module JamRuby
  class MusicSession < ActiveRecord::Base

    self.primary_key = 'id'

    attr_accessible :creator, :musician_access, :approval_required, :fan_chat, :fan_access

    belongs_to :creator, :inverse_of => :music_sessions, :class_name => "JamRuby::User", :foreign_key => "user_id"

    has_many :connections, :class_name => "JamRuby::Connection"
    has_many :users, :through => :connections, :class_name => "JamRuby::User"
    has_and_belongs_to_many :genres, :class_name => "::JamRuby::Genre", :join_table => "genres_music_sessions"
    has_many :join_requests, :foreign_key => "music_session_id", :inverse_of => :music_session, :class_name => "JamRuby::JoinRequest"
    has_many :invitations, :foreign_key => "music_session_id", :inverse_of => :music_session, :class_name => "JamRuby::Invitation"
    has_many :invited_musicians, :through => :invitations, :class_name => "JamRuby::User", :foreign_key => "receiver_id", :source => :receiver

    has_many :fan_invitations, :foreign_key => "music_session_id", :inverse_of => :music_session, :class_name => "JamRuby::FanInvitation"
    has_many :invited_fans, :through => :fan_invitations, :class_name => "JamRuby::User", :foreign_key => "receiver_id", :source => :receiver

    belongs_to :band, :inverse_of => :music_sessions, :class_name => "JamRuby::Band", :foreign_key => "band_id"

    after_save :require_at_least_one_genre, :limit_to_three_genres

    validates :fan_chat, :inclusion => {:in => [true, false]}
    validates :fan_access, :inclusion => {:in => [true, false]}
    validates :approval_required, :inclusion => {:in => [true, false]}
    validates :musician_access, :inclusion => {:in => [true, false]}
    validates :creator, :presence => true
    validate :creator_is_musician

    def creator_is_musician
      unless creator.musician?
        errors.add(:creator, "creator must be a musician")
      end
    end

    def self.index(current_user)
      return MusicSession
        .joins(:creator)
        .joins(
          %Q{
            LEFT OUTER JOIN 
              friendships 
            ON 
              users.id = friendships.user_id 
            AND 
              friendships.friend_id = '#{current_user.id}'
          }
        )
        .joins(
          %Q{
            LEFT OUTER JOIN
              invitations
            ON
              invitations.receiver_id = '#{current_user.id}'
          }
        )
        .order(
          %Q{
            invitations.id is NULL ASC, 
            friendships.user_id IS NULL ASC, 
            music_sessions.created_at DESC
          }
        )
        .where(
          %Q{
            musician_access = true
          }
        )
    end

    # Verifies that the specified user can join this music session
    def can_join? user, as_musician
      if as_musician
        if !user.musician
          return false # "a fan can not join a music session as a musician"
          raise PermissionError, "a fan can not join a music session as a musician"
        end
        
        if self.musician_access
          if self.approval_required
            return self.invited_musicians.exists?(user)
          else
            return true
          end

        else
          # the creator can always join, and the invited users can join
          return self.creator == user || self.invited_musicians.exists?(user)
        end
      else
        # it's a fan, and the only way a fan can join is if fan_access is true
        return self.fan_access
      end

    end

    # Verifies that the specified user can see this music session
    def can_see? user
      if self.musician_access
        return true
      else
        # the creator can always see, and the invited users can see it too
        return self.creator == user || self.invited_musicians.exists?(user)
      end
    end

    # Verifies that the specified user can delete this music session
    def can_delete? user
      # the creator can delete
      return self.creator == user
    end

    def access? user
      return self.users.exists? user
    end

    def to_s
      return description
    end

    private

    def require_at_least_one_genre
      if genres.count < Limits::MIN_GENRES_PER_RECORDING
        errors.add(:genres, ValidationMessages::GENRE_MINIMUM_NOT_MET)
      end
    end

    def limit_to_three_genres
      if genres.count > Limits::MAX_GENRES_PER_RECORDING
        errors.add(:genres, ValidationMessages::GENRE_LIMIT_EXCEEDED)
      end
    end
  end
end