/*
 * Copyright (C) 2022 The Android Open Source Project
 *
 * 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 android.view.inputmethod;

import android.annotation.IntDef;
import android.annotation.NonNull;
import android.annotation.Nullable;
import android.annotation.TestApi;
import android.graphics.RectF;
import android.inputmethodservice.InputMethodService;
import android.os.CancellationSignal;
import android.os.Parcel;
import android.os.Parcelable;
import android.view.MotionEvent;

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.util.List;
import java.util.concurrent.Executor;
import java.util.function.IntConsumer;

/**
 * Base class for stylus handwriting gestures.
 * <p>
 * During a stylus handwriting session, user can perform a stylus gesture operation like
 * {@link SelectGesture}, {@link DeleteGesture}, {@link InsertGesture} on an
 * area of text. IME is responsible for listening to stylus {@link MotionEvent}s using
 * {@link InputMethodService#onStylusHandwritingMotionEvent} and interpret if it can translate to a
 * gesture operation.
 * <p>
 * While creating gesture operations {@link SelectGesture} and {@link DeleteGesture},
 * {@code Granularity} helps pick the correct granular level of text like word level
 * {@link #GRANULARITY_WORD}, or character level {@link #GRANULARITY_CHARACTER}.
 *
 * @see InputConnection#performHandwritingGesture(HandwritingGesture, Executor, IntConsumer)
 * @see InputConnection#previewHandwritingGesture(PreviewableHandwritingGesture, CancellationSignal)
 * @see InputMethodService#onStartStylusHandwriting()
 */
public abstract class HandwritingGesture {

    HandwritingGesture() {}

    static final int GRANULARITY_UNDEFINED = 0;

    /**
     * Operate text per word basis. e.g. if selection includes width-wise center of the word,
     * whole word is selected.
     * <p> Strategy of operating at a granular level is maintained in the UI toolkit.
     *     A character/word/line is included if its center is within the gesture rectangle.
     *     e.g. if a selection {@link RectF} with {@link #GRANULARITY_WORD} includes width-wise
     *     center of the word, it should be selected.
     *     Similarly, text in a line should be included in the operation if rectangle includes
     *     line height center.</p>
     * Refer to https://www.unicode.org/reports/tr29/#Word_Boundaries for more detail on how word
     * breaks are decided.
     */
    public static final int GRANULARITY_WORD = 1;

    /**
     * Operate on text per character basis. i.e. each character is selected based on its
     * intersection with selection rectangle.
     * <p> Strategy of operating at a granular level is maintained in the UI toolkit.
     *     A character/word/line is included if its center is within the gesture rectangle.
     *     e.g. if a selection {@link RectF} with {@link #GRANULARITY_CHARACTER} includes width-wise
     *     center of the character, it should be selected.
     *     Similarly, text in a line should be included in the operation if rectangle includes
     *     line height center.</p>
     */
    public static final int GRANULARITY_CHARACTER = 2;

    /**
     * Granular level on which text should be operated.
     */
    @IntDef({GRANULARITY_CHARACTER, GRANULARITY_WORD})
    @Retention(RetentionPolicy.SOURCE)
    @interface Granularity {}

    /**
     * Undefined gesture type.
     * @hide
     */
    @TestApi
    public static final int GESTURE_TYPE_NONE = 0x0000;

    /**
     * Gesture of type {@link SelectGesture} to select an area of text.
     * @hide
     */
    @TestApi
    public static final int GESTURE_TYPE_SELECT = 0x0001;

    /**
     * Gesture of type {@link InsertGesture} to insert text at a designated point.
     * @hide
     */
    @TestApi
    public static final int GESTURE_TYPE_INSERT = 1 << 1;

    /**
     * Gesture of type {@link DeleteGesture} to delete an area of text.
     * @hide
     */
    @TestApi
    public static final int GESTURE_TYPE_DELETE = 1 << 2;

    /**
     * Gesture of type {@link RemoveSpaceGesture} to remove whitespace from text.
     * @hide
     */
    @TestApi
    public static final int GESTURE_TYPE_REMOVE_SPACE = 1 << 3;

    /**
     * Gesture of type {@link JoinOrSplitGesture} to join or split text.
     * @hide
     */
    @TestApi
    public static final int GESTURE_TYPE_JOIN_OR_SPLIT = 1 << 4;

    /**
     * Gesture of type {@link SelectRangeGesture} to select range of text.
     * @hide
     */
    @TestApi
    public static final int GESTURE_TYPE_SELECT_RANGE = 1 << 5;

    /**
     * Gesture of type {@link DeleteRangeGesture} to delete range of text.
     * @hide
     */
    @TestApi
    public static final int GESTURE_TYPE_DELETE_RANGE = 1 << 6;

    /**
     * Gesture of type {@link InsertModeGesture} to begin an insert mode at a designated point.
     * @hide
     */
    @TestApi
    public static final int GESTURE_TYPE_INSERT_MODE = 1 << 7;

    /**
     * Type of gesture like {@link #GESTURE_TYPE_SELECT}, {@link #GESTURE_TYPE_INSERT},
     * or {@link #GESTURE_TYPE_DELETE}.
     */
    @IntDef(prefix = {"GESTURE_TYPE_"}, value = {
            GESTURE_TYPE_NONE,
            GESTURE_TYPE_SELECT,
            GESTURE_TYPE_SELECT_RANGE,
            GESTURE_TYPE_INSERT,
            GESTURE_TYPE_INSERT_MODE,
            GESTURE_TYPE_DELETE,
            GESTURE_TYPE_DELETE_RANGE,
            GESTURE_TYPE_REMOVE_SPACE,
            GESTURE_TYPE_JOIN_OR_SPLIT})
    @Retention(RetentionPolicy.SOURCE)
    @interface GestureType{}

    /**
     * Flags which can be any combination of {@link #GESTURE_TYPE_SELECT},
     * {@link #GESTURE_TYPE_INSERT}, or {@link #GESTURE_TYPE_DELETE}.
     * {@link GestureTypeFlags} can be used by editors to declare what gestures are supported
     *  and report them in {@link EditorInfo#setSupportedHandwritingGestures(List)}.
     * @hide
     */
    @IntDef(flag = true, prefix = {"GESTURE_TYPE_"}, value = {
            GESTURE_TYPE_SELECT,
            GESTURE_TYPE_SELECT_RANGE,
            GESTURE_TYPE_INSERT,
            GESTURE_TYPE_INSERT_MODE,
            GESTURE_TYPE_DELETE,
            GESTURE_TYPE_DELETE_RANGE,
            GESTURE_TYPE_REMOVE_SPACE,
            GESTURE_TYPE_JOIN_OR_SPLIT})
    @Retention(RetentionPolicy.SOURCE)
    public @interface GestureTypeFlags{}

    @GestureType int mType = GESTURE_TYPE_NONE;

    /**
     * Returns the gesture type {@link GestureType}.
     * {@link GestureType} can be used by editors to declare what gestures are supported and report
     * them in {@link EditorInfo#setSupportedHandwritingGestures(List)}.
     * @hide
     */
    @TestApi
    public final @GestureType int getGestureType() {
        return mType;
    }

    @Nullable
    String mFallbackText;

    /**
     * The fallback text that will be committed at current cursor position if there is no applicable
     * text beneath the area of gesture.
     * For example, select can fail if gesture is drawn over area that has no text beneath.
     * example 2: join can fail if the gesture is drawn over text but there is no whitespace.
     */
    @Nullable
    public final String getFallbackText() {
        return mFallbackText;
    }

    /**
     * Dump data into a byte array so that you can pass the data across process boundary.
     *
     * @return byte array data.
     * @see #fromByteArray(byte[])
     * @hide
     */
    @TestApi
    @NonNull
    public final byte[] toByteArray() {
        if (!(this instanceof Parcelable)) {
            throw new UnsupportedOperationException(getClass() + " is not Parcelable");
        }
        final Parcelable self = (Parcelable) this;
        if ((self.describeContents() & Parcelable.CONTENTS_FILE_DESCRIPTOR) != 0) {
            throw new UnsupportedOperationException("Gesture that contains FD is not supported");
        }
        Parcel parcel = null;
        try {
            parcel = Parcel.obtain();
            ParcelableHandwritingGesture.of(this).writeToParcel(parcel, 0);
            return parcel.marshall();
        } finally {
            if (parcel != null) {
                parcel.recycle();
            }
        }
    }

    /**
     * Create a new instance from byte array obtained from {@link #toByteArray()}.
     *
     * @param buffer byte array obtained from {@link #toByteArray()}
     * @return A new instance of {@link HandwritingGesture} subclass.
     * @hide
     */
    @TestApi
    @NonNull
    public static HandwritingGesture fromByteArray(@NonNull byte[] buffer) {
        Parcel parcel = null;
        try {
            parcel = Parcel.obtain();
            parcel.unmarshall(buffer, 0, buffer.length);
            parcel.setDataPosition(0);
            return ParcelableHandwritingGesture.CREATOR.createFromParcel(parcel).get();
        } finally {
            if (parcel != null) {
                parcel.recycle();
            }
        }
    }
}