require 'serialize_and_symbolize'
require 'assignable_types'
require 'markdown_class_attributes'
require 'utils'

class Agent < ActiveRecord::Base
  include SerializeAndSymbolize
  include AssignableTypes
  include MarkdownClassAttributes

  serialize_and_symbolize :options, :memory
  markdown_class_attributes :description, :event_description

  load_types_in "Agents"

  SCHEDULES = %w[every_2m every_5m every_10m every_30m every_1h every_2h every_5h every_12h every_1d every_2d every_7d
                 midnight 1am 2am 3am 4am 5am 6am 7am 8am 9am 10am 11am noon 1pm 2pm 3pm 4pm 5pm 6pm 7pm 8pm 9pm 10pm 11pm]

  attr_accessible :options, :memory, :name, :type, :schedule, :source_ids

  validates_presence_of :name, :user
  validate :sources_are_owned
  validate :validate_schedule

  after_initialize :set_default_schedule
  before_validation :set_default_schedule
  before_validation :unschedule_if_cannot_schedule
  before_save :unschedule_if_cannot_schedule

  belongs_to :user, :inverse_of => :agents
  has_many :events, :dependent => :delete_all, :inverse_of => :agent, :order => "events.id desc"
  has_many :received_events, :through => :sources, :class_name => "Event", :source => :events, :order => "events.id desc"
  has_many :links_as_source, :dependent => :delete_all, :foreign_key => "source_id", :class_name => "Link", :inverse_of => :source
  has_many :links_as_receiver, :dependent => :delete_all, :foreign_key => "receiver_id", :class_name => "Link", :inverse_of => :receiver
  has_many :sources, :through => :links_as_receiver, :class_name => "Agent", :inverse_of => :receivers
  has_many :receivers, :through => :links_as_source, :class_name => "Agent", :inverse_of => :sources

  scope :of_type, lambda { |type|
    type = case type
             when String, Symbol, Class
               type.to_s
             when Agent
               type.class.to_s
             else
               type.to_s
           end
    where(:type => type)
  }

  def check
    # Implement me in your subclass of Agent.
  end

  def default_options
    # Implement me in your subclass of Agent.
    {}
  end

  def receive(events)
    # Implement me in your subclass of Agent.
  end

  # Implement me in your subclass to decide if your Agent is working.
  def working?
    raise "Implement me in your subclass"
  end

  def event_created_within(seconds)
    last_event = events.first
    last_event && last_event.created_at > seconds.ago && last_event
  end

  def sources_are_owned
    errors.add(:sources, "must be owned by you") unless sources.all? {|s| s.user == user }
  end

  def create_event(attrs)
    events.create!({ :user => user }.merge(attrs))
  end

  def validate_schedule
    unless cannot_be_scheduled?
      errors.add(:schedule, "is not a valid schedule") unless SCHEDULES.include?(schedule.to_s)
    end
  end

  def make_message(payload, message = options[:message])
    message.gsub(/<([^>]+)>/) { Utils.value_at(payload, $1) || "??" }
  end

  def set_default_schedule
    self.schedule = default_schedule unless schedule.present? || cannot_be_scheduled?
  end

  def unschedule_if_cannot_schedule
    self.schedule = nil if cannot_be_scheduled?
  end

  def last_event_at
    @memoized_last_event_at ||= events.select(:created_at).first.try(:created_at)
  end

  def async_check
    check
    self.last_check_at = Time.now
    save!
  end
  handle_asynchronously :async_check #, :priority => 10, :run_at => Proc.new { 5.minutes.from_now }

  def async_receive(event_ids)
    receive(Event.where(:id => event_ids))
    self.last_receive_at = Time.now
    save!
  end
  handle_asynchronously :async_receive #, :priority => 10, :run_at => Proc.new { 5.minutes.from_now }

  def default_schedule
    self.class.default_schedule
  end

  def cannot_be_scheduled?
    self.class.cannot_be_scheduled?
  end

  def can_be_scheduled?
    !cannot_be_scheduled?
  end

  def cannot_receive_events?
    self.class.cannot_receive_events?
  end

  def can_receive_events?
    !cannot_receive_events?
  end

  # Class Methods

  def self.cannot_be_scheduled!
    @cannot_be_scheduled = true
  end

  def self.cannot_be_scheduled?
    !!@cannot_be_scheduled
  end

  def self.default_schedule(schedule = nil)
    @default_schedule = schedule unless schedule.nil?
    @default_schedule
  end

  def self.cannot_receive_events!
    @cannot_receive_events = true
  end

  def self.cannot_receive_events?
    !!@cannot_receive_events
  end

  def self.receive!
    sql = Agent.
            select("agents.id AS receiver_agent_id, sources.id AS source_agent_id, events.id AS event_id").
            joins("JOIN links ON (links.receiver_id = agents.id)").
            joins("JOIN agents AS sources ON (links.source_id = sources.id)").
            joins("JOIN events ON (events.agent_id = sources.id)").
            where("agents.last_checked_event_id IS NULL OR events.id > agents.last_checked_event_id").to_sql

    agents_to_events = {}
    Agent.connection.select_rows(sql).each do |receiver_agent_id, source_agent_id, event_id|
      agents_to_events[receiver_agent_id] ||= []
      agents_to_events[receiver_agent_id] << event_id
    end

    event_ids = agents_to_events.values.flatten.uniq.compact

    Agent.where(:id => agents_to_events.keys).each do |agent|
      agent.update_attribute :last_checked_event_id, event_ids.max
      agent.async_receive(agents_to_events[agent.id].uniq)
    end

    {
        :agent_count => agents_to_events.keys.length,
        :event_count => event_ids.length
    }
  end

  def self.run_schedule(schedule)
    types = where(:schedule => schedule).group(:type).pluck(:type)
    types.each do |type|
      type.constantize.bulk_check(schedule)
    end
  end

  # You can override this to define a custom bulk_check for your type of Agent.
  def self.bulk_check(schedule)
    raise "Call #bulk_check on the appropriate subclass of Agent" if self == Agent
    where(:schedule => schedule).find_each do |agent|
      agent.async_check
    end
  end
end