/*
 * Copyright 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 androidx.camera.core.processing;

import static androidx.camera.core.ImageProcessingUtil.writeJpegBytesToSurface;
import static androidx.camera.core.impl.ImageFormatConstants.INTERNAL_DEFINED_IMAGE_FORMAT_PRIVATE;
import static androidx.camera.core.impl.utils.TransformUtils.rotateSize;
import static androidx.core.util.Preconditions.checkState;

import static java.util.Objects.requireNonNull;

import android.graphics.Bitmap;
import android.graphics.ImageFormat;
import android.graphics.SurfaceTexture;
import android.os.Handler;
import android.os.HandlerThread;
import android.util.Size;
import android.view.Surface;

import androidx.annotation.IntRange;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.annotation.RequiresApi;
import androidx.annotation.VisibleForTesting;
import androidx.annotation.WorkerThread;
import androidx.arch.core.util.Function;
import androidx.camera.core.DynamicRange;
import androidx.camera.core.Logger;
import androidx.camera.core.SurfaceOutput;
import androidx.camera.core.SurfaceProcessor;
import androidx.camera.core.SurfaceRequest;
import androidx.camera.core.impl.utils.MatrixExt;
import androidx.camera.core.impl.utils.executor.CameraXExecutors;
import androidx.camera.core.impl.utils.futures.Futures;
import androidx.concurrent.futures.CallbackToFutureAdapter;

import com.google.auto.value.AutoValue;
import com.google.common.util.concurrent.ListenableFuture;

import kotlin.Triple;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Executor;
import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.atomic.AtomicBoolean;

/**
 * A default implementation of {@link SurfaceProcessor}.
 *
 * <p> This implementation simply copies the frame from the source to the destination with the
 * transformation defined in {@link SurfaceOutput#updateTransformMatrix}.
 */
@RequiresApi(21)
public class DefaultSurfaceProcessor implements SurfaceProcessorInternal,
        SurfaceTexture.OnFrameAvailableListener {
    private static final String TAG = "DefaultSurfaceProcessor";

    private final OpenGlRenderer mGlRenderer;
    @VisibleForTesting
    final HandlerThread mGlThread;
    private final Executor mGlExecutor;
    @VisibleForTesting
    final Handler mGlHandler;
    private final AtomicBoolean mIsReleaseRequested = new AtomicBoolean(false);
    private final float[] mTextureMatrix = new float[16];
    private final float[] mSurfaceOutputMatrix = new float[16];
    // Map of current set of available outputs. Only access this on GL thread.
    @SuppressWarnings("WeakerAccess") /* synthetic access */
    final Map<SurfaceOutput, Surface> mOutputSurfaces = new LinkedHashMap<>();

    // Only access this on GL thread.
    private int mInputSurfaceCount = 0;
    // Only access this on GL thread.
    private boolean mIsReleased = false;
    // Only access this on GL thread.
    private final List<PendingSnapshot> mPendingSnapshots = new ArrayList<>();

    /** Constructs {@link DefaultSurfaceProcessor} with default shaders. */
    DefaultSurfaceProcessor(@NonNull DynamicRange dynamicRange) {
        this(dynamicRange, ShaderProvider.DEFAULT);
    }

    /**
     * Constructs {@link DefaultSurfaceProcessor} with custom shaders.
     *
     * @param shaderProvider custom shader provider for OpenGL rendering.
     * @throws IllegalArgumentException if the shaderProvider provides invalid shader.
     */
    DefaultSurfaceProcessor(@NonNull DynamicRange dynamicRange,
            @NonNull ShaderProvider shaderProvider) {
        mGlThread = new HandlerThread("GL Thread");
        mGlThread.start();
        mGlHandler = new Handler(mGlThread.getLooper());
        mGlExecutor = CameraXExecutors.newHandlerExecutor(mGlHandler);
        mGlRenderer = new OpenGlRenderer();
        try {
            initGlRenderer(dynamicRange, shaderProvider);
        } catch (RuntimeException e) {
            release();
            throw e;
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void onInputSurface(@NonNull SurfaceRequest surfaceRequest) {
        if (mIsReleaseRequested.get()) {
            surfaceRequest.willNotProvideSurface();
            return;
        }
        executeSafely(() -> {
            mInputSurfaceCount++;
            SurfaceTexture surfaceTexture = new SurfaceTexture(mGlRenderer.getTextureName());
            surfaceTexture.setDefaultBufferSize(surfaceRequest.getResolution().getWidth(),
                    surfaceRequest.getResolution().getHeight());
            Surface surface = new Surface(surfaceTexture);
            surfaceRequest.provideSurface(surface, mGlExecutor, result -> {
                surfaceTexture.setOnFrameAvailableListener(null);
                surfaceTexture.release();
                surface.release();
                mInputSurfaceCount--;
                checkReadyToRelease();
            });
            surfaceTexture.setOnFrameAvailableListener(this, mGlHandler);
        }, surfaceRequest::willNotProvideSurface);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void onOutputSurface(@NonNull SurfaceOutput surfaceOutput) {
        if (mIsReleaseRequested.get()) {
            surfaceOutput.close();
            return;
        }
        executeSafely(() -> {
            Surface surface = surfaceOutput.getSurface(mGlExecutor, event -> {
                surfaceOutput.close();
                Surface removedSurface = mOutputSurfaces.remove(surfaceOutput);
                if (removedSurface != null) {
                    mGlRenderer.unregisterOutputSurface(removedSurface);
                }
            });
            mGlRenderer.registerOutputSurface(surface);
            mOutputSurfaces.put(surfaceOutput, surface);
        }, surfaceOutput::close);
    }

    /**
     * Release the {@link DefaultSurfaceProcessor}.
     */
    @Override
    public void release() {
        if (mIsReleaseRequested.getAndSet(true)) {
            return;
        }
        executeSafely(() -> {
            mIsReleased = true;
            checkReadyToRelease();
        });
    }

    @Override
    @NonNull
    public ListenableFuture<Void> snapshot(
            @IntRange(from = 0, to = 100) int jpegQuality,
            @IntRange(from = 0, to = 359) int rotationDegrees) {
        return Futures.nonCancellationPropagating(CallbackToFutureAdapter.getFuture(
                completer -> {
                    PendingSnapshot pendingSnapshot = PendingSnapshot.of(jpegQuality,
                            rotationDegrees, completer);
                    executeSafely(
                            () -> mPendingSnapshots.add(pendingSnapshot),
                            () -> completer.setException(new Exception(
                                    "Failed to snapshot: OpenGLRenderer not ready.")));
                    return "DefaultSurfaceProcessor#snapshot";
                }));
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void onFrameAvailable(@NonNull SurfaceTexture surfaceTexture) {
        if (mIsReleaseRequested.get()) {
            // Ignore frame update if released.
            return;
        }
        surfaceTexture.updateTexImage();
        surfaceTexture.getTransformMatrix(mTextureMatrix);
        // Surface, size and transform matrix for JPEG Surface if exists
        Triple<Surface, Size, float[]> jpegOutput = null;

        for (Map.Entry<SurfaceOutput, Surface> entry : mOutputSurfaces.entrySet()) {
            Surface surface = entry.getValue();
            SurfaceOutput surfaceOutput = entry.getKey();
            surfaceOutput.updateTransformMatrix(mSurfaceOutputMatrix, mTextureMatrix);
            if (surfaceOutput.getFormat() == INTERNAL_DEFINED_IMAGE_FORMAT_PRIVATE) {
                // Render GPU output directly.
                try {
                    mGlRenderer.render(surfaceTexture.getTimestamp(), mSurfaceOutputMatrix,
                            surface);
                } catch (RuntimeException e) {
                    // This should not happen. However, when it happens, we catch the exception
                    // to prevent the crash.
                    Logger.e(TAG, "Failed to render with OpenGL.", e);
                }
            } else {
                checkState(surfaceOutput.getFormat() == ImageFormat.JPEG,
                        "Unsupported format: " + surfaceOutput.getFormat());
                checkState(jpegOutput == null, "Only one JPEG output is supported.");
                jpegOutput = new Triple<>(surface, surfaceOutput.getSize(),
                        mSurfaceOutputMatrix.clone());
            }
        }

        // Execute all pending snapshots.
        try {
            takeSnapshotAndDrawJpeg(jpegOutput);
        } catch (RuntimeException e) {
            // Propagates error back to the app if failed to take snapshot.
            failAllPendingSnapshots(e);
        }
    }

    /**
     * Takes a snapshot of the current frame and draws it to given JPEG surface.
     *
     * @param jpegOutput The <Surface, Surface size, transform matrix> tuple for drawing.
     */
    @WorkerThread
    private void takeSnapshotAndDrawJpeg(@Nullable Triple<Surface, Size, float[]> jpegOutput) {
        if (mPendingSnapshots.isEmpty()) {
            // No pending snapshot requests, do nothing.
            return;
        }

        // No JPEG Surface, fail all snapshot requests.
        if (jpegOutput == null) {
            failAllPendingSnapshots(new Exception("Failed to snapshot: no JPEG Surface."));
            return;
        }

        // Write to JPEG surface, once for each snapshot request.
        try (ByteArrayOutputStream outputStream = new ByteArrayOutputStream()) {
            byte[] jpegBytes = null;
            int jpegQuality = -1;
            int rotationDegrees = -1;
            Bitmap bitmap = null;
            Iterator<PendingSnapshot> iterator = mPendingSnapshots.iterator();
            while (iterator.hasNext()) {
                PendingSnapshot pendingSnapshot = iterator.next();
                // Take a new snapshot if the rotation is different.
                if (rotationDegrees != pendingSnapshot.getRotationDegrees() || bitmap == null) {
                    rotationDegrees = pendingSnapshot.getRotationDegrees();
                    // Recycle the previous bitmap to free up memory.
                    if (bitmap != null) {
                        bitmap.recycle();
                    }
                    bitmap = getBitmap(jpegOutput.getSecond(), jpegOutput.getThird(),
                            rotationDegrees);
                    // Clear JPEG quality to force re-encoding.
                    jpegQuality = -1;
                }
                // Re-encode the bitmap if the quality is different.
                if (jpegQuality != pendingSnapshot.getJpegQuality()) {
                    outputStream.reset();
                    jpegQuality = pendingSnapshot.getJpegQuality();
                    bitmap.compress(Bitmap.CompressFormat.JPEG, jpegQuality, outputStream);
                    jpegBytes = outputStream.toByteArray();
                }
                writeJpegBytesToSurface(jpegOutput.getFirst(), requireNonNull(jpegBytes));
                pendingSnapshot.getCompleter().set(null);
                iterator.remove();
            }
        } catch (IOException e) {
            failAllPendingSnapshots(e);
        }
    }

    private void failAllPendingSnapshots(@NonNull Throwable throwable) {
        for (PendingSnapshot pendingSnapshot : mPendingSnapshots) {
            pendingSnapshot.getCompleter().setException(throwable);
        }
        mPendingSnapshots.clear();
    }

    @NonNull
    private Bitmap getBitmap(@NonNull Size size,
            @NonNull float[] textureTransform,
            int rotationDegrees) {
        float[] snapshotTransform = textureTransform.clone();

        // Rotate the output if requested.
        MatrixExt.preRotate(snapshotTransform, rotationDegrees, 0.5f, 0.5f);

        // Flip the snapshot. This is for reverting the GL transform added in SurfaceOutputImpl.
        MatrixExt.preVerticalFlip(snapshotTransform, 0.5f);

        // Update the size based on the rotation degrees.
        size = rotateSize(size, rotationDegrees);

        // Take a snapshot Bitmap and compress it to JPEG.
        return mGlRenderer.snapshot(size, snapshotTransform);
    }

    @WorkerThread
    private void checkReadyToRelease() {
        if (mIsReleased && mInputSurfaceCount == 0) {
            // Once release is called, we can stop sending frame to output surfaces.
            for (SurfaceOutput surfaceOutput : mOutputSurfaces.keySet()) {
                surfaceOutput.close();
            }
            for (PendingSnapshot pendingSnapshot : mPendingSnapshots) {
                pendingSnapshot.getCompleter().setException(
                        new Exception("Failed to snapshot: DefaultSurfaceProcessor is released."));
            }
            mOutputSurfaces.clear();
            mGlRenderer.release();
            mGlThread.quit();
        }
    }

    private void initGlRenderer(@NonNull DynamicRange dynamicRange,
            @NonNull ShaderProvider shaderProvider) {
        ListenableFuture<Void> initFuture = CallbackToFutureAdapter.getFuture(completer -> {
            executeSafely(() -> {
                try {
                    mGlRenderer.init(dynamicRange, shaderProvider);
                    completer.set(null);
                } catch (RuntimeException e) {
                    completer.setException(e);
                }
            });
            return "Init GlRenderer";
        });
        try {
            initFuture.get();
        } catch (ExecutionException | InterruptedException e) {
            // If the cause is a runtime exception, throw it directly. Otherwise convert to runtime
            // exception and throw.
            Throwable cause = e instanceof ExecutionException ? e.getCause() : e;
            if (cause instanceof RuntimeException) {
                throw (RuntimeException) cause;
            } else {
                throw new IllegalStateException("Failed to create DefaultSurfaceProcessor", cause);
            }
        }
    }

    private void executeSafely(@NonNull Runnable runnable) {
        executeSafely(runnable, () -> {
            // Do nothing.
        });
    }

    private void executeSafely(@NonNull Runnable runnable, @NonNull Runnable onFailure) {
        try {
            mGlExecutor.execute(() -> {
                if (mIsReleased) {
                    onFailure.run();
                } else {
                    runnable.run();
                }
            });
        } catch (RejectedExecutionException e) {
            Logger.w(TAG, "Unable to executor runnable", e);
            onFailure.run();
        }
    }

    /**
     * A pending snapshot request to be executed on the next frame available.
     */
    @AutoValue
    abstract static class PendingSnapshot {

        @IntRange(from = 0, to = 100)
        abstract int getJpegQuality();

        @IntRange(from = 0, to = 359)
        abstract int getRotationDegrees();

        @NonNull
        abstract CallbackToFutureAdapter.Completer<Void> getCompleter();

        @NonNull
        static AutoValue_DefaultSurfaceProcessor_PendingSnapshot of(
                @IntRange(from = 0, to = 100) int jpegQuality,
                @IntRange(from = 0, to = 359) int rotationDegrees,
                @NonNull CallbackToFutureAdapter.Completer<Void> completer) {
            return new AutoValue_DefaultSurfaceProcessor_PendingSnapshot(
                    jpegQuality, rotationDegrees, completer);
        }
    }

    /**
     * Factory class that produces {@link DefaultSurfaceProcessor}.
     *
     * <p> This is for working around the limit that OpenGL cannot be initialized in unit tests.
     */
    public static class Factory {
        private Factory() {
        }

        private static Function<DynamicRange, SurfaceProcessorInternal> sSupplier =
                DefaultSurfaceProcessor::new;

        /**
         * Creates a new {@link DefaultSurfaceProcessor} with no-op shader.
         */
        @NonNull
        public static SurfaceProcessorInternal newInstance(@NonNull DynamicRange dynamicRange) {
            return sSupplier.apply(dynamicRange);
        }

        /**
         * Overrides the {@link DefaultSurfaceProcessor} supplier for testing.
         */
        @VisibleForTesting
        public static void setSupplier(
                @NonNull Function<DynamicRange, SurfaceProcessorInternal> supplier) {
            sSupplier = supplier;
        }
    }
}