/**
 * This class is made by Google
 *
 * visit https://codelabs.developers.google.com/codelabs/arcore-cloud-anchors/#4
 */

package it.norangeb.cloudanchors;

import android.content.Context;
import android.util.Log;
import com.google.firebase.FirebaseApp;
import com.google.firebase.database.*;

/** Helper class for Firebase storage of cloud anchor IDs. */
class StorageManager {

    /** Listener for a new Cloud Anchor ID from the Firebase Database. */
    interface CloudAnchorIdListener {
        void onCloudAnchorIdAvailable(String cloudAnchorId);
    }

    /** Listener for a new short code from the Firebase Database. */
    interface ShortCodeListener {
        void onShortCodeAvailable(Integer shortCode);
    }

    private static final String TAG = StorageManager.class.getName();
    private static final String KEY_ROOT_DIR = "shared_anchor_codelab_root";
    private static final String KEY_NEXT_SHORT_CODE = "next_short_code";
    private static final String KEY_PREFIX = "anchor;";
    private static final int INITIAL_SHORT_CODE = 142;
    private final DatabaseReference rootRef;

    StorageManager(Context context) {
        FirebaseApp firebaseApp = FirebaseApp.initializeApp(context);
        rootRef = FirebaseDatabase.getInstance(firebaseApp).getReference().child(KEY_ROOT_DIR);
        DatabaseReference.goOnline();
    }

    /** Gets a new short code that can be used to store the anchor ID. */
    void nextShortCode(ShortCodeListener listener) {
        // Run a transaction on the node containing the next short code available. This increments the
        // value in the database and retrieves it in one atomic all-or-nothing operation.
        rootRef
                .child(KEY_NEXT_SHORT_CODE)
                .runTransaction(
                        new Transaction.Handler() {
                            @Override
                            public Transaction.Result doTransaction(MutableData currentData) {
                                Integer shortCode = currentData.getValue(Integer.class);
                                if (shortCode == null) {
                                    shortCode = INITIAL_SHORT_CODE - 1;
                                }
                                currentData.setValue(shortCode + 1);
                                return Transaction.success(currentData);
                            }

                            @Override
                            public void onComplete(
                                    DatabaseError error, boolean committed, DataSnapshot currentData) {
                                if (!committed) {
                                    Log.e(TAG, "Firebase Error", error.toException());
                                    listener.onShortCodeAvailable(null);
                                } else {
                                    listener.onShortCodeAvailable(currentData.getValue(Integer.class));
                                }
                            }
                        });
    }

    /** Stores the cloud anchor ID in the configured Firebase Database. */
    void storeUsingShortCode(int shortCode, String cloudAnchorId) {
        rootRef.child(KEY_PREFIX + shortCode).setValue(cloudAnchorId);
    }

    /**
     * Retrieves the cloud anchor ID using a short code. Returns an empty string if a cloud anchor ID
     * was not stored for this short code.
     */
    void getCloudAnchorID(int shortCode, CloudAnchorIdListener listener) {
        rootRef
                .child(KEY_PREFIX + shortCode)
                .addListenerForSingleValueEvent(
                        new ValueEventListener() {
                            @Override
                            public void onDataChange(DataSnapshot dataSnapshot) {
                                listener.onCloudAnchorIdAvailable(String.valueOf(dataSnapshot.getValue()));
                            }

                            @Override
                            public void onCancelled(DatabaseError error) {
                                Log.e(TAG, "The database operation for getCloudAnchorID was cancelled.",
                                        error.toException());
                                listener.onCloudAnchorIdAvailable(null);
                            }
                        });
    }
}