src/android/src/com/google/android/inputmethod/japanese/keyboard/KeyState.java

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package org.mozc.android.inputmethod.japanese.keyboard;

import com.google.common.base.Objects;
import com.google.common.base.Preconditions;
import com.google.common.collect.Sets;

import java.util.Arrays;
import java.util.Collection;
import java.util.EnumMap;
import java.util.EnumSet;
import java.util.Map;
import java.util.Set;

/**
 * This is a model class of a key's state, corresponding to a {@code <KeyState>} element
 * in a xml resource file.
 *
 * Each key can have multiple state based on meta keys' condition. This class represents such
 * various state of each key.
 *
 * Each key state can have multiple {@code Flick} instances. See also the class for the details.
 *
 */
public class KeyState {
  public enum MetaState {
    SHIFT(1, true),
    CAPS_LOCK(2, false),
    ALT(4, false),

    // Actions
    // c.f, http://developer.android.com/reference/android/view/inputmethod/EditorInfo.html
    // TODO(matsuzakit): Implement me.
    ACTION_DONE(8, false),
    ACTION_GO(16, false),
    ACTION_NEXT(32, false),
    ACTION_NONE(64, false),
    ACTION_PREVIOUS(128, false),
    ACTION_SEARCH(256, false),
    ACTION_SEND(512, false),

    // Text variation
    // c.f., http://developer.android.com/reference/android/text/InputType.html
    // Raw InputType uses 30 bits field so directly representing it into a flag is impossible.
    // Therefore only some important ones are listed up here.
    // TYPE_TEXT_VARIATION_URI
    VARIATION_URI(1024, false),
    // TYPE_TEXT_VARIATION_WEB_EMAIL_ADDRESS, TYPE_TEXT_VARIATION_EMAIL_ADDRESS
    VARIATION_EMAIL_ADDRESS(2048, false),

    // Set if Globe button is enabled by preference.
    // TODO(matsuzakit): Implement me.
    GLOBE(4096, false),

    // Set if there is composition string.
    // TODO(matsuzakit): Implement me. This is mandatory when implementing ACTION_*.
    COMPOSING(8192, false),
    ;

    private final int bitFlag;

    /**
     * If this flag is set to {@code true}, the flag should be removed from the meta states
     * when a user type a key under this state.
     */
    final boolean isOneTimeMetaState;

    private MetaState(int bitFlag, boolean isOneTimeMetaState) {
      this.bitFlag = bitFlag;
      this.isOneTimeMetaState = isOneTimeMetaState;
    }

    public static MetaState valueOf(int bitFlag) {
      for (MetaState metaState : values()) {
        if (metaState.bitFlag == bitFlag) {
          return metaState;
        }
      }
      throw new IllegalArgumentException("Corresponding MetaState is not found: " + bitFlag);
    }

    // MetaStates for character type.
    public static final Set<MetaState> CHAR_TYPE_EXCLUSIVE_GROUP =
        Sets.immutableEnumSet(MetaState.SHIFT, MetaState.CAPS_LOCK, MetaState.ALT);
    // MetaStates for actions.
    public static final Set<MetaState> ACTION_EXCLUSIVE_GROUP =
        Sets.immutableEnumSet(EnumSet.range(MetaState.ACTION_DONE, MetaState.ACTION_SEND));
    // MetaStates for text variations.
    public static final Set<MetaState> VARIATION_EXCLUSIVE_GROUP =
        Sets.immutableEnumSet(MetaState.VARIATION_URI, MetaState.VARIATION_EMAIL_ADDRESS);
    @SuppressWarnings("unchecked")
    private static final Collection<Set<MetaState>> EXCLUSIVE_GROUP =
        Arrays.<Set<MetaState>>asList(CHAR_TYPE_EXCLUSIVE_GROUP,
                                      ACTION_EXCLUSIVE_GROUP,
                                      VARIATION_EXCLUSIVE_GROUP);

    /**
     * Checks if {@code testee} is valid set.
     * <p>
     * Note that this check might be a little bit heavy.
     * Do not call from chokepoint.
     */
    public static boolean isValidSet(Set<MetaState> testee) {
      // Set#retainAll can make the implementation simpler, but it requires instantiation of
      // (Enum)Set for each iteration.
      for (Set<MetaState> exclusiveGroup : EXCLUSIVE_GROUP) {
        int count = 0;
        for (MetaState metaState : exclusiveGroup) {
          if (testee.contains(metaState)) {
            ++count;
            if (count >= 2) {
              return false;
            }
          }
        }
      }
      return true;
    }
  }

  private final String contentDescription;
  private final Set<MetaState> metaState;
  private final Set<MetaState> nextAddMetaStates;
  private final Set<MetaState> nextRemoveMetaStates;
  private final EnumMap<Flick.Direction, Flick> flickMap;

  public KeyState(String contentDescription,
                  Set<MetaState> metaStates,
                  Set<MetaState> nextAddMetaStates,
                  Set<MetaState> nextRemoveMetaStates,
                  Collection<? extends Flick> flickCollection) {
    this.contentDescription = Preconditions.checkNotNull(contentDescription);
    Preconditions.checkNotNull(metaStates);
    this.metaState = Sets.newEnumSet(metaStates, MetaState.class);
    this.nextAddMetaStates = nextAddMetaStates;
    this.nextRemoveMetaStates = nextRemoveMetaStates;
    this.flickMap = new EnumMap<Flick.Direction, Flick>(Flick.Direction.class);
    for (Flick flick : flickCollection) {
      if (this.flickMap.put(flick.getDirection(), flick) != null) {
        throw new IllegalArgumentException(
            "Duplicate flick direction is found: " + flick.getDirection());
      }
    }
  }

  public String getContentDescription() {
    return contentDescription;
  }

  public Set<MetaState> getMetaStateSet() {
    return metaState;
  }

  /**
   * Gets next MetaState.
   * <p>
   * First, flags in {@code nextRemoveMetaState} are removed from {@code originalMetaState}.
   * Then, flags in {@code nextAddMetaState} are added into {@code originalMetaState}.
   * <p>
   * The result is "valid" in the light of {@code MetaState#isValidSet(Set)}.
   */
  public Set<MetaState> getNextMetaStates(Set<MetaState> originalMetaStates) {
    return Sets.union(Sets.difference(originalMetaStates,
                                      nextRemoveMetaStates), nextAddMetaStates).immutableCopy();
  }

  public Flick getFlick(Flick.Direction direction) {
    return flickMap.get(direction);
  }

  @Override
  public String toString() {
    Objects.ToStringHelper helper = Objects.toStringHelper(this);
    helper.add("metaStates", metaState.toString());
    for (Map.Entry<Flick.Direction, Flick> entry : flickMap.entrySet()) {
      helper.add("flickMap(" + entry.getKey().toString() + ")", entry.getValue().toString());
    }
    return helper.toString();
  }
}