pinafore/routes/_components/compose/ComposeAutosuggest.html

<div class="compose-autosuggest {shown ? 'shown' : ''} {realm === 'dialog' ? 'is-dialog' : ''}"
       aria-hidden="true" >
  <ComposeAutosuggestionList
    items={searchResults}
    on:click="onClick(event)"
    {type}
    {selected}
  />
</div>
<style>
  .compose-autosuggest {
    position: absolute;
    left: 5px;
    top: 0;
    pointer-events: none;
    opacity: 0;
    transition: opacity 0.1s linear;
    min-width: 400px;
    max-width: calc(100vw - 20px);
    z-index: 7000;
  }
  .compose-autosuggest.is-dialog {
    z-index: 11000;
  }
  .compose-autosuggest.shown {
    pointer-events: auto;
    opacity: 1;
  }

  @media (max-width: 479px) {
    .compose-autosuggest {
      /* hack: move this over to the left on mobile so it's easier to see */
      transform: translateX(-58px); /* avatar size 48px + 10px padding */
      min-width: 0;
      width: calc(100vw - 20px);
    }
  }

</style>
<script>
  import { store } from '../../_store/store'
  import { insertUsername } from '../../_actions/compose'
  import { insertEmojiAtPosition } from '../../_actions/emoji'
  import { scheduleIdleTask } from '../../_utils/scheduleIdleTask'
  import { once } from '../../_utils/once'
  import ComposeAutosuggestionList from './ComposeAutosuggestionList.html'
  import {
    searchAccountsByUsername as searchAccountsByUsernameInDatabase
  } from '../../_database/accountsAndRelationships'
  import { observe } from 'svelte-extras'

  const SEARCH_RESULTS_LIMIT = 4
  const DATABASE_SEARCH_RESULTS_LIMIT = 30
  const MIN_PREFIX_LENGTH = 1
  const ACCOUNT_SEARCH_REGEX = new RegExp(`(?:\\s|^)(@\\S{${MIN_PREFIX_LENGTH},})$`)
  const EMOJI_SEARCH_REGEX = new RegExp(`(?:\\s|^)(:[^:]{${MIN_PREFIX_LENGTH},})$`)

  export default {
    oncreate () {
      // perf improves for input responsiveness
      this.observe('composeSelectionStart', () => {
        scheduleIdleTask(() => {
          let { composeSelectionStart } = this.get()
          this.set({composeSelectionStartDeferred: composeSelectionStart})
        })
      })
      this.observe('composeFocused', (composeFocused) => {
        let updateFocusedState = () => {
          scheduleIdleTask(() => {
            let { composeFocused } = this.get()
            this.set({composeFocusedDeferred: composeFocused})
          })
        }

        // TODO: hack so that when the user clicks the button, and the textarea blurs,
        // we don't immediately hide the dropdown which would cause the click to get lost
        if (composeFocused) {
          updateFocusedState()
        } else {
          Promise.race([
            new Promise(resolve => setTimeout(resolve, 200)),
            new Promise(resolve => this.once('autosuggestItemSelected', resolve))
          ]).then(updateFocusedState)
        }
      })
      this.observe('searchText', async searchText => {
        let { thisComposeFocused } = this.get()
        if (!thisComposeFocused || !searchText) {
          return
        }
        let type = searchText.startsWith('@') ? 'account' : 'emoji'
        let results = (type === 'account')
          ? await this.searchAccounts(searchText)
          : await this.searchEmoji(searchText)
        this.store.set({
          composeAutosuggestionSelected: 0,
          composeAutosuggestionSearchText: searchText,
          composeAutosuggestionSearchResults: results,
          composeAutosuggestionType: type
        })
      })
      this.observe('shown', shown => {
        let { thisComposeFocused } = this.get()
        if (!thisComposeFocused) {
          return
        }
        this.store.set({composeAutosuggestionShown: shown})
      })
    },
    methods: {
      observe,
      once,
      onClick (item) {
        this.fire('autosuggestItemSelected')
        let { realm } = this.get()
        let { composeSelectionStart, composeAutosuggestionSearchText } = this.store.get()
        let startIndex = composeSelectionStart - composeAutosuggestionSearchText.length
        let endIndex = composeSelectionStart
        if (item.acct) {
          /* no await */ insertUsername(realm, item.acct, startIndex, endIndex)
        } else {
          /* no await */ insertEmojiAtPosition(realm, item, startIndex, endIndex)
        }
      },
      async searchAccounts (searchText) {
        searchText = searchText.substring(1)
        let { currentInstance } = this.store.get()
        let results = await searchAccountsByUsernameInDatabase(
          currentInstance, searchText, DATABASE_SEARCH_RESULTS_LIMIT)
        return results.slice(0, SEARCH_RESULTS_LIMIT)
      },
      searchEmoji (searchText) {
        searchText = searchText.toLowerCase().substring(1)
        let { currentCustomEmoji } = this.store.get()
        let results = currentCustomEmoji.filter(emoji => emoji.shortcode.toLowerCase().startsWith(searchText))
          .sort((a, b) => a.shortcode.toLowerCase() < b.shortcode.toLowerCase() ? -1 : 1)
          .slice(0, SEARCH_RESULTS_LIMIT)
        return results
      }
    },
    computed: {
      composeSelectionStart: ({ $composeSelectionStart }) => $composeSelectionStart,
      composeFocused: ({ $composeFocused }) => $composeFocused,
      thisComposeFocused: ({ composeFocusedDeferred, realm }) => composeFocusedDeferred === realm,
      searchResults: ({ $composeAutosuggestionSearchResults }) => $composeAutosuggestionSearchResults || [],
      type: ({ $composeAutosuggestionType }) => $composeAutosuggestionType || 'account',
      selected: ({ $composeAutosuggestionSelected }) => $composeAutosuggestionSelected || 0,
      searchText: ({ text, composeSelectionStartDeferred, thisComposeFocused }) => {
        if (!thisComposeFocused) {
          return
        }
        let selectionStart = composeSelectionStartDeferred
        if (!text || selectionStart < MIN_PREFIX_LENGTH) {
          return
        }

        let textUpToCursor = text.substring(0, selectionStart)
        let match = textUpToCursor.match(ACCOUNT_SEARCH_REGEX) || textUpToCursor.match(EMOJI_SEARCH_REGEX)
        return match && match[1]
      },
      shown: ({ thisComposeFocused, searchText, searchResults }) => {
        return !!(thisComposeFocused &&
          searchText &&
          searchResults.length)
      }
    },
    data: () => ({
      composeFocusedDeferred: void 0,
      composeSelectionStartDeferred: 0
    }),
    store: () => store,
    components: {
      ComposeAutosuggestionList
    }
  }
</script>