import type { ToolSet, ModelMessage, LanguageModelV3 } from './plugins.js';

export interface IAgentRunOptions {
  /** The LanguageModelV3 to use — from smartai.getModel() */
  model: LanguageModelV3;
  /** Initial user message or task description */
  prompt: string;
  /** System prompt override */
  system?: string;
  /** Tools available to the agent */
  tools?: ToolSet;
  /**
   * Maximum number of LLM↔tool round trips.
   * Each step may execute multiple tools in parallel.
   * Default: 20
   */
  maxSteps?: number;
  /** Prior conversation messages to include */
  messages?: ModelMessage[];
  /** Called for each streamed text delta */
  onToken?: (delta: string) => void;
  /** Called when a tool call starts */
  onToolCall?: (toolName: string, input: unknown) => void;
  /** Called when a tool call completes */
  onToolResult?: (toolName: string, result: unknown) => void;
  /**
   * Called when total token usage approaches the model's context limit.
   * Receives the full message history and must return a compacted replacement.
   * If not provided, runAgent throws a ContextOverflowError instead.
   */
  onContextOverflow?: (messages: ModelMessage[]) => Promise<ModelMessage[]>;
  /** AbortSignal to cancel the run mid-flight */
  abort?: AbortSignal;
}

export interface IAgentRunResult {
  /** Final text output from the model */
  text: string;
  /** All messages in the completed conversation */
  messages: ModelMessage[];
  /** Total steps taken */
  steps: number;
  /** Finish reason from the final step */
  finishReason: string;
  /** Accumulated token usage across all steps */
  usage: { inputTokens: number; outputTokens: number; totalTokens: number };
}

export class ContextOverflowError extends Error {
  constructor(message = 'Agent context limit reached and no onContextOverflow handler provided') {
    super(message);
    this.name = 'ContextOverflowError';
  }
}