class Dry::Types::Compiler

def call(ast) = visit(ast)

def compile_fn(fn)
  type, *node = fn
  case type
  when :id
    ::Dry::Types::FnContainer[node.fetch(0)]
  when :callable
    node.fetch(0)
  when :method
    target, method = node
    target.method(method)
  else
    raise ::ArgumentError, "Cannot build callable from #{fn.inspect}"
  end
end

def initialize(registry)
  @registry = registry
end

def visit(node)
  type, body = node
  send(:"visit_#{type}", body)
end

def visit_any(meta)
  registry["any"].meta(meta)
end

def visit_array(node)
  member, meta = node
  member = visit(member) unless member.is_a?(::Class)
  registry["nominal.array"].of(member).meta(meta)
end

def visit_constrained(node)
  nominal, rule = node
  type = visit(nominal)
  type.constrained_type.new(type, rule: visit_rule(rule))
end

def visit_constructor(node)
  nominal, fn = node
  primitive = visit(nominal)
  primitive.constructor(compile_fn(fn))
end

def visit_enum(node)
  type, mapping = node
  Enum.new(visit(type), mapping: mapping)
end

def visit_hash(node)
  opts, meta = node
  registry["nominal.hash"].with(**opts, meta: meta)
end

def visit_json_array(node)
  member, meta = node
  registry["json.array"].of(visit(member)).meta(meta)
end

def visit_json_hash(node)
  keys, meta = node
  registry["json.hash"].schema(keys.map { |key| visit(key) }, meta)
end

def visit_key(node)
  name, required, type = node
  Schema::Key.new(visit(type), name, required: required)
end

def visit_lax(node)
  Types::Lax.new(visit(node))
end

def visit_map(node)
  key_type, value_type, meta = node
  registry["nominal.hash"].map(visit(key_type), visit(value_type)).meta(meta)
end

def visit_nominal(node)
  type, meta = node
  nominal_name = "nominal.#{Types.identifier(type)}"
  if registry.registered?(nominal_name)
    registry[nominal_name].meta(meta)
  else
    Nominal.new(type, meta: meta)
  end
end

def visit_params_array(node)
  member, meta = node
  registry["params.array"].of(visit(member)).meta(meta)
end

def visit_params_hash(node)
  keys, meta = node
  registry["params.hash"].schema(keys.map { |key| visit(key) }, meta)
end

def visit_rule(node)
  ::Dry::Types.rule_compiler.([node])[0]
end

def visit_schema(node)
  keys, options, meta = node
  registry["nominal.hash"].schema(keys.map { |key| visit(key) }).with(**options, meta: meta)
end

def visit_sum(node)
  *types, meta = node
  types.map { |type| visit(type) }.reduce(:|).meta(meta)
end