"use client";

import { useRef, useState } from "react";
import Link from "next/link";
import { useRouter } from "next/navigation";
import { ArrowLeft, Loader2, Save } from "lucide-react";
import {
  apiAdminCreateSitePage,
  apiAdminUpdateSitePage,
  type SitePage,
  type SitePageInput,
} from "@/lib/api";
import { toast } from "@/lib/toast";
import MarkdownEditor from "@/components/MarkdownEditor";
import { AdminSegmented, AdminSwitch } from "@/components/admin";

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,
  };
}

/** 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 [form, setForm] = useState<FormState>(() => toForm(initial));
  const formRef = useRef(form);
  const [saving, setSaving] = useState(false);
  const isEdit = mode === "edit" && initial != null;

  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);
    }
  }

  return (
    <div className="j13-compose-page w-full">
      <div className="j13-compose-stage">
        <header className="j13-compose-toolbar">
          <h1 className="j13-compose-toolbar-title">{isEdit ? "编辑单页" : "新建单页"}</h1>
          <div className="j13-compose-toolbar-actions">
            <Link href="/admin/pages" className="btn btn-line btn-sm">
              <ArrowLeft size={14} /> 返回列表
            </Link>
            <button
              type="button"
              className="btn btn-primary btn-sm min-w-[4.5rem]"
              disabled={saving}
              onClick={() => void save()}
            >
              {saving ? <Loader2 size={14} className="animate-spin" /> : <Save size={14} />}
              保存
            </button>
          </div>
        </header>

        <div className="j13-compose-body">
          <section className="j13-compose-section" aria-label="页面设置">
            <h2 className="j13-compose-section-title">页面设置</h2>
            <div className="j13-compose-typepanel space-y-4">
              <div>
                <label className="field-label" htmlFor="page-slug">
                  URL slug
                </label>
                <div className="flex items-center gap-1.5">
                  <span className="meta text-[13px]">/p/</span>
                  <input
                    id="page-slug"
                    className="j13-compose-field flex-1 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>

              <div>
                <label className="field-label" htmlFor="page-excerpt">
                  摘要（侧栏展示）
                </label>
                <textarea
                  id="page-excerpt"
                  className="j13-compose-field w-full"
                  rows={3}
                  maxLength={300}
                  value={form.excerpt}
                  onChange={(e) => patchForm({ excerpt: e.target.value })}
                  placeholder="一句话介绍本页…"
                />
              </div>

              <div>
                <label className="field-label" htmlFor="page-sort">
                  排序（越小越靠前）
                </label>
                <input
                  id="page-sort"
                  type="number"
                  className="j13-compose-field w-28"
                  value={form.sort_order}
                  onChange={(e) =>
                    patchForm({ sort_order: parseInt(e.target.value, 10) || 0 })
                  }
                />
              </div>

              <div>
                <p className="field-label">发布状态</p>
                <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" },
                  ]}
                />
              </div>

              <div className="flex items-center justify-between gap-3 flex-wrap">
                <div>
                  <p className="text-[14px] font-medium" style={{ color: "var(--ink)" }}>
                    显示在首页侧栏
                  </p>
                  <p className="meta text-[12px] mt-0.5">开启后出现在「关于本站」模块</p>
                </div>
                <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"
                />
              </div>
            </div>
          </section>

          <section className="j13-compose-section j13-compose-section-writing" aria-label="标题与正文">
            <h2 className="j13-compose-section-title">标题与正文</h2>
            <input
              className="j13-compose-title"
              maxLength={200}
              value={form.title}
              onChange={(e) => patchForm({ title: e.target.value })}
              placeholder="页面标题"
              aria-label="页面标题"
            />
            <div className="j13-compose-canvas">
              <MarkdownEditor
                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>
          </section>
        </div>

        <div className="j13-compose-actions">
          <div className="j13-compose-actions-end">
            <Link href="/admin/pages" className="btn btn-line">
              取消
            </Link>
            <button
              type="button"
              className="btn btn-primary"
              disabled={saving}
              onClick={() => void save()}
            >
              {saving ? (
                <>
                  <Loader2 size={15} className="animate-spin" /> 保存中…
                </>
              ) : (
                <>
                  <Save size={15} /> {isEdit ? "保存修改" : form.published ? "发布页面" : "保存草稿"}
                </>
              )}
            </button>
          </div>
        </div>
      </div>
    </div>
  );
}