module MailyHerald
  # Represents subscriptions list.
  #
  # Entities can be subscribed to lists by creating {Subscription} object for them.
  #
  # List have {Context} assigned. Only entities from Context scope can be subscribed to list.
  #
  # @attr [String]    name
  # @attr [String]    title
  # @attr [String]    context_name    Name of the {Context} used by List.
  class List < ActiveRecord::Base
    include MailyHerald::Autonaming

    if Rails::VERSION::MAJOR == 3
      attr_accessible :name, :title, :context_name
    end

    has_many :dispatches, class_name: "MailyHerald::Dispatch"
    has_many :subscriptions, class_name: "MailyHerald::Subscription"

    validates :context, presence: true

    validate do |list|
      list.errors.add(:base, "Can't change this list because it is locked.") if list.locked?
    end
    before_destroy do |list|
      if list.locked?
        list.errors.add(:base, "Can't destroy this list because it is locked.") 
        false
      end
    end

    # Returns {Context} object associated with List.
    def context
      @context ||= MailyHerald.context self.context_name
    end

    # Subscribes entity to List.
    #
    # @param entity [Object] Entity object. Need to be in the {Context} scope.
    def subscribe! entity
      s = subscription_for(entity) 
      s ? s.activate! : s = create_subscription_for(entity, true)
      s
    end

    # Unsubscribes entity from List.
    #
    # @param entity [Object] Entity object.
    def unsubscribe! entity
      s = subscription_for(entity) 
      s ? s.deactivate! : s = create_subscription_for(entity, false)
      s
    end

    # Checks whether entity is subscribed to List.
    def subscribed? entity
      s = Subscription.get_from(entity) || subscription_for(entity)
      s.try(:active?)
    end

    # Checks whether entity is not subscribed to List.
    #
    # True if user has inactive subscription or never been subscribed.
    def unsubscribed? entity
      s = Subscription.get_from(entity) || subscription_for(entity)
      s ? !s.active? : true
    end

    # Checks whether entity has been removed from List.
    #
    # True only if user was intentionally unsubscribed.
    def opted_out? entity
      s = subscription_for(entity)
      s ? !s.active? : false
    end

    # Returns subscription for given entity.
    def subscription_for entity
      self.subscriptions.for_entity(entity).first
    end

    # Returns number of List subscribers.
    def active_subscription_count
      subscribers.count(:id)
    end

    # Returns entities within the context's scope with active subscription.
    def subscribers
      context.scope_with_subscription(self).where("#{Subscription.table_name}.active = (?)", true).where("#{Subscription.table_name}.list_id = (?)", self.id)
    end

    # Returns entities within the context's scope with inactive subscription.
    def opt_outs
      context.scope_with_subscription(self).where("#{Subscription.table_name}.active = (?)", false).where("#{Subscription.table_name}.list_id = (?)", self.id)
    end

    # Returns entities within the context's scope without subscription.
    def potential_subscribers
      sq = context.scope_with_subscription(self, :outer).where("#{Subscription.table_name}.list_id = (?)", self.id).pluck("#{context.model.table_name}.id")
      context.scope.where(context.model.arel_table[:id].not_in(sq))
    end

    # Returns {Log} objects collection related to this List.
    def logs
      #Log.for_mailings(self.dispatches.select("id"))
      Log.for_mailings(Dispatch.where("sequence_id IN (?) OR list_id = (?)", Sequence.where(list_id: self.id).select("id"), self.id).select("id"))
    end

    # Check if List is locked.
    # @see MailyHerald.list_locked?
    def locked?
      MailyHerald.list_locked?(self.name)
    end

    private

    def create_subscription_for entity, active = false
      s = self.subscriptions.build.tap do |s|
        s.entity = entity
        s.active = active
      end
      s.save!
      s
    end

  end
end