aws-dynamodb.html

<link rel="import" href="../polymer/polymer.html">
<script src="https://sdk.amazonaws.com/js/aws-sdk-2.2.5.min.js"></script>

<!--
A custom polymer element that communicates with AWS DynamoDB

Example:

    <aws-dynamodb data="{{data}}"></aws-dynamodb>

@demo

@todo:
- Implement authentication check
-->
<script>
  (function() {
    'use strict';

    var AWSDynamoDB = Polymer({
      is: 'aws-dynamodb',

      properties: {

        /**
         * An ordered array of data items produced by the current DynamoDb Query instance.
         */
        data: {
          type: Array,
          readOnly: false, // @todo: should be true
          notify: true,
          value: function () {
            return [];
          }
        },

        /**
         * A string that contains the region the DynamoDB is located in
         */
        region: {
          type: String,
          value: function () {
            return 'eu-west-1';
          }
        },

        /**
         * Boolean that indicates the authentication state
         */
        authenticated: {
          type: Boolean,
          value: true
        },

        /**
         * String containing the endpoint of the DynamoDB on AWS
         */
        endpoint: {
          type: String,
          value: ''
        },

        /**
         * String containing the accessKeyId for AWS
         */
        accessKeyId: {
          type: String,
          value: ''
        },

        /**
         * String containg the secretAccessKey for AWS
         */
        secretAccessKey: {
          type: String,
          value: ''
        },

        /**
         * String containing the table name to be used
         */
        tableName: {
          type: String,
          value: ''
        },

        /**
         * Number limiting the nummer of results
         */
        limit: {
          type: Number,
          value: 100
        },

        /**
         * String containing the name of the index to be used in queries
         */
        indexName: {
          type: String,
          value: ''
        },

        /**
         * String containing the condition expression
         */
        conditionExpression: {
          type: String,
          value: ''
        },

        /**
         * Object containing the condition names
         */
        conditionNames: {
          type: Object,
          value: {}
        },

        /**
         * Object containing the condition values
         */
        conditionValues: {
          type: Object,
          value: {}
        },

        /**
         * Boolean indicating whether the results should be ordered ascending or descending
         */
        ascending: {
          type: Boolean,
          value: false
        },

        /**
         * Object containing the query parameters
         */
        query: {
          type: Object,
          computed: '_computeQuery(_db, tableName, limit, indexName, conditionExpression, conditionNames, conditionValues, ascending)',
          observer: '_queryChanged'
        },

        /**
         * String containing the sort of operation (scan or query)
         */
        operation: {
          type: String,
          value: function () {
            return 'scan';
          },
          observer: '_operationChanged'
        },

        _db: {
          type: Object
        }
      },

      observers: [
        '_populateDb(region, accessKeyId, secretAccessKey, endpoint)'
      ],

      /**
       * Creates an instance for the AWS connection
       */
      _populateDb: function (region, accessKeyId, secretAccessKey, endpoint, tableName) {
        AWS.config.region = region;

        this.set( '_db', new AWS.DynamoDB({
          'accessKeyId': accessKeyId,
          'secretAccessKey': secretAccessKey,
          'endpoint': endpoint
        }));
      },

      _queryChanged: function () {
        var save = function (context, nothing, data) {
          context.data = data.Items;
          context.fire('dynamodb-data', data.Items, { bubbles: false });
        };

        if ( this.query.TableName !== '' ) {
          // Execute the request
          if ( this.operation === 'scan' ) {
            this._db.scan(this.query, save.bind(null, this));
          } else {
            this._db.query(this.query, save.bind(null, this));
          }
        }
      },

      _computeQuery: function () {
        var params = {
          TableName: this.tableName,
          Limit: this.limit,
        };

        if ( this.indexName !== '' &&
             this.conditionExpression !== '' &&
             this.conditionNames !== {} &&
             this.conditionValues !== {}
        ) {
          params.IndexName = this.indexName;
          params.KeyConditionExpression = this.conditionExpression;
          params.ExpressionAttributeNames = this.conditionNames;
          params.ExpressionAttributeValues = this.conditionValues;
          params.ScanIndexForward = this.ascending;
        }

        return params;
      },

      _operationChanged: function () {
        this._queryChanged();
      }
    });
  })();
</script>