/**
 * A2A 消息格式转换层
 *
 * 负责 A2A 协议类型与内部业务类型之间的双向转换：
 * - Agent 数据行 ↔ Agent Card
 * - A2A Message ↔ 纯文本输入（用于 generateText）
 * - 纯文本输出 ↔ A2A Message
 * - A2A Part ↔ StoredPart（预留，当前仅 TextPart）
 */

import type { AgentRow } from "../agent/types";
import type { StoredPart } from "../agent/stored-part";
import type {
  A2AAgentCard,
  A2ASkill,
  A2AMessage,
  A2APart,
  A2ATextPart,
  A2ADataPart,
  A2AFilePart,
} from "./types";
import { A2A_PROTOCOL_VERSION } from "./types";

// ============ Agent Row → Agent Card ============

export function agentRowToCard(agent: AgentRow, baseUrl: string): A2AAgentCard {
  const url = `${baseUrl}/api/agents/${agent.slug}/a2a`;

  const skills: A2ASkill[] = [
    {
      id: agent.slug,
      name: agent.name,
      description: agent.description ?? agent.systemPrompt.slice(0, 200),
      tags: agent.isCallable ? ["callable", "agent"] : ["agent"],
      inputModes: ["text/plain"],
      outputModes: ["text/plain"],
    },
  ];

  return {
    name: agent.name,
    description: agent.description ?? "",
    url,
    version: "1.0.0",
    protocolVersion: A2A_PROTOCOL_VERSION,
    capabilities: {
      streaming: true,
      pushNotifications: false,
      stateTransition: true,
    },
    defaultInputModes: ["text/plain"],
    defaultOutputModes: ["text/plain"],
    skills,
  };
}

// ============ A2A Message ↔ 纯文本 ============

export function a2aMessageToText(message: A2AMessage): string {
  const textParts = message.parts.filter((p): p is A2ATextPart => p.type === "text");
  if (textParts.length === 0) return "";
  return textParts.map((p) => p.text).join("\n");
}

export function textToA2AMessage(text: string, role: "user" | "agent" = "agent"): A2AMessage {
  return {
    role,
    parts: [{ type: "text", text }],
  };
}

// ============ A2A Part ↔ StoredPart（预留） ============

export function a2aPartsToStoredParts(parts: A2APart[]): StoredPart[] {
  return parts
    .filter((p): p is A2ATextPart => p.type === "text")
    .map((p, i) => ({
      id: `a2a-part-${i}`,
      type: "text",
      text: p.text,
    }));
}

export function storedPartsToA2AParts(parts: StoredPart[]): A2APart[] {
  return parts
    .filter((p) => p.type === "text" && p.text !== undefined)
    .map((p) => ({
      type: "text" as const,
      text: p.text!,
    }));
}

// ============ Part 类型守卫 ============

export function isTextPart(part: A2APart): part is A2ATextPart {
  return part.type === "text";
}

export function isDataPart(part: A2APart): part is A2ADataPart {
  return part.type === "data";
}

export function isFilePart(part: A2APart): part is A2AFilePart {
  return part.type === "file";
}