// Copyright 2020 Google LLC
//
// 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
//
//     https://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.

#ifndef THIRD_PARTY_NEARBY_INTERNAL_PLATFORM_UUID_H_
#define THIRD_PARTY_NEARBY_INTERNAL_PLATFORM_UUID_H_

#include <array>
#include <cstdint>
#include <optional>
#include <string>

#include "absl/strings/string_view.h"

namespace nearby {

// A type 3 name-based
// (https://en.wikipedia.org/wiki/Universally_unique_identifier#Versions_3_and_5_(namespace_name-based))
// UUID.
//
// https://developer.android.com/reference/java/util/UUID.html
class Uuid final {
 public:
  Uuid() = default;

  // Constructs a UUID from the canonical string format as
  // xxxxxABCD-xxxx-xxxx-xxxxxxxxxxxxxx
  static std::optional<Uuid> FromString(absl::string_view data);

  // Constructs a type 3 (name based) UUID based on the input string.
  explicit Uuid(absl::string_view data);
  // Constructs a new UUID using the specified most_sig_bits for the most
  // significant 64 bits of the UUID and least_sig_bits for the least
  // significant 64 bits of the UUID.
  constexpr Uuid(std::uint64_t most_sig_bits, std::uint64_t least_sig_bits)
      : most_sig_bits_(most_sig_bits), least_sig_bits_(least_sig_bits) {}

  // Returns a 16-size char array representing this UUID.
  std::array<char, 16> data() const;

  // Returns the canonical textual representation
  // (https://en.wikipedia.org/wiki/Universally_unique_identifier#Format) of the
  // UUID.
  explicit operator std::string() const;

  // Get ABCD fom xxxxABCD-xxxx-xxxx-xxxx-xxxxxxxxxxxxxxxx
  //
  // This is needed because Android only support UUID 16 bits in service data
  // section in advertising data
  std::string Get16BitAsString() const;
  // If the UUID has a valid Bluetooth UUID16 alias, return it, otherwise
  // return nullopt.
  // See Bluetooth Core Specification 6.0 Vol.3, Part B, Section 2.5.1
  std::optional<uint16_t> GetBtUuid16() const;

  std::uint64_t GetMostSigBits() const { return most_sig_bits_; }
  std::uint64_t GetLeastSigBits() const { return least_sig_bits_; }

  bool operator<(const Uuid &rhs) const;
  // Hashable
  bool operator==(const Uuid &rhs) const;
  bool operator!=(const Uuid &rhs) const;
  template <typename H>
  friend H AbslHashValue(H h, const Uuid &b) {
    return H::combine(std::move(h), b.most_sig_bits_, b.least_sig_bits_);
  }

  // Returns true if both most_sig_bits_ and least_sig_bits_ are zero.
  bool IsEmpty() const { return most_sig_bits_ == 0 && least_sig_bits_ == 0; }

 private:
  std::string ToCanonicalString(const std::array<char, 16> &data) const;

  std::uint64_t most_sig_bits_{0};
  std::uint64_t least_sig_bits_{0};
};

}  // namespace nearby

#endif  // THIRD_PARTY_NEARBY_INTERNAL_PLATFORM_UUID_H_