# Copyright (C) 2012-2016 Zammad Foundation, http://zammad-foundation.org/

class Channel < ApplicationModel
  include Channel::Assets

  belongs_to :group, optional: true

  store :options
  store :preferences

  after_create   :email_address_check
  after_update   :email_address_check
  after_destroy  :email_address_check

  after_initialize :refresh_xoaut2!

  # rubocop:disable Style/ClassVars
  @@channel_stream = {}
  @@channel_stream_started_till_at = {}
# rubocop:enable Style/ClassVars

=begin

fetch all accounts

  Channel.fetch

=end

  def self.fetch
    channels = Channel.where('active = ? AND area LIKE ?', true, '%::Account')
    channels.each(&:fetch)
  end

=begin

fetch one account

  channel = Channel.where(area: 'Email::Account').first
  channel.fetch

=end

  def fetch(force = false)
    adapter         = options[:adapter]
    adapter_options = options
    if options[:inbound] && options[:inbound][:adapter]
      adapter         = options[:inbound][:adapter]
      adapter_options = options[:inbound][:options]
    end

    begin
      driver_class    = self.class.driver_class(adapter)
      driver_instance = driver_class.new
      return if !force && !driver_instance.fetchable?(self)

      result = driver_instance.fetch(adapter_options, self)
      self.status_in   = result[:result]
      self.last_log_in = result[:notice]
      preferences[:last_fetch] = Time.zone.now
      save!
      true
    rescue => e
      error = "Can't use Channel::Driver::#{adapter.to_classname}: #{e.inspect}"
      logger.error error
      logger.error e
      self.status_in = 'error'
      self.last_log_in = error
      preferences[:last_fetch] = Time.zone.now
      save!
      false
    end
  end

=begin

stream instance of account

  channel = Channel.where(area: 'Twitter::Account').first
  stream_instance = channel.stream_instance

  # start stream
  stream_instance.stream

=end

  def stream_instance

    adapter = options[:adapter]

    begin
      driver_class    = self.class.driver_class(adapter)
      driver_instance = driver_class.new

      # check is stream exists
      return if !driver_instance.respond_to?(:stream_instance)

      driver_instance.stream_instance(self)

      # set scheduler job to active

      driver_instance
    rescue => e
      error = "Can't use Channel::Driver::#{adapter.to_classname}: #{e.inspect}"
      logger.error error
      logger.error e
      self.status_in = 'error'
      self.last_log_in = error
      save!
    end

  end

=begin

stream all accounts

  Channel.stream

=end

  def self.stream
    Thread.abort_on_exception = true

    auto_reconnect_after = 180
    delay_before_reconnect = 70
    last_channels = []

    loop do
      logger.debug { 'stream controll loop' }

      current_channels = []
      channels = Channel.where('active = ? AND area LIKE ?', true, '%::Account')
      channels.each do |channel|
        adapter = channel.options[:adapter]
        next if adapter.blank?

        driver_class = self.driver_class(adapter)
        next if !driver_class.respond_to?(:streamable?)
        next if !driver_class.streamable?

        channel_id = channel.id.to_s

        current_channels.push channel_id

        # exit it channel has changed or connection is older then 180 minutes
        if @@channel_stream[channel_id].present?
          if @@channel_stream[channel_id][:options] != channel.options
            logger.info "channel options (#{channel.id}) has changed, stop stream thread"
            @@channel_stream[channel_id][:thread].exit
            @@channel_stream[channel_id][:thread].join
            @@channel_stream[channel_id][:stream_instance].disconnect
            @@channel_stream.delete(channel_id)
            @@channel_stream_started_till_at[channel_id] = Time.zone.now
            next
          elsif @@channel_stream[channel_id][:started_at] && @@channel_stream[channel_id][:started_at] < Time.zone.now - auto_reconnect_after.minutes
            logger.info "channel (#{channel.id}) reconnect - stream thread is older then #{auto_reconnect_after} minutes, restart thread"
            @@channel_stream[channel_id][:thread].exit
            @@channel_stream[channel_id][:thread].join
            @@channel_stream[channel_id][:stream_instance].disconnect
            @@channel_stream.delete(channel_id)
            @@channel_stream_started_till_at[channel_id] = Time.zone.now
            next
          end
        end

        local_delay_before_reconnect = delay_before_reconnect
        if channel.status_in == 'error'
          local_delay_before_reconnect = local_delay_before_reconnect * 2
        end
        if @@channel_stream[channel_id].blank? && @@channel_stream_started_till_at[channel_id].present?
          wait_in_seconds = @@channel_stream_started_till_at[channel_id] - (Time.zone.now - local_delay_before_reconnect.seconds)
          if wait_in_seconds.positive?
            logger.info "skipp channel (#{channel_id}) for streaming, already tried to connect or connection was active within the last #{local_delay_before_reconnect} seconds - wait another #{wait_in_seconds} seconds"
            next
          end
        end

        #logger.info "thread stream for channel (#{channel.id}) already running" if @@channel_stream[channel_id].present?
        next if @@channel_stream[channel_id].present?

        @@channel_stream[channel_id] = {
          options:    channel.options,
          started_at: Time.zone.now,
        }

        # start channels with delay
        sleep @@channel_stream.count

        # start threads for each channel
        @@channel_stream[channel_id][:thread] = Thread.new do

          logger.info "Started stream channel for '#{channel.id}' (#{channel.area})..."
          channel.status_in = 'ok'
          channel.last_log_in = ''
          channel.save!
          @@channel_stream_started_till_at[channel_id] = Time.zone.now
          @@channel_stream[channel_id] ||= {}
          @@channel_stream[channel_id][:stream_instance] = channel.stream_instance
          @@channel_stream[channel_id][:stream_instance].stream
          @@channel_stream[channel_id][:stream_instance].disconnect
          @@channel_stream.delete(channel_id)
          @@channel_stream_started_till_at[channel_id] = Time.zone.now
          logger.info " ...stopped stream thread for '#{channel.id}'"
        rescue => e
          error = "Can't use stream for channel (#{channel.id}): #{e.inspect}"
          logger.error error
          logger.error e
          channel.status_in = 'error'
          channel.last_log_in = error
          channel.save!
          @@channel_stream.delete(channel_id)
          @@channel_stream_started_till_at[channel_id] = Time.zone.now

        end
      end

      # cleanup deleted channels
      last_channels.each do |channel_id|
        next if @@channel_stream[channel_id].blank?
        next if current_channels.include?(channel_id)

        logger.info "channel (#{channel_id}) not longer active, stop stream thread"
        @@channel_stream[channel_id][:thread].exit
        @@channel_stream[channel_id][:thread].join
        @@channel_stream[channel_id][:stream_instance].disconnect
        @@channel_stream.delete(channel_id)
        @@channel_stream_started_till_at[channel_id] = Time.zone.now
      end

      last_channels = current_channels

      sleep 20
    end

  end

=begin

send via account

  channel = Channel.where(area: 'Email::Account').first
  channel.deliver(params, notification)

=end

  def deliver(params, notification = false)
    adapter         = options[:adapter]
    adapter_options = options
    if options[:outbound] && options[:outbound][:adapter]
      adapter         = options[:outbound][:adapter]
      adapter_options = options[:outbound][:options]
    end
    result = nil
    begin
      driver_class    = self.class.driver_class(adapter)
      driver_instance = driver_class.new
      result = driver_instance.send(adapter_options, params, notification)
      self.status_out   = 'ok'
      self.last_log_out = ''
      save!
    rescue => e
      error = "Can't use Channel::Driver::#{adapter.to_classname}: #{e.inspect}"
      logger.error error
      logger.error e
      self.status_out = 'error'
      self.last_log_out = error
      save!
      raise error
    end
    result
  end

=begin

process via account

  channel = Channel.where(area: 'Email::Account').first
  channel.process(params)

=end

  def process(params)
    adapter         = options[:adapter]
    adapter_options = options
    if options[:inbound] && options[:inbound][:adapter]
      adapter         = options[:inbound][:adapter]
      adapter_options = options[:inbound][:options]
    end
    result = nil
    begin
      driver_class    = self.class.driver_class(adapter)
      driver_instance = driver_class.new
      result = driver_instance.process(adapter_options, params, self)
      self.status_in   = 'ok'
      self.last_log_in = ''
      save!
    rescue => e
      error = "Can't use Channel::Driver::#{adapter.to_classname}: #{e.inspect}"
      logger.error error
      logger.error e
      self.status_in = 'error'
      self.last_log_in = error
      save!
      raise e, error
    end
    result
  end

=begin

load channel driver and return class

  klass = Channel.driver_class('Imap')

=end

  def self.driver_class(adapter)
    # we need to require each channel backend individually otherwise we get a
    # 'warning: toplevel constant Twitter referenced by Channel::Driver::Twitter' error e.g.
    # so we have to convert the channel name to the filename via Rails String.underscore
    # http://stem.ps/rails/2015/01/25/ruby-gotcha-toplevel-constant-referenced-by.html
    require_dependency "channel/driver/#{adapter.to_filename}"

    "::Channel::Driver::#{adapter.to_classname}".constantize
  end

=begin

get instance of channel driver

  channel.driver_instance

=end

  def driver_instance
    self.class.driver_class(options[:adapter])
  end

  def refresh_xoaut2!
    return if options.dig(:auth, :type) != 'XOAUTH2'

    result = ExternalCredential.refresh_token(options[:auth][:provider], options[:auth])

    options[:auth]                          = result
    options[:inbound][:options][:password]  = result[:access_token]
    options[:outbound][:options][:password] = result[:access_token]

    return if new_record?

    # ATTENTION: We don't want to execute any other callbacks here
    # because `after_initialize` leaks the current scope of the Channel class
    # as described here: https://api.rubyonrails.org/classes/ActiveRecord/Relation.html#method-i-new
    # which leads to unexpected effects like:
    # Channel.where(area: 'Google::Account').limit(1).find_each { |c| puts Channel.all.to_sql }
    # => "SELECT "channels".* FROM "channels" WHERE "channels"."area" = 'Google::Account'"
    update_column(:options, options) # rubocop:disable Rails/SkipsModelValidations
  rescue => e
    logger.error e
    raise "Failed to refresh XOAUTH2 access_token of provider '#{options[:auth][:provider]}'! #{e.inspect}"
  end

  private

  def email_address_check

    # reset non existing channel_ids
    EmailAddress.channel_cleanup
  end

end