class ActiveRecord::ConnectionAdapters::Transaction

def add_record(record, ensure_finalize = true)
  @records ||= []
  if ensure_finalize
    @records << record
  else
    @lazy_enrollment_records ||= ObjectSpace::WeakMap.new
    @lazy_enrollment_records[record] = record
  end
end

def after_commit(&block)
  if @state.finalized?
    raise ActiveRecordError, "Cannot register callbacks on a finalized transaction"
  end
  (@callbacks ||= []) << Callback.new(:after_commit, block)
end

def after_rollback(&block)
  if @state.finalized?
    raise ActiveRecordError, "Cannot register callbacks on a finalized transaction"
  end
  (@callbacks ||= []) << Callback.new(:after_rollback, block)
end

def append_callbacks(callbacks) # :nodoc:
  (@callbacks ||= []).concat(callbacks)
end

def before_commit(&block)
  if @state.finalized?
    raise ActiveRecordError, "Cannot register callbacks on a finalized transaction"
  end
  (@callbacks ||= []) << Callback.new(:before_commit, block)
end

def before_commit_records
  if @run_commit_callbacks
    if records
      if ActiveRecord.before_committed_on_all_records
        ite = unique_records
        instances_to_run_callbacks_on = records.each_with_object({}) do |record, candidates|
          candidates[record] = record
        end
        run_action_on_records(ite, instances_to_run_callbacks_on) do |record, should_run_callbacks|
          record.before_committed! if should_run_callbacks
        end
      else
        records.uniq.each(&:before_committed!)
      end
    end
    @callbacks&.each(&:before_commit)
  end
  # Note: When @run_commit_callbacks is false #commit_records takes care of appending
  # remaining callbacks to the parent transaction
end

def closed?
  false
end

def commit_records
  if records
    begin
      ite = unique_records
      if @run_commit_callbacks
        instances_to_run_callbacks_on = prepare_instances_to_run_callbacks_on(ite)
        run_action_on_records(ite, instances_to_run_callbacks_on) do |record, should_run_callbacks|
          record.committed!(should_run_callbacks: should_run_callbacks)
        end
      else
        while record = ite.shift
          # if not running callbacks, only adds the record to the parent transaction
          connection.add_transaction_record(record)
        end
      end
    ensure
      ite&.each { |i| i.committed!(should_run_callbacks: false) }
    end
  end
  if @run_commit_callbacks
    @callbacks&.each(&:after_commit)
  elsif @callbacks
    connection.current_transaction.append_callbacks(@callbacks)
  end
end

def dirty!
  @dirty = true
end

def dirty?
  @dirty
end

def full_rollback?; true; end

def incomplete!
  @instrumenter.finish(:incomplete) if materialized?
end

def initialize(connection, isolation: nil, joinable: true, run_commit_callbacks: false)
  super()
  @connection = connection
  @state = TransactionState.new
  @callbacks = nil
  @records = nil
  @isolation_level = isolation
  @materialized = false
  @joinable = joinable
  @run_commit_callbacks = run_commit_callbacks
  @lazy_enrollment_records = nil
  @dirty = false
  @user_transaction = joinable ? ActiveRecord::Transaction.new(self) : ActiveRecord::Transaction::NULL_TRANSACTION
  @instrumenter = TransactionInstrumenter.new(connection: connection, transaction: @user_transaction)
end

def joinable?; @joinable; end

def materialize!
  @materialized = true
  @instrumenter.start
end

def materialized?
  @materialized
end

def open?
  true
end

def prepare_instances_to_run_callbacks_on(records)
  records.each_with_object({}) do |record, candidates|
    next unless record.trigger_transactional_callbacks?
    earlier_saved_candidate = candidates[record]
    next if earlier_saved_candidate && record.class.run_commit_callbacks_on_first_saved_instances_in_transaction
    # If the candidate instance destroyed itself in the database, then
    # instances which were added to the transaction afterwards, and which
    # think they updated themselves, are wrong. They should not replace
    # our candidate as an instance to run callbacks on
    next if earlier_saved_candidate&.destroyed? && !record.destroyed?
    # If the candidate instance was created inside of this transaction,
    # then instances which were subsequently loaded from the database
    # and updated need that state transferred to them so that
    # the after_create_commit callbacks are run
    record._new_record_before_last_commit = true if earlier_saved_candidate&._new_record_before_last_commit
    # The last instance to save itself is likeliest to have internal
    # state that matches what's committed to the database
    candidates[record] = record
  end
end

def records
  if @lazy_enrollment_records
    @records.concat @lazy_enrollment_records.values
    @lazy_enrollment_records = nil
  end
  @records
end

def restartable?
  joinable? && !dirty?
end

def restore!
  if materialized?
    incomplete!
    @materialized = false
    materialize!
  end
end

def rollback_records
  if records
    begin
      ite = unique_records
      instances_to_run_callbacks_on = prepare_instances_to_run_callbacks_on(ite)
      run_action_on_records(ite, instances_to_run_callbacks_on) do |record, should_run_callbacks|
        record.rolledback!(force_restore_state: full_rollback?, should_run_callbacks: should_run_callbacks)
      end
    ensure
      ite&.each do |i|
        i.rolledback!(force_restore_state: full_rollback?, should_run_callbacks: false)
      end
    end
  end
  @callbacks&.each(&:after_rollback)
end

def run_action_on_records(records, instances_to_run_callbacks_on)
  while record = records.shift
    should_run_callbacks = record.__id__ == instances_to_run_callbacks_on[record].__id__
    yield record, should_run_callbacks
  end
end

def unique_records
  records.uniq(&:__id__)
end