import type { ChatMessage } from "../llm/types";
import { getSummaryPrompt, getSystemPrompt } from "../llm/prompts";
import {
  buildMetadataBlock,
  extractPdfContext,
  type ExtractResult,
} from "./extractor";

export interface BuiltContext {
  messages: ChatMessage[];
  extract: ExtractResult;
  warning?: string;
}

export async function buildChatMessages(options: {
  item: Zotero.Item;
  history: ChatMessage[];
  userText: string;
  selection?: string;
  mode?: "chat" | "summary";
}): Promise<BuiltContext> {
  const extract = await extractPdfContext(options.item);
  const warnings: string[] = [];

  if (!extract.text) {
    warnings.push(
      "未能提取 PDF 文本（可能是扫描版或尚无文本层）。请检查附件后重试。",
    );
  } else if (extract.truncated) {
    warnings.push("论文较长，已按设置截断上下文。");
  }

  const meta = extract.parentItem
    ? buildMetadataBlock(extract.parentItem)
    : "";

  const systemParts = [getSystemPrompt()];
  if (meta) {
    systemParts.push(`论文元数据：\n${meta}`);
  }
  if (extract.text) {
    systemParts.push(
      `论文正文（页之间可能以换页符分隔）：\n${extract.text}`,
    );
  }

  const messages: ChatMessage[] = [
    { role: "system", content: systemParts.join("\n\n") },
  ];

  // Keep recent history (exclude old system)
  const history = options.history
    .filter((m) => m.role !== "system")
    .slice(-20);
  messages.push(...history);

  if (options.mode === "summary") {
    const summaryAsk = getSummaryPrompt();
    messages.push({
      role: "user",
      content: summaryAsk,
    });
  } else {
    let content = options.userText.trim();
    if (options.selection?.trim()) {
      content =
        `【选中原文】\n${options.selection.trim()}\n\n【问题】\n${content}`;
    }
    messages.push({ role: "user", content });
  }

  return {
    messages,
    extract,
    warning: warnings.length ? warnings.join(" ") : undefined,
  };
}