flynn/src/tools/executor.ts

import type { ToolResult } from './types.js';
import type { ToolRegistry } from './registry.js';
import type { HookEngine } from '../hooks/engine.js';
import type { ToolPolicyContext } from './policy.js';

export interface ToolExecutorConfig {
  defaultTimeoutMs?: number;
  maxOutputBytes?: number;
}

export class ToolExecutor {
  private registry: ToolRegistry;
  private hooks: HookEngine;
  private defaultTimeoutMs: number;
  private maxOutputBytes: number;

  constructor(registry: ToolRegistry, hooks: HookEngine, config?: ToolExecutorConfig) {
    this.registry = registry;
    this.hooks = hooks;
    this.defaultTimeoutMs = config?.defaultTimeoutMs ?? 30_000;
    this.maxOutputBytes = config?.maxOutputBytes ?? 51_200;
  }

  async execute(toolName: string, args: unknown, context?: ToolPolicyContext): Promise<ToolResult> {
    const tool = this.registry.getByApiName(toolName);
    if (!tool) {
      return { success: false, output: '', error: `Tool '${toolName}' not found` };
    }

    // Policy check (defense in depth — tools should also be filtered at listing time)
    const policy = this.registry.getPolicy();
    if (policy) {
      const allNames = this.registry.list().map(t => t.name);
      if (!policy.isAllowed(toolName, allNames, context)) {
        return {
          success: false,
          output: '',
          error: `Tool '${toolName}' is not allowed by tool policy`,
        };
      }
    }

    // Check hooks
    const action = this.hooks.getAction(toolName);
    if (action === 'confirm') {
      const hookResult = await this.hooks.requestConfirmation(
        toolName,
        args as Record<string, unknown>,
      );
      if (!hookResult.approved) {
        return {
          success: false,
          output: '',
          error: `Tool '${toolName}' denied by user: ${hookResult.reason ?? 'no reason'}`,
        };
      }
    }

    // Execute with timeout
    try {
      const result = await Promise.race([
        tool.execute(args),
        new Promise<ToolResult>((_, reject) =>
          setTimeout(() => reject(new Error(`Tool '${toolName}' timed out after ${this.defaultTimeoutMs}ms`)), this.defaultTimeoutMs)
        ),
      ]);

      // Truncate output if too large
      if (result.output.length > this.maxOutputBytes) {
        result.output = result.output.slice(0, this.maxOutputBytes) + '\n[truncated]';
      }

      return result;
    } catch (error) {
      return {
        success: false,
        output: '',
        error: error instanceof Error ? error.message : String(error),
      };
    }
  }
}