com.squarespace.less.core.MapFormat.java Source code

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Here is the source code for com.squarespace.less.core.MapFormat.java

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/**
 * Copyright (c) 2014 SQUARESPACE, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.squarespace.less.core;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.apache.commons.lang3.StringEscapeUtils;

/**
 * Support class for formatting error messages flexibly using a Map.
 */
public class MapFormat {

    /**
     * Pattern used to extract the keys from the format string. These will end
     * up being the keys in the resulting map.
     */
    private static final Pattern KEY_ESCAPE = Pattern.compile("%\\([a-zA-Z][a-zA-Z0-9]*\\)");

    /**
     * Default for {@link #nullPlaceholder}
     */
    private static final String EMPTY_STRING = "";

    /**
     * Keys in the map.
     */
    private final List<String> keys = new ArrayList<>();

    /**
     * Format string used to construct the message. See {@link #apply(Map)}
     */
    private final String format;

    /**
     * String to be emitted if a value is {@code null}
     */
    private final String nullPlaceholder;

    /**
     * Constructs an instance using the given format string.
     */
    public MapFormat(String raw) {
        this(raw, EMPTY_STRING);
    }

    /**
     * Constructs an instance using the given format string and null placeholder.
     */
    public MapFormat(String raw, String nullPlaceholder) {
        this.nullPlaceholder = nullPlaceholder;
        this.format = init(raw);
    }

    /**
     * Extracts the keys from the pattern and generates the format string.
     */
    private String init(String raw) {
        StringBuffer buf = new StringBuffer();
        Matcher matcher = KEY_ESCAPE.matcher(raw);
        int mark = 0;
        int length = raw.length();
        while (matcher.find()) {
            int start0 = matcher.start();
            if (mark < start0) {
                buf.append(raw.substring(mark, start0));
            }
            buf.append(raw.charAt(start0));
            keys.add(raw.substring(start0 + 2, matcher.end() - 1));
            mark = matcher.end();
        }
        if (mark < length) {
            buf.append(raw.substring(mark, length));
        }
        return buf.toString();
    }

    /**
     * Returns the internal format string.
     */
    public String getFormat() {
        return format;
    }

    /**
     * Applies the {@code params} to producing the formatted message.
     */
    public String apply(Map<String, Object> params) {
        List<Object> values = new ArrayList<>(params.size());
        for (String key : keys) {
            Object obj = params.get(key);
            if (obj == null) {
                obj = nullPlaceholder;
            }
            values.add(obj);
        }
        return StringEscapeUtils.escapeJava(String.format(format, values.toArray()));
    }
}