# Only confirmed combinations belong here; all others retain the existing behaviour.
class CountsDefaults
  POST_COLUMNS = ['resource_id', 'version_no', 'is_latest', 'title', 'url',
                  'thumbnail_base', 'tags', 'parents', 'original_created_from',
                  'original_created_before', 'event_type', 'user', 'created_at'].freeze

  def self.entries(resource)
    result = [{ definition: 'history', mode: 'summary', params: {
        'rows' => 'created_at:month',
        'cols' => 'event_type',
        'sort' => 'a0:desc', 'conditions' => '' } }]
    result << { definition: 'latest', mode: 'summary', params: {
        'rows' => '', 'cols' => '', 'conditions' => '', 'tags' => '' } }
    details = detail_params(resource)
    if details
      ['latest', 'history'].each do |definition|
        result << { definition:, mode: 'details', params: details }
      end
    end
    result
  end

  def self.detail_params(resource)
    if resource == 'posts'
      return { 'columns' => POST_COLUMNS.join(' '), 'order' => POST_COLUMNS.join(' '),
               'children' => 'tags.name parents.id', 'nested_json' => '0',
               'conditions' => '', 'tags' => '' }
    end
    unless resource == 'tags'
      return { 'columns' => CountsExportProjection.default_columns(resource).join(' '),
               'children' => CountsExportProjection.default_children(resource).join(' ') }
    end

    columns = ['resource_id', 'version_no', 'is_latest', 'name', 'category',
               'aliases', 'parents', 'deprecated', 'event_type', 'user', 'created_at']
    { 'columns' => columns.join(' '), 'order' => columns.join(' '),
      'children' => 'aliases.name parents.name', 'nested_json' => '0' }
  end

  def self.for(params)
    settings = entries(params.fetch('resource', 'posts')).find do |entry|
      entry[:definition] == params.fetch('definition', 'latest') &&
          entry[:mode] == params.fetch('mode', 'summary')
    end&.fetch(:params) || {}
    if settings.key?('sort') && params.key?('rows')
      actual = QueryState.axes(params['rows'])
      expected = QueryState.axes(settings.fetch('rows'))
      compatible = actual.is_a?(Array) && actual.first.is_a?(Hash) &&
          actual.first['field'] == expected.first['field'] &&
          actual.first.fetch('grain', 'month') == expected.first['grain']
      unless compatible
        settings = settings.except('sort')
      end
    end
    settings
  end

  def self.metadata(resource)
    entries(resource).map do |entry|
      entry.merge(params: entry[:params].map { |key, value| { key:, value: } })
    end
  end
end