/**
 * Copyright (c) 2015-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 */

package com.facebook.react.modules.storage;

import javax.annotation.Nullable;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;

import com.facebook.common.logging.FLog;
import com.facebook.react.common.ReactConstants;

/**
 * Database supplier of the database used by react native. This creates, opens and deletes the
 * database as necessary.
 */
public class ReactDatabaseSupplier extends SQLiteOpenHelper {

  // VisibleForTesting
  public static final String DATABASE_NAME = "RKStorage";

  private static final int DATABASE_VERSION = 1;
  private static final int SLEEP_TIME_MS = 30;

  static final String TABLE_CATALYST = "catalystLocalStorage";
  static final String KEY_COLUMN = "key";
  static final String VALUE_COLUMN = "value";

  static final String VERSION_TABLE_CREATE =
      "CREATE TABLE " + TABLE_CATALYST + " (" +
          KEY_COLUMN + " TEXT PRIMARY KEY, " +
          VALUE_COLUMN + " TEXT NOT NULL" +
          ")";

  private static @Nullable ReactDatabaseSupplier sReactDatabaseSupplierInstance;

  private Context mContext;
  private @Nullable SQLiteDatabase mDb;
  private long mMaximumDatabaseSize =  6L * 1024L * 1024L; // 6 MB in bytes

  private ReactDatabaseSupplier(Context context) {
    super(context, DATABASE_NAME, null, DATABASE_VERSION);
    mContext = context;
  }

  public static ReactDatabaseSupplier getInstance(Context context) {
    if (sReactDatabaseSupplierInstance == null) {
      sReactDatabaseSupplierInstance = new ReactDatabaseSupplier(context.getApplicationContext());
    }
    return sReactDatabaseSupplierInstance;
  }

  @Override
  public void onCreate(SQLiteDatabase db) {
    db.execSQL(VERSION_TABLE_CREATE);
  }

  @Override
  public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    if (oldVersion != newVersion) {
      deleteDatabase();
      onCreate(db);
    }
  }

  /**
   * Verify the database exists and is open.
   */
  /* package */ synchronized boolean ensureDatabase() {
    if (mDb != null && mDb.isOpen()) {
      return true;
    }
    // Sometimes retrieving the database fails. We do 2 retries: first without database deletion
    // and then with deletion.
    SQLiteException lastSQLiteException = null;
    for (int tries = 0; tries < 2; tries++) {
      try {
        if (tries > 0) {
          deleteDatabase();
        }
        mDb = getWritableDatabase();
        break;
      } catch (SQLiteException e) {
        lastSQLiteException = e;
      }
      // Wait before retrying.
      try {
        Thread.sleep(SLEEP_TIME_MS);
      } catch (InterruptedException ie) {
        Thread.currentThread().interrupt();
      }
    }
    if (mDb == null) {
      throw lastSQLiteException;
    }
    // This is a sane limit to protect the user from the app storing too much data in the database.
    // This also protects the database from filling up the disk cache and becoming malformed
    // (endTransaction() calls will throw an exception, not rollback, and leave the db malformed).
    mDb.setMaximumSize(mMaximumDatabaseSize);
    return true;
  }

  /**
   * Create and/or open the database.
   */
  public synchronized SQLiteDatabase get() {
    ensureDatabase();
    return mDb;
  }

  public synchronized void clearAndCloseDatabase() throws RuntimeException {
    try {
      clear();
      closeDatabase();
      FLog.d(ReactConstants.TAG, "Cleaned " + DATABASE_NAME);
    } catch (Exception e) {
      // Clearing the database has failed, delete it instead.
      if (deleteDatabase()) {
        FLog.d(ReactConstants.TAG, "Deleted Local Database " + DATABASE_NAME);
        return;
      }
      // Everything failed, throw
      throw new RuntimeException("Clearing and deleting database " + DATABASE_NAME + " failed");
    }
  }

  /* package */ synchronized void clear() {
    get().delete(TABLE_CATALYST, null, null);
  }

  /**
   * Sets the maximum size the database will grow to. The maximum size cannot
   * be set below the current size.
   */
  public synchronized void setMaximumSize(long size) {
    mMaximumDatabaseSize = size;
    if (mDb != null) {
      mDb.setMaximumSize(mMaximumDatabaseSize);
    }
  }

  private synchronized boolean deleteDatabase() {
    closeDatabase();
    return mContext.deleteDatabase(DATABASE_NAME);
  }

  private synchronized void closeDatabase() {
    if (mDb != null && mDb.isOpen()) {
      mDb.close();
      mDb = null;
    }
  }

  // For testing purposes only!
  public static void deleteInstance() {
    sReactDatabaseSupplierInstance = null;
  }
}