Resource prototypes

rfcs/resource-prototypes.md

@@ -0,0 +1,237 @@
+---
+RFC: XXXX
+Author: Egor Baranov
+Status: Draft
+Created: 2017-05-03
+Last Modified: 2017-05-03
+---
+
+# API Blueprint RFC XXXX: Resource prototypes
+
+## Table of Contents
+
+- [Abstract](#abstract)
+- [Motivation](#motivation)
+- [Rationale](#rationale)
+- [Backwards Compatibility](#backwards-compatibility)
+
+## Abstract
+
+This RFC proposes an ability to craete resource prototypes and use it to reduce
+code duplication.
+
+## Motivation
+
+When you describe big API several resources can have identical responses.
+Good examples of such problem are:
+
+* request format checks - when several requests can return common error like
+  `WrongFormat`
+* limit rate - when API checks how many requests have user done during some
+  period of time and any request can return error like `LimitExceeded`
+* authorization checking - some part of API can require authorization so several
+  actions can return HTTP 403 forbidden
+* deferred actions - when API request don't perform its job synchronously but
+  put them into queue and return an identifier back to user; such actions will
+  have same response format
+
+All these cases leads to code duplication: you have to write the same response
+again and again. This problem can be cause of misspellings and logical errors.
+So ability to add common responses and headers in one place for multiple actions
+is required.
+
+## Rationale
+
+### Resource prototypes
+
+One of the possible solutions to reduce duplication is creating resource
+prototype and setting it to
+[resource](https://github.com/apiaryio/api-blueprint/blob/master/API%20Blueprint%20Specification.md#resource-section)
+or
+[resource group](https://github.com/apiaryio/api-blueprint/blob/master/API%20Blueprint%20Specification.md#def-resourcegroup-section)
+
+We have complicated API with several duplicate responses:
+
+```apib
+# Data Structures
+
+## Post
+
++ title: `test` (string, required)
++ body: `hello world` (string, required)
+
+## User
+
++ name: `John Smith` (string, required)
++ email: `[email protected]` (string, required)
+
+## Posts [/posts]
+
+### List posts [GET]
+
++ Response 200
+    + Attributes (array[Post], required, fixed-type)
+
++ Response 429 (application/json)
+    + Attributes
+        + status: tooManyRequests (string, required, fixed)
+        + waitFor: `10` (number, required) - wait before next request
+
++ Response 400 (application/json)
+    + Attributes
+        + status: badRequest (string, required, fixed)
+        + errors (array[string], required, fixed-type) - list of errors in request
+
+### Show post [GET]
+
++ Response 200
+    + Attributes (Post, required)
+
++ Response 429 (application/json)
+    + Attributes
+        + status: tooManyRequests (string, required, fixed)
+        + waitFor: `10` (number, required) - wait before next request
+
++ Response 400 (application/json)
+    + Attributes
+        + status: badRequest (string, required, fixed)
+        + errors (array[string], required, fixed-type) - list of errors in request
+
+## Users [/users]
+
+### List users [GET]
+
++ Response 200
+    + Attributes (array[User], required, fixed-type)
+
++ Response 429 (application/json)
+    + Attributes
+        + status: tooManyRequests (string, required, fixed)
+        + waitFor: `10` (number, required) - wait before next request
+
++ Response 400 (application/json)
+    + Attributes
+        + status: badRequest (string, required, fixed)
+        + errors (array[string], required, fixed-type) - list of errors in request
+
++ Response 403 (application/json)
+    + Attributes
+        + status: forbidden (string, required, fixed)
+
+### Create user [POST]
+
++ Response 200
+    + Attributes (User, required)
+
++ Response 429 (application/json)
+    + Attributes
+        + status: tooManyRequests (string, required, fixed)
+        + waitFor: `10` (number, required) - wait before next request
+
++ Response 400 (application/json)
+    + Attributes
+        + status: badRequest (string, required, fixed)
+        + errors (array[string], required, fixed-type) - list of errors in request
+
++ Response 403 (application/json)
+    + Attributes
+        + status: forbidden (string, required, fixed)
+```
+
+As you can see responses 429, 400 and 403 are duplicated several times. It is
+possible to extract response description into
+[Data Structures](https://github.com/apiaryio/api-blueprint/blob/master/API%20Blueprint%20Specification.md#def-data-structures)
+section and it will help to reduce duplication but you have to write something
+like
+
+```apib
++ Response 429 (application/json)
+    + Attributes (TooManyRequestsError)
+```
+
+for every resource. It is possible to remove duplication completely using new
+proposed syntax:
+
+```apib
+# Data Structures
+
+## Post
+
++ title: `test` (string, required)
++ body: `hello world` (string, required)
+
+## User
+
++ name: `John Smith` (string, required)
++ email: `[email protected]` (string, required)
+
+## Authorized (Resource Prototype)
+
++ Response 403 (application/json)
+    + Attributes
+        + status: forbidden (string, required, fixed)
+
+## Common Resource (Resource Prototype)
+
++ Response 429 (application/json)
+    + Attributes
+        + status: tooManyRequests (string, required, fixed)
+        + waitFor: `10` (number, required) - wait before next request
+
++ Response 400 (application/json)
+    + Attributes
+        + status: badRequest (string, required, fixed)
+        + errors (array[string], required, fixed-type) - list of errors in request
+
+# Group Blog (Common Resource)
+
+## Posts [/posts]
+
+### List posts [GET]
+
++ Response 200
+    + Attributes (array[Post], required, fixed-type)
+
+### Show post [GET]
+
++ Response 200
+    + Attributes (Post, required)
+
+## Users (Authorized) [/users]
+
+### List users [GET]
+
++ Response 200
+    + Attributes (array[User], required, fixed-type)
+
+### Create user [POST]
+
++ Response 200
+    + Attributes (User, required)
+```
+
+In `Data Structures` section two prototypes were defined: `Common Resource`
+and `Authorized` with base type `Resource Prototype`.  Both of them have some
+responses. To assign prototype for all resources of resource group you need to
+use such syntax: `Section name (Prototype Name)`. If section has nested section
+then all resources of nested section will have responses defined in prototype.
+`Users` resource group will have responces from `Common Resource` prototype
+(because it's a prototype of its parent group) and from `Authorized` prototype.
+
+It is possible to assign several prototypes for one resource or resource group:
+
+```apib
+# Group Blog (Common Resource, Authorized)
+```
+
+It is possible when one prototype has its own prototype:
+
+```apib
+# Data Structures
+
+## Common Resource (Rate, Format)
+```
+
+## Backwards Compatibility
+
+There will be no backward compatibility problems.