/*
 * Copyright 2021 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 androidx.camera.camera2.internal;

import android.content.Context;
import android.graphics.Point;
import android.hardware.display.DisplayManager;
import android.util.Size;
import android.view.Display;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.annotation.VisibleForTesting;
import androidx.camera.camera2.internal.compat.workaround.DisplaySizeCorrector;
import androidx.camera.camera2.internal.compat.workaround.MaxPreviewSize;
import androidx.camera.core.internal.utils.SizeUtil;

/**
 * A singleton class to retrieve display related information.
 */
public class DisplayInfoManager {
    private static final Size MAX_PREVIEW_SIZE = new Size(1920, 1080);
    /**
     * This is the smallest size from a device which had issue reported to CameraX.
     */
    private static final Size ABNORMAL_DISPLAY_SIZE_THRESHOLD = new Size(320, 240);
    /**
     * The fallback display size for the case that the retrieved display size is abnormally small
     * and no correct display size can be retrieved from DisplaySizeCorrector.
     */
    private static final Size FALLBACK_DISPLAY_SIZE = new Size(640, 480);
    private static final Object INSTANCE_LOCK = new Object();
    private static volatile DisplayInfoManager sInstance;
    @NonNull
    private final DisplayManager mDisplayManager;
    private volatile Size mPreviewSize = null;
    private final MaxPreviewSize mMaxPreviewSize = new MaxPreviewSize();
    private final DisplaySizeCorrector mDisplaySizeCorrector = new DisplaySizeCorrector();

    private DisplayInfoManager(@NonNull Context context) {
        mDisplayManager = (DisplayManager) context.getSystemService(Context.DISPLAY_SERVICE);
    }

    /**
     * Gets the singleton instance of DisplayInfoManager.
     */
    @NonNull
    public static DisplayInfoManager getInstance(@NonNull Context context) {
        if (sInstance == null) {
            synchronized (INSTANCE_LOCK) {
                if (sInstance == null) {
                    sInstance = new DisplayInfoManager(context);
                }
            }
        }
        return sInstance;
    }

    /**
     * Test purpose only. To release the instance so that the test can create a new instance.
     */
    @VisibleForTesting
    static void releaseInstance() {
        sInstance = null;
    }

    /**
     * Update the preview size according to current display size.
     */
    void refresh() {
        mPreviewSize = calculatePreviewSize();
    }

    /**
     * Retrieves the display which has the max size among all displays.
     *
     * @param skipStateOffDisplay true to skip the displays with off state
     */
    @NonNull
    public Display getMaxSizeDisplay(boolean skipStateOffDisplay) {
        Display[] displays = mDisplayManager.getDisplays();
        if (displays.length == 1) {
            return displays[0];
        }

        // Try to find the max size display according to the skipStateOffDisplay parameter
        Display maxDisplay = getMaxSizeDisplayInternal(displays, skipStateOffDisplay);

        // Try to find the max size display from all displays again if no display can be found
        // when only checking the non-state-off displays.
        if (maxDisplay == null && skipStateOffDisplay) {
            maxDisplay = getMaxSizeDisplayInternal(displays, false);
        }

        // If still no display found, throw IllegalArgumentException.
        if (maxDisplay == null) {
            throw new IllegalArgumentException("No display can be found from the input display "
                    + "manager!");
        }

        return maxDisplay;
    }

    @Nullable
    @SuppressWarnings("deprecation") /* getRealSize */
    private Display getMaxSizeDisplayInternal(@NonNull Display[] displays,
            boolean skipStateOffDisplay) {
        Display maxDisplay = null;
        int maxDisplaySize = -1;

        for (Display display : displays) {
            // Skips displays with state off if the input skipStateOffDisplay parameter is true
            if (skipStateOffDisplay && display.getState() == Display.STATE_OFF) {
                continue;
            }

            Point displaySize = new Point();
            display.getRealSize(displaySize);
            if (displaySize.x * displaySize.y > maxDisplaySize) {
                maxDisplaySize = displaySize.x * displaySize.y;
                maxDisplay = display;
            }
        }

        return maxDisplay;
    }

    /**
     * PREVIEW refers to the best size match to the device's screen resolution, or to 1080p
     * (1920x1080), whichever is smaller.
     */
    @NonNull
    Size getPreviewSize() {
        // Use cached value to speed up since this would be called multiple times.
        if (mPreviewSize != null) {
            return mPreviewSize;
        }

        mPreviewSize = calculatePreviewSize();
        return mPreviewSize;
    }

    private Size calculatePreviewSize() {
        Size displayViewSize = getCorrectedDisplaySize();
        if (displayViewSize.getWidth() * displayViewSize.getHeight()
                > MAX_PREVIEW_SIZE.getWidth() * MAX_PREVIEW_SIZE.getHeight()) {
            displayViewSize = MAX_PREVIEW_SIZE;
        }
        return mMaxPreviewSize.getMaxPreviewResolution(displayViewSize);
    }

    @NonNull
    @SuppressWarnings("deprecation") /* getRealSize */
    private Size getCorrectedDisplaySize() {
        Point displaySize = new Point();
        // The PREVIEW size should be determined by the max display size among all displays on
        // the device no matter its state is on or off. The PREVIEW size is used for the
        // guaranteed configurations tables which are related to the camera's capability. The
        // PREVIEW size should not be affected by the display state.
        Display display = getMaxSizeDisplay(false);
        display.getRealSize(displaySize);
        Size displayViewSize = new Size(displaySize.x, displaySize.y);

        // Checks whether the display size is abnormally small.
        if (SizeUtil.isSmallerByArea(displayViewSize, ABNORMAL_DISPLAY_SIZE_THRESHOLD)) {
            // Gets the display size from DisplaySizeCorrector if the display size retrieved from
            // DisplayManager is abnormally small.
            displayViewSize = mDisplaySizeCorrector.getDisplaySize();

            // Falls back the display size to 640x480 if DisplaySizeCorrector doesn't contain the
            // device's display size info.
            if (displayViewSize == null) {
                displayViewSize = FALLBACK_DISPLAY_SIZE;
            }
        }

        // Flips the size to landscape orientation
        if (displayViewSize.getHeight() > displayViewSize.getWidth()) {
            displayViewSize = new Size(/* width= */ displayViewSize.getHeight(), /* height=
            */ displayViewSize.getWidth());
        }

        return displayViewSize;
    }
}