Starting to modularize into separate cli / server packages. (#55)

* Starting to move a lot of code into packages/server

* More of the massive refactor, builds and runs, some issues though.

* Fixing outstanding issue with double messages.

* Fixing a minor UI issue.

* Fixing the build post-merge.

* Running formatting.

* Addressing comments.

packages/server/src/tools/tools.ts

@@ -0,0 +1,150 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { FunctionDeclaration, Schema } from '@google/genai';
+// Removed import for ../ui/types.js as confirmation is UI-specific
+
+/**
+ * Interface representing the base Tool functionality
+ */
+export interface Tool<
+  TParams = unknown,
+  TResult extends ToolResult = ToolResult,
+> {
+  /**
+   * The internal name of the tool (used for API calls)
+   */
+  name: string;
+
+  /**
+   * The user-friendly display name of the tool
+   */
+  displayName: string;
+
+  /**
+   * Description of what the tool does
+   */
+  description: string;
+
+  /**
+   * Function declaration schema from @google/genai
+   */
+  schema: FunctionDeclaration;
+
+  /**
+   * Validates the parameters for the tool
+   * @param params Parameters to validate
+   * @returns An error message string if invalid, null otherwise
+   */
+  validateToolParams(params: TParams): string | null;
+
+  /**
+   * Gets a pre-execution description of the tool operation
+   * @param params Parameters for the tool execution
+   * @returns A markdown string describing what the tool will do
+   * Optional for backward compatibility
+   */
+  getDescription(params: TParams): string;
+
+  // Removed shouldConfirmExecute as it's UI-specific
+
+  /**
+   * Executes the tool with the given parameters
+   * @param params Parameters for the tool execution
+   * @returns Result of the tool execution
+   */
+  execute(params: TParams): Promise<TResult>;
+}
+
+/**
+ * Base implementation for tools with common functionality
+ */
+export abstract class BaseTool<
+  TParams = unknown,
+  TResult extends ToolResult = ToolResult,
+> implements Tool<TParams, TResult>
+{
+  /**
+   * Creates a new instance of BaseTool
+   * @param name Internal name of the tool (used for API calls)
+   * @param displayName User-friendly display name of the tool
+   * @param description Description of what the tool does
+   * @param parameterSchema JSON Schema defining the parameters
+   */
+  constructor(
+    readonly name: string,
+    readonly displayName: string,
+    readonly description: string,
+    readonly parameterSchema: Record<string, unknown>,
+  ) {}
+
+  /**
+   * Function declaration schema computed from name, description, and parameterSchema
+   */
+  get schema(): FunctionDeclaration {
+    return {
+      name: this.name,
+      description: this.description,
+      parameters: this.parameterSchema as Schema,
+    };
+  }
+
+  /**
+   * Validates the parameters for the tool
+   * This is a placeholder implementation and should be overridden
+   * @param params Parameters to validate
+   * @returns An error message string if invalid, null otherwise
+   */
+  // eslint-disable-next-line @typescript-eslint/no-unused-vars
+  validateToolParams(params: TParams): string | null {
+    // Implementation would typically use a JSON Schema validator
+    // This is a placeholder that should be implemented by derived classes
+    return null;
+  }
+
+  /**
+   * Gets a pre-execution description of the tool operation
+   * Default implementation that should be overridden by derived classes
+   * @param params Parameters for the tool execution
+   * @returns A markdown string describing what the tool will do
+   */
+  getDescription(params: TParams): string {
+    return JSON.stringify(params);
+  }
+
+  // Removed shouldConfirmExecute as it's UI-specific
+
+  /**
+   * Abstract method to execute the tool with the given parameters
+   * Must be implemented by derived classes
+   * @param params Parameters for the tool execution
+   * @returns Result of the tool execution
+   */
+  abstract execute(params: TParams): Promise<TResult>;
+}
+
+export interface ToolResult {
+  /**
+   * Content meant to be included in LLM history.
+   * This should represent the factual outcome of the tool execution.
+   */
+  llmContent: string;
+
+  /**
+   * Markdown string for user display.
+   * This provides a user-friendly summary or visualization of the result.
+   * NOTE: This might also be considered UI-specific and could potentially be
+   * removed or modified in a further refactor if the server becomes purely API-driven.
+   * For now, we keep it as the core logic in ReadFileTool currently produces it.
+   */
+  returnDisplay: ToolResultDisplay;
+}
+
+export type ToolResultDisplay = string | FileDiff;
+
+export interface FileDiff {
+  fileDiff: string;
+}