// Copyright (c) 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "tools/gn/functions.h"
#include "tools/gn/parse_tree.h"
#include "tools/gn/scope.h"
#include "tools/gn/value.h"

namespace functions {

const char kDefineRule[] = "define_rule";
const char kDefileRule_Help[] =
    "TODO(brettw) write this.";

Value RunDefineRule(Scope* scope,
                    const FunctionCallNode* function,
                    const std::vector<Value>& args,
                    BlockNode* block,
                    Err* err) {
  // TODO(brettw) determine if the function is built-in and throw an error if
  // it is.
  if (args.size() != 1) {
    *err = Err(function->function(),
               "Need exactly one string arg to define_rule.");
    return Value();
  }
  if (!args[0].VerifyTypeIs(Value::STRING, err))
    return Value();
  std::string rule_name = args[0].string_value();

  const FunctionCallNode* existing_rule = scope->GetRule(rule_name);
  if (existing_rule) {
    *err = Err(function, "Duplicate rule definition.",
               "A rule with this name was already defined.");
    err->AppendSubErr(Err(existing_rule->function(), "Previous definition."));
    return Value();
  }

  scope->AddRule(rule_name, function);
  return Value();
}

}  // namespace functions