// Copyright (C) 2025 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

import m from 'mithril';
import {HTMLAttrs} from './common';
import {assertExists} from '../base/logging';

export interface SettingsPageAttrs extends HTMLAttrs {
  readonly title: string;
  readonly stickyHeaderContent?: m.Children;
}

export class SettingsPage implements m.ClassComponent<SettingsPageAttrs> {
  private observer?: IntersectionObserver;

  view(vnode: m.Vnode<SettingsPageAttrs>) {
    const {
      title,
      stickyHeaderContent: headerContent,
      ...htmlAttrs
    } = vnode.attrs;
    return m(
      '.pf-settings-page',
      htmlAttrs,
      m(
        '.pf-settings-page__title',
        m('.pf-settings-page__centred', m('h1', title)),
      ),
      m(
        '.pf-settings-page__header',
        m('.pf-settings-page__centred', headerContent),
      ),
      m(
        '.pf-settings-page__content',
        m('.pf-settings-page__centred', vnode.children),
      ),
    );
  }

  oncreate(vnode: m.VnodeDOM<SettingsPageAttrs, this>) {
    const canary = assertExists(
      vnode.dom.querySelector('.pf-settings-page__title'),
    );
    const header = assertExists(
      vnode.dom.querySelector('.pf-settings-page__header'),
    );

    this.observer = new IntersectionObserver(
      ([entry]) => {
        header.classList.toggle(
          'pf-settings-page__header--stuck',
          !entry.isIntersecting,
        );
      },
      {threshold: [0]},
    );

    this.observer.observe(canary);
  }

  onremove() {
    this.observer?.disconnect();
  }
}