{%- assign errors = '' | split: ',' -%}

{%- unless site.data.lang.version -%}
  {%- unless site.conference.lang == "en" -%}
    {%- assign errors = errors | push : "The internationalization file containing different strings for this template seems to be missing. Have you copied the `_data/lang.yml` file from the [theme's repository](https://github.com/DigitaleGesellschaft/jekyll-theme-conference/blob/master/_data/lang.yml) to you local website folder?" -%}
  {%- endunless -%}
{%- elsif site.data.lang.version != 6 -%}
  {%- assign errors = errors | push : "The internationalization file in `_data/lang.yml` seems to be outdated and does not correspond to the current version of the theme. Grab the current version from the [theme's repository](https://github.com/DigitaleGesellschaft/jekyll-theme-conference/blob/master/_data/lang.yml)." -%}
{%- endunless -%}
{%- unless site.conference.lang == "en" or site.conference.lang == "de" or site.conference.lang == "fr" or site.conference.lang == "pt" -%}
  {%- assign errors = errors | push : "Unknown language selected for `site.conference.lang` parameter. Supported are `en`, `de`, `fr`, and `pt`." -%}
{%- endunless -%}

{%- assign main_category_size = site.conference.talks.main_categories | size -%}
{%- if main_category_size == 0 -%}
  {%- assign errors = errors | push : "Your `_config.yml` configuration file does not define any main category for your talks. Have you set the `conference.talks.main_categories` property? See also [Talk Settings](https://github.com/DigitaleGesellschaft/jekyll-theme-conference/#talk-settings) section in the theme's README file." -%}
{%- endif -%}

{%- assign nbr_days = site.data.program.days | size -%}
{%- if nbr_days == 0 -%}
  {%- assign errors = errors | push : "Your schedule in `_data/program.yml` does not seem to contain any days. Have you already created the file?" -%}
{%- endif -%}
{%- if site.conference.live -%}
  {%- for d in site.data.program.days -%}
    {%- unless d.date or d.date == "" -%}
      {%- assign error_msg = "Day " | append: forloop.index | append: " in your schedule should have a (non-empty) `date` property."  -%}
      {%- assign errors = errors | push : error_msg -%}
    {%- endunless -%}
  {%- endfor -%}
{%- endif -%}

{%- assign nbr_rooms = site.rooms | size -%}
{%- if nbr_rooms == 0 -%}
  {%- assign errors = errors | push : "The `rooms` collection does not seem to contain any entry. Have you accidentially renamed the collection or is your `_rooms/` folder empty?" -%}
{%- else -%}
  {%- for room in site.rooms -%}
    {%- assign nbr_rooms_name = site.rooms | where: 'name', room.name | size %}
    {%- if nbr_rooms_name > 1 -%}
      {%- assign error_msg = "The room with the `name` _" | append: room.name | append: "_ oocures more than once but should be unique."  -%}
      {%- assign errors = errors | push : error_msg -%}
    {%- endif -%}
  {%- endfor -%}
{%- endif -%}

{%- assign nbr_speakers = site.speakers | size -%}
{%- if nbr_speakers == 0 -%}
  {%- assign errors = errors | push : "The `speakers` collection does not seem to contain any entry. Have you accidentially renamed the collection or is your `_speakers/` folder empty?" -%}
{%- else -%}
  {%- for speaker in site.speakers -%}
    {%- assign nbr_speakers_name = site.speakers | where: 'name', speaker.name | size %}
    {%- if nbr_speakers_name > 1 -%}
      {%- assign error_msg = "The speaker with the `name` _" | append: speaker.name | append: "_ oocures more than once but should be unique."  -%}
      {%- assign errors = errors | push : error_msg -%}
    {%- endif -%}
  {%- endfor -%}
{%- endif -%}

{%- assign nbr_talks = site.talks | size -%}
{%- if nbr_talks == 0 -%}
  {%- assign errors = errors | push : "The `talks` collection does not seem to contain any entry. Have you accidentially renamed the collection or is your `_talks/` folder empty?" -%}
{%- else -%}
  {%- for talk in site.talks -%}
    {%- assign nbr_talks_name = site.talks | where: 'name', talk.name | size %}
    {%- if nbr_talks_name > 1 -%}
      {%- assign error_msg = "The talk with the `name` _" | append: talk.name | append: "_ oocures more than once but should be unique."  -%}
      {%- assign errors = errors | push : error_msg -%}
    {%- endif -%}
  {%- endfor -%}
{%- endif -%}