Add code comments for storage events

src/providers/storage.ts

@@ -34,17 +34,22 @@ export const provider = 'google.storage';
 export const service = 'storage.googleapis.com';
 
 /**
- * The optional bucket function allows you to choose which buckets' events to handle.
- * This step can be bypassed by calling object() directly, which will use the default
- * Cloud Storage for Firebase bucket.
- * @param bucket Name of the Google Cloud Storage bucket to listen to.
+ * Registers a Cloud Function scoped to a specific storage bucket.
+ *
+ * @param bucket Name of the bucket to which this Cloud Function is
+ *   scoped.
+ *
+ * @return Storage bucket builder interface.
  */
 export function bucket(bucket?: string) {
   return _bucketWithOptions({}, bucket);
 }
 
 /**
- * Handle events related to Cloud Storage objects.
+ * Registers a Cloud Function scoped to the default storage bucket for the
+ * project.
+ *
+ * @return Storage object builder interface.
  */
 export function object() {
   return _objectWithOptions({});
@@ -76,19 +81,34 @@ export function _objectWithOptions(options: DeploymentOptions): ObjectBuilder {
   return _bucketWithOptions(options).object();
 }
 
+/**
+ * The Google Cloud Storage bucket builder interface.
+ *
+ * Access via [`functions.storage.bucket()`](functions.storage#.bucket).
+ */
 export class BucketBuilder {
   /** @hidden */
   constructor(
     private triggerResource: () => string,
     private options: DeploymentOptions
   ) {}
 
-  /** Handle events for objects in this bucket. */
+  /**
+   * Event handler which fires every time a Google Cloud Storage change occurs.
+   *
+   * @return Storage object builder interface scoped to the specified storage
+   *   bucket.
+   */
   object() {
     return new ObjectBuilder(this.triggerResource, this.options);
   }
 }
 
+/**
+ * The Google Cloud Storage object builder interface.
+ *
+ * Access via [`functions.storage.object()`](functions.storage#.object).
+ */
 export class ObjectBuilder {
   /** @hidden */
   constructor(
@@ -104,7 +124,17 @@ export class ObjectBuilder {
     );
   }
 
-  /** Respond to archiving of an object, this is only for buckets that enabled object versioning. */
+  /**
+   * Event handler sent only when a bucket has enabled object versioning.
+   * This event indicates that the live version of an object has become an
+   * archived version, either because it was archived or because it was
+   * overwritten by the upload of an object of the same name.
+   *
+   * @param handler Event handler which is run every time a Google Cloud Storage
+   *   archival occurs.
+   *
+   * @return A Cloud Function which you can export and deploy.
+   */
   onArchive(
     handler: (
       object: ObjectMetadata,
@@ -114,7 +144,20 @@ export class ObjectBuilder {
     return this.onOperation(handler, 'object.archive');
   }
 
-  /** Respond to the deletion of an object (not to archiving, if object versioning is enabled). */
+  /**
+   * Event handler which fires every time a Google Cloud Storage deletion occurs.
+   *
+   * Sent when an object has been permanently deleted. This includes objects
+   * that are overwritten or are deleted as part of the bucket's lifecycle
+   * configuration. For buckets with object versioning enabled, this is not
+   * sent when an object is archived, even if archival occurs
+   * via the `storage.objects.delete` method.
+   *
+   * @param handler Event handler which is run every time a Google Cloud Storage
+   *   deletion occurs.
+   *
+   * @return A Cloud Function which you can export and deploy.
+   */
   onDelete(
     handler: (
       object: ObjectMetadata,
@@ -124,7 +167,19 @@ export class ObjectBuilder {
     return this.onOperation(handler, 'object.delete');
   }
 
-  /** Respond to the successful creation of an object. */
+  /**
+   * Event handler which fires every time a Google Cloud Storage object
+   * creation occurs.
+   *
+   * Sent when a new object (or a new generation of an existing object)
+   * is successfully created in the bucket. This includes copying or rewriting
+   * an existing object. A failed upload does not trigger this event.
+   *
+   * @param handler Event handler which is run every time a Google Cloud Storage
+   *   object creation occurs.
+   *
+   * @return A Cloud Function which you can export and deploy.
+   */
   onFinalize(
     handler: (
       object: ObjectMetadata,
@@ -134,7 +189,15 @@ export class ObjectBuilder {
     return this.onOperation(handler, 'object.finalize');
   }
 
-  /** Respond to metadata updates of existing objects. */
+  /**
+   * Event handler which fires every time the metadata of an existing object
+   * changes.
+   *
+   * @param handler Event handler which is run every time a Google Cloud Storage
+   *   metadata update occurs.
+   *
+   * @return A Cloud Function which you can export and deploy.
+   */
   onMetadataUpdate(
     handler: (
       object: ObjectMetadata,
@@ -144,6 +207,7 @@ export class ObjectBuilder {
     return this.onOperation(handler, 'object.metadataUpdate');
   }
 
+  /** @hidden */
   private onOperation(
     handler: (
       object: ObjectMetadata,
@@ -162,30 +226,101 @@ export class ObjectBuilder {
   }
 }
 
+/** Interface representing a Google Google Cloud Storage object metadata object. */
 export interface ObjectMetadata {
+  /** The kind of the object, which is always `storage#object`. */
   kind: string;
+
+  /**
+   * The ID of the object, including the bucket name, object name, and
+   * generation number.
+   */
   id: string;
+
+  /** Storage bucket that contains the object. */
   bucket: string;
+
+  /** Storage class of the object. */
   storageClass: string;
+
+  /**
+   * The value of the `Content-Length` header, used to determine  the length of
+   * the object data in bytes.
+   */
   size: string;
+
+  /** The creation time of the object in RFC 3339 format. */
   timeCreated: string;
+
+  /**
+   * The modification time of the object metadata in RFC 3339 format.
+   */
   updated: string;
+
+  /** Link to access the object, assuming you have sufficient permissions. */
   selfLink?: string;
+
+  /**The object's name. */
   name?: string;
+
+  /**
+   * Generation version number that changes each time the object is
+   * overwritten.
+   */
   generation?: string;
+
+  /** The object's content type, also known as the MIME type. */
   contentType?: string;
+
+  /**
+   * Meta-generation version number that changes each time the object's metadata
+   * is updated.
+   */
   metageneration?: string;
+
+  /**
+   * The deletion time of the object in RFC 3339 format. Returned
+   * only if this version of the object has been deleted.
+   */
   timeDeleted?: string;
+
   timeStorageClassUpdated?: string;
+
+  /**
+   * MD5 hash for the object. All Google Cloud Storage objects
+   * have a CRC32C hash or MD5 hash.
+   */
   md5Hash?: string;
+
+  /** Media download link. */
   mediaLink?: string;
+
+  /**
+   * Content-Encoding to indicate that an object is compressed
+   * (for example, with gzip compression) while maintaining its Content-Type.
+   */
   contentEncoding?: string;
+
+  /**
+   * The value of the `Content-Disposition` header, used to specify presentation
+   * information about the data being transmitted.
+   */
   contentDisposition?: string;
+
+  /** ISO 639-1 language code of the content. */
   contentLanguage?: string;
+
+  /**
+   * The value of the `Cache-Control` header, used to determine whether Internet
+   * caches are allowed to cache public data for an object.
+   */
   cacheControl?: string;
+
+  /** User-provided metadata. */
   metadata?: {
     [key: string]: string;
   };
+
   acl?: [
     {
       kind?: string;
@@ -206,13 +341,37 @@ export interface ObjectMetadata {
       etag?: string;
     }
   ];
+
   owner?: {
     entity?: string;
     entityId?: string;
   };
+
+  /**
+   * The object's CRC32C hash. All Google Cloud Storage objects
+   * have a CRC32C hash or MD5 hash.
+   */
   crc32c?: string;
+
+  /**
+   * Specifies the number of originally uploaded objects from which
+   * a composite object was created.
+   */
   componentCount?: string;
+
   etag?: string;
+
+  /**
+   * Customer-supplied encryption key.
+   *
+   * This object contains the following properties:
+   * * `encryptionAlgorithm` (`string|undefined`): The encryption algorithm that
+   *   was used. Always contains the value `AES256`.
+   * * `keySha256` (`string|undefined`): An RFC 4648 base64-encoded string of the
+   *   SHA256 hash of your encryption key. You can use this SHA256 hash to
+   *   uniquely identify the AES-256 encryption key required to decrypt the
+   *   object, which you must store securely.
+   */
   customerEncryption?: {
     encryptionAlgorithm?: string;
     keySha256?: string;