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

/**
 * Options for creating a ChatSession.
 */
export interface IChatSessionOptions {
  /** The language model to use */
  model: LanguageModelV3;
  /** System prompt for the agent */
  system?: string;
  /** Tools available to the agent */
  tools?: ToolSet;
  /** Maximum agentic steps per turn */
  maxSteps?: number;
}

/**
 * Callbacks for real-time streaming events during a turn.
 */
export interface IChatCallbacks {
  /** Called for each streamed text token */
  onToken?: (delta: string) => void;
  /** Called when a tool call starts */
  onToolCall?: (name: string, input: unknown) => void;
  /** Called when a tool call completes */
  onToolResult?: (name: string, result: string) => void;
  /** Called when a turn completes */
  onTurnComplete?: (result: IAgentRunResult) => void;
  /** Called on error */
  onError?: (error: Error) => void;
}

/**
 * Events emitted during chat.
 */
export type TChatEvent =
  | { type: 'token'; delta: string }
  | { type: 'tool_call_start'; name: string; input: unknown }
  | { type: 'tool_call_end'; name: string; result: string }
  | { type: 'turn_start' }
  | { type: 'turn_complete'; result: IAgentRunResult }
  | { type: 'error'; error: Error };

/**
 * Usage stats accumulated across all turns.
 */
export interface IChatUsage {
  inputTokens: number;
  outputTokens: number;
  totalTokens: number;
  turns: number;
}