// Copyright 2018 The ChromiumOS Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef PATCHPANEL_SUBNET_H_
#define PATCHPANEL_SUBNET_H_

#include <stdint.h>

#include <memory>
#include <string>
#include <vector>

#include <base/functional/callback.h>
#include <base/functional/callback_helpers.h>
#include <base/memory/weak_ptr.h>
#include <brillo/brillo_export.h>
#include <chromeos/net-base/ipv4_address.h>

namespace patchpanel {

// Represents an allocated IPv4 subnet.
class BRILLO_EXPORT Subnet {
 public:
  // Creates a new Subnet with the given base CIDR.
  // |release_cb| runs in the destructor of this class and can be used to free
  // other resources associated with the subnet.
  Subnet(const net_base::IPv4CIDR& base_cidr, base::OnceClosure release_cb);
  Subnet(const Subnet&) = delete;
  Subnet& operator=(const Subnet&) = delete;

  ~Subnet();

  // Returns the CIDR which address is at the given |offset| and the same prefix
  // length as |base_cidr_|. Returns std::nullopt if the offset exceeds the
  // available IPs in the subnet. Available IPs do not include the subnet base
  // address or the broadcast address. |offset| is relative to the base address.
  std::optional<net_base::IPv4CIDR> CIDRAtOffset(uint32_t offset) const;

  // Returns the number of available IPs in this subnet.
  uint32_t AvailableCount() const;

  // Returns the base CIDR of the subnet.
  const net_base::IPv4CIDR& base_cidr() const { return base_cidr_; }

 private:
  // Returns true if the address that is relative to the base address by
  // |offset| is in the subnet.
  // Note: the base address and the broadcast address are considered invalid.
  // So IsValidOffset(0) and IsValidOffset(addrs_.size() - 1) are false.
  bool IsValidOffset(uint32_t offset) const;

  // Marks the address at |offset| as free.
  void Free(uint32_t offset);

  // Base CIDR of the subnet.
  net_base::IPv4CIDR base_cidr_;

  // Callback to run when this object is deleted.
  base::ScopedClosureRunner release_cb_;

  // Keeps track of allocated addresses.
  std::vector<bool> addrs_;

  base::WeakPtrFactory<Subnet> weak_factory_{this};
};

}  // namespace patchpanel

#endif  // PATCHPANEL_SUBNET_H_