let Autocomplete = {};

Autocomplete.VERSION = 1; // This should be bumped whenever the /autocomplete API changes in order to invalid client caches.
Autocomplete.MAX_RESULTS = 20;

Autocomplete.initialize_all = function() {
  $.widget("ui.autocomplete", $.ui.autocomplete, {
    options: {
      delay: 0,
      minLength: 1,
      autoFocus: false,
      focus: function() { return false; },
    },
    _create: function() {
      this.element.on("keydown.Autocomplete.tab", null, "tab", Autocomplete.on_tab);
      this._super();
    },
    _renderItem: Autocomplete.render_item,
    search: function(value, event) {
      if ($(this).data("ui-autocomplete")) {
        $(this).data("ui-autocomplete").menu.bindings = $();
      }
      this._super(value, event);
    },
  });

  this.initialize_tag_autocomplete();
  this.initialize_mention_autocomplete($("form div.input.dtext textarea"));
  this.initialize_fields($('[data-autocomplete="tag"]'), "tag");
  this.initialize_fields($('[data-autocomplete="artist"]'), "artist");
  this.initialize_fields($('[data-autocomplete="pool"]'), "pool");
  this.initialize_fields($('[data-autocomplete="user"]'), "user");
  this.initialize_fields($('[data-autocomplete="wiki-page"]'), "wiki_page");
  this.initialize_fields($('[data-autocomplete="favorite-group"]'), "favorite_group");
  this.initialize_fields($('[data-autocomplete="saved-search-label"]'), "saved_search_label");
}

Autocomplete.initialize_fields = function($fields, type) {
  $fields.autocomplete({
    source: async function(request, respond) {
      let results = await Autocomplete.autocomplete_source(request.term, type);
      respond(results);
    },
  });
};

Autocomplete.initialize_mention_autocomplete = function($fields) {
  $fields.autocomplete({
    select: function(event, ui) {
      Autocomplete.insert_completion(this, ui.item.value);
      return false;
    },
    source: async function(req, resp) {
      var cursor = this.element.get(0).selectionStart;
      var name = null;

      for (var i = cursor; i >= 1; --i) {
        if (req.term[i - 1] === " ") {
          return;
        }

        if (req.term[i - 1] === "@") {
          if (i === 1 || /[ \r\n]/.test(req.term[i - 2])) {
            name = req.term.substring(i, cursor);
            break;
          } else {
            return;
          }
        }
      }

      if (name) {
        let results = await Autocomplete.autocomplete_source(name, "mention");
        resp(results);
      }
    }
  });
}

Autocomplete.initialize_tag_autocomplete = function() {
  var $fields_multiple = $('[data-autocomplete="tag-query"], [data-autocomplete="tag-edit"]');

  $fields_multiple.autocomplete({
    select: function(event, ui) {
      Autocomplete.insert_completion(this, ui.item.value);
      return false;
    },
    source: async function(req, resp) {
      let term = Autocomplete.current_term(this.element);
      let results = await Autocomplete.autocomplete_source(term, "tag_query");
      resp(results);
    }
  });
}

Autocomplete.current_term = function($input) {
  let query = $input.get(0).value;
  let caret = $input.get(0).selectionStart;
  let regexp = new RegExp(`^[-~(]*(${Autocomplete.tag_prefixes().join("|")})?`);
  let match = query.substring(0, caret).match(/\S*$/)[0].replace(regexp, "").toLowerCase();
  return match;
};

// Update the input field with the item currently focused in the
// autocomplete menu, then position the caret just after the inserted completion.
Autocomplete.insert_completion = function(input, completion) {
  // Trim all whitespace (tabs, spaces) except for line returns
  var before_caret_text = input.value.substring(0, input.selectionStart).replace(/^[ \t]+|[ \t]+$/gm, "");
  var after_caret_text = input.value.substring(input.selectionStart).replace(/^[ \t]+|[ \t]+$/gm, "");

  var regexp = new RegExp(`([-~(]*(?:${Autocomplete.tag_prefixes().join("|")})?)\\S+$`, "g");
  before_caret_text = before_caret_text.replace(regexp, "$1") + completion + " ";

  input.value = before_caret_text + after_caret_text;
  input.selectionStart = input.selectionEnd = before_caret_text.length;
};

// If we press tab while the autocomplete menu is open but nothing is
// focused, complete the first item and close the menu.
Autocomplete.on_tab = function(event) {
  var input = this;
  var autocomplete = $(input).autocomplete("instance");
  var $autocomplete_menu = autocomplete.menu.element;

  if (!$autocomplete_menu.is(":visible")) {
    return;
  }

  if ($autocomplete_menu.has(".ui-state-active").length === 0) {
    var $first_item = $autocomplete_menu.find(".ui-menu-item").first();
    var completion = $first_item.data().uiAutocompleteItem.value;

    Autocomplete.insert_completion(input, completion);
    autocomplete.close();
  }

  // Prevent the tab key from moving focus to the next element.
  event.preventDefault();
};

Autocomplete.render_item = function(list, item) {
  item.html.data("ui-autocomplete-item", item);
  return list.append(item.html);
};

Autocomplete.autocomplete_source = async function(query, type) {
  if (query === "") {
    return [];
  }

  let html = await $.get("/autocomplete", {
    "search[query]": query,
    "search[type]": type,
    "version": Autocomplete.VERSION,
    "limit": Autocomplete.MAX_RESULTS
  });

  let items = $(html).find("li").toArray().map(item => {
    let $item = $(item);
    return { value: $item.attr("data-autocomplete-value"), html: $item };
  });

  return items;
}

Autocomplete.tag_prefixes = function() {
  return JSON.parse($("meta[name=autocomplete-tag-prefixes]").attr("content"));
};

$(document).ready(function() {
  Autocomplete.initialize_all();
});

export default Autocomplete;