#-- 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.
#++

class Relation < ApplicationRecord
  include VirtualAttribute

  scope :of_work_package,
        ->(work_package) { where('from_id = ? OR to_id = ?', work_package, work_package) }

  virtual_attribute :relation_type do
    types = ((TYPES.keys + [TYPE_HIERARCHY]) & Relation.column_names).select do |name|
      send(name).positive?
    end

    case types.length
    when 1
      types[0]
    when 0
      nil
    else
      TYPE_MIXED
    end
  end

  TYPE_RELATES      = 'relates'.freeze
  TYPE_DUPLICATES   = 'duplicates'.freeze
  TYPE_DUPLICATED   = 'duplicated'.freeze
  TYPE_BLOCKS       = 'blocks'.freeze
  TYPE_BLOCKED      = 'blocked'.freeze
  TYPE_PRECEDES     = 'precedes'.freeze
  TYPE_FOLLOWS      = 'follows'.freeze
  TYPE_INCLUDES     = 'includes'.freeze
  TYPE_PARTOF       = 'partof'.freeze
  TYPE_REQUIRES     = 'requires'.freeze
  TYPE_REQUIRED     = 'required'.freeze
  TYPE_HIERARCHY    = 'hierarchy'.freeze
  TYPE_MIXED        = 'mixed'.freeze

  TYPES = {
    TYPE_RELATES => {
      name: :label_relates_to, sym_name: :label_relates_to, order: 1, sym: TYPE_RELATES
    },
    TYPE_DUPLICATES => {
      name: :label_duplicates, sym_name: :label_duplicated_by, order: 2, sym: TYPE_DUPLICATED
    },
    TYPE_DUPLICATED => {
      name: :label_duplicated_by, sym_name: :label_duplicates, order: 3,
      sym: TYPE_DUPLICATES, reverse: TYPE_DUPLICATES
    },
    TYPE_BLOCKS => {
      name: :label_blocks, sym_name: :label_blocked_by, order: 4, sym: TYPE_BLOCKED
    },
    TYPE_BLOCKED => {
      name: :label_blocked_by, sym_name: :label_blocks, order: 5,
      sym: TYPE_BLOCKS, reverse: TYPE_BLOCKS
    },
    TYPE_PRECEDES => {
      name: :label_precedes, sym_name: :label_follows, order: 6,
      sym: TYPE_FOLLOWS, reverse: TYPE_FOLLOWS
    },
    TYPE_FOLLOWS => {
      name: :label_follows, sym_name: :label_precedes, order: 7,
      sym: TYPE_PRECEDES
    },
    TYPE_INCLUDES => {
      name: :label_includes, sym_name: :label_part_of, order: 8,
      sym: TYPE_PARTOF
    },
    TYPE_PARTOF => {
      name: :label_part_of, sym_name: :label_includes, order: 9,
      sym: TYPE_INCLUDES, reverse: TYPE_INCLUDES
    },
    TYPE_REQUIRES => {
      name: :label_requires, sym_name: :label_required, order: 10,
      sym: TYPE_REQUIRED
    },
    TYPE_REQUIRED => {
      name: :label_required, sym_name: :label_requires, order: 11,
      sym: TYPE_REQUIRES, reverse: TYPE_REQUIRES
    }
  }.freeze

  validates_numericality_of :delay, allow_nil: true

  validate :validate_sanity_of_relation

  before_validation :reverse_if_needed

  before_save :set_type_column

  [TYPE_RELATES,
   TYPE_DUPLICATES,
   TYPE_BLOCKS,
   TYPE_PRECEDES,
   TYPE_FOLLOWS,
   TYPE_INCLUDES,
   TYPE_REQUIRES,
   TYPE_HIERARCHY].each do |type|
    define_method "#{type}=" do |value|
      instance_variable_set(:"@relation_type_set", nil)
      super(value)
    end
  end

  def self.relation_column(type)
    if TYPES.key?(type) && TYPES[type][:reverse]
      TYPES[type][:reverse]
    elsif TYPES.key?(type) || type == TYPE_HIERARCHY
      type
    end
  end

  def self.visible(user = User.current)
    direct
      .where(from_id: WorkPackage.visible(user))
      .where(to_id: WorkPackage.visible(user))
  end

  def self.from_work_package_or_ancestors(work_package)
    ancestor_or_self_ids = work_package
                           .ancestors_relations
                           .or(where(from_id: work_package.id))
                           .select(:from_id)

    where(from_id: ancestor_or_self_ids)
  end

  def self.from_parent_to_self_and_descendants(work_package)
    from_work_package_or_ancestors(work_package.parent)
      .where(to_id: work_package.self_and_descendants.select(:id))
  end

  def self.from_self_and_descendants_to_ancestors(work_package)
    # using parent.self_and_ancestors to be able to cope with unpersisted parent
    where(from_id: work_package.self_and_descendants.select(:id))
      .where(to_id: work_package.parent.self_and_ancestors.select(:id))
  end

  def self.hierarchy_or_follows
    with_type_columns_0(_dag_options.type_columns - %i(hierarchy follows))
      .non_reflexive
  end

  def self.hierarchy_or_reflexive
    with_type_columns_0(_dag_options.type_columns - %i(hierarchy))
  end

  def self.non_hierarchy_of_work_package(work_package)
    of_work_package(work_package)
      .non_hierarchy
      .direct
  end

  def self.to_root(work_package)
    # MySQL does not support limit inside a subquery.
    # As this is intended to be used inside a subquery, we have to avoid using limit
    joins("LEFT OUTER JOIN relations r2
          ON relations.to_id = r2.to_id
          AND relations.hierarchy < r2.hierarchy")
      .where('r2.id IS NULL')
      .where(to_id: work_package.id)
      .hierarchy_or_reflexive
  end

  def self.tree_of(work_package)
    root_id = to_root(work_package)
              .select(:from_id)

    hierarchy
      .where(from_id: root_id)
  end

  def self.sibling_of(work_package)
    hierarchy
      .where(from_id: work_package.parent_id)
  end

  def other_work_package(work_package)
    from_id == work_package.id ? to : from
  end

  # Returns the relation type for +work_package+
  def relation_type_for(work_package)
    if TYPES[relation_type]
      if from_id == work_package.id
        relation_type
      else
        TYPES[relation_type][:sym]
      end
    end
  end

  def reverse_type
    Relation::TYPES[relation_type] && Relation::TYPES[relation_type][:sym]
  end

  def label_for(work_package)
    key = from_id == work_package.id ? :name : :sym_name

    TYPES[relation_type] ? TYPES[relation_type][key] : :unknown
  end

  def successor_soonest_start
    if relation_type == TYPE_FOLLOWS && (to.start_date || to.due_date)
      (to.due_date || to.start_date) + 1 + (delay || 0)
    end
  end

  def <=>(other)
    TYPES[relation_type][:order] <=> TYPES[other.relation_type][:order]
  end

  # delay is an attribute of Relation but its getter is masked by delayed_job's #delay method
  # here we overwrite dj's delay method with the one reading the attribute
  # since we don't plan to use dj with Relation objects, this should be fine
  def delay
    self[:delay]
  end

  def canonical_type
    self.class.canonical_type(relation_type)
  end

  def self.canonical_type(relation_type)
    if TYPES.key?(relation_type) &&
       TYPES[relation_type][:reverse]
      TYPES[relation_type][:reverse]
    else
      relation_type
    end
  end

  private

  def shared_hierarchy?
    to_from = hierarchy_but_not_self(to: to, from: from)
    from_to = hierarchy_but_not_self(to: from, from: to)

    to_from
      .or(from_to)
      .any?
  end

  def validate_sanity_of_relation
    return unless from && to

    errors.add :to_id, :invalid if from_id == to_id
    errors.add :to_id, :not_same_project unless from.project_id == to.project_id ||
                                                Setting.cross_project_work_package_relations?
    errors.add :base, :cant_link_a_work_package_with_a_descendant if shared_hierarchy?
  end

  def set_type_column
    if relation_type_changed? && relation_type_was
      was_column = self.class.relation_column(relation_type_was)
      write_attribute was_column, 0
    end

    return unless relation_type

    new_column = self.class.relation_column(relation_type)

    send("#{new_column}=", 1) if new_column
  end

  # Reverses the relation if needed so that it gets stored in the proper way
  def reverse_if_needed
    if TYPES.key?(relation_type) && TYPES[relation_type][:reverse]
      work_package_tmp = to
      self.to = from
      self.from = work_package_tmp
      self.relation_type = TYPES[relation_type][:reverse]
    end
  end

  def hierarchy_but_not_self(to:, from:)
    Relation.hierarchy.where(to: to, from: from).where.not(id: id)
  end
end