cEP-0030: Next Generation Action System

Closes #181

cEP-0030.md

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+# Next Generation Action System
+
+| Metadata |                                                |
+| -------- | -----------------------------------------------|
+| cEP      | 30                                             |
+| Version  | 1.0                                            |
+| Title    | Next Generation Action System                  |
+| Authors  | Akshat Karani <mailto: [email protected]> |
+| Status   | Proposed                                       |
+| Type     | Process                                        |
+
+# Abstract
+
+This cEP describes the details about Next Generation Action System which
+will allow bears to define their own actions as a part of [GSoC'19 project].(https: // summerofcode.withgoogle.com / projects /  # 5450946933424128)
+
+# Introduction
+
+Bears run some analysis and output is in form of a `Result` object. Then some action from a predefined set of actions is applied to that `Result` object. This system is a bit restrictive as action from predefined set of actions can be taken. If there is a system which will support bears defining their own actions, then it will make bears more useful.
+This project is about changing the current action system so that bears can define their own actions. This involves changing the current `Result` class and also modifying the existing action classes.
+
+# Implementation
+
+## Changing the `Result` class
+
+1. The first step is to change the Result class so that it facilitates bears defining their own actions. A new attribute `applicable_actions` is added to Result class. This is a list of all the actions applicable to this Result object.
+2. The `__init__` method of `Result` class is also changed so the when bears yield a result, a list of bear specific actions can be passed. Then in `__init__` method we can add applicable actions from bear specific action and predefined actions to `Result.applicable_actions`.
+
+```python
+class Result:
+    def __init__(actions=[], ..):
+        self.applicable_actions=[]
+        for action in actions:
+            if action.is_applicable():
+                self.applicable_actions.append(action)
+        for action in cli_actions:
+            if action(..).is_applicable():
+                self.applicable_actions.append(action)
+```
+
+## Modifying the existing action classes
+
+Currently, we need to pass Result object as an argument for methods of Action classes and Action classes access attributes of that Result object. Now that we are defining action objects inside a result object, action are modified. `__init__` method is added to all the action classes and while instantiating necessary arguments are passed. Then the methods of action objects are changed accordingly.