Add Agent.

- Takes in a function (from the PluginCommand) alongside the
  Engine you want to run the query one.
- Various checks to make sure the user passes in the right types.
- TODO: Limit number of tokens.
- TODO: Send the query.

Relate #3.

Author: WhatTheFuzz

src/agent.py

@@ -0,0 +1,54 @@
+import os
+
+import openai
+from openai.api_resources.engine import Engine
+from openai.error import APIError
+
+from binaryninja.lowlevelil import LowLevelILFunction
+from binaryninja.mediumlevelil import MediumLevelILFunction
+from binaryninja.highlevelil import HighLevelILFunction
+
+from .exceptions import InvalidEngineException
+
+
+class Agent:
+
+    def ___init__(self, function: LowLevelILFunction | MediumLevelILFunction |
+                                  HighLevelILFunction, engine: str) -> None:
+
+        # Read the API key from the environment variable.
+        openai.api_key = os.getenv('OPENAI_API_KEY')
+        if openai.api_key is None:
+            raise APIError('No API key found. Please set the environment '
+                           'variable OPENAI_API_KEY to your API key.')
+
+        # Ensure that a function type was passed in.
+        if not isinstance(
+                function,
+            (LowLevelILFunction, MediumLevelILFunction, HighLevelILFunction)):
+            raise TypeError(f'Expected a BNIL function of type '
+                            f'LowLevelILFunction, MediumLevelILFunction, or '
+                            f'HighLevelILFunction, got {type(function)}.')
+
+        # Get the list of available engines.
+        engines: list[Engine] = openai.Engine.list().data
+        # Ensure the user's selected engine is available.
+        # pylint: disable=unnecessary-comprehension
+        if engine not in [i.id for i in engines]:
+            InvalidEngineException(f'Invalid engine: {engine}. Valid engines '
+                                   f'are: {[id for id in engines.id]}')
+
+        # Set instance attributes.
+        self.function = function
+        self.engine = engine
+
+    def instruction_list(self, function: LowLevelILFunction |
+                                         MediumLevelILFunction |
+                                         HighLevelILFunction) -> list[str]:
+        '''Generates a list of instructions in string representation given a
+        BNIL function.
+        '''
+        instructions: list[str] = []
+        for instruction in function.instructions:
+            instructions.append(str(instruction))
+        return instructions

src/exceptions.py

@@ -0,0 +1,4 @@
+from openai.error import OpenAIError
+
+class InvalidEngineException(OpenAIError):
+    pass