DBMagic

class DBMagic {
  constructor( db_name, db_version, stores ) {
    if ( typeof stores === 'string' ) stores = [ stores ];

    this.stores = stores;
    this.db_name = db_name;
    this.db_version = db_version;
    var indexedDB = window.indexedDB || window.mozIndexedDB || window.webkitIndexedDB || window.msIndexedDB;
    this.indexedDB = indexedDB;

//    this.db_delete();
    this.db_create();
    this.tables = {};
  }

  store( name, mode ) {
    return new Promise( (resolve, reject) => {
      const req = this.indexedDB.open( this.db_name, this.db_version );
      req.onerror = ( e ) => { reject( e ); };
      req.onsuccess = () => {
        let db = req.result;
        let tx = db.transaction ( [ name ], mode );
        resolve( tx.objectStore( name ) );
      };
    } );
  }

  add( name, items ) {
    if ( ! Array.isArray( items ) ) items = [ items ];

    return new Promise( ( resolve, reject ) => {
      this.store( name, 'readwrite' ).then( store => {
        items.forEach( item => {
          const req = store.add( item );
          req.onerror = () => {
            resolve( item.id );
          };
          req.onsuccess = ( e ) => {
            if ( debug )
              console.log( 'SUCCESS: Added key ['+ item.id +'] to store [' +
              name + '] on database [' + this.db_name + ']' );
            resolve( item.id );
          };
        } );
      } );
    } );
  }

  get( name, items ) {
    if ( typeof items === 'string' ) items = [ items ];

    return new Promise( ( resolve, reject ) => {
      this.store( name, 'readonly' ).then( store => {
        items.forEach( item => {
          const req = store.get( item );
          req.onerror = ( e ) => {
            if ( debug )
              console.log('ERROR: Could not connect to database [' +
              this.db_name +']\n', e.srcElement.error );
            reject( e );
          };
          req.onsuccess = ( e ) => {
            if ( debug )
              console.log( 'SUCCESS: Retrieved key ['+ item +'] from store [' +
              name + '] on database ['+ this.db_name +']' );
            resolve( req.result );
          };
        } );
      } );
    } );
  }

  getAll( name, callback ) {
    this.store( name, 'readonly' ).then( store => {
      const req = store.getAll();
      req.onsuccess = ( e ) => {
        if ( debug )
          console.log( 'SUCCESS: Retrieved all keys from store [' + name + '] on database ['+ this.db_name +']' );
        if ( callback ) callback( req.result );
      };
    } );
  }

  update( name, items, callback ) {
    if ( typeof items === 'string' ) items = [ items ];

    this.store( name, 'readwrite' ).then( store => {
      items.forEach( item => {
        const req = store.put( item );
        req.onerror = ( e ) => {
          if ( debug )
            console.log( 'ERROR: Updating key ['+ item.id +'] in store [' +
            name + '] on database [' + this.db_name + ']\n', e.srcElement.error );
          if ( callback ) callback( e );
        };
        req.onsuccess = ( e ) => {
          if ( debug )
            console.log( 'SUCCESS: Updated key ['+ item.id +'] in store [' +
            name + '] on database [' + this.db_name + ']' );
          if ( callback ) callback( e );
        };
      });
    } );
  }

  delete( name, items, callback ) {
    if ( typeof items === 'string' ) items = [ items ];

    this.store( name, 'readwrite' ).then( store => {
      items.forEach( item => {
        const req = store.delete( item );
        req.onerror = ( e ) => {
          if ( debug )
            console.log('ERROR: Deleted key ['+ item +'] from store ['+ name +']\n', e.srcElement.error );

          if ( callback ) callback( e );
        };
        req.onsuccess = ( e ) => {
          if ( debug )
            console.log('SUCCESS: Deleted key ['+ item +'] from store ['+ name +']');
          if ( callback ) callback( e );
        };
      } );
    } );

  }

  deleteAll( name, callback ) {
    this.store( name, 'readwrite' ).then( store => {
      const req = store.clear();
      req.onerror = ( e ) => {
        if ( debug )
          console.log('ERROR: Could not delete keys from store ['+ name +'] on database ['+ db_name +']\n', e.srcElement.error );
        if ( callback ) callback( e );
      };
      req.onsuccess = ( e ) => {
        if ( debug )
          console.log('SUCCESS: Deleted all keys from store ['+ name +'] on database ['+ db_name +']' );
        if ( callback ) callback( e );
      };
    });
  }

  db_create( callback ) {
    const req = this.indexedDB.open( this.db_name, this.db_version );

    req.onerror = () => {
      let db = req.result;
      if ( debug )
        console.log('ERROR: Database ['+ this.db_name +'] could not be opened successfully, [ version = ' + db.version + ' ]');
      if ( callback ) callback( true );
    };

    req.onsuccess = () => {
      let db = req.result;
      if ( debug )
        console.log('SUCCESS: Database ['+ this.db_name +'] opened successfully, [ version = ' + db.version + ' ]');
      if ( callback ) callback( true );
    };

    req.onupgradeneeded = ( e ) => {
      let db = req.result;

      switch( e.oldVersion ) {
        case 0:
          this.stores.forEach( name => {
            db.createObjectStore( name, { keyPath: 'id' } );
          } );
        case 1:
          let oldVersion = e.oldVersion;
          let newVersion = e.newVersion;
          if ( debug ) log( db.objectStoreNames );
      }
    };
  }

  db_delete( callback ) {
    const db_name = this.db_name;
    this.indexedDB.deleteDatabase( db_name );

    if ( debug )
      console.log('SUCCESS: Database ['+ db_name +'] deleted successfully.');
    if ( callback ) callback( true );
  }
}