docs: add Storage guide

Author: AsifArmanRahman

docs/guide/firebase-rest-api.rst

@@ -126,7 +126,6 @@ A Firebase app can use multiple Firebase services.
 
 ``firebaseApp.database()`` - :ref:`Database<guide/database:Database>`
 
-``firebaseApp.storage()`` - `Storage`
+``firebaseApp.storage()`` - :ref:`Storage<guide/storage:Storage>`
 
 Check out the documentation for each service for further details.
-

docs/guide/storage.rst

@@ -0,0 +1,104 @@
+Storage
+=======
+
+The storage service allows you to upload files (eg. text, image,
+video) to Firebase.
+
+child
+-----
+
+Just like with the Database service, you can build paths to your data
+with the Storage service.
+
+.. code-block:: python
+
+   storage.child("images/example.jpg")
+..
+
+put
+---
+
+The put method takes the path to the local file and an optional user
+token.
+
+.. code-block:: python
+
+   storage = firebaseApp.storage()
+   # as admin
+   storage.child("images/example.jpg").put("example2.jpg")
+   # as user
+   storage.child("images/example.jpg").put("example2.jpg", user['idToken'])
+..
+
+download
+--------
+
+The download method takes the path to the saved database file and the
+name you want the downloaded file to have.
+
+.. code-block:: python
+
+   storage.child("images/example.jpg").download("downloaded.jpg")
+..
+
+get_url
+-------
+
+The get_url method takes the path to the saved database file and user
+token which returns the storage url.
+
+.. code-block:: python
+
+   storage.child("images/example.jpg").get_url(user["idToken"])
+   # https://firebasestorage.googleapis.com/v0/b/storage-url.appspot.com/o/images%2Fexample.jpg?alt=media
+..
+
+delete
+------
+
+The delete method takes the path to the saved database file and user
+token.
+
+.. code-block:: python
+
+   storage.delete("images/example.jpg",user["idToken"])
+..
+
+
+Helper Methods
+--------------
+
+generate_key
+^^^^^^^^^^^^
+
+``db.generate_key()`` is an implementation of Firebase's `key generation
+algorithm <https://www.firebase.com/blog/2015-02-11-firebase-unique-identifiers.html>`__.
+
+See multi-location updates for a potential use case.
+
+
+sort
+^^^^
+
+Sometimes we might want to sort our data multiple times. For example, we
+might want to retrieve all articles written between a certain date then
+sort those articles based on the number of likes.
+
+Currently the REST API only allows us to sort our data once, so the
+``sort()`` method bridges this gap.
+
+.. code-block:: python
+
+   articles = db.child("articles").order_by_child("date").start_at(startDate).end_at(endDate).get()
+   articles_by_likes = db.sort(articles, "likes")
+..
+
+
+Common Errors
+-------------
+
+Index not defined
+^^^^^^^^^^^^^^^^^
+
++`Indexing<https://firebase.google.com/docs/database/security/indexing-data>`__
+is **not enabled** for the database reference.