class Dry::Types::Compiler

def call(ast)
  visit(ast)
end

def initialize(registry)
  @registry = registry
end

def merge_with(hash_id, constructor, schema)
  registry[hash_id].__send__(
    constructor, schema.map { |key| visit(key) }.reduce({}, :merge)
  )
end

def visit(node, *args)
  send(:"visit_#{node[0]}", node[1], *args)
end

def visit_array(node)
  registry['array'].member(call(node))
end

def visit_constructor(node)
  primitive, fn = node
  Types::Constructor.new(primitive, &fn)
end

def visit_form_array(node)
  registry['form.array'].member(call(node))
end

def visit_form_hash(node)
  if node
    constructor, schema = node
    merge_with('form.hash', constructor, schema)
  else
    registry['form.hash']
  end
end

def visit_hash(node)
  constructor, schema = node
  merge_with('hash', constructor, schema)
end

def visit_json_array(node)
  registry['json.array'].member(call(node))
end

def visit_json_hash(node)
  if node
    constructor, schema = node
    merge_with('json.hash', constructor, schema)
  else
    registry['json.hash']
  end
end

def visit_key(node)
  name, types = node
  { name => visit(types) }
end

def visit_sum(node)
  node.map { |type| visit(type) }.reduce(:|)
end

def visit_type(node)
  type, args = node
  meth = :"visit_#{type.tr('.', '_')}"
  if respond_to?(meth) && args
    send(meth, args)
  else
    registry[type]
  end
end