#!/usr/bin/env ruby
require 'byebug'
require 'dry-validation'

module MyPredicates

  include Dry::Logic::Predicates

  predicate(:nested_one?) do |value|
    (value.is_a? Hash) && value.key?(:alpha)
  end

  predicate(:nested_two?) do |value|
    (value.is_a? Hash) && value.key?(:bravo)
  end

end

NestedSchemaOne = Dry::Validation.Schema do
  required(:alpha).filled
  required(:bravo).filled
end

NestedSchemaTwo = Dry::Validation.Schema do
  required(:charlie).filled
  required(:delta).filled
end

ParentSchema = Dry::Validation.Schema do
  configure do
    predicates(MyPredicates)
  end

  required(:foo).filled

  required(:nested) do
    (nested_one?.then(schema(NestedSchemaOne))).or(
     nested_two?.then(schema(NestedSchemaTwo)))
  end

end

print(ParentSchema.(
  foo: 'bar',
  nested: { alpha: '123' }
).messages)
print(ParentSchema.(
  foo: 'bar2',
  nested: { charlie: '123' }
).messages)