//===-- UserIDResolver.h ----------------------------------------*- C++ -*-===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

//===----------------------------------------------------------------------===//

#ifndef LLDB_UTILITY_USERIDRESOLVER_H

#define LLDB_UTILITY_USERIDRESOLVER_H

#include "llvm/ADT/DenseMap.h"

#include "llvm/ADT/StringRef.h"

#include <mutex>

#include <optional>

namespace lldb_private {

/// An abstract interface for things that know how to map numeric user/group IDs

/// into names. It caches the resolved names to avoid repeating expensive

/// queries. The cache is internally protected by a mutex, so concurrent queries

/// are safe.

class UserIDResolver {

public:

  typedef uint32_t id_t;

  virtual ~UserIDResolver(); // anchor

  std::optional<llvm::StringRef> GetUserName(id_t uid) {

    return Get(uid, m_uid_cache, &UserIDResolver::DoGetUserName);

  }

  std::optional<llvm::StringRef> GetGroupName(id_t gid) {

    return Get(gid, m_gid_cache, &UserIDResolver::DoGetGroupName);

  }

  /// Returns a resolver which returns a failure value for each query. Useful as

  /// a fallback value for the case when we know all lookups will fail.

  static UserIDResolver &GetNoopResolver();

protected:

  virtual std::optional<std::string> DoGetUserName(id_t uid) = 0;

  virtual std::optional<std::string> DoGetGroupName(id_t gid) = 0;

private:

  using Map = llvm::DenseMap<id_t, std::optional<std::string>>;

  std::optional<llvm::StringRef>

  Get(id_t id, Map &cache,

      std::optional<std::string> (UserIDResolver::*do_get)(id_t));

  std::mutex m_mutex;

  Map m_uid_cache;

  Map m_gid_cache;

};

} // namespace lldb_private

#endif // LLDB_UTILITY_USERIDRESOLVER_H