module JamRuby

  class ResultStub
    extend  ActiveModel::Naming
    extend  ActiveModel::Translation
    include ActiveModel::Validations
    include ActiveModel::Conversion

    attr_accessor :vals

    def initialize(vals)
      @vals = vals
    end

    def self.stubs(sql)
      ActiveRecord::Base.connection.execute(sql).collect { |rr| self.new(rr) }
    end

    def persisted?; false; end
  end

  # Temporary Tables created by this class:

  # tmp_candidate_sessions
  # ----------------------
  #
  # These are 'open' sessions that have any open slots left, and fall within a certain start time.
  # The session creator must also have a locidispid.
  #
  # session_id          - music_session.id
  # creator_id          - music_session.user_id
  # creator_score_idx   - this is the creator's users.last_jam_locidispid
  # instrument_id       - instruments that are open as gleamed from the RSVP.  If this is NULL, it means 'ANY INSTRUMENT'
  # invited_user_id     - the ID of a user who was invited. Can be NULL.
  #
  # tmp_candidate_recipients
  # ------------------------
  #
  # These are musicians, that allow email notifications, that have an instrument which matches the session's open RSVP slot's instrument.
  # The musician must also have a locidispid.
  #
  # receiver_id         - user ID that could be in the session
  # receiver_score_idx  - the user's last_jam_locidispid
  # instrument_id       - the user's matching instrument for a open session slot. If this is NULL, it means 'ANY INSTRUMENT'
  # invited_user_id
  #
  # tmp_matches
  # -----------
  #
  # These are 'candidate_recipients' that have a decent enough score with the creator of the music sessions in tmp_candidate_sessions
  #
  # receiver_id         - the user.id that should receive an Daily Session email
  # session_id          - the music_session.id for the email
  # latency             - the score.score between the creator and the candidate (needs to be full score soon)
  class EmailBatchScheduledSessions < EmailBatchPeriodic

    BATCH_SIZE = 500
    SINCE_DAYS = 2
    MIN_HOURS_START = 2

    ENV_MAX_LATENCY = 'env_max_latency'
    ENV_QUERY_LIMIT = 'env_query_limit'
    SNAPSHOT_QUERY_LIMIT = '500'

    def self.refresh_snapshot!
      self.where(:aasm_state => 'snapshot').limit(1).first.try(:destroy)
      oo = self.create
      oo.snapshoting!
      oo
    end

    def self.subject
      "New sessions have been scheduled that may be a good match for you!"
    end

    def earliest_session_create_time 
      time_since_last_batch(SINCE_DAYS)
    end

    def latest_session_create_time 
      self.created_at
    end

    def earliest_session_start_time
      self.created_at + MIN_HOURS_START.hours
    end

    def snapshot_eligible_sessions
      rr = ActiveRecord::Base.connection.execute("SELECT COUNT(*) AS num FROM tmp_candidate_sessions")
      [0 < rr.count ? rr[0]['num'].to_i : 0, ResultStub.stubs("SELECT * FROM tmp_candidate_sessions")]
    end

    def snapshot_eligible_recipients
      rr = ActiveRecord::Base.connection.execute("SELECT COUNT(*) AS num FROM tmp_candidate_recipients")
      [0 < rr.count ? rr[0]['num'].to_i : 0, ResultStub.stubs("SELECT * FROM tmp_candidate_recipients")]
    end

    def snapshot_scored_recipients
      rr = ActiveRecord::Base.connection.execute("SELECT COUNT(*) AS num FROM tmp_matches")
      [0 < rr.count ? rr[0]['num'].to_i : 0, ResultStub.stubs("SELECT * FROM tmp_matches")]
    end

    def take_snapshot
      _load_recipients
      _count_recipients
      self.update_attribute(:test_emails, @counters.inspect)
    end

    def fetch_recipients(per_page=BATCH_SIZE)
      objs = []

      _load_recipients

      @per_page = per_page
      num_recip = _select_scored_recipients(-1)
      loops = (num_recip / @per_page) + (num_recip % @per_page) - 1

      0.upto(loops) do |nn|
        offset = nn * @per_page
        # now just get the sessions/latency for each distinct mail recipient
        _select_scored_recipients(offset).each do |result|
          receiver = User.find_by_id(result['receiver_id'])
          sessions = MusicSession.select("music_sessions.*, tmp_matches.latency")
            .joins("INNER JOIN tmp_matches ON tmp_matches.session_id = music_sessions.id")
            .where(["tmp_matches.receiver_id = ?", receiver.id])
            .order('tmp_matches.latency')
            .limit(20)
            .includes([:genre, :creator])
          block_given? ? yield(receiver, sessions) : objs << [receiver, sessions]
        end
      end
      objs
    end

    def deliver_batch_sets!
      self.opt_in_count = 0
      self.fetch_recipients do |receiver, sessions_and_latency|
        self.opt_in_count += 1
        bset = EmailBatchSet.scheduled_session_set(self, receiver, sessions_and_latency)
        UserMailer.scheduled_session_daily(receiver, sessions_and_latency).deliver_now
      end

      self.test_emails = _count_recipients.inspect

      self.sent_count = self.opt_in_count
      self.save
      self.did_batch_run!
    end

    def self.send_daily_session_batch
      oo = self.create
      oo.deliver_batch
      oo
    end

    private

    # inserts eligible sessions to temp table
    def _collect_eligible_sessions
      ActiveRecord::Base.connection.execute("DROP TABLE IF EXISTS tmp_candidate_sessions")
      limit_sql = (self.snapshot? && 0 < ENV[ENV_QUERY_LIMIT].to_i) ? "LIMIT #{ENV[ENV_QUERY_LIMIT]}" : ''
      sql =<<SQL
SELECT 
    msess.id AS session_id, 
    msess.user_id AS creator_id,
    users.last_jam_locidispid AS creator_score_idx,
    rs.instrument_id,
    invitations.receiver_id AS invited_user_id,
    msess.is_unstructured_rsvp,
    msess.open_rsvps
INTO TEMP TABLE tmp_candidate_sessions 
FROM music_sessions msess
INNER JOIN users ON users.id = msess.user_id
INNER JOIN rsvp_slots AS rs ON rs.music_session_id = msess.id
LEFT JOIN rsvp_requests_rsvp_slots AS rrrs ON rrrs.rsvp_slot_id = rs.id
LEFT JOIN invitations ON open_rsvps = FALSE AND invitations.music_session_id = msess.id
WHERE
    (msess.is_unstructured_rsvp = TRUE OR (rrrs.id IS NULL OR rrrs.chosen != TRUE)) AND
    users.last_jam_locidispid IS NOT NULL AND
    msess.created_at > '#{earliest_session_create_time}' AND
    msess.created_at < '#{latest_session_create_time}' AND
    scheduled_start >= '#{earliest_session_start_time}'
#{limit_sql}
SQL
      ActiveRecord::Base.connection.execute(sql)
    end
    
    def _collect_eligible_recipients
      ActiveRecord::Base.connection.execute("DROP TABLE IF EXISTS tmp_candidate_recipients").check
      limit_sql = (self.snapshot? && 0 < ENV[ENV_QUERY_LIMIT].to_i) ? "LIMIT #{ENV[ENV_QUERY_LIMIT]}" : ''
      # load eligible recipients into tmp table
      sql =<<SQL
SELECT 
    users.id AS receiver_id, 
    users.last_jam_locidispid AS receiver_score_idx,
    mi.instrument_id,
    tmp_candidate_sessions.invited_user_id,
    tmp_candidate_sessions.session_id AS session_id,
    tmp_candidate_sessions.creator_id AS creator_id,
    tmp_candidate_sessions.creator_score_idx AS creator_score_idx
INTO TEMP TABLE tmp_candidate_recipients
FROM users
INNER JOIN musicians_instruments AS mi ON mi.player_id = users.id
INNER JOIN tmp_candidate_sessions ON tmp_candidate_sessions.is_unstructured_rsvp = TRUE OR
                                    (tmp_candidate_sessions.open_rsvps = TRUE AND tmp_candidate_sessions.instrument_id = mi.instrument_id) OR
                                    tmp_candidate_sessions.invited_user_id = users.id
WHERE
    users.last_jam_locidispid IS NOT NULL AND
    users.musician = TRUE AND
    users.subscribe_email = TRUE AND
    users.id != tmp_candidate_sessions.creator_id
#{limit_sql}
SQL
      ActiveRecord::Base.connection.execute(sql)
    end

    def _collect_scored_recipients
      ActiveRecord::Base.connection.execute("DROP TABLE IF EXISTS tmp_matches")
      if !self.snapshot? || 0 == (max_score = ENV[ENV_MAX_LATENCY].to_i)
        max_score = APP_CONFIG.max_yellow_full_score
      end
      limit_sql = (self.snapshot? && 0 < ENV[ENV_QUERY_LIMIT].to_i) ? "LIMIT #{ENV[ENV_QUERY_LIMIT]}" : ''
      sql =<<SQL
SELECT DISTINCT
    tmp_candidate_recipients.receiver_id,
    tmp_candidate_recipients.session_id,
    current_scores.full_score AS latency
INTO TEMP TABLE tmp_matches
FROM current_scores
INNER JOIN tmp_candidate_recipients ON
    tmp_candidate_recipients.creator_id = current_scores.a_userid AND
    tmp_candidate_recipients.receiver_id = current_scores.b_userid
WHERE
    current_scores.full_score < #{max_score}
GROUP BY
    tmp_candidate_recipients.receiver_id,
    tmp_candidate_recipients.session_id,
    latency
#{limit_sql}
SQL
      ActiveRecord::Base.connection.execute(sql)
    end

    # select recipients whose score is below minimum threshold
    def _select_scored_recipients(offset=0)
      if 0 > offset
        sql = "SELECT COUNT(DISTINCT receiver_id) AS num FROM tmp_matches"
        rr = ActiveRecord::Base.connection.execute(sql)
        return 0 < rr.count ? rr[0]['num'].to_i : 0
      else
        sql =<<SQL
SELECT DISTINCT receiver_id 
FROM tmp_matches 
ORDER BY receiver_id ASC
LIMIT #{@per_page}
OFFSET #{offset}
SQL
        return ActiveRecord::Base.connection.execute(sql)
      end
    end

    def _load_recipients
      # load eligible sessions into tmp table
      _collect_eligible_sessions

      # load eligible mail recipients into tmp table
      _collect_eligible_recipients

      # load mail recipients with minimum score into tmp table
      _collect_scored_recipients

    end

    def _count_recipients(load_tmp_tables = false)
      return @counters if @counters || !self.snapshot?
      _load_recipients if load_tmp_tables

      rr = ActiveRecord::Base.connection.execute("SELECT COUNT(*) AS num FROM tmp_candidate_sessions")
      session_count = 0 < rr.count ? rr[0]['num'].to_i : 0
      rr = ActiveRecord::Base.connection.execute("SELECT COUNT(*) AS num FROM tmp_candidate_recipients")
      receiver_candidate_count = 0 < rr.count ? rr[0]['num'].to_i : 0
      rr = ActiveRecord::Base.connection.execute("SELECT COUNT(*) AS num FROM tmp_matches")
      receiver_match_count = 0 < rr.count ? rr[0]['num'].to_i : 0

      @counters = {
        :sessions => session_count,
        :receiver_candidates => receiver_candidate_count,
        :receiver_match => receiver_match_count
      }
    end

  end
end