"use client";

import { useCallback, useEffect, useRef } from "react";
import { Check, Plus, X } from "lucide-react";

import { ThinkingIndicator } from "@/components/ThinkingIndicator";
import { Button } from "@/components/ui/Button";
import { SectionHeader } from "@/components/ui/SectionHeader";
import { StatusNote } from "@/components/ui/StatusNote";
import { useContinue } from "@/lib/workbench/useContinue";
import type { AiTurnInput } from "@/lib/workbench/useAiConversation";

interface ContinuePanelProps {
  projectId: string;
  chapterNo: number;
  // 插入选中候选到正文（追加到章末）。
  onInsert: (text: string) => void;
  // 留痕：每条候选记一条 ai 气泡（续写无作者输入，故无 author 气泡）。
  appendMessages: (turn: AiTurnInput) => void;
  onClose: () => void;
}

// 续写结果卡（内联，非模态）：打开即读该章前文续写一条候选；可「再来一个」累加多候选，
// 作者点某条「插入正文」才落回草稿（HITL，不静默写入）。
export function ContinuePanel({
  projectId,
  chapterNo,
  onInsert,
  appendMessages,
  onClose,
}: ContinuePanelProps) {
  const { status, candidates, generate } = useContinue();
  const ranRef = useRef(false);
  // 本面板一次会话 = 一个 thread；多条候选归此组，candidate_index 本地累加。
  const threadId = useRef(crypto.randomUUID()).current;
  const candidateIdxRef = useRef(0);

  // 生成一条候选并（成功时）留痕：ai-only，meta 存候选序号。
  const runGenerate = useCallback(async (): Promise<void> => {
    const text = await generate(projectId, chapterNo);
    if (!text) return;
    const candidateIndex = candidateIdxRef.current;
    candidateIdxRef.current += 1;
    appendMessages({
      threadId,
      kind: "continue",
      toolKey: "continue",
      chapterNo,
      messages: [
        { role: "ai", content: text, meta: { candidate_index: candidateIndex } },
      ],
    });
  }, [generate, projectId, chapterNo, appendMessages, threadId]);

  useEffect(() => {
    if (ranRef.current) return;
    ranRef.current = true;
    void runGenerate();
  }, [runGenerate]);

  const busy = status === "generating";

  return (
    <div className="border-b border-line bg-panel px-4 py-3 sm:px-6">
      <div className="flex items-center justify-between gap-3">
        <SectionHeader
          title="续写候选"
          description="承接本章前文续写；点「再来一个」多生成几版，选中意的插入正文。"
        />
        <Button onClick={onClose} variant="ghost" size="icon" aria-label="关闭续写">
          <X className="h-4 w-4" aria-hidden="true" />
        </Button>
      </div>

      {candidates.length === 0 && busy ? (
        <div className="mt-3">
          <ThinkingIndicator label="续写中" className="text-xs text-cinnabar" />
        </div>
      ) : null}

      {candidates.length === 0 && status === "error" ? (
        <StatusNote variant="danger" className="mt-3 text-xs" title="续写失败">
          <button
            type="button"
            onClick={() => void runGenerate()}
            className="mt-1 inline-flex items-center gap-1 text-cinnabar hover:underline"
          >
            重试
          </button>
        </StatusNote>
      ) : null}

      <ul className="mt-3 space-y-2">
        {candidates.map((text, i) => (
          <li
            key={i}
            className="rounded border border-line bg-bg p-3"
          >
            <div className="mb-1 flex items-center justify-between gap-2">
              <span className="text-2xs text-ink-soft">候选 {i + 1}</span>
              <Button
                onClick={() => onInsert(text)}
                variant="primary"
                size="sm"
              >
                <Check className="h-4 w-4" aria-hidden="true" />
                插入正文
              </Button>
            </div>
            <p className="whitespace-pre-wrap text-sm text-ink">{text}</p>
          </li>
        ))}
      </ul>

      <div className="mt-3">
        <Button
          onClick={() => void runGenerate()}
          disabled={busy}
          variant="secondary"
          size="sm"
        >
          <Plus className="h-4 w-4" aria-hidden="true" />
          再来一个候选
        </Button>
      </div>
    </div>
  );
}