<div class="timeline"
     role="feed"
     aria-label="{{label}}"
     on:focusWithCapture="saveFocus(event)"
     on:blurWithCapture="clearFocus(event)"
>
  {{#if !$initialized}}
    <LoadingPage />
  {{/if}}
  {{#if virtual}}
    <VirtualList component="{{VirtualListComponent}}"
                 realm="{{$currentInstance + '/' + timeline}}"
                 containerQuery=".container"
                 :makeProps
                 items="{{$timelineItemIds}}"
                 shown="{{$initialized}}"
                 showFooter="{{$initialized && $runningUpdate}}"
                 footerComponent="{{LoadingFooter}}"
                 showHeader="{{$showHeader}}"
                 headerComponent="{{MoreHeaderVirtualWrapper}}"
                 :headerProps
                 on:scrollToBottom="onScrollToBottom()"
                 on:scrollToTop="onScrollToTop()"
                 on:scrollTopChanged="onScrollTopChanged(event)"
                 on:initializedVisibleItems="initialize()"
    />
  {{else}}
    {{#await importPseudoVirtualList}}
    {{then PseudoVirtualList}}
      <!-- if this is a status thread, it's easier to just render the
           whole thing rather than use a virtual list -->
      <:Component {PseudoVirtualList}
                 component="{{VirtualListComponent}}"
                 realm="{{$currentInstance + '/' + timeline}}"
                 containerQuery=".container"
                 :makeProps
                 items="{{$timelineItemIds}}"
                 shown="{{$initialized}}"
                 scrollToItem="{{scrollToItem}}"
                 on:initializedVisibleItems="initialize()"
      />
    {{catch error}}
      <div>Component failed to load. Try refreshing! {{error}}</div>
    {{/await}}
  {{/if}}
</div>
<style>
  .timeline {
    min-height: 60vh;
    position: relative;
  }
</style>
<script>
  import { store } from '../../_store/store'
  import StatusVirtualListItem from './StatusVirtualListItem.html'
  import NotificationVirtualListItem from './NotificationVirtualListItem.html'
  import Status from '../status/Status.html'
  import LoadingFooter from './LoadingFooter.html'
  import MoreHeaderVirtualWrapper from './MoreHeaderVirtualWrapper.html'
  import VirtualList from '../virtualList/VirtualList.html'
  import { timelines } from '../../_static/timelines'
  import { database } from '../../_database/database'
  import { initializeTimeline, fetchTimelineItemsOnScrollToBottom, setupTimeline } from '../../_actions/timeline'
  import LoadingPage from '../LoadingPage.html'
  import { focusWithCapture, blurWithCapture } from '../../_utils/events'
  import { showMoreItemsForCurrentTimeline } from '../../_actions/timeline'
  import { scheduleIdleTask } from '../../_utils/scheduleIdleTask'
  import { mark, stop } from '../../_utils/marks'
  import { importPseudoVirtualList } from '../../_utils/asyncModules'

  export default {
    oncreate() {
      console.log('timeline oncreate()')
      this.setupFocus()
      setupTimeline()
      if (this.store.get('initialized')) {
        this.restoreFocus()
      }
      this.setupStreaming()
    },
    ondestroy() {
      console.log('ondestroy')
      this.teardownFocus()
    },
    data: () => ({
      LoadingFooter,
      MoreHeaderVirtualWrapper,
      Status,
      scrollTop: 0
    }),
    computed: {
      importPseudoVirtualList: (virtual) => {
        return !virtual && importPseudoVirtualList()
      },
      VirtualListComponent: (timelineType) => {
        return timelineType === 'notifications' ? NotificationVirtualListItem : StatusVirtualListItem
      },
      makeProps: ($currentInstance, timelineType, timelineValue) => async (itemId) => {
        let res = { timelineType, timelineValue }
        if (timelineType === 'notifications') {
          res.notification = await database.getNotification($currentInstance, itemId)
        } else {
          res.status = await database.getStatus($currentInstance, itemId)
        }
        return res
      },
      label: (timeline, $currentInstance, timelineType, timelineValue) => {
        if (timelines[timeline]) {
          return `${timelines[timeline].label} timeline for ${$currentInstance}`
        }

        switch (timelineType) {
          case 'tag':
            return `#${timelineValue} timeline for ${$currentInstance}`
          case 'status':
            return 'Status context'
          case 'account':
            return `Account #${timelineValue} on ${$currentInstance}`
          case 'list':
            return `List #${timelineValue} on ${$currentInstance}`
        }
      },
      timelineType: (timeline) => {
        return timeline.split('/')[0]
      },
      timelineValue: (timeline) => {
        return timeline.split('/').slice(-1)[0]
      },
      // for threads, it's simpler to just render all items as a pseudo-virtual list
      // due to need to scroll to the right item and thus calculate all item heights up-front
      virtual: (timelineType) => timelineType !=='status',
      scrollToItem: (timelineType, timelineValue, $firstTimelineItemId) => {
        // Scroll to the first item if this is a "status in own thread" timeline.
        // Don't scroll to the first item because it obscures the "back" button.
        return timelineType === 'status'
          && $firstTimelineItemId
          && timelineValue !== $firstTimelineItemId
          && timelineValue
      },
      itemIdsToAdd: ($itemIdsToAdd) => $itemIdsToAdd,
      // TODO: hack to avoid getting called too often
      itemIdsToAddStringified: (itemIdsToAdd) => JSON.stringify(itemIdsToAdd),
      headerProps: (itemIdsToAdd) => {
        return {
          count: (itemIdsToAdd && itemIdsToAdd.length) || 0,
          onClick: showMoreItemsForCurrentTimeline
        }
      }
    },
    store: () => store,
    components: {
      VirtualList,
      LoadingPage
    },
    events: {
      focusWithCapture,
      blurWithCapture
    },
    methods: {
      initialize() {
        if (this.get('initializeStarted')) {
          return
        }
        this.set({initializeStarted: true})
        console.log('timeline initialize()')
        initializeTimeline()
      },
      onScrollTopChanged(scrollTop) {
        this.set({scrollTop: scrollTop})
      },
      onScrollToBottom() {
        if (!this.store.get('initialized') ||
            this.store.get('runningUpdate') ||
            this.get('timelineType') === 'status') { // for status contexts, we've already fetched the whole thread
          return
        }
        fetchTimelineItemsOnScrollToBottom()
      },
      onScrollToTop() {
        if (this.store.get('shouldShowHeader')) {
          this.store.setForCurrentTimeline({
            showHeader: true,
            shouldShowHeader: false
          })
        }
      },
      setupStreaming() {
        let instanceName = this.store.get('currentInstance')
        let timelineName = this.get('timeline')
        let handleItemIdsToAdd = () => {
          let itemIdsToAdd = this.get('itemIdsToAdd')
          if (!itemIdsToAdd || !itemIdsToAdd.length) {
            return
          }
          mark('handleItemIdsToAdd')
          let scrollTop = this.get('scrollTop')
          let shouldShowHeader = this.store.get('shouldShowHeader')
          let showHeader = this.store.get('showHeader')
          //console.log('handleItemIdsToAdd', (itemIdsToAdd && itemIdsToAdd.length) || 0)
          if (scrollTop === 0 && !shouldShowHeader && !showHeader) {
            // if the user is scrolled to the top and we're not showing the header, then
            // just insert the statuses. this is "chat room mode"
            showMoreItemsForCurrentTimeline()
          } else {
            // user hasn't scrolled to the top, show a header instead
            this.store.setForTimeline(instanceName, timelineName, {shouldShowHeader: true})
          }
          stop('handleItemIdsToAdd')
        }
        this.observe('itemIdsToAddStringified', itemIdsToAddStringified => {
          scheduleIdleTask(handleItemIdsToAdd)
        })
      },
      setupFocus() {
        this.onPushState = this.onPushState.bind(this)
        this.store.setForCurrentTimeline({ignoreBlurEvents: false})
        window.addEventListener('pushState', this.onPushState)
      },
      teardownFocus() {
        window.removeEventListener('pushState', this.onPushState)
      },
      onPushState() {
        this.store.setForCurrentTimeline({ ignoreBlurEvents: true })
      },
      saveFocus(e) {
        let instanceName = this.store.get('currentInstance')
        let timelineName = this.get('timeline')
        let lastFocusedElementSelector
        let activeElement = e.target
        if (activeElement) {
          let focusKey = activeElement.getAttribute('focus-key')
          if (focusKey) {
            lastFocusedElementSelector = `[focus-key=${focusKey}]`
          }
        }
        console.log('saving focus to ', lastFocusedElementSelector)
        this.store.setForTimeline(instanceName, timelineName, {
          lastFocusedElementSelector
        })
      },
      clearFocus() {
        if (this.store.get('ignoreBlurEvents')) {
          return
        }
        console.log('clearing focus')
        let instanceName = this.store.get('currentInstance')
        let timelineName = this.get('timeline')
        this.store.setForTimeline(instanceName, timelineName, {
          lastFocusedElementSelector: null
        })
      },
      restoreFocus() {
        let lastFocusedElementSelector = this.store.get('lastFocusedElementSelector')
        console.log('lastFocused', lastFocusedElementSelector)
        if (lastFocusedElementSelector) {
          requestAnimationFrame(() => {
            requestAnimationFrame(() => {
              let element = document.querySelector(lastFocusedElementSelector)
              console.log('el', element)
              if (element) {
                element.focus()
              }
            })
          })
        }
      },
    }
  }
</script>