function getCurrentWordFromCursor(s, cursor) {
  return s.substring(s.lastIndexOf(' ', cursor - 1) + 1, cursor);
}

function mySplice(s, idx, del, n) {
  return s.substring(0, idx) + n + s.substring(idx + del);
}

document.addEventListener('alpine:init', () => {
  Alpine.data('tagsSuggestions', (initialSearch = '') => ({
    items: [],
    activeItem: null,
    search: initialSearch,
    cursor: 0,
    currentWord: '',
    open: false,

    get sortedItems() {
      return this.items.toSorted((a, b) => b.count - a.count);
    },

    async fetchSuggestions() {
      const currentWord = getCurrentWordFromCursor(this.search, this.cursor);
      if (!currentWord)
        return;
      if (currentWord === this.currentWord) {
        /* Show previous items, if any. */
        this.open = true;
        return;
      }
      this.currentWord = currentWord;

      const params = new URLSearchParams({q: currentWord});
      const response = await fetch(`${endpoints.search}?${params}`);

      if (!response.ok) {
        this.items = [];
        return;
      }

      this.items = await response.json();
      this.open = true;
    },

    fetchSuggestionsOnInput(evt) {
      this.cursor = evt.target.selectionStart;
      this.fetchSuggestions();
    },

    autocompleteSuggestion() {
      if (this.items.length === 0)
        return;

      const pos = Math.max(this.cursor - this.currentWord.length, 0);
      const tag = this.items[this.activeItem ?? 0].display;

      this.activeItem = null;
      this.search = mySplice(this.search, pos, this.currentWord.length,
        tag + ' ');
      this.cursor =
        this.$refs.search.selectionStart =
        this.$refs.search.selectionEnd =
        pos + tag.length + 1;
      this.currentWord = '';
      this.open = false;

      this.$refs.search.focus();
    },

    autocompleteItem(evt) {
      if (this.currentWord !== '') {
        this.autocompleteSuggestion();
        evt.preventDefault();
      }
    },

    getListItemIndexOf(el) {
      return [...this.$refs.suggestions.querySelectorAll('li')].indexOf(el);
    },

    autocompletePointedItem(evt) {
      this.activeItem = this.getListItemIndexOf(evt.currentTarget);
      this.autocompleteSuggestion();
    },

    setHoveredItem(evt) {
      this.activeItem = this.getListItemIndexOf(evt.currentTarget);
    },

    previousItem(evt) {
      const len = this.items.length;
      let item = this.activeItem === null ? -1 : this.activeItem - 1;
      item = item % len;
      if (item < 0)
        item += len;
      this.activeItem = item;
    },

    nextItem(evt) {
      const len = this.items.length;
      let item = this.activeItem === null ? 0 : this.activeItem + 1;
      item = item % len;
      this.activeItem = item;
    },
  }));
});