class DossierProjectionService
  class DossierProjection < Struct.new(:dossier_id, :state, :archived, :hidden_by_user_at, :hidden_by_administration_at, :hidden_at, :for_tiers, :prenom, :nom, :batch_operation_id, :sva_svr_decision_on, :corrections, :columns) do
      def pending_correction?
        return false if corrections.blank?

        corrections.any? { _1[:resolved_at].nil? }
      end

      def resolved_corrections?
        return false if corrections.blank?

        corrections.all? { _1[:resolved_at].present? }
      end
    end
  end

  def self.for_tiers_translation(array)
    for_tiers, email, first_name, last_name = array
    if for_tiers == true
      "#{email} #{I18n.t('views.instructeurs.dossiers.acts_on_behalf')} #{first_name} #{last_name}"
    else
      email
    end
  end

  TABLE = 'table'
  COLUMN = 'column'

  # Returns [DossierProjection(dossier, columns)] ordered by dossiers_ids
  # and the columns orderd by fields.
  #
  # It tries to be fast by using `pluck` (or at least `select`)
  # to avoid deserializing entire records.
  #
  # It stores its intermediary queries results in an hash in the corresponding field.
  # ex: field_email[:id_value_h] = { dossier_id_1: email_1, dossier_id_3: email_3 }
  #
  # Those hashes are needed because:
  # - the order of the intermediary query results are unknown
  # - some values can be missing (if a revision added or removed them)
  def self.project(dossiers_ids, fields)
    state_field = { TABLE => 'self', COLUMN => 'state' }
    archived_field = { TABLE => 'self', COLUMN => 'archived' }
    batch_operation_field = { TABLE => 'self', COLUMN => 'batch_operation_id' }
    hidden_by_user_at_field = { TABLE => 'self', COLUMN => 'hidden_by_user_at' }
    hidden_by_administration_at_field = { TABLE => 'self', COLUMN => 'hidden_by_administration_at' }
    hidden_at_field = { TABLE => 'self', COLUMN => 'hidden_at' }
    for_tiers_field = { TABLE => 'self', COLUMN => 'for_tiers' }
    individual_first_name = { TABLE => 'individual', COLUMN => 'prenom' }
    individual_last_name = { TABLE => 'individual', COLUMN => 'nom' }
    sva_svr_decision_on_field = { TABLE => 'self', COLUMN => 'sva_svr_decision_on' }
    dossier_corrections = { TABLE => 'dossier_corrections', COLUMN => 'resolved_at' }
    champ_value = champ_value_formatter(dossiers_ids, fields)
    ([state_field, archived_field, sva_svr_decision_on_field, hidden_by_user_at_field, hidden_by_administration_at_field, hidden_at_field, for_tiers_field, individual_first_name, individual_last_name, batch_operation_field, dossier_corrections] + fields)
      .each { |f| f[:id_value_h] = {} }
      .group_by { |f| f[TABLE] } # one query per table
      .each do |table, fields|
      case table
      when 'type_de_champ', 'type_de_champ_private'
        Champ
          .where(
            stable_id: fields.map { |f| f[COLUMN] },
            dossier_id: dossiers_ids
          )
          .select(:dossier_id, :value, :stable_id, :type, :external_id, :data, :value_json) # we cannot pluck :value, as we need the champ.to_s method
          .group_by(&:stable_id) # the champs are redispatched to their respective fields
          .map do |stable_id, champs|
            field = fields.find { |f| f[COLUMN] == stable_id.to_s }
            field[:id_value_h] = champs.to_h { |c| [c.dossier_id, champ_value.(c)] }
          end
      when 'self'
        Dossier
          .where(id: dossiers_ids)
          .pluck(:id, *fields.map { |f| f[COLUMN].to_sym })
          .each do |id, *columns|
            fields.zip(columns).each do |field, value|
              if [state_field, archived_field, hidden_by_user_at_field, hidden_by_administration_at_field, hidden_at_field, for_tiers_field, batch_operation_field, sva_svr_decision_on_field].include?(field)
                field[:id_value_h][id] = value
              else
                field[:id_value_h][id] = value&.strftime('%d/%m/%Y') # other fields are datetime
              end
            end
          end
      when 'individual'
        Individual
          .where(dossier_id: dossiers_ids)
          .pluck(:dossier_id, *fields.map { |f| f[COLUMN].to_sym })
          .each { |id, *columns| fields.zip(columns).each { |field, value| field[:id_value_h][id] = value } }
      when 'etablissement'
        Etablissement
          .where(dossier_id: dossiers_ids)
          .pluck(:dossier_id, *fields.map { |f| f[COLUMN].to_sym })
          .each { |id, *columns| fields.zip(columns).each { |field, value| field[:id_value_h][id] = value } }
      when 'user'

        fields[0][:id_value_h] = Dossier # there is only one field available for user table
          .joins(:user)
          .includes(:individual)
          .where(id: dossiers_ids)
          .pluck('dossiers.id, dossiers.for_tiers, users.email, individuals.prenom, individuals.nom')
          .to_h { |dossier_id, *array| [dossier_id, for_tiers_translation(array)] }
      when 'groupe_instructeur'
        fields[0][:id_value_h] = Dossier
          .joins(:groupe_instructeur)
          .where(id: dossiers_ids)
          .pluck('dossiers.id, groupe_instructeurs.label')
          .to_h
      when 'dossier_corrections'
        columns = fields.map { _1[COLUMN].to_sym }

        id_value_h = DossierCorrection.where(dossier_id: dossiers_ids)
          .pluck(:dossier_id, *columns)
          .group_by(&:first) # group corrections by dossier_id
          .transform_values do |values| # build each correction has an hash column => value
            values.map { Hash[columns.zip(_1[1..-1])] }
          end

        fields[0][:id_value_h] = id_value_h

      when 'procedure'
        Dossier
          .joins(:procedure)
          .where(id: dossiers_ids)
          .pluck(:id, *fields.map { |f| f[COLUMN].to_sym })
          .each { |id, *columns| fields.zip(columns).each { |field, value| field[:id_value_h][id] = value } }
      when 'followers_instructeurs'
        # rubocop:disable Style/HashTransformValues
        fields[0][:id_value_h] = Follow
          .active
          .joins(instructeur: :user)
          .where(dossier_id: dossiers_ids)
          .pluck('dossier_id, users.email')
          .group_by { |dossier_id, _| dossier_id }
          .to_h { |dossier_id, dossier_id_emails| [dossier_id, dossier_id_emails.sort.map { |_, email| email }&.join(', ')] }
        # rubocop:enable Style/HashTransformValues
      when 'avis'
        # rubocop:disable Style/HashTransformValues
        fields[0][:id_value_h] = Avis
          .where(dossier_id: dossiers_ids)
          .pluck('dossier_id', 'question_answer')
          .group_by { |dossier_id, _| dossier_id }
          .to_h { |dossier_id, question_answer| [dossier_id, question_answer.map { |_, answer| answer }&.compact&.tally&.map { |k, v| I18n.t("helpers.label.question_answer_with_count.#{k}", count: v) }&.join(' / ')] }
        # rubocop:enable Style/HashTransformValues
      end
    end

    dossiers_ids.map do |dossier_id|
      DossierProjection.new(
        dossier_id,
        state_field[:id_value_h][dossier_id],
        archived_field[:id_value_h][dossier_id],
        hidden_by_user_at_field[:id_value_h][dossier_id],
        hidden_by_administration_at_field[:id_value_h][dossier_id],
        hidden_at_field[:id_value_h][dossier_id],
        for_tiers_field[:id_value_h][dossier_id],
        individual_first_name[:id_value_h][dossier_id],
        individual_last_name[:id_value_h][dossier_id],
        batch_operation_field[:id_value_h][dossier_id],
        sva_svr_decision_on_field[:id_value_h][dossier_id],
        dossier_corrections[:id_value_h][dossier_id],
        fields.map { |f| f[:id_value_h][dossier_id] }
      )
    end
  end

  class << self
    private

    def champ_value_formatter(dossiers_ids, fields)
      stable_ids = fields.filter { _1[TABLE].in?(['type_de_champ', 'type_de_champ_private']) }.map { _1[COLUMN] }
      revision_ids_by_dossier_ids = Dossier.where(id: dossiers_ids).pluck(:id, :revision_id).to_h
      stable_ids_and_types_champ_by_revision_ids = ProcedureRevisionTypeDeChamp.includes(:type_de_champ)
        .where(revision_id: revision_ids_by_dossier_ids.values.uniq, type_de_champ: { stable_id: stable_ids })
        .pluck(:revision_id, 'type_de_champ.stable_id', 'type_de_champ.type_champ')
        .group_by(&:first)
        .transform_values { _1.map { |_, stable_id, type_champ| [stable_id, type_champ] }.to_h }
      stable_ids_and_types_champ_by_dossier_ids = revision_ids_by_dossier_ids.transform_values { stable_ids_and_types_champ_by_revision_ids[_1] }.compact
      -> (champ) {
        type_champ = stable_ids_and_types_champ_by_dossier_ids.fetch(champ.dossier_id, {})[champ.stable_id]
        if type_champ.present? && TypeDeChamp.type_champ_to_champ_class_name(type_champ) == champ.type
          TypeDeChamp.champ_value(type_champ, champ)
        else
          ''
        end
      }
    end
  end
end