import type { ChatMessage } from "../llm/types";

/** Detect messages that already embed full paper dumps (should not be in UI history). */
export function isPaperDump(content: string): boolean {
  return (
    content.includes("【论文正文】") ||
    content.includes("【论文 1】") ||
    content.startsWith("【论文元数据】") ||
    content.startsWith("已收到论文内容") ||
    content.includes("【说明】以上为本次会话的论文材料")
  );
}

/**
 * Keep short Q&A turns for the model. Truncate very long assistant replies
 * so paper context + latest question are less likely to be dropped.
 */
export function sanitizeChatHistory(
  history: ChatMessage[],
  options?: { maxMessages?: number; maxAssistantChars?: number },
): ChatMessage[] {
  const maxMessages = options?.maxMessages ?? 10;
  const maxAssistantChars = options?.maxAssistantChars ?? 5000;

  const cleaned = history
    .filter((m) => m.role === "user" || m.role === "assistant")
    .filter((m) => !isPaperDump(m.content))
    .map((m) => {
      if (
        m.role === "assistant" &&
        m.content &&
        m.content.length > maxAssistantChars
      ) {
        return {
          ...m,
          content:
            m.content.slice(0, maxAssistantChars) +
            "\n\n…（为保留论文上下文，历史回复已截断）",
        };
      }
      return m;
    });

  return cleaned.slice(-maxMessages);
}

/**
 * Pin paper corpus near the start of the request, then prior Q&A, then the
 * current task. Avoids stuffing full papers only into the latest message
 * (which providers often truncate under context pressure on turn 2+).
 */
export function assemblePaperChatMessages(options: {
  system: string;
  paperBlock: string;
  taskBlock: string;
  history: ChatMessage[];
}): ChatMessage[] {
  const messages: ChatMessage[] = [
    { role: "system", content: options.system },
    {
      role: "user",
      content: `${options.paperBlock}

【说明】以上为本次会话的论文材料。后续所有问题与分析任务均基于这些论文；无需用户再次提供全文或文本。`,
    },
    {
      role: "assistant",
      content:
        "已收到并理解以上论文材料。请继续提问或下达分析任务，我将基于这些论文作答，不会要求你再次提供全文。",
    },
  ];

  messages.push(...sanitizeChatHistory(options.history));
  messages.push({ role: "user", content: options.taskBlock });
  return messages;
}