ConversionState();

        for (char part : regex.toCharArray()) {
            if (state.getAndResetLastCharWasDot()) {
                handleCharFollowingDot(state, res, part);
            } else if (state.getAndResetEscaped()) {
                handleEscapedChar(res, part);
            } else {
                handleNormalChar(state, res, part);
            }
        }

        if (state.getAndResetEscaped()) {
            throw new UnsupportedOperationException("Cannot convert to "
                    + "simple expression: trailing backslash");
        } else if (state.getAndResetLastCharWasDot()) {
            res.append('?');
        }

        return res.toString();
    }

    /**
     * Handles a single char that was preceded by a '.' when converting from a regex.
     *
     * @param state The current state of conversion.
     * @param builder The builder to append data to.
     * @param character The character in question.
     */
    private static void handleCharFollowingDot(final ConversionState state,
            final StringBuilder builder, final char character) {
        if (character == '*') {
            builder.append('*');
        } else {
            builder.append('?');
            handleNormalChar(state, builder, character);
        }
    }

    /**
     * Handles a single char that was escaped when converting from a regex.
     *
     * @param builder The builder to append data to.
     * @param character The character in question.
     */
    private static void handleEscapedChar(final StringBuilder builder, final char character) {
        if (character == '?' || character == '*') {
            throw new UnsupportedOperationException("Cannot convert to"
                    + " simple expression: ? or * is escaped.");
        }

        builder.append(character);
    }

    /**
     * Handles a single normal character when converting from a regex.
     *
     * @param state The current state of conversion.
     * @param builder The builder to append data to.
     * @param character The character in question.
     */
    private static void handleNormalChar(final ConversionState state,
            final StringBuilder builder, final char character) {
        if (character == '\\') {
            state.setEscaped();
        } else if (character == '.') {
            state.setLastCharWasDot();
        } else if ("^$[](){}|+*?".indexOf(character) > -1) {
            throw new UnsupportedOperationException("Cannot convert to"
                    + " simple expression: unescaped special char: " + character);
        } else {
            builder.append(character);
        }
    }

    /**
     * Converts a simple expression to a regular expression.
     *
     * @param regex The simple expression to be converted
     * @return A corresponding regular expression
     */
    protected static String simpleToRegex(final String regex) {
        final StringBuilder res = new StringBuilder(regex.length());

        for (char part : regex.toCharArray()) {
            switch (part) {
                case '.':
                case '^':
                case '$':
                case '[':
                case ']':
                case '\\':
                case '(':
                case ')':
                case '{':
                case '}':
                case '|':
                case '+':
                    res.append('\\').append(part);
                    break;
                case '?':
                    res.append('.');
                    break;
                case '*':
                    res.append(".*");
                    break;
                default:
                    res.append(part);
                    break;
            }
        }

        return res.toString();
    }

    /**
     * Utility class to represent state while converting a regex to a simple form.
     */
    private static final class ConversionState {

        private boolean escaped;
        private boolean lastCharWasDot;

        public boolean getAndResetLastCharWasDot() {
            final boolean oldValue = lastCharWasDot;
            lastCharWasDot = false;
            return oldValue;
        }

        public void setLastCharWasDot() {
            lastCharWasDot = true;
        }

        public boolean getAndResetEscaped() {
            final boolean oldValue = escaped;
            escaped = false;
            return oldValue;
        }

        public void setEscaped() {
            escaped = true;
        }

    }

}