export interface ConversationTurn {
  role: "user" | "assistant";
  text: string;
  speakerId?: string;
  speakerName?: string;
  createdAt: number;
}

export interface UserUtterance {
  speakerId: string;
  speakerName: string;
  text: string;
}

export class ConversationMemory {
  private readonly turns: ConversationTurn[] = [];

  constructor(private readonly maxTurns: number) {}

  addUserTurn(utterance: UserUtterance): void {
    this.turns.push({
      role: "user",
      text: utterance.text,
      speakerId: utterance.speakerId,
      speakerName: utterance.speakerName,
      createdAt: Date.now(),
    });
    this.trim();
  }

  addAssistantTurn(text: string): void {
    this.turns.push({
      role: "assistant",
      text,
      createdAt: Date.now(),
    });
    this.trim();
  }

  clear(): void {
    this.turns.splice(0, this.turns.length);
  }

  recentTurns(): ConversationTurn[] {
    return [...this.turns];
  }

  buildPrompt(currentUtterance: UserUtterance): string {
    const recent = this.turns
      .slice(-this.maxTurns)
      .map((turn) => {
        if (turn.role === "assistant") {
          return `[assistant]\n${turn.text}`;
        }
        return `[user speaker_id=${turn.speakerId ?? "unknown"} speaker_name=${turn.speakerName ?? "unknown"}]\n${turn.text}`;
      })
      .join("\n\n");

    const historyBlock = recent.length > 0 ? recent : "(이전 대화 없음)";

    return [
      "최근 대화:",
      historyBlock,
      "",
      "이번 발화:",
      `[user speaker_id=${currentUtterance.speakerId} speaker_name=${currentUtterance.speakerName}]`,
      currentUtterance.text,
    ].join("\n");
  }

  private trim(): void {
    const overflow = this.turns.length - this.maxTurns;
    if (overflow > 0) {
      this.turns.splice(0, overflow);
    }
  }
}