class SyntaxTree::CallChainFormatter

def format(q)
  children = [node]
  threshold = 3
  # First, walk down the chain until we get to the point where we're not
  # longer at a chainable node.
  loop do
    case (child = children.last)
    when CallNode
      case (receiver = child.receiver)
      when CallNode
        if receiver.receiver.nil?
          break
        else
          children << receiver
        end
      when MethodAddBlock
        if (call = receiver.call).is_a?(CallNode) && !call.receiver.nil?
          children << receiver
        else
          break
        end
      else
        break
      end
    when MethodAddBlock
      if (call = child.call).is_a?(CallNode) && !call.receiver.nil?
        children << call
      else
        break
      end
    else
      break
    end
  end
  # Here, we have very specialized behavior where if we're within a sig
  # block, then we're going to assume we're creating a Sorbet type
  # signature. In that case, we really want the threshold to be lowered so
  # that we create method chains off of any two method calls within the
  # block. For more details, see
  # https://github.com/prettier/plugin-ruby/issues/863.
  parents = q.parents.take(4)
  if (parent = parents[2])
    # If we're at a block with the `do` keywords, then we want to go one
    # more level up. This is because do blocks have BodyStmt nodes instead
    # of just Statements nodes.
    parent = parents[3] if parent.is_a?(BlockNode) && parent.keywords?
    if parent.is_a?(MethodAddBlock) &&
         (call = parent.call).is_a?(CallNode) && call.message.value == "sig"
      threshold = 2
    end
  end
  if children.length >= threshold
    q.group do
      q
        .if_break { format_chain(q, children) }
        .if_flat { node.format_contents(q) }
    end
  else
    node.format_contents(q)
  end
end