Beginning to refactor the prototype into modules.

2 files changed, 327 insertions, 0 deletions

diff --git a/lib/PodcastView.js b/lib/PodcastView.js
new file mode 100644
index 0000000..15970cf
--- /dev/null
+++ b/lib/PodcastView.js
@@ -0,0 +1,127 @@
+var _ = require('underscore');
+
+var AWS = require('aws-sdk');
+var s3 = new AWS.S3();
+
+var doc = require('dynamodb-doc');
+var dynamo = new doc.DynamoDB();
+
+var DDB_VIEWS_TABLE = 'podcast-views';
+
+/**
+ * PodcastView represents a pre-rendered view template.
+ *
+ * @param {Object} view - properties to set on the view and pass to the
+ *                        template.
+ * @constructor
+ */
+modules.exports = function PodcastView(view) {
+  for (var property in view) {
+    if (view.hasOwnProperty(property)) {
+      this[property] = source[property];
+    }
+  }
+};
+
+/**
+ * Find a view in DynamoDB by Id.
+ *
+ * @param {Object} id - The view id.
+ * @param {Function} - Callback to call with an error or view.
+ */
+PodcastView.findById = function(id, callback) {
+  var params = {
+    TableName: DDB_VIEWS_TABLE,
+    Key: id
+  };
+
+  dynamo.getItem(params, function(error, data) {
+    if (error) {
+      callback(error);
+      return;
+    }
+
+    var view = new PodcastView(data.Item);
+    callback(null, view);
+  });
+}
+
+/**
+ * Find all views for a given feed.
+ *
+ * @param {Object} feedId - The feed id.
+ * @param {Function} - Callback with signature function(error, view, last)
+ */
+PodcastView.forEachView = function(feedId, callback) {
+  forEachView(feedId, callback);
+};
+
+function forEachView(feedId, callback, startKey) {
+  var params = {
+    TableName: DDB_VIEWS_TABLE,
+    KeyConditionExpression: "feedId = :feedId",
+    ExpressionAttributeValues: {
+      ':feedId': feedId
+    }
+  };
+
+  if (startKey) {
+    params['ExclusiveStartKey'] = startKey;
+  }
+
+  dynamo.query(params, function(error, data) {
+    if (error != null) {
+      callback(error);
+      return;
+    }
+
+    var lastResponse = !data.LastEvaluatedKey;
+
+    data.Items.forEach(function(viewData, index, array) {
+      var view = new PodcastView(viewData);
+      var last = lastResponse && index == (array.length - 1);
+      callback(null, view, last);
+    });
+
+    // If this is not the last set of responses, get more.
+    if (!lastResponse) {
+      forEachView(feedId, callback, data.LastEvaluatedKey);
+    }
+  });
+}
+
+PodcastView.prototype.render = function(episodes, callback) {
+  var template = this.template;
+
+  var data = {
+    view: this,
+    episodes: episodes,
+  };
+  var renderedView = _.template(template)(data);
+
+  saveView(renderedView, callback);
+};
+
+function saveView(renderedView, callback) {
+  var params = {
+    Bucket: this.bucket,
+    Key: this.key,
+    Body: renderedView
+  };
+
+  s3.putObject(params, callback);
+}
+
+PodcastView.prototype.remove = function(callback) {
+  if (!this.bucket || !this.key) {
+    callback(new Error("View is missing bucket or key"));
+    return;
+  }
+
+  var params = {
+    Bucket: this.bucket,
+    Key: this.key
+  };
+
+  s3.deleteObject(params, callback);
+}
diff --git a/lib/UpdateHandlers.js b/lib/UpdateHandlers.js
new file mode 100644
index 0000000..6483020
--- /dev/null
+++ b/lib/UpdateHandlers.js
@@ -0,0 +1,200 @@
+var AWS = require('aws-sdk');
+AWS.config.update({region: "us-west-2"});
+
+var doc = require('dynamodb-doc');
+var dynamo = new doc.DynamoDB();
+
+var PodcastView = require('./PodcastView');
+
+var DDB_EPISODES_TABLE = 'podcast-episodes';
+
+exports.handleViewUpdate = function(event, context) {
+  // Handle dynamo event for the views table.
+
+  // Each modified view is added as a key in this Object to dedupe multiple
+  // updates for the same key.
+  var viewsToUpdate = {};
+
+  event.Records.forEach(function(record) {
+    var eventName = record.eventName;
+    var viewKey = record.dynamodb.Keys;
+
+    switch (eventName) {
+      case 'INSERT':
+      case 'MODIFY':
+        viewsToUpdate[viewKey] = 'update';
+        break;
+      case 'REMOVE':
+        viewsToUpdate[viewKey] = 'remove';
+        break;
+      default:
+        context.fail(new Error('Unrecognized eventName "' + eventname + '"'));
+    }
+  });
+
+  var viewIds = Object.keys(viewsToUpdate);
+
+  var remainingCount = 0;
+  var errors = [];
+  var callback = function(error, data) {
+    // When all are done, call context callback.
+    remainingCount--;
+    if (error != null) {
+      errors.push(error);
+    }
+
+    if (remainingCount == 0) {
+      if (errors.length == 0) {
+        context.succeed();
+      } else {
+        context.fail(new Error("Failures updating views"), errors);
+      }
+    }
+  };
+
+  // Start each update/remove operation.
+  viewIds.forEach(function(viewId) {
+    var operation = viewsToUpdate[viewId];
+    PodcastView.findById(viewId, function(error, view) {
+      if (operation == 'update') {
+        remainingCount++;
+        view.render(callback);
+      } else if (operation == 'remove') {
+        remainingCount++;
+        view.remove(callback);
+      }
+    });
+  });
+};
+
+exports.handleEpisodeUpdate = function(event, context) {
+  // Handle dynamo event for the episodes table.
+
+  // Each modified feed is added as a key in this Object to dedupe multiple
+  // updates for the same feed.
+  var feedsToUpdate = {};
+
+  event.Records.forEach(function(record) {
+    var eventName = record.eventName;
+
+    switch (eventName) {
+      case 'INSERT':
+        feedsToUpdate[record.dynamodb.NewImage.feedId] = true;
+        break;
+      case 'MODIFY':
+        var oldImageFeed = record.dynamodb.OldImage.feedId;
+        var newImageFeed = record.dynamodb.NewImage.feedId;
+        if (oldImageFeed != newImageFeed) {
+          feedsToUpdate[oldImageFeed] = true;
+        }
+        feedsToUpdate[newImageFeed] = true;
+        break;
+      case 'REMOVE':
+        feedsToUpdate[record.dynamodb.OldImage.feedId] = true;
+        break;
+      default:
+        context.fail(new Error('Unrecognized eventName "' + eventname + '"'));
+    }
+  });
+
+  var feedIds = Object.keys(feedsToUpdate);
+
+  var remainingCount = 0;
+  var errors = [];
+  var callback = function(error, data) {
+    // When all are done, call context callback.
+    remainingCount--;
+    if (error != null) {
+      errors.push(error);
+    }
+
+    if (remainingCount == 0) {
+      if (errors.length == 0) {
+        context.succeed();
+      } else {
+        context.fail(new Error("Failures updating feeds"), errors);
+      }
+    }
+  };
+
+  // Start updates for each feed.
+  feedIds.forEach(function(feedId) {
+    remainingCount++;
+    renderViewsForFeed(feedId, callback);
+  });
+};
+
+function renderViewsForFeed(feedId, callback) {
+  getEpisodesForFeed(feedId, function(error, episodes) {
+    if (error) {
+      callback(error);
+      return;
+    }
+    console.log("Got episodes " + JSON.stringify(episodes));
+
+    var remainingCount = 0;
+    var errors = [];
+    var renderCallback = function(error, data) {
+      // When all are done, call context callback.
+      remainingCount--;
+      console.log("Remaining is " + remainingCount);
+      if (error != null) {
+        errors.push(error);
+      }
+
+      if (remainingCount == 0) {
+        if (errors.length == 0) {
+          callback();
+        } else {
+          callback(new Error("Failures rendering feeds"), errors);
+        }
+      }
+    };
+
+    // Get all of the views for the feed.
+    PodcastView.forEachView(feedId, function(error, view, last) {
+      remainingCount++;
+      if (error != null) {
+        renderCallback(error);
+      } else {
+        view.render(episodes, renderCallback);
+      }
+    });
+  });
+}
+
+function getEpisodesForFeed(feedId, callback, startKey, episodes) {
+  var params = {
+    TableName: DDB_EPISODES_TABLE,
+    ConsistentRead: true,
+    KeyConditionExpression: "feedId = :feedId",
+    ExpressionAttributeValues: {
+      ':feedId': feedId
+    }
+  };
+
+  if (startKey) {
+    params['ExclusiveStartKey'] = startKey;
+  }
+
+  dynamo.query(params, function(error, data) {
+    if (error != null) {
+      callback(error);
+      return;
+    }
+
+    if (!episodes) {
+      episodes = data.Items;
+    } else {
+      episodes = episodes.concat(data.Items);
+    }
+
+    // If this is not the last set of responses, get more.
+    var lastKey = data.LastEvaluatedKey;
+    if (lastKey) {
+      getEpisodesForFeed(feedId, callback, lastKey, episodes);
+    } else {
+      callback(null, episodes);
+    }
+  });
+}