/*
 * Copyright (C) 2017 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 com.android.tv.twopanelsettings.slices.base;

import android.app.PendingIntent;
import android.app.slice.Slice;
import android.app.slice.SliceSpec;
import android.content.ContentProvider;
import android.content.ContentResolver;
import android.content.ContentValues;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.content.pm.ProviderInfo;
import android.database.ContentObserver;
import android.database.Cursor;
import android.net.Uri;
import android.os.Binder;
import android.os.Bundle;
import android.os.CancellationSignal;
import android.os.Handler;
import android.os.Looper;
import android.os.Parcelable;
import android.os.Process;
import android.os.StrictMode;
import android.os.StrictMode.ThreadPolicy;
import android.util.ArraySet;
import android.util.Log;
import androidx.annotation.NonNull;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Set;

/**
 * A SliceProvider allows an app to provide content to be displayed in system spaces. This content
 * is templated and can contain actions, and the behavior of how it is surfaced is specific to the
 * system surface.
 *
 * <p>Slices are not currently live content. They are bound once and shown to the user. If the
 * content changes due to a callback from user interaction, then {@link
 * ContentResolver#notifyChange(Uri, ContentObserver)} should be used to notify the system.
 *
 * <p>The provider needs to be declared in the manifest to provide the authority for the app. The
 * authority for most slices is expected to match the package of the application.
 *
 * <pre class="prettyprint">
 * {@literal
 * <provider
 *     android:name="com.example.mypkg.MySliceProvider"
 *     android:authorities="com.example.mypkg" />}
 * </pre>
 *
 * <p>Slices can be identified by a Uri or by an Intent. To link an Intent with a slice, the
 * provider must have an {@link IntentFilter} matching the slice intent. When a slice is being
 * requested via an intent, {@link #onMapIntentToUri(Intent)} can be called and is expected to
 * return an appropriate Uri representing the slice.
 *
 * <pre class="prettyprint">
 * {@literal
 * <provider
 *     android:name="com.example.mypkg.MySliceProvider"
 *     android:authorities="com.example.mypkg">
 *     <intent-filter>
 *         <action android:name="com.example.mypkg.intent.action.MY_SLICE_INTENT" />
 *         <category android:name="android.app.slice.category.SLICE" />
 *     </intent-filter>
 * </provider>}
 * </pre>
 *
 * @see Slice
 */
public abstract class SliceProvider extends ContentProvider {
  /**
   * This is the Android platform's MIME type for a URI containing a slice implemented through
   * {@link SliceProvider}.
   */
  public static final String SLICE_TYPE = "vnd.android.slice";

  private static final String TAG = "SliceProvider";
  public static final String EXTRA_BIND_URI = "slice_uri";
  public static final String EXTRA_SUPPORTED_SPECS = "supported_specs";
  public static final String METHOD_SLICE = "bind_slice";
  public static final String METHOD_MAP_INTENT = "map_slice";
  public static final String METHOD_MAP_ONLY_INTENT = "map_only";
  public static final String METHOD_PIN = "pin";
  public static final String METHOD_UNPIN = "unpin";
  public static final String METHOD_GET_DESCENDANTS = "get_descendants";
  public static final String METHOD_GET_PERMISSIONS = "get_permissions";
  public static final String EXTRA_INTENT = "slice_intent";
  public static final String EXTRA_SLICE = "slice";
  public static final String EXTRA_SLICE_DESCENDANTS = "slice_descendants";
  public static final String EXTRA_PKG = "pkg";
  public static final String EXTRA_RESULT = "result";

  private static final boolean DEBUG = false;

  private static final long SLICE_BIND_ANR = 2000;
  private static final Handler sMainHandler = new Handler(Looper.getMainLooper());
  private final String[] mAutoGrantPermissions;

  private String mCallback;
  private SliceManager mSliceManager;

  /**
   * A version of constructing a SliceProvider that allows autogranting slice permissions to apps
   * that hold specific platform permissions.
   *
   * <p>When an app tries to bind a slice from this provider that it does not have access to, This
   * provider will check if the caller holds permissions to any of the autoGrantPermissions
   * specified, if they do they will be granted persisted uri access to all slices of this provider.
   *
   * @param autoGrantPermissions List of permissions that holders are auto-granted access to slices.
   */
  public SliceProvider(@NonNull String... autoGrantPermissions) {
    mAutoGrantPermissions = autoGrantPermissions;
  }

  public SliceProvider() {
    mAutoGrantPermissions = new String[0];
  }

  @Override
  public void attachInfo(Context context, ProviderInfo info) {
    super.attachInfo(context, info);
    mSliceManager = SliceManager.from(context);
  }

  /**
   * Implemented to create a slice.
   *
   * <p>onBindSlice should return as quickly as possible so that the UI tied to this slice can be
   * responsive. No network or other IO will be allowed during onBindSlice. Any loading that needs
   * to be done should happen in the background with a call to {@link
   * ContentResolver#notifyChange(Uri, ContentObserver)} when the app is ready to provide the
   * complete data in onBindSlice.
   *
   * <p>The slice returned should have a spec that is compatible with one of the supported specs.
   *
   * @param sliceUri Uri to bind.
   * @param supportedSpecs List of supported specs.
   * @see Slice
   * @see Slice#HINT_PARTIAL
   */
  public Parcelable onBindSlice(Uri sliceUri, Set<SliceSpec> supportedSpecs, Bundle extras) {
    return null;
  }

  /**
   * Called to inform an app that a slice has been pinned.
   *
   * <p>Pinning is a way that slice hosts use to notify apps of which slices they care about updates
   * for. When a slice is pinned the content is expected to be relatively fresh and kept up to date.
   *
   * <p>Being pinned does not provide any escalated privileges for the slice provider. So apps
   * should do things such as turn on syncing or schedule a job in response to a onSlicePinned.
   *
   * <p>Pinned state is not persisted through a reboot, and apps can expect a new call to
   * onSlicePinned for any slices that should remain pinned after a reboot occurs.
   *
   * @param sliceUri The uri of the slice being unpinned.
   * @see #onSliceUnpinned(Uri)
   */
  public void onSlicePinned(Uri sliceUri) {}

  /**
   * Called to inform an app that a slices is no longer pinned.
   *
   * <p>This means that no other apps on the device care about updates to this slice anymore and
   * therefore it is not important to be updated. Any syncs or jobs related to this slice should be
   * cancelled.
   *
   * @see #onSlicePinned(Uri)
   */
  public void onSliceUnpinned(Uri sliceUri) {}

  /**
   * Obtains a list of slices that are descendants of the specified Uri.
   *
   * <p>Implementing this is optional for a SliceProvider, but does provide a good discovery
   * mechanism for finding slice Uris.
   *
   * @param uri The uri to look for descendants under.
   * @return All slices within the space.
   * @see SliceManager#getSliceDescendants(Uri)
   */
  public @NonNull Collection<Uri> onGetSliceDescendants(@NonNull Uri uri) {
    return Collections.emptyList();
  }

  /**
   * This method must be overridden if an {@link IntentFilter} is specified on the SliceProvider. In
   * that case, this method can be called and is expected to return a non-null Uri representing a
   * slice. Otherwise this will throw {@link UnsupportedOperationException}.
   *
   * <p>Any intent filter added to a slice provider should also contain {@link
   * SliceManager#CATEGORY_SLICE}, because otherwise it will not be detected by {@link
   * SliceManager#mapIntentToUri(Intent)}.
   *
   * @return Uri representing the slice associated with the provided intent.
   * @see Slice
   * @see SliceManager#mapIntentToUri(Intent)
   */
  public @NonNull Uri onMapIntentToUri(Intent intent) {
    throw new UnsupportedOperationException(
        "This provider has not implemented intent to uri mapping");
  }

  /**
   * Called when an app requests a slice it does not have write permission to the uri for.
   *
   * <p>The return value will be the action on a slice that prompts the user that the calling app
   * wants to show slices from this app. The default implementation launches a dialog that allows
   * the user to grant access to this slice. Apps that do not want to allow this user grant, can
   * override this and instead launch their own dialog with different behavior.
   *
   * @param sliceUri the Uri of the slice attempting to be bound.
   * @see #getCallingPackage()
   */
  public @NonNull PendingIntent onCreatePermissionRequest(Uri sliceUri) {
    return createPermissionPendingIntent(getContext(), sliceUri, getCallingPackage());
  }

  @Override
  public final int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
    if (DEBUG) {
      Log.d(TAG, "update " + uri);
    }
    return 0;
  }

  @Override
  public final int delete(Uri uri, String selection, String[] selectionArgs) {
    if (DEBUG) {
      Log.d(TAG, "delete " + uri);
    }
    return 0;
  }

  @Override
  public final Cursor query(
      Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
    if (DEBUG) {
      Log.d(TAG, "query " + uri);
    }
    return null;
  }

  @Override
  public final Cursor query(
      Uri uri,
      String[] projection,
      String selection,
      String[] selectionArgs,
      String sortOrder,
      CancellationSignal cancellationSignal) {
    if (DEBUG) {
      Log.d(TAG, "query " + uri);
    }
    return null;
  }

  @Override
  public final Cursor query(
      Uri uri, String[] projection, Bundle queryArgs, CancellationSignal cancellationSignal) {
    if (DEBUG) {
      Log.d(TAG, "query " + uri);
    }
    return null;
  }

  @Override
  public final Uri insert(Uri uri, ContentValues values) {
    if (DEBUG) {
      Log.d(TAG, "insert " + uri);
    }
    return null;
  }

  @Override
  public final String getType(Uri uri) {
    if (DEBUG) {
      Log.d(TAG, "getType " + uri);
    }
    return SLICE_TYPE;
  }

  @Override
  public Bundle call(String method, String arg, Bundle extras) {
    if (method.equals(METHOD_SLICE)) {
      Uri uri =
          getUriWithoutUserId(
              validateIncomingUriOrNull(
                  BundleCompat.getParcelable(extras, EXTRA_BIND_URI, android.net.Uri.class)));
      List<SliceSpec> supportedSpecs =
          BundleCompat.getParcelableArrayList(extras, EXTRA_SUPPORTED_SPECS, SliceSpec.class);

      String callingPackage = getCallingPackage();
      int callingUid = Binder.getCallingUid();
      int callingPid = Binder.getCallingPid();

      Parcelable s =
          handleBindSlice(uri, supportedSpecs, callingPackage, callingUid, callingPid, extras);
      Bundle b = new Bundle();
      b.putParcelable(EXTRA_SLICE, s);
      return b;
    } else if (method.equals(METHOD_MAP_INTENT)) {
      Intent intent =
          BundleCompat.getParcelable(extras, EXTRA_INTENT, android.content.Intent.class);
      if (intent == null) {
        return null;
      }
      Uri uri = validateIncomingUriOrNull(onMapIntentToUri(intent));
      List<SliceSpec> supportedSpecs =
          BundleCompat.getParcelableArrayList(extras, EXTRA_SUPPORTED_SPECS, SliceSpec.class);
      Bundle b = new Bundle();
      if (uri != null) {
        Parcelable s =
            handleBindSlice(
                uri,
                supportedSpecs,
                getCallingPackage(),
                Binder.getCallingUid(),
                Binder.getCallingPid(),
                extras);
        b.putParcelable(EXTRA_SLICE, s);
      } else {
        b.putParcelable(EXTRA_SLICE, null);
      }
      return b;
    } else if (method.equals(METHOD_MAP_ONLY_INTENT)) {
      Intent intent =
          BundleCompat.getParcelable(extras, EXTRA_INTENT, android.content.Intent.class);
      if (intent == null) {
        return null;
      }
      Uri uri = validateIncomingUriOrNull(onMapIntentToUri(intent));
      Bundle b = new Bundle();
      b.putParcelable(EXTRA_SLICE, uri);
      return b;
    } else if (method.equals(METHOD_PIN)) {
      Uri uri =
          getUriWithoutUserId(
              validateIncomingUriOrNull(
                  BundleCompat.getParcelable(extras, EXTRA_BIND_URI, android.net.Uri.class)));
      handlePinSlice(uri);
    } else if (method.equals(METHOD_UNPIN)) {
      Uri uri =
          getUriWithoutUserId(
              validateIncomingUriOrNull(
                  BundleCompat.getParcelable(extras, EXTRA_BIND_URI, android.net.Uri.class)));
      handleUnpinSlice(uri);
    } else if (method.equals(METHOD_GET_DESCENDANTS)) {
      Uri uri =
          getUriWithoutUserId(
              validateIncomingUriOrNull(
                  BundleCompat.getParcelable(extras, EXTRA_BIND_URI, android.net.Uri.class)));
      Bundle b = new Bundle();
      b.putParcelableArrayList(EXTRA_SLICE_DESCENDANTS, new ArrayList<>(handleGetDescendants(uri)));
      return b;
    } else if (method.equals(METHOD_GET_PERMISSIONS)) {
      if (Binder.getCallingUid() != Process.SYSTEM_UID) {
        throw new SecurityException("Only the system can get permissions");
      }
      Bundle b = new Bundle();
      b.putStringArray(EXTRA_RESULT, mAutoGrantPermissions);
      return b;
    }
    return super.call(method, arg, extras);
  }

  private Uri validateIncomingUriOrNull(Uri uri) {
    return uri;
  }

  public static String getAuthorityWithoutUserId(String auth) {
    if (auth == null) {
      return null;
    }
    int end = auth.lastIndexOf('@');
    return auth.substring(end + 1);
  }

  public static Uri getUriWithoutUserId(Uri uri) {
    if (uri == null) {
      return null;
    }
    Uri.Builder builder = uri.buildUpon();
    builder.authority(getAuthorityWithoutUserId(uri.getAuthority()));
    return builder.build();
  }

  private Collection<Uri> handleGetDescendants(Uri uri) {
    mCallback = "onGetSliceDescendants";
    return onGetSliceDescendants(uri);
  }

  private void handlePinSlice(Uri sliceUri) {
    mCallback = "onSlicePinned";
    sMainHandler.postDelayed(mAnr, SLICE_BIND_ANR);
    try {
      onSlicePinned(sliceUri);
    } finally {
      sMainHandler.removeCallbacks(mAnr);
    }
  }

  private void handleUnpinSlice(Uri sliceUri) {
    mCallback = "onSliceUnpinned";
    sMainHandler.postDelayed(mAnr, SLICE_BIND_ANR);
    try {
      onSliceUnpinned(sliceUri);
    } finally {
      sMainHandler.removeCallbacks(mAnr);
    }
  }

  private Parcelable handleBindSlice(
      Uri sliceUri,
      List<SliceSpec> supportedSpecs,
      String callingPkg,
      int callingUid,
      int callingPid,
      Bundle extras) {
    // This can be removed once Slice#bindSlice is removed and everyone is using
    // SliceManager#bindSlice.
    String pkg =
        callingPkg != null
            ? callingPkg
            : getContext().getPackageManager().getNameForUid(callingUid);
    try {
      mSliceManager.enforceSlicePermission(sliceUri, callingPid, callingUid, mAutoGrantPermissions);
    } catch (SecurityException e) {
      return createPermissionSlice(getContext(), sliceUri, pkg);
    }
    mCallback = "onBindSlice";
    sMainHandler.postDelayed(mAnr, SLICE_BIND_ANR);
    try {
      return onBindSliceStrict(sliceUri, supportedSpecs, extras);
    } finally {
      sMainHandler.removeCallbacks(mAnr);
    }
  }

  public Slice createPermissionSlice(Context context, Uri sliceUri, String callingPackage) {
    return new Slice.Builder(sliceUri, null).build();
  }

  public static PendingIntent createPermissionPendingIntent(
      Context context, Uri sliceUri, String callingPackage) {
    return PendingIntent.getActivity(
        context,
        0,
        createPermissionIntent(context, sliceUri, callingPackage),
        PendingIntent.FLAG_IMMUTABLE);
  }

  public static Intent createPermissionIntent(
      Context context, Uri sliceUri, String callingPackage) {
    Intent intent = new Intent(SliceManager.ACTION_REQUEST_SLICE_PERMISSION);
    intent.putExtra(EXTRA_BIND_URI, sliceUri);
    intent.putExtra(EXTRA_PKG, callingPackage);
    // Unique pending intent.
    intent.setData(sliceUri.buildUpon().appendQueryParameter("package", callingPackage).build());
    return intent;
  }

  private Parcelable onBindSliceStrict(
      Uri sliceUri, List<SliceSpec> supportedSpecs, Bundle extras) {
    return onBindSlice(sliceUri, new ArraySet<>(supportedSpecs), extras);
  }

  private final Runnable mAnr =
      () -> {
        Process.sendSignal(Process.myPid(), Process.SIGNAL_QUIT);
        Log.wtf(TAG, "Timed out while handling slice callback " + mCallback);
      };
}