class Steep::Typing

def self.summary(node)
  src = node.loc.expression.source.split(/\n/).first
  line = node.loc.first_line
  col = node.loc.column
  "#{line}:#{col}:#{src}"
end

def add_error(error)
  errors << error
end

def add_typing(node, type)
  typing[node.__id__] = type
  nodes[node.__id__] = node
  if should_update
    @last_update += 1
    @should_update = false
  end
  type
end

def dump(io)
  io.puts "Typing: "
  nodes.each_value do |node|
    io.puts "  #{Typing.summary(node)} => #{type_of(node: node).inspect}"
  end
  io.puts "Errors: "
  errors.each do |error|
    io.puts "  #{Typing.summary(error.node)} => #{error.inspect}"
  end
end

def each_typing
  nodes.each do |id, node|
    yield node, typing[id]
  end
end

def has_type?(node)
  typing.key?(node.__id__)
end

def initialize(parent: nil, parent_last_update: parent&.last_update)
  @parent = parent
  @parent_last_update = parent_last_update
  @last_update = parent&.last_update || 0
  @should_update = false
  @errors = []
  @nodes = {}
  @var_typing = {}
  @typing = {}
end

def new_child
  child = self.class.new(parent: self)
  @should_update = true
  if block_given?
    yield child
  else
    child
  end
end

def save!
  raise "Unexpected save!" unless parent
  raise "Parent modified since new_child" unless parent.last_update == parent_last_update
  each_typing do |node, type|
    parent.add_typing(node, type)
  end
  errors.each do |error|
    parent.add_error error
  end
end

def type_of(node:)
  type = typing[node.__id__]
  if type
    type
  else
    if parent
      parent.type_of(node: node)
    else
      raise "Unknown node for typing: #{node.inspect}"
    end
  end
end