#-- encoding: UTF-8
#-- copyright
# OpenProject is an open source project management software.
# Copyright (C) 2012-2020 the OpenProject GmbH
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License version 3.
#
# OpenProject is a fork of ChiliProject, which is a fork of Redmine. The copyright follows:
# Copyright (C) 2006-2017 Jean-Philippe Lang
# Copyright (C) 2010-2013 the ChiliProject Team
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# of the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
#
# See docs/COPYRIGHT.rdoc for more details.
#++

module CustomField::OrderStatements
  # Returns a ORDER BY clause that can used to sort customized
  # objects by their value of the custom field.
  # Returns false, if the custom field can not be used for sorting.
  def order_statements
    case field_format
    when 'list'
      if multi_value?
        [select_custom_values_joined_options_as_group]
      else
        [select_custom_option_position]
      end
    when 'string', 'text', 'date', 'bool'
      if multi_value?
        [select_custom_values_as_group]
      else
        [coalesce_select_custom_value_as_string]
      end
    when 'int', 'float'
      # Make the database cast values into numeric
      # Postgresql will raise an error if a value can not be casted!
      # CustomValue validations should ensure that it doesn't occur
      [select_custom_value_as_decimal]
    when 'user'
      [
        order_by_user_sql('lastname'),
        order_by_user_sql('firstname'),
        order_by_user_sql('id')
      ]
    when 'version'
      [order_by_version_sql('name')]
    end
  end

  ##
  # Returns the null handling for the given direction
  def null_handling(asc)
    return unless %w[int float].include?(field_format)

    null_direction = asc ? 'FIRST' : 'LAST'
    Arel.sql("NULLS #{null_direction}")
  end

  # Returns the grouping result
  # which differ for multi-value select fields,
  # because in this case we do want the primary CV values
  def group_by_statement
    return order_statements unless field_format == 'list'

    if multi_value?
      # We want to return the internal IDs in the case of grouping
      select_custom_values_as_group
    else
      coalesce_select_custom_value_as_string
    end
  end

  private

  def coalesce_select_custom_value_as_string
    # COALESCE is here to make sure that blank and NULL values are sorted equally
    <<-SQL
      COALESCE(#{select_custom_value_as_string}, '')
    SQL
  end

  def select_custom_value_as_string
    <<-SQL
    (SELECT cv_sort.value FROM #{CustomValue.table_name} cv_sort
        WHERE #{cv_sort_only_custom_field_condition_sql}
        LIMIT 1)
    SQL
  end

  def select_custom_option_position
    <<-SQL
    (SELECT co_sort.position FROM #{CustomOption.table_name} co_sort
        LEFT JOIN #{CustomValue.table_name} cv_sort
        ON co_sort.id = CAST(cv_sort.value AS decimal(60,3))
        WHERE #{cv_sort_only_custom_field_condition_sql}
        LIMIT 1
    )
    SQL
  end

  def select_custom_values_as_group
    <<-SQL
      COALESCE((SELECT string_agg(cv_sort.value, '.') FROM #{CustomValue.table_name} cv_sort
        WHERE #{cv_sort_only_custom_field_condition_sql}
          AND cv_sort.value IS NOT NULL), '')
    SQL
  end

  def select_custom_values_joined_options_as_group
    <<-SQL
      COALESCE((SELECT string_agg(co_sort.value, '.' ORDER BY co_sort.position ASC) FROM #{CustomOption.table_name} co_sort
        LEFT JOIN #{CustomValue.table_name} cv_sort
        ON cv_sort.value IS NOT NULL AND co_sort.id = cv_sort.value::numeric
        WHERE #{cv_sort_only_custom_field_condition_sql}), '')
    SQL
  end

  def select_custom_value_as_decimal
    <<-SQL
    (SELECT CAST(cv_sort.value AS decimal(60,3)) FROM #{CustomValue.table_name} cv_sort
      WHERE #{cv_sort_only_custom_field_condition_sql}
      AND cv_sort.value <> ''
      AND cv_sort.value IS NOT NULL
    LIMIT 1)
    SQL
  end

  def order_by_user_sql(column)
    <<-SQL
    (SELECT #{column} user_cv_#{column} FROM #{User.table_name} cv_user
     WHERE cv_user.id = #{select_custom_value_as_decimal}
     LIMIT 1)
    SQL
  end

  def order_by_version_sql(column)
    <<-SQL
    (SELECT #{column} version_cv_#{column} FROM #{Version.table_name} cv_version
     WHERE cv_version.id = #{select_custom_value_as_decimal}
     LIMIT 1)
    SQL
  end

  private

  def cv_sort_only_custom_field_condition_sql
    <<-SQL
      cv_sort.customized_type='#{self.class.customized_class.name}'
      AND cv_sort.customized_id=#{self.class.customized_class.table_name}.id
      AND cv_sort.custom_field_id=#{id}
    SQL
  end
end