Inference plugin: Add Bedrock model adapter (elastic#191434)

## Summary

Add the `bedrock` (well, bedrock-claude) model adapter for the inference
plugin. Also had to perform minor changes on the associated connector to
add support for new capabilities.

---------

Co-authored-by: kibanamachine <42973632+kibanamachine@users.noreply.github.com>

x-pack/plugins/inference/server/chat_complete/adapters/bedrock/bedrock_claude_adapter.test.ts

@@ -0,0 +1,310 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+import { PassThrough } from 'stream';
+import type { InferenceExecutor } from '../../utils/inference_executor';
+import { MessageRole } from '../../../../common/chat_complete';
+import { ToolChoiceType } from '../../../../common/chat_complete/tools';
+import { bedrockClaudeAdapter } from './bedrock_claude_adapter';
+import { addNoToolUsageDirective } from './prompts';
+
+describe('bedrockClaudeAdapter', () => {
+  const executorMock = {
+    invoke: jest.fn(),
+  } as InferenceExecutor & { invoke: jest.MockedFn<InferenceExecutor['invoke']> };
+
+  beforeEach(() => {
+    executorMock.invoke.mockReset();
+    executorMock.invoke.mockImplementation(async () => {
+      return {
+        actionId: '',
+        status: 'ok',
+        data: new PassThrough(),
+      };
+    });
+  });
+
+  function getCallParams() {
+    const params = executorMock.invoke.mock.calls[0][0].subActionParams as Record<string, any>;
+    return {
+      system: params.system,
+      messages: params.messages,
+      tools: params.tools,
+      toolChoice: params.toolChoice,
+    };
+  }
+
+  describe('#chatComplete()', () => {
+    it('calls `executor.invoke` with the right fixed parameters', () => {
+      bedrockClaudeAdapter.chatComplete({
+        executor: executorMock,
+        messages: [
+          {
+            role: MessageRole.User,
+            content: 'question',
+          },
+        ],
+      });
+
+      expect(executorMock.invoke).toHaveBeenCalledTimes(1);
+      expect(executorMock.invoke).toHaveBeenCalledWith({
+        subAction: 'invokeStream',
+        subActionParams: {
+          messages: [
+            {
+              role: 'user',
+              rawContent: [{ type: 'text', text: 'question' }],
+            },
+          ],
+          temperature: 0,
+          stopSequences: ['\n\nHuman:'],
+        },
+      });
+    });
+
+    it('correctly format tools', () => {
+      bedrockClaudeAdapter.chatComplete({
+        executor: executorMock,
+        messages: [
+          {
+            role: MessageRole.User,
+            content: 'question',
+          },
+        ],
+        tools: {
+          myFunction: {
+            description: 'myFunction',
+          },
+          myFunctionWithArgs: {
+            description: 'myFunctionWithArgs',
+            schema: {
+              type: 'object',
+              properties: {
+                foo: {
+                  type: 'string',
+                  description: 'foo',
+                },
+              },
+              required: ['foo'],
+            },
+          },
+        },
+      });
+
+      expect(executorMock.invoke).toHaveBeenCalledTimes(1);
+
+      const { tools } = getCallParams();
+      expect(tools).toEqual([
+        {
+          name: 'myFunction',
+          description: 'myFunction',
+          input_schema: {
+            properties: {},
+            type: 'object',
+          },
+        },
+        {
+          name: 'myFunctionWithArgs',
+          description: 'myFunctionWithArgs',
+          input_schema: {
+            properties: {
+              foo: {
+                description: 'foo',
+                type: 'string',
+              },
+            },
+            required: ['foo'],
+            type: 'object',
+          },
+        },
+      ]);
+    });
+
+    it('correctly format messages', () => {
+      bedrockClaudeAdapter.chatComplete({
+        executor: executorMock,
+        messages: [
+          {
+            role: MessageRole.User,
+            content: 'question',
+          },
+          {
+            role: MessageRole.Assistant,
+            content: 'answer',
+          },
+          {
+            role: MessageRole.User,
+            content: 'another question',
+          },
+          {
+            role: MessageRole.Assistant,
+            content: null,
+            toolCalls: [
+              {
+                function: {
+                  name: 'my_function',
+                  arguments: {
+                    foo: 'bar',
+                  },
+                },
+                toolCallId: '0',
+              },
+            ],
+          },
+          {
+            role: MessageRole.Tool,
+            toolCallId: '0',
+            response: {
+              bar: 'foo',
+            },
+          },
+        ],
+      });
+
+      expect(executorMock.invoke).toHaveBeenCalledTimes(1);
+
+      const { messages } = getCallParams();
+      expect(messages).toEqual([
+        {
+          rawContent: [
+            {
+              text: 'question',
+              type: 'text',
+            },
+          ],
+          role: 'user',
+        },
+        {
+          rawContent: [
+            {
+              text: 'answer',
+              type: 'text',
+            },
+          ],
+          role: 'assistant',
+        },
+        {
+          rawContent: [
+            {
+              text: 'another question',
+              type: 'text',
+            },
+          ],
+          role: 'user',
+        },
+        {
+          rawContent: [
+            {
+              id: '0',
+              input: {
+                foo: 'bar',
+              },
+              name: 'my_function',
+              type: 'tool_use',
+            },
+          ],
+          role: 'assistant',
+        },
+        {
+          rawContent: [
+            {
+              content: '{"bar":"foo"}',
+              tool_use_id: '0',
+              type: 'tool_result',
+            },
+          ],
+          role: 'user',
+        },
+      ]);
+    });
+
+    it('correctly format system message', () => {
+      bedrockClaudeAdapter.chatComplete({
+        executor: executorMock,
+        system: 'Some system message',
+        messages: [
+          {
+            role: MessageRole.User,
+            content: 'question',
+          },
+        ],
+      });
+
+      expect(executorMock.invoke).toHaveBeenCalledTimes(1);
+
+      const { system } = getCallParams();
+      expect(system).toEqual('Some system message');
+    });
+
+    it('correctly format tool choice', () => {
+      bedrockClaudeAdapter.chatComplete({
+        executor: executorMock,
+        messages: [
+          {
+            role: MessageRole.User,
+            content: 'question',
+          },
+        ],
+        toolChoice: ToolChoiceType.required,
+      });
+
+      expect(executorMock.invoke).toHaveBeenCalledTimes(1);
+
+      const { toolChoice } = getCallParams();
+      expect(toolChoice).toEqual({
+        type: 'any',
+      });
+    });
+
+    it('correctly format tool choice for named function', () => {
+      bedrockClaudeAdapter.chatComplete({
+        executor: executorMock,
+        messages: [
+          {
+            role: MessageRole.User,
+            content: 'question',
+          },
+        ],
+        toolChoice: { function: 'foobar' },
+      });
+
+      expect(executorMock.invoke).toHaveBeenCalledTimes(1);
+
+      const { toolChoice } = getCallParams();
+      expect(toolChoice).toEqual({
+        type: 'tool',
+        name: 'foobar',
+      });
+    });
+
+    it('correctly adapt the request for ToolChoiceType.None', () => {
+      bedrockClaudeAdapter.chatComplete({
+        executor: executorMock,
+        system: 'some system instruction',
+        messages: [
+          {
+            role: MessageRole.User,
+            content: 'question',
+          },
+        ],
+        tools: {
+          myFunction: {
+            description: 'myFunction',
+          },
+        },
+        toolChoice: ToolChoiceType.none,
+      });
+
+      expect(executorMock.invoke).toHaveBeenCalledTimes(1);
+
+      const { toolChoice, tools, system } = getCallParams();
+      expect(toolChoice).toBeUndefined();
+      expect(tools).toEqual([]);
+      expect(system).toEqual(addNoToolUsageDirective('some system instruction'));
+    });
+  });
+});