class Dry::Logic::RuleCompiler

def call(ast)
  ast.map { |node| visit(node) }
end

def initialize(predicates)
  @predicates = predicates
end

def visit(node)
  name, nodes = node
  send(:"visit_#{name}", nodes)
end

def visit_and(node)
  left, right = node
  visit(left).and(visit(right))
end

def visit_attr(node)
  name, predicate = node
  Operations::Attr.new(visit(predicate), name: name)
end

def visit_check(node)
  keys, predicate = node
  Operations::Check.new(visit(predicate), keys: keys)
end

def visit_each(node)
  Operations::Each.new(visit(node))
end

def visit_implication(node)
  left, right = node
  visit(left).then(visit(right))
end

def visit_key(node)
  name, predicate = node
  Operations::Key.new(visit(predicate), name: name)
end

def visit_not(node)
  Operations::Negation.new(visit(node))
end

def visit_or(node)
  left, right = node
  visit(left).or(visit(right))
end

def visit_predicate(node)
  name, params = node
  predicate = Rule::Predicate.build(predicates[name])
  if params.size > 1
    args = params.map(&:last).reject { |val| val == Undefined }
    predicate.curry(*args)
  else
    predicate
  end
end

def visit_set(node)
  Operations::Set.new(*call(node))
end

def visit_xor(node)
  left, right = node
  visit(left).xor(visit(right))
end