json.h

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//
// Copyright (C) 2022 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
 
#pragma once
 
#include <string>
#include <string_view>
#include <vector>
 
#include <json/json.h>
 
#include "cuttlefish/common/libs/fs/shared_fd.h"
#include "cuttlefish/common/libs/utils/result.h"
 
namespace cuttlefish {
 
Result<Json::Value> ParseJson(std::string_view input);
 
Result<Json::Value> LoadFromFile(SharedFD json_fd);
Result<Json::Value> LoadFromFile(const std::string& path_to_file);
 
template <typename T>
Result<T> As(const Json::Value& v);
 
template <>
inline Result<int> As(const Json::Value& v) {
  CF_EXPECT(v.isInt());
  return v.asInt();
}
 
template <>
inline Result<std::string> As(const Json::Value& v) {
  CF_EXPECT(v.isString());
  return v.asString();
}
 
template <>
inline Result<bool> As(const Json::Value& v) {
  CF_EXPECT(v.isBool());
  return v.asBool();
}
 
template <>
inline Result<Json::Value> As(const Json::Value& v) {
  return v;
}
 
template <typename T>
Result<T> GetValue(const Json::Value& root,
                   const std::vector<std::string>& selectors) {
  const Json::Value* traversal = &root;
  for (const auto& selector : selectors) {
    CF_EXPECTF(traversal->isMember(selector),
               "JSON selector \"{}\" does not exist", selector);
    traversal = &(*traversal)[selector];
  }
  return CF_EXPECT(As<T>(*traversal));
}
 
template <typename T>
Result<std::vector<T>> GetArrayValues(
    const Json::Value& array, const std::vector<std::string>& selectors) {
  std::vector<T> result;
  for (const auto& element : array) {
    result.emplace_back(CF_EXPECT(GetValue<T>(element, selectors)));
  }
  return result;
}
 
inline bool HasValue(const Json::Value& root,
                     const std::vector<std::string>& selectors) {
  const Json::Value* traversal = &root;
  for (const auto& selector : selectors) {
    if (!traversal->isMember(selector)) {
      return false;
    }
    traversal = &(*traversal)[selector];
  }
  return true;
}
 
}  // namespace cuttlefish