MusicalKey.java

package org.jaudiotagger.tag.reference;

import java.util.EnumSet;
import java.util.HashMap;

/**
 * Musical key used by the Key tagFieldKey
 * <p/>
 * It is not enforced but can be used to verify the Musical key according to the ID3 specification of the TKEY field
 */
public enum MusicalKey {
    NOTE_A("A"),
    NOTE_B("B"),
    NOTE_C("C"),
    NOTE_D("D"),
    NOTE_E("E"),
    NOTE_F("F"),
    NOTE_G("G"),
    FLAT("b"),
    SHARP("#"),
    MINOR("m"),
    OFF_KEY("o");

    private String value;

    MusicalKey(String value) {
        this.value = value;
    }

    public String getValue() {
        return value;
    }

    private static final int MAX_KEY_LENGTH = 3;

    private final static HashMap<String, MusicalKey> groundKeyMap;
    private final static HashMap<String, MusicalKey> halfKeyMap;

    static {
        EnumSet<MusicalKey> groundKey = EnumSet.of(NOTE_A, NOTE_B, NOTE_C, NOTE_D, NOTE_E, NOTE_F, NOTE_G);
        groundKeyMap = new HashMap<String, MusicalKey>(MusicalKey.values().length);
        for (MusicalKey curr : groundKey) {
            groundKeyMap.put(curr.getValue(), curr);
        }
        EnumSet<MusicalKey> halfKey = EnumSet.of(FLAT, SHARP, MINOR);
        halfKeyMap = new HashMap<String, MusicalKey>(MusicalKey.values().length);
        for (MusicalKey curr : halfKey) {
            halfKeyMap.put(curr.getValue(), curr);
        }
    }

    public static boolean isValid(String musicalKey) {
        if (musicalKey == null || musicalKey.length() > MAX_KEY_LENGTH || musicalKey.length() == 0) {
            return false;
        }


        if (musicalKey.length() == 1) {
            if (musicalKey.equals(OFF_KEY.getValue())) {
                return true;
            }
        }

        if (!groundKeyMap.containsKey(musicalKey.substring(0, 1))) {
            return false;
        }

        if (musicalKey.length() == 2 || musicalKey.length() == 3) {
            if (!halfKeyMap.containsKey(musicalKey.substring(1, 2))) {
                return false;
            }
        }

        if (musicalKey.length() == 3) {
            if (!musicalKey.substring(2, 3).equals(MINOR.getValue())) {
                return false;
            }
        }
        return true;
    }
}