RelaxedNames.java

package com.github.ltsopensource.autoconfigure;

import com.github.ltsopensource.core.commons.utils.StringUtils;

import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.Set;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * Generates relaxed name variations from a given source.
 *
 * @author Phillip Webb
 * @author Dave Syer
 */
public final class RelaxedNames implements Iterable<String> {

    private static final Pattern CAMEL_CASE_PATTERN = Pattern.compile("([^A-Z-])([A-Z])");

    private static final Pattern SEPARATED_TO_CAMEL_CASE_PATTERN = Pattern
            .compile("[_\\-.]");

    private final String name;

    private final Set<String> values = new LinkedHashSet<String>();

    /**
     * Create a new {@link RelaxedNames} instance.
     * @param name the source name. For the maximum number of variations specify the name
     * using dashed notation (e.g. {@literal my-property-name}
     */
    public RelaxedNames(String name) {
        this.name = (name == null ? "" : name);
        initialize(RelaxedNames.this.name, this.values);
    }

    @Override
    public Iterator<String> iterator() {
        return this.values.iterator();
    }

    private void initialize(String name, Set<String> values) {
        if (values.contains(name)) {
            return;
        }
        for (Variation variation : Variation.values()) {
            for (Manipulation manipulation : Manipulation.values()) {
                String result = name;
                result = manipulation.apply(result);
                result = variation.apply(result);
                values.add(result);
                initialize(result, values);
            }
        }
    }

    /**
     * Name variations.
     */
    enum Variation {

        NONE {
            @Override
            public String apply(String value) {
                return value;
            }
        },

        LOWERCASE {
            @Override
            public String apply(String value) {
                return value.toLowerCase();
            }
        },

        UPPERCASE {
            @Override
            public String apply(String value) {
                return value.toUpperCase();
            }
        };

        public abstract String apply(String value);

    }

    /**
     * Name manipulations.
     */
    enum Manipulation {

        NONE {
            @Override
            public String apply(String value) {
                return value;
            }
        },

        HYPHEN_TO_UNDERSCORE {
            @Override
            public String apply(String value) {
                return value.replace("-", "_");
            }
        },

        UNDERSCORE_TO_PERIOD {
            @Override
            public String apply(String value) {
                return value.replace("_", ".");
            }
        },

        PERIOD_TO_UNDERSCORE {
            @Override
            public String apply(String value) {
                return value.replace(".", "_");
            }
        },

        CAMELCASE_TO_UNDERSCORE {
            @Override
            public String apply(String value) {
                Matcher matcher = CAMEL_CASE_PATTERN.matcher(value);
                StringBuffer result = new StringBuffer();
                while (matcher.find()) {
                    matcher.appendReplacement(result, matcher.group(1) + '_'
                            + StringUtils.uncapitalize(matcher.group(2)));
                }
                matcher.appendTail(result);
                return result.toString();
            }
        },

        CAMELCASE_TO_HYPHEN {
            @Override
            public String apply(String value) {
                Matcher matcher = CAMEL_CASE_PATTERN.matcher(value);
                StringBuffer result = new StringBuffer();
                while (matcher.find()) {
                    matcher.appendReplacement(result, matcher.group(1) + '-'
                            + StringUtils.uncapitalize(matcher.group(2)));
                }
                matcher.appendTail(result);
                return result.toString();
            }
        },

        SEPARATED_TO_CAMELCASE {
            @Override
            public String apply(String value) {
                return separatedToCamelCase(value, false);
            }
        },

        CASE_INSENSITIVE_SEPARATED_TO_CAMELCASE {
            @Override
            public String apply(String value) {
                return separatedToCamelCase(value, true);
            }
        };

        public abstract String apply(String value);

        private static String separatedToCamelCase(String value,
                                                   boolean caseInsensitive) {
            StringBuilder builder = new StringBuilder();
            for (String field : SEPARATED_TO_CAMEL_CASE_PATTERN.split(value)) {
                field = (caseInsensitive ? field.toLowerCase() : field);
                builder.append(
                        builder.length() == 0 ? field : StringUtils.capitalize(field));
            }
            for (String suffix : new String[] { "_", "-", "." }) {
                if (value.endsWith(suffix)) {
                    builder.append(suffix);
                }
            }
            return builder.toString();

        }
    }

    /**
     * Return a {@link RelaxedNames} for the given source camelCase source name.
     * @param name the source name in camelCase
     * @return the relaxed names
     */
    public static RelaxedNames forCamelCase(String name) {
        return new RelaxedNames(Manipulation.CAMELCASE_TO_HYPHEN.apply(name));
    }

}