"use client";

import { useEffect, useMemo, useRef, useState } from "react";
import Link from "next/link";
import { useRouter, useSearchParams } from "next/navigation";
import { ArrowLeft, Copy, ExternalLink, FileText, Loader2 } from "lucide-react";
import {
  apiAdminCreateSitePage,
  apiAdminUpdateSitePage,
  type SitePage,
  type SitePageInput,
} from "@/lib/api";
import { sitePagePublicPath, sitePagePublicURL } from "@/lib/sitePagePath";
import { toast } from "@/lib/toast";
import MarkdownEditor from "@/components/MarkdownEditor";
import { AdminField, AdminSegmented, AdminStatusChip, AdminSwitch } from "@/components/admin";
import ConfirmDialog from "@/components/ConfirmDialog";
import useUnsavedGuard from "@/hooks/useUnsavedGuard";

type PublishKey = "published" | "draft";
type StatusFilter = "all" | "published" | "draft";

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

type FieldErrors = {
  slug?: string;
  title?: string;
  content?: string;
  excerpt?: string;
  form?: string;
};

const SLUG_RE = /^[a-z0-9]+(?:-[a-z0-9]+)*$/;

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
  );
}

function runeCount(s: string): number {
  return Array.from(s).length;
}

function normalizeSlug(raw: string): string {
  return raw.trim().toLowerCase();
}

function validate(form: FormState): FieldErrors {
  const errors: FieldErrors = {};
  const slug = normalizeSlug(form.slug);
  if (!slug) errors.slug = "slug 不能为空";
  else if (slug.length > 64) errors.slug = "slug 不能超过 64 字符";
  else if (!SLUG_RE.test(slug)) errors.slug = "slug 仅允许小写字母、数字与连字符";

  const title = form.title.trim();
  if (!title) errors.title = "标题不能为空";
  else if (runeCount(title) > 200) errors.title = "标题不能超过 200 字";

  if (!form.content.trim()) errors.content = "内容不能为空";

  if (runeCount(form.excerpt.trim()) > 300) errors.excerpt = "摘要不能超过 300 字";
  return errors;
}

function errorsFromServer(msg: string): FieldErrors {
  if (msg.includes("slug")) return { slug: msg };
  if (msg.includes("标题")) return { title: msg };
  if (msg.includes("摘要")) return { excerpt: msg };
  if (msg.includes("内容") || msg.includes("隐藏")) return { content: msg };
  return { form: msg };
}

function hasErrors(errors: FieldErrors): boolean {
  return Object.values(errors).some(Boolean);
}

function readStatus(raw: string | null): StatusFilter {
  if (raw === "published" || raw === "draft") return raw;
  return "all";
}

function listHref(status: StatusFilter): string {
  return status === "all" ? "/admin/pages" : `/admin/pages?status=${status}`;
}

function primaryLabel(savedPublished: boolean | null, targetPublished: boolean): string {
  if (savedPublished !== true && !targetPublished) return "保存草稿";
  if (savedPublished !== true && targetPublished) return "发布页面";
  if (savedPublished && targetPublished) return "保存并更新";
  return "转为草稿";
}

export default function PageComposeClient({
  mode,
  initial,
}: {
  mode: "create" | "edit";
  initial?: SitePage | null;
}) {
  const router = useRouter();
  const searchParams = useSearchParams();
  const status = readStatus(searchParams.get("status"));
  const backHref = listHref(status);
  const loaded = useMemo(() => toForm(initial), [initial]);
  const [baseline, setBaseline] = useState<FormState>(loaded);
  const [savedPage, setSavedPage] = useState<SitePage | null>(initial ?? null);
  const [form, setForm] = useState<FormState>(loaded);
  const formRef = useRef(form);
  const [saving, setSaving] = useState(false);
  const [errors, setErrors] = useState<FieldErrors>({});
  const [origin, setOrigin] = useState("");
  const [pendingSave, setPendingSave] = useState<{ slugChange: boolean; unpublish: boolean } | null>(
    null
  );
  const isEdit = mode === "edit" && savedPage != null;
  const dirty = !sameForm(form, baseline);
  const { leaveOpen, confirmLeave, cancelLeave } = useUnsavedGuard(dirty && !saving);
  const savedPublished = isEdit ? baseline.published : null;

  useEffect(() => {
    setOrigin(window.location.origin);
  }, []);

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

  const slugPreview = normalizeSlug(form.slug);
  const publicPath = sitePagePublicPath(slugPreview);
  const canViewOnline = savedPage?.published === true;

  async function commit() {
    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,
    };
    setSaving(true);
    setErrors({});
    try {
      if (isEdit && savedPage) {
        const res = await apiAdminUpdateSitePage(savedPage.id, payload);
        const page = res.page;
        const next = toForm(page);
        formRef.current = next;
        setForm(next);
        setBaseline(next);
        setSavedPage(page);
        const wasPublished = baseline.published;
        const nowPublished = page.published;
        const msg = !wasPublished && nowPublished
          ? "页面已发布"
          : wasPublished && !nowPublished
            ? "已转为草稿"
            : wasPublished
              ? "页面已更新"
              : "草稿已保存";
        toast(msg, "ok");
        router.refresh();
      } else {
        const res = await apiAdminCreateSitePage(payload);
        toast(payload.published ? "页面已发布" : "草稿已保存", "ok");
        const id = res.page?.id;
        if (id) {
          const q = status === "all" ? "" : `?status=${status}`;
          router.replace(`/admin/pages/${id}/edit${q}`);
        } else {
          router.push(backHref);
        }
        router.refresh();
      }
    } catch (e) {
      const msg = e instanceof Error ? e.message : "保存失败";
      setErrors(errorsFromServer(msg));
      toast(msg);
    } finally {
      setSaving(false);
      setPendingSave(null);
    }
  }

  function requestSave() {
    if (saving) return;
    const current = formRef.current;
    const nextErrors = validate(current);
    if (hasErrors(nextErrors)) {
      setErrors(nextErrors);
      toast("请先修正标出的字段");
      return;
    }
    const slug = normalizeSlug(current.slug);
    const slugChange = isEdit && baseline.published && slug !== baseline.slug;
    const unpublish = isEdit && baseline.published && !current.published;
    if (slugChange || unpublish) {
      setPendingSave({ slugChange, unpublish });
      return;
    }
    void commit();
  }

  function discard() {
    formRef.current = baseline;
    setForm(baseline);
    setErrors({});
  }

  async function copyAddress() {
    const slug = normalizeSlug(formRef.current.slug);
    const nextErrors = validate({ ...formRef.current, slug });
    if (nextErrors.slug) {
      setErrors((prev) => ({ ...prev, slug: nextErrors.slug }));
      return;
    }
    const url = sitePagePublicURL(origin || window.location.origin, slug);
    try {
      await navigator.clipboard.writeText(url);
      toast("已复制访问地址", "ok");
    } catch {
      toast("复制失败");
    }
  }

  const saveLabel = primaryLabel(savedPublished, form.published);
  const statusText = saving
    ? "正在保存…"
    : errors.form
      ? errors.form
      : dirty
        ? "有未保存的修改"
        : isEdit
          ? "已保存"
          : "尚未保存";

  const confirmBits: string[] = [];
  if (pendingSave?.unpublish) {
    confirmBits.push(
      "转为草稿后，前台将无法打开此页。这里没有单独的修订版本，线上内容会一起下线，不会保留旧版。"
    );
  }
  if (pendingSave?.slugChange) {
    confirmBits.push(
      `访问地址将从 ${sitePagePublicPath(baseline.slug)} 改为 ${sitePagePublicPath(normalizeSlug(form.slug))}。系统不会把旧地址转到新地址，已经分享的旧链接会打不开。`
    );
  }

  return (
    <div className="admin-doc-page admin-doc-editor">
      <header className="admin-doc-sticky">
        <div className="admin-doc-sticky-inner">
          <div className="admin-doc-sticky-title">
            <Link href={backHref} className="admin-doc-back" aria-label="返回单页列表">
              <ArrowLeft size={15} aria-hidden />
              <span className="admin-doc-back-text">返回列表</span>
            </Link>
            <span className="admin-doc-sticky-icon" aria-hidden>
              <FileText size={15} />
            </span>
            <h1>{isEdit ? "编辑单页" : "新建单页"}</h1>
            <AdminStatusChip tone={savedPublished ? "ok" : savedPublished === false ? "warn" : "accent"}>
              {savedPublished ? "已发布" : savedPublished === false ? "草稿" : "尚未保存"}
            </AdminStatusChip>
          </div>
          <div className="admin-doc-sticky-actions">
            {canViewOnline && savedPage ? (
              <a
                href={sitePagePublicPath(savedPage.slug)}
                target="_blank"
                rel="noopener noreferrer"
                className="btn btn-line btn-sm"
                title="打开已发布内容。未保存的修改不会出现在这里。"
              >
                <ExternalLink size={14} aria-hidden /> 线上页面
              </a>
            ) : null}
            <AdminSegmented<PublishKey>
              role="group"
              ariaLabel="保存后状态"
              size="sm"
              value={form.published ? "published" : "draft"}
              onChange={(key) => patchForm({ published: key === "published" })}
              options={[
                { key: "draft", label: "草稿" },
                { key: "published", label: "发布" },
              ]}
            />
            <button type="button" className="btn btn-line btn-sm" disabled={!dirty || saving} onClick={discard}>
              撤销修改
            </button>
            <button
              type="button"
              className="btn btn-primary btn-sm"
              disabled={!dirty || saving}
              onClick={requestSave}
              aria-busy={saving || undefined}
            >
              {saving ? <Loader2 size={14} className="animate-spin" aria-hidden /> : null}
              {saving ? "保存中…" : saveLabel}
            </button>
            <p className={`admin-doc-status${errors.form ? " is-error" : ""}`} aria-live="polite">
              {statusText}
            </p>
          </div>
        </div>
      </header>

      <div className="admin-doc-split">
        <div className="admin-doc-main">
          <AdminField
            className="admin-doc-title"
            id="page-title"
            label="标题"
            maxLength={200}
            value={form.title}
            error={errors.title}
            onChange={(title) => {
              setErrors((prev) => ({ ...prev, title: undefined }));
              patchForm({ title });
            }}
            placeholder="页面标题"
          />
          <div className="admin-doc-md">
            <label className="admin-doc-label" htmlFor="page-content">
              正文
            </label>
            <MarkdownEditor
              id="page-content"
              value={form.content}
              onChange={(content) => {
                setErrors((prev) => ({ ...prev, content: undefined }));
                patchForm({ content });
              }}
              allowHide={false}
              placeholder="请输入页面正文，支持 Markdown…"
              rows={16}
              onSubmitShortcut={requestSave}
            />
            {errors.content ? (
              <p className="admin-settings-row-error" role="alert">
                {errors.content}
              </p>
            ) : null}
          </div>
        </div>

        <details className="admin-doc-rail" open>
          <summary>页面设置</summary>
          <div className="admin-doc-rail-body">
            <div className="admin-doc-field">
              <label className="admin-doc-label" htmlFor="page-slug">
                访问地址
              </label>
              <div className={`admin-doc-slug${errors.slug ? " is-invalid" : ""}`}>
                <span className="admin-doc-slug-prefix">/p/</span>
                <input
                  id="page-slug"
                  className="admin-doc-slug-input"
                  maxLength={64}
                  value={form.slug}
                  aria-invalid={errors.slug ? true : undefined}
                  aria-describedby="page-slug-hint"
                  autoCapitalize="none"
                  autoCorrect="off"
                  spellCheck={false}
                  onChange={(e) => {
                    setErrors((prev) => ({ ...prev, slug: undefined }));
                    patchForm({ slug: e.target.value });
                  }}
                  onBlur={() => patchForm((f) => ({ ...f, slug: normalizeSlug(f.slug) }))}
                  placeholder="about"
                />
              </div>
              <p className="admin-doc-hint" id="page-slug-hint">
                完整路径 {publicPath || "/p/"}。小写字母、数字和连字符，最多 64 字符。
                {origin && slugPreview ? ` 线上地址 ${sitePagePublicURL(origin, slugPreview)}` : ""}
              </p>
              {isEdit && baseline.published && slugPreview !== baseline.slug ? (
                <p className="admin-doc-hint">保存后访问地址会改变。旧链接不会自动跳转。</p>
              ) : null}
              {errors.slug ? (
                <p className="admin-settings-row-error" role="alert">
                  {errors.slug}
                </p>
              ) : null}
              <button type="button" className="btn btn-line admin-doc-copy" onClick={() => void copyAddress()}>
                <Copy size={14} aria-hidden /> 复制地址
              </button>
            </div>

            <AdminField
              id="page-excerpt"
              label="摘要"
              hint="用于首页侧栏「关于本站」、关于本站导航和单页页眉。未填写时这些位置不显示简介。"
              as="textarea"
              maxLength={300}
              minHeight="5.5rem"
              value={form.excerpt}
              error={errors.excerpt}
              onChange={(excerpt) => {
                setErrors((prev) => ({ ...prev, excerpt: undefined }));
                patchForm({ excerpt });
              }}
              placeholder="一句话介绍本页"
            />

            <div className="admin-doc-field">
              <p className="admin-doc-label">展示位置</p>
              <div className="admin-doc-switchline">
                <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"
                />
                <span>显示在首页侧栏</span>
              </div>
              <p className="admin-doc-hint">
                已发布且开启后，出现在首页右栏「关于本站」。草稿即使开启也不会出现。已发布的单页不会自动进入侧栏。
              </p>
            </div>

            <div className="admin-doc-field">
              <label className="admin-doc-label" htmlFor="page-sort">
                排序
              </label>
              <input
                id="page-sort"
                type="number"
                className="admin-doc-number"
                value={form.sort_order}
                onChange={(e) => {
                  const n = Number.parseInt(e.target.value, 10);
                  patchForm({ sort_order: Number.isNaN(n) ? 0 : n });
                }}
              />
              <p className="admin-doc-hint">数字越小越靠前，可以为负数。</p>
            </div>
          </div>
        </details>
      </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}
      />
      <ConfirmDialog
        open={pendingSave != null}
        title={pendingSave?.unpublish ? "转为草稿" : "访问地址将变化"}
        message={confirmBits.join(" ")}
        confirmLabel={pendingSave?.unpublish ? "转为草稿" : "仍然保存"}
        danger={!!pendingSave?.unpublish}
        busy={saving}
        onCancel={() => saving || setPendingSave(null)}
        onConfirm={() => void commit()}
      />
    </div>
  );
}