"use client";

import { useMemo, useRef, useState } from "react";
import Link from "next/link";
import { useRouter } from "next/navigation";
import { ArrowLeft, FileText } from "lucide-react";
import {
  apiAdminCreateSitePage,
  apiAdminUpdateSitePage,
  type SitePage,
  type SitePageInput,
} from "@/lib/api";
import { toast } from "@/lib/toast";
import MarkdownEditor from "@/components/MarkdownEditor";
import {
  AdminField,
  AdminPageHeader,
  AdminSegmented,
  AdminSettingsActions,
  AdminSettingsGroup,
  AdminSettingsPage,
  AdminSettingsRow,
  AdminSwitch,
} from "@/components/admin";
import ConfirmDialog from "@/components/ConfirmDialog";
import useUnsavedGuard from "@/hooks/useUnsavedGuard";

type PublishKey = "published" | "draft";

type FormState = {
  slug: string;
  title: string;
  content: string;
  excerpt: string;
  published: boolean;
  show_in_sidebar: boolean;
  sort_order: number;
};

function toForm(p?: SitePage | null): FormState {
  return {
    slug: p?.slug ?? "",
    title: p?.title ?? "",
    content: p?.content ?? "",
    excerpt: p?.excerpt ?? "",
    published: p?.published ?? true,
    show_in_sidebar: p?.show_in_sidebar ?? false,
    sort_order: p?.sort_order ?? 0,
  };
}

function sameForm(a: FormState, b: FormState): boolean {
  return (
    a.slug === b.slug &&
    a.title === b.title &&
    a.content === b.content &&
    a.excerpt === b.excerpt &&
    a.published === b.published &&
    a.show_in_sidebar === b.show_in_sidebar &&
    a.sort_order === b.sort_order
  );
}

/** slug 仅允许小写字母数字与连字符 */
function normalizeSlug(raw: string): string {
  return raw
    .trim()
    .toLowerCase()
    .replace(/[^a-z0-9-]+/g, "-")
    .replace(/-+/g, "-")
    .replace(/^-|-$/g, "");
}

export default function PageComposeClient({
  mode,
  initial,
}: {
  mode: "create" | "edit";
  initial?: SitePage | null;
}) {
  const router = useRouter();
  const baseline = useMemo(() => toForm(initial), [initial]);
  const [form, setForm] = useState<FormState>(baseline);
  const formRef = useRef(form);
  const [saving, setSaving] = useState(false);
  const isEdit = mode === "edit" && initial != null;
  const dirty = !sameForm(form, baseline);
  const { leaveOpen, confirmLeave, cancelLeave } = useUnsavedGuard(dirty && !saving);

  const patchForm = (patch: Partial<FormState> | ((prev: FormState) => FormState)) => {
    setForm((prev) => {
      const next = typeof patch === "function" ? patch(prev) : { ...prev, ...patch };
      formRef.current = next;
      return next;
    });
  };

  async function save() {
    if (saving) return;
    const current = formRef.current;
    const slug = normalizeSlug(current.slug);
    const payload: SitePageInput = {
      slug,
      title: current.title.trim(),
      content: current.content.trim(),
      excerpt: current.excerpt.trim(),
      published: current.published,
      show_in_sidebar: current.show_in_sidebar,
      sort_order: current.sort_order,
    };
    if (!payload.slug || !payload.title || !payload.content) {
      toast("slug、标题和内容不能为空");
      return;
    }
    setSaving(true);
    try {
      if (isEdit) {
        await apiAdminUpdateSitePage(initial.id, payload);
        toast("页面已更新", "ok");
      } else {
        await apiAdminCreateSitePage(payload);
        toast(payload.published ? "页面已发布" : "草稿已保存", "ok");
      }
      router.push("/admin/pages");
      router.refresh();
    } catch (e) {
      toast(e instanceof Error ? e.message : "保存失败");
    } finally {
      setSaving(false);
    }
  }

  const saveLabel = isEdit ? "保存修改" : form.published ? "发布页面" : "保存草稿";

  return (
    <AdminSettingsPage className="is-fill">
      <AdminPageHeader
        icon={FileText}
        title={isEdit ? "编辑单页" : "新建单页"}
        description="关于本站、隐私政策等 Markdown 单页；可展示在首页右栏。"
        actions={
          <Link href="/admin/pages" className="btn btn-line btn-sm">
            <ArrowLeft size={14} /> 返回列表
          </Link>
        }
      />

      <div className="admin-settings-main admin-settings-stack">
        <AdminSettingsGroup title="页面设置" description="slug 写入后即是前台地址 /p/…">
          <AdminSettingsRow label="URL slug" htmlFor="page-slug" hint="/p/ 后的路径">
            <div className="admin-settings-control-text flex items-center gap-1.5 min-w-0">
              <span className="meta text-[13px] shrink-0">/p/</span>
              <div className="admin-field-shell min-w-0 flex-1">
                <input
                  id="page-slug"
                  className="admin-field-input font-mono text-[13px]"
                  maxLength={64}
                  value={form.slug}
                  onChange={(e) => patchForm({ slug: e.target.value })}
                  onBlur={() => patchForm((f) => ({ ...f, slug: normalizeSlug(f.slug) }))}
                  placeholder="about"
                />
              </div>
            </div>
          </AdminSettingsRow>
          <AdminSettingsRow label="摘要" htmlFor="page-excerpt" hintBelow="侧栏「关于本站」使用这一句" wide>
            <AdminField
              id="page-excerpt"
              label="摘要"
              embed
              as="textarea"
              className="admin-settings-control-long"
              maxLength={300}
              minHeight="4.5rem"
              value={form.excerpt}
              onChange={(excerpt) => patchForm({ excerpt })}
              placeholder="一句话介绍本页…"
            />
          </AdminSettingsRow>
          <AdminSettingsRow label="排序" htmlFor="page-sort" hintBelow="数字越小越靠前">
            <input
              id="page-sort"
              type="number"
              className="j13-compose-field admin-settings-control-num"
              value={form.sort_order}
              onChange={(e) => patchForm({ sort_order: parseInt(e.target.value, 10) || 0 })}
            />
          </AdminSettingsRow>
          <AdminSettingsRow label="发布状态">
            <AdminSegmented<PublishKey>
              role="group"
              ariaLabel="发布状态"
              value={form.published ? "published" : "draft"}
              onChange={(key) => patchForm({ published: key === "published" })}
              options={[
                { key: "published", label: "立即发布" },
                { key: "draft", label: "存为草稿" },
              ]}
            />
          </AdminSettingsRow>
          <AdminSettingsRow label="首页侧栏" hintBelow="开启后出现在「关于本站」模块">
            <AdminSwitch
              checked={form.show_in_sidebar}
              onChange={() => patchForm((f) => ({ ...f, show_in_sidebar: !f.show_in_sidebar }))}
              label="显示在首页侧栏"
            />
          </AdminSettingsRow>
        </AdminSettingsGroup>

        <AdminSettingsGroup
          className="is-fill"
          title="标题与正文"
          footer={
            <AdminSettingsActions
              dirty={dirty}
              saving={saving}
              saveLabel={saveLabel}
              onSave={() => void save()}
              onDiscard={() => {
                formRef.current = baseline;
                setForm(baseline);
              }}
            />
          }
        >
          <AdminSettingsRow label="标题" htmlFor="page-title" wide>
            <AdminField
              id="page-title"
              label="标题"
              embed
              maxLength={200}
              value={form.title}
              onChange={(title) => patchForm({ title })}
              placeholder="页面标题"
            />
          </AdminSettingsRow>
          <AdminSettingsRow className="admin-settings-md-editor" label="正文" htmlFor="page-content" wide>
            <div className="admin-settings-md">
              <MarkdownEditor
                id="page-content"
                value={form.content}
                onChange={(content) => patchForm({ content })}
                allowHide={false}
                placeholder="请输入页面正文，支持 Markdown…"
                rows={18}
                onSubmitShortcut={() => void save()}
              />
            </div>
          </AdminSettingsRow>
        </AdminSettingsGroup>
      </div>

      <ConfirmDialog
        open={leaveOpen}
        title="有未保存的修改"
        message="离开后，尚未写入的修改会丢失。确定离开？"
        confirmLabel="离开"
        danger
        onCancel={cancelLeave}
        onConfirm={confirmLeave}
      />
    </AdminSettingsPage>
  );
}