/**
 * 知识阅读页（`/w/:wsId/knowledge/:itemId`）。
 *
 * 为什么阅读要独立成页而不是抽屉：抽屉贴在右边、最大也就 1150px 的六成宽，
 * 长文在这个位置读十几屏，视线一直偏在屏幕右侧，很累。阅读本来就该是
 * 一整页、正文落在视线中间的一列（这里限宽 40rem，约 40 个汉字一行）。
 * 抽屉留给"改一下"——那是短时间的动作，也不常对同一篇反复做。
 */
import { useCallback, useEffect, useMemo, useState } from "react";
import { Link, useNavigate, useParams } from "react-router-dom";
import { AppShell } from "../components/AppShell";
import { AttachmentPanel } from "../components/AttachmentPanel";
import { Markdown } from "../components/Markdown";
import { ChevronLeft, Link2, Pencil, Trash } from "../components/icons";
import { Button, InlineAlert, SkeletonRows, StatusPill } from "../components/ui";
import { ApiError, api } from "../lib/client";
import { ACTION_LABEL, DOC_TYPE_LABEL, STATUS_LABEL, categoryColor } from "../lib/knowledge";
import type { Attachment, Knowledge, KnowledgeCategoryNode } from "../lib/types";
import { KnowledgeDrawer } from "./Knowledge";

export function KnowledgeDocPage() {
  const { wsId = "", itemId = "" } = useParams();
  const navigate = useNavigate();
  const [doc, setDoc] = useState<Knowledge | null>(null);
  const [categories, setCategories] = useState<KnowledgeCategoryNode[]>([]);
  const [error, setError] = useState<string | null>(null);
  const [loading, setLoading] = useState(true);
  const [editing, setEditing] = useState(false);
  const [busy, setBusy] = useState(false);

  const load = useCallback(async () => {
    setLoading(true);
    setError(null);
    try {
      const data = await api.get<Knowledge>(`/workspaces/${wsId}/knowledge/${itemId}`);
      setDoc(data);
    } catch (err) {
      setError(err instanceof ApiError ? err.message : "知识加载失败");
    } finally {
      setLoading(false);
    }
  }, [wsId, itemId]);

  useEffect(() => {
    void load();
  }, [load]);

  // 换一篇就回到顶部：否则从长文点进短文，会停在上一页的滚动位置
  useEffect(() => {
    window.scrollTo({ top: 0 });
  }, [itemId]);

  useEffect(() => {
    void (async () => {
      try {
        const page = await api.get<{ items: KnowledgeCategoryNode[] }>(
          `/workspaces/${wsId}/knowledge/categories`,
        );
        setCategories(page.items);
      } catch {
        // 分类只是编辑时的下拉选项，取不到不影响阅读
      }
    })();
  }, [wsId]);

  /** 附件直链：正文里的图片按 attachment id 换成带签名的 raw_url */
  const resources = useMemo(() => {
    const map: Record<string, string> = {};
    for (const row of (doc?.attachments ?? []) as Attachment[]) {
      if (row.raw_url) map[row.id] = row.raw_url;
    }
    return map;
  }, [doc]);

  async function act(action: string) {
    if (!doc) return;
    setBusy(true);
    setError(null);
    try {
      const next = await api.post<Knowledge>(`/workspaces/${wsId}/knowledge/${itemId}/status`, {
        action,
        version: doc.version,
      });
      setDoc(next);
    } catch (err) {
      setError(err instanceof ApiError ? err.message : "操作失败");
      await load();
    } finally {
      setBusy(false);
    }
  }

  const status = doc?.knowledge.status_hint;
  const canEdit = status === "draft" || status === "in_review" || status === "published";

  /** 删除：确认后回列表页。后端是软删，但界面按"没了"处理最不容易让人误会。 */
  async function remove() {
    if (!doc) return;
    if (!window.confirm(`删除「${doc.title}」？删了不会回来，检索里也会一起消失。`)) return;
    setBusy(true);
    setError(null);
    try {
      await api.del(`/workspaces/${wsId}/knowledge/${itemId}?confirm=true`);
      navigate(`/w/${wsId}/knowledge`, { replace: true });
    } catch (err) {
      setError(err instanceof ApiError ? err.message : "删除失败");
    } finally {
      setBusy(false);
    }
  }
  const actions: { key: string; label: string; show: boolean }[] = [
    { key: "submit_review", label: ACTION_LABEL.submit_review, show: status === "draft" },
    { key: "withdraw", label: ACTION_LABEL.withdraw, show: status === "in_review" },
    { key: "publish", label: ACTION_LABEL.publish, show: status === "draft" || status === "in_review" },
    {
      key: "archive",
      label: ACTION_LABEL.archive,
      show: status === "draft" || status === "in_review" || status === "published",
    },
    { key: "restore", label: ACTION_LABEL.restore, show: status === "archived" },
  ];

  return (
    <AppShell wsId={wsId} active="knowledge">
      {/* 宽屏上别把正文挤成窄条：整块跟到 78rem，正文列限宽到 56rem（约 55 个汉字一行）。
          再宽眼睛就要来回扫行了，留白比字长更难读。 */}
      <div className="mx-auto w-full max-w-[78rem]">
        <div className="mb-4 flex flex-wrap items-center gap-2">
          <Link
            to={`/w/${wsId}/knowledge`}
            className="inline-flex items-center gap-1 text-xs text-ink-500 transition hover:text-ink-800"
          >
            <ChevronLeft size={13} />
            返回知识库
          </Link>
          <span className="text-2xs text-ink-300">/</span>
          <span className="max-w-[18rem] truncate text-2xs text-ink-400">
            {doc?.category?.full_path ?? "未分类"}
          </span>
        </div>

        {error && (
          <div className="mb-4">
            <InlineAlert>{error}</InlineAlert>
          </div>
        )}

        {loading && !doc ? (
          <div className="card overflow-hidden">
            <SkeletonRows rows={4} />
          </div>
        ) : !doc ? (
          <div className="card p-6 text-center">
            <p className="text-sm text-ink-600">这条知识不在了，或者你没有权限看它。</p>
            <div className="mt-4">
              <Button variant="ghost" onClick={() => navigate(`/w/${wsId}/knowledge`)}>
                回到知识库
              </Button>
            </div>
          </div>
        ) : (
          <article className="card px-5 py-6 sm:px-8 sm:py-8">
            <div className="mx-auto w-full max-w-[56rem]">
              <div className="flex flex-wrap items-center gap-1.5">
                <span className="chip bg-primary-50 text-primary-700">
                  {DOC_TYPE_LABEL[doc.knowledge.doc_type] ?? doc.knowledge.doc_type}
                </span>
                <StatusPill
                  status={doc.knowledge.status_hint}
                  label={STATUS_LABEL[doc.knowledge.status_hint]}
                />
                {doc.category ? (
                  <span className="chip max-w-[18rem] truncate bg-paper-200 text-ink-600">
                    <span
                      aria-hidden
                      className="mr-1 inline-block h-1.5 w-1.5 shrink-0 rounded-full align-middle"
                      style={{ background: categoryColor(doc.category) }}
                    />
                    {doc.category.full_path}
                  </span>
                ) : null}
              </div>

              <h1 className="mt-3 text-2xl font-semibold leading-snug text-ink-900 sm:text-[28px]">
                {doc.title}
              </h1>

              <p className="mt-2 flex flex-wrap items-center gap-x-3 gap-y-1 text-2xs text-ink-400">
                <span>更新于 {new Date(doc.updated_at).toLocaleString("zh-CN")}</span>
                {doc.knowledge.published_at ? (
                  <span>发布于 {new Date(doc.knowledge.published_at).toLocaleString("zh-CN")}</span>
                ) : (
                  <span>尚未发布，只有工作区里的人能看到</span>
                )}
                {doc.knowledge.chunk_count > 0 ? (
                  <span>检索切片 {doc.knowledge.chunk_count} 段</span>
                ) : null}
              </p>

              {doc.tags.length > 0 ? (
                <div className="mt-3 flex flex-wrap gap-1">
                  {doc.tags.map((t) => (
                    <span key={t.id} className="chip bg-primary-50 text-primary-700">
                      #{t.name}
                    </span>
                  ))}
                </div>
              ) : null}

              <div className="mt-4 flex flex-wrap items-center gap-2 border-b border-line-200 pb-4">
                {canEdit ? (
                  <Button variant="primary" onClick={() => setEditing(true)}>
                    <Pencil size={13} />
                    编辑
                  </Button>
                ) : null}
                {actions
                  .filter((a) => a.show)
                  .map((a) => (
                    <Button
                      key={a.key}
                      variant={a.key === "publish" ? "clay" : "ghost"}
                      disabled={busy}
                      onClick={() => void act(a.key)}
                    >
                      {a.label}
                    </Button>
                  ))}
                {/* 删除放最后、用弱色 + 垃圾桶：它是不可逆的，不该和"发布"抢注意力 */}
                <Button variant="ghost" disabled={busy} className="ml-auto text-ink-400 hover:text-red-600" onClick={() => void remove()}>
                  <Trash size={13} />
                  删除
                </Button>
              </div>

              <div className="mt-6">
                <Markdown source={doc.body_md} resources={resources} />
              </div>

              {doc.source ? (
                <div className="mt-8 rounded-xl border border-line-200 bg-paper-50 p-3.5 text-xs leading-relaxed text-ink-600">
                  <div className="flex items-center gap-1.5">
                    <Link2 size={12} className="text-ink-400" />
                    <span>
                      来源：{doc.source.kind === "ticket" ? "工单" : "任务"}「
                      <Link
                        to={
                          doc.source.kind === "ticket"
                            ? `/w/${wsId}/tickets?open=${doc.source.id}`
                            : `/w/${wsId}?open=${doc.source.id}`
                        }
                        className="link"
                      >
                        {doc.source.title}
                      </Link>
                      」
                    </span>
                  </div>
                  {doc.knowledge.generated_by === "rule" ? (
                    <p className="mt-1 text-ink-400">这份草稿由系统整理，请核对后再发布。</p>
                  ) : null}
                </div>
              ) : null}

              {(doc.attachments?.length ?? 0) > 0 ? (
                <div className="mt-4 rounded-xl border border-line-200 bg-paper-50 px-3 py-2.5">
                  <AttachmentPanel
                    wsId={wsId}
                    itemId={doc.id}
                    attachments={(doc.attachments ?? []) as Attachment[]}
                    onChange={() => void load()}
                    onError={(message) => setError(message)}
                    disabled
                  />
                </div>
              ) : null}
            </div>
          </article>
        )}
      </div>

      {editing && doc ? (
        <KnowledgeDrawer
          wsId={wsId}
          itemId={doc.id}
          categories={categories}
          initialEditing
          onClose={() => setEditing(false)}
          onChanged={() => void load()}
        />
      ) : null}
    </AppShell>
  );
}