/*
 * Copyright (C) 2018 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.
 */

#ifndef CHRE_HOST_FRAGMENTED_LOAD_TRANSACTION_H_
#define CHRE_HOST_FRAGMENTED_LOAD_TRANSACTION_H_

#include <cinttypes>
#include <vector>

#ifndef CHRE_HOST_DEFAULT_FRAGMENT_SIZE
// Use 30KB fragment size to fit within 32KB memory fragments at the kernel
// for most devices.
#define CHRE_HOST_DEFAULT_FRAGMENT_SIZE (30 * 1024)
#endif

namespace android {
namespace chre {

// A special fragment id indicating the loading is not started yet. First
// fragment starts from id 1.
static constexpr uint32_t kNoFragmentId = 0;

/**
 * A struct which represents a single fragmented request. The caller should use
 * this class along with FragmentedLoadTransaction to get global attributes for
 * the transaction and encode the load request using
 * HostProtocolHost::encodeFragmentedLoadNanoappRequest.
 */
struct FragmentedLoadRequest {
  size_t fragmentId;
  uint32_t transactionId;
  uint64_t appId;
  uint32_t appVersion;
  uint32_t appFlags;
  uint32_t targetApiVersion;
  size_t appTotalSizeBytes;
  std::vector<uint8_t> binary;

  FragmentedLoadRequest(size_t fragmentId, uint32_t transactionId,
                        uint64_t appId, const std::vector<uint8_t> &binary)
      : FragmentedLoadRequest(fragmentId, transactionId, appId, 0, 0, 0, 0,
                              binary) {}

  FragmentedLoadRequest(size_t fragmentId, uint32_t transactionId,
                        uint64_t appId, uint32_t appVersion, uint32_t appFlags,
                        uint32_t targetApiVersion, size_t appTotalSizeBytes,
                        const std::vector<uint8_t> &binary)
      : fragmentId(fragmentId),
        transactionId(transactionId),
        appId(appId),
        appVersion(appVersion),
        appFlags(appFlags),
        targetApiVersion(targetApiVersion),
        appTotalSizeBytes(appTotalSizeBytes),
        binary(binary) {}
};

/**
 * A class which splits a load transaction into separate requests with
 * fragmented binaries. This class can be used to send smaller chunks of data
 * when the kernel is under memory pressure and has limited contiguous memory.
 * The caller should use the getNextRequest() to retrieve the next available
 * fragment and send a load request with the fragmented binary and the fragment
 * ID.
 */
class FragmentedLoadTransaction {
 public:
  /**
   * @param transactionId the unique ID of the unfragmented load transaction
   * @param appId the unique ID of the nanoapp
   * @param appVersion the version of the nanoapp
   * @param appFlags the flags specified by the nanoapp to be loaded.
   * @param targetApiVersion the API version this nanoapp is targeted for
   * @param appBinary the nanoapp binary data
   * @param fragmentSize the size of each fragment in bytes
   */
  FragmentedLoadTransaction(uint32_t transactionId, uint64_t appId,
                            uint32_t appVersion, uint32_t appFlags,
                            uint32_t targetApiVersion,
                            const std::vector<uint8_t> &appBinary,
                            size_t fragmentSize = kDefaultFragmentSize);

  /**
   * Retrieves the FragmentedLoadRequest including the next fragment of the
   * binary. Invoking getNextRequest() will prepare the next fragment for a
   * subsequent invocation.
   *
   * Invoking this method when there is no next request (i.e. isComplete()
   * returns true) is illegal.
   *
   * @return returns a reference to the next fragment.
   */
  const FragmentedLoadRequest &getNextRequest();

  /**
   * @return true if the last fragment has been retrieved by getNextRequest(),
   *         false otherwise.
   */
  [[nodiscard]] bool isComplete() const;

  [[nodiscard]] uint32_t getTransactionId() const {
    return mFragmentRequests[0].transactionId;
  }

  [[nodiscard]] uint64_t getNanoappId() const {
    return mFragmentRequests[0].appId;
  }

  [[nodiscard]] size_t getNanoappTotalSize() const {
    return !mFragmentRequests[0].appTotalSizeBytes;
  }

  [[nodiscard]] uint32_t getNanoappVersion() const {
    return mFragmentRequests[0].appVersion;
  }

 private:
  std::vector<FragmentedLoadRequest> mFragmentRequests;
  size_t mCurrentRequestIndex = 0;

  static constexpr size_t kDefaultFragmentSize =
      CHRE_HOST_DEFAULT_FRAGMENT_SIZE;
};

}  // namespace chre
}  // namespace android

#endif  // CHRE_HOST_FRAGMENTED_LOAD_TRANSACTION_H_