module RedmineCrm
  module FormTagHelper
    # Allows include select2 into your views.
    #
    # ==== Examples
    #   select2_tag 'city_id', '<option value="1">Lisbon</option>...'
    #   select2_tag 'city_id', options_for_select(...)
    #   select2_tag 'tag_list', nil, :multiple => true, :data => [{ id: 0, text: 'deal' }, ...], :tags => true, :include_hidden => false %>
    #   select2_tag 'tag_list', options_for_select(...), :multiple => true, :style => 'width: 100%;', :url => '/tags', :placeholder => '+ add tag', :tags => true %>
    #
    # You may use select_tag options and additional options.
    #
    # ==== Additional options
    # * <tt>:url</tt> Allows searches for remote data using the ajax.
    # * <tt>:data</tt> Load dropdown options from a local array if +url+ option not set.
    # * <tt>:placeholder</tt> Supports displaying a placeholder value.
    # * <tt>:include_hidden</tt> Adds hidden field after select when +multiple+ option true. Default value true.
    #
    # <b>Note:</b> The HTML specification says when +multiple+ parameter passed to select and all options got deselected
    # web browsers do not send any value to server.
    #
    # In case if you don't want the helper to generate this hidden field you can specify
    # <tt>include_hidden: false</tt> option.
    #
    # Also aliased as: select2
    #
    #   select2 'city_id', options_for_select(...)
    #
    def select2_tag(name, option_tags = nil, options = {})
      id = sanitize_to_id(name)
      placeholder = options[:placeholder] || 'Select ...'

      content_for(:header_tags) { select2_assets }
      result = select_tag(name, option_tags, options)
      if options[:multiple] && options.fetch(:include_hidden, true)
        result << hidden_field_tag("#{name}[]", '')
      end

      result << javascript_tag(<<-JS)
        $(function () {
            $('select#' + '#{id}').select2({
                #{select2_data_source_options(options)},
                #{select2_tags_options(options)},
                placeholder: '#{placeholder}'
            });
        });
      JS
    end

    alias select2 select2_tag

    # Transforms select filter field into select2
    #
    # ==== Examples
    #   transform_to_select2 'issue_tags', url: auto_complete_tags_url
    #   transform_to_select2 'manager_id', format_state: 'formatStateWithAvatar', min_input_length: 1, url: '/managers'
    #
    # ==== Options
    # * <tt>:url</tt> Defines URL to search remote data using the ajax.
    # * <tt>:format_state</tt> Defines template of search results in the drop-down.
    # * <tt>:min_input_length</tt> Minimum number of characters required to start a search. Default value 0.
    # * <tt>:width</tt> Sets the width of the control. Default value '60%'.
    #
    def transform_to_select2(field, options = {})
      return if field.empty?

      result = ''.html_safe
      unless @transform_to_select2_included
      result << javascript_include_tag('select2_helpers', plugin: 'redmine_crm')
        @transform_to_select2_included = true
      end

      result << javascript_tag(<<-JS)
          select2Filters['#{field}'] = {
              url: '#{options[:url].to_s}',
              formatState: #{options.fetch(:format_state, 'undefined')},
              minimumInputLength: #{options.fetch(:min_input_length, 0)},
              width: '#{options.fetch(:with, '60%')}'
          };
      JS
    end

    private

    def select2_data_source_options(options = {})
      if options[:url].to_s.empty?
        "data: #{options.fetch(:data, []).to_json}"
      else
        "ajax: {
             url: '#{options[:url]}',
             dataType: 'json',
             delay: 250,
             data: function (params) {
                 return { q: params.term };
             },
             processResults: function (data, params) {
                 return { results: data };
             },
             cache: true
         }"
      end
    end

    def select2_tags_options(options = {})
      if options.fetch(:tags, false)
        "tags: true,
         tokenSeparators: [','],
         createTag: function (params) {
             var term = $.trim(params.term);
             if (term === '' || term.indexOf(',') > -1) {
                 return null; // Return null to disable tag creation
             }
             return {
                 id: term,
                 text: term
             }
         }"
      else
        'tags: false'
      end
    end
  end
end