// Copyright (C) 2020 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 {channelChanged, getNextChannel, setChannel} from '../../core/channels';
import {featureFlags} from '../../core/feature_flags';
import {Flag, OverrideState} from '../../public/feature_flag';
import {raf} from '../../core/raf_scheduler';
import {PageAttrs} from '../../public/page';
import {Router} from '../../core/router';

const RELEASE_PROCESS_URL =
  'https://perfetto.dev/docs/visualization/perfetto-ui-release-process';

interface FlagOption {
  id: string;
  name: string;
}

interface SelectWidgetAttrs {
  id: string;
  label: string;
  description: m.Children;
  options: FlagOption[];
  selected: string;
  onSelect: (id: string) => void;
}

class SelectWidget implements m.ClassComponent<SelectWidgetAttrs> {
  view(vnode: m.Vnode<SelectWidgetAttrs>) {
    const route = Router.parseUrl(window.location.href);
    const attrs = vnode.attrs;
    const cssClass = route.subpage === `/${attrs.id}` ? '.focused' : '';
    return m(
      '.flag-widget' + cssClass,
      {id: attrs.id},
      m('label', attrs.label),
      m(
        'select',
        {
          onchange: (e: InputEvent) => {
            const value = (e.target as HTMLSelectElement).value;
            attrs.onSelect(value);
            raf.scheduleFullRedraw();
          },
        },
        attrs.options.map((o) => {
          const selected = o.id === attrs.selected;
          return m('option', {value: o.id, selected}, o.name);
        }),
      ),
      m('.description', attrs.description),
    );
  }
}

interface FlagWidgetAttrs {
  flag: Flag;
}

class FlagWidget implements m.ClassComponent<FlagWidgetAttrs> {
  view(vnode: m.Vnode<FlagWidgetAttrs>) {
    const flag = vnode.attrs.flag;
    const defaultState = flag.defaultValue ? 'Enabled' : 'Disabled';
    return m(SelectWidget, {
      label: flag.name,
      id: flag.id,
      description: flag.description,
      options: [
        {id: OverrideState.DEFAULT, name: `Default (${defaultState})`},
        {id: OverrideState.TRUE, name: 'Enabled'},
        {id: OverrideState.FALSE, name: 'Disabled'},
      ],
      selected: flag.overriddenState(),
      onSelect: (value: string) => {
        switch (value) {
          case OverrideState.TRUE:
            flag.set(true);
            break;
          case OverrideState.FALSE:
            flag.set(false);
            break;
          default:
          case OverrideState.DEFAULT:
            flag.reset();
            break;
        }
      },
    });
  }
}

export class FlagsPage implements m.ClassComponent<PageAttrs> {
  view() {
    const needsReload = channelChanged();
    return m(
      '.flags-page',
      m(
        '.flags-content',
        m('h1', 'Feature flags'),
        needsReload && [
          m('h2', 'Please reload for your changes to take effect'),
        ],
        m(SelectWidget, {
          label: 'Release channel',
          id: 'releaseChannel',
          description: [
            'Which release channel of the UI to use. See ',
            m(
              'a',
              {
                href: RELEASE_PROCESS_URL,
              },
              'Release Process',
            ),
            ' for more information.',
          ],
          options: [
            {id: 'stable', name: 'Stable (default)'},
            {id: 'canary', name: 'Canary'},
            {id: 'autopush', name: 'Autopush'},
          ],
          selected: getNextChannel(),
          onSelect: (id) => setChannel(id),
        }),
        m(
          'button',
          {
            onclick: () => {
              featureFlags.resetAll();
              raf.scheduleFullRedraw();
            },
          },
          'Reset all below',
        ),

        featureFlags.allFlags().map((flag) => m(FlagWidget, {flag})),
      ),
    );
  }

  oncreate(vnode: m.VnodeDOM<PageAttrs>) {
    const flagId = /[/](\w+)/.exec(vnode.attrs.subpage ?? '')?.slice(1, 2)[0];
    if (flagId) {
      const flag = vnode.dom.querySelector(`#${flagId}`);
      if (flag) {
        flag.scrollIntoView({block: 'center'});
      }
    }
  }
}