/*
 * 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.
 */

#include "chre/core/gnss_manager.h"

#include "chre/core/event_loop_manager.h"
#include "chre/platform/assert.h"
#include "chre/platform/fatal_error.h"
#include "chre/util/system/debug_dump.h"

namespace chre {

GnssManager::GnssManager()
    : mLocationSession(CHRE_EVENT_GNSS_LOCATION),
      mMeasurementSession(CHRE_EVENT_GNSS_DATA) {
}

void GnssManager::init() {
  mPlatformGnss.init();
}

uint32_t GnssManager::getCapabilities() {
  return mPlatformGnss.getCapabilities();
}

bool GnssManager::logStateToBuffer(
    char *buffer, size_t *bufferPos, size_t bufferSize) const {
  bool success = debugDumpPrint(buffer, bufferPos, bufferSize,"\nGNSS:");
  success &= mLocationSession.logStateToBuffer(buffer, bufferPos, bufferSize);
  success &= mMeasurementSession
      .logStateToBuffer(buffer, bufferPos, bufferSize);
  return success;
}

GnssSession::GnssSession(uint16_t reportEventType)
    : mReportEventType(reportEventType) {
  switch (mReportEventType) {
    case CHRE_EVENT_GNSS_LOCATION:
      mStartRequestType = CHRE_GNSS_REQUEST_TYPE_LOCATION_SESSION_START;
      mStopRequestType = CHRE_GNSS_REQUEST_TYPE_LOCATION_SESSION_STOP;
      mName = "Location";
      break;

    case CHRE_EVENT_GNSS_DATA:
      mStartRequestType = CHRE_GNSS_REQUEST_TYPE_MEASUREMENT_SESSION_START;
      mStopRequestType = CHRE_GNSS_REQUEST_TYPE_MEASUREMENT_SESSION_STOP;
      mName = "Measurement";
      break;

    default:
      CHRE_ASSERT_LOG(false, "Unsupported eventType %" PRIu16, reportEventType);
  }

  if (!mRequests.reserve(1)) {
    FATAL_ERROR_OOM();
  }
}

bool GnssSession::addRequest(Nanoapp *nanoapp, Milliseconds minInterval,
                             Milliseconds minTimeToNext, const void *cookie) {
  CHRE_ASSERT(nanoapp);
  return configure(nanoapp, true /* enable */, minInterval, minTimeToNext,
                   cookie);
}

bool GnssSession::removeRequest(Nanoapp *nanoapp, const void *cookie) {
  CHRE_ASSERT(nanoapp);
  return configure(nanoapp, false /* enable */, Milliseconds(UINT64_MAX),
                   Milliseconds(UINT64_MAX), cookie);
}

void GnssSession::handleStatusChange(bool enabled, uint8_t errorCode) {
  struct CallbackState {
    bool enabled;
    uint8_t errorCode;
    GnssSession *session;
  };

  auto *cbState = memoryAlloc<CallbackState>();
  if (cbState == nullptr) {
    LOGE("Failed to allocate callback state for GNSS session state change");
  } else {
    cbState->enabled = enabled;
    cbState->errorCode = errorCode;
    cbState->session = this;

    auto callback = [](uint16_t /* eventType */, void *eventData) {
      auto *state = static_cast<CallbackState *>(eventData);
      state->session->handleStatusChangeSync(state->enabled, state->errorCode);
      memoryFree(state);
    };

    EventLoopManagerSingleton::get()->deferCallback(
        SystemCallbackType::GnssSessionStatusChange, cbState, callback);
  }
}

void GnssSession::handleReportEvent(void *event) {
  EventLoopManagerSingleton::get()->getEventLoop()
      .postEvent(mReportEventType, event, freeReportEventCallback);
}

bool GnssSession::logStateToBuffer(
    char *buffer, size_t *bufferPos, size_t bufferSize) const {
  bool success = debugDumpPrint(buffer, bufferPos, bufferSize,
                                "\n %s: Current interval(ms)=%" PRIu64 "\n",
                                mName, mCurrentInterval.getMilliseconds());

  success &= debugDumpPrint(buffer, bufferPos, bufferSize, "  Requests:\n");
  for (const auto& request : mRequests) {
    success &= debugDumpPrint(buffer, bufferPos, bufferSize,
                              "   minInterval(ms)=%" PRIu64 " nanoappId=%"
                              PRIu32 "\n",
                              request.minInterval.getMilliseconds(),
                              request.nanoappInstanceId);
  }

  success &= debugDumpPrint(buffer, bufferPos, bufferSize,
                            "  Transition queue:\n");
  for (const auto& transition : mStateTransitions) {
    success &= debugDumpPrint(buffer, bufferPos, bufferSize,
                              "   minInterval(ms)=%" PRIu64 " enable=%d"
                              " nanoappId=%" PRIu32 "\n",
                              transition.minInterval.getMilliseconds(),
                              transition.enable, transition.nanoappInstanceId);
  }

  return success;
}

bool GnssSession::configure(
    Nanoapp *nanoapp, bool enable, Milliseconds minInterval,
    Milliseconds minTimeToNext, const void *cookie) {
  bool success = false;
  uint32_t instanceId = nanoapp->getInstanceId();
  size_t requestIndex = 0;
  bool hasRequest = nanoappHasRequest(instanceId, &requestIndex);
  if (!mStateTransitions.empty()) {
    success = addRequestToQueue(instanceId, enable, minInterval, cookie);
  } else if (isInRequestedState(enable, minInterval, hasRequest)) {
    success = postAsyncResultEvent(
        instanceId, true /* success */, enable, minInterval, CHRE_ERROR_NONE,
        cookie);
  } else if (stateTransitionIsRequired(enable, minInterval, hasRequest,
                                       requestIndex)) {
    success = addRequestToQueue(instanceId, enable, minInterval, cookie);
    if (success) {
      success = controlPlatform(enable, minInterval, minTimeToNext);
      if (!success) {
        mStateTransitions.pop_back();
        LOGE("Failed to enable a GNSS session for nanoapp instance %" PRIu32,
             instanceId);
      }
    }
  } else {
    CHRE_ASSERT_LOG(false, "Invalid GNSS session configuration");
  }

  return success;
}

bool GnssSession::nanoappHasRequest(
    uint32_t instanceId, size_t *requestIndex) const {
  bool hasRequest = false;
  for (size_t i = 0; i < mRequests.size(); i++) {
    if (mRequests[i].nanoappInstanceId == instanceId) {
      hasRequest = true;
      if (requestIndex != nullptr) {
        *requestIndex = i;
      }

      break;
    }
  }

  return hasRequest;
}

bool GnssSession::addRequestToQueue(
    uint32_t instanceId, bool enable, Milliseconds minInterval,
    const void *cookie) {
  StateTransition stateTransition;
  stateTransition.nanoappInstanceId = instanceId;
  stateTransition.enable = enable;
  stateTransition.minInterval = minInterval;
  stateTransition.cookie = cookie;

  bool success = mStateTransitions.push(stateTransition);
  if (!success) {
    LOGW("Too many session state transitions");
  }

  return success;
}

bool GnssSession::isEnabled() const {
  return !mRequests.empty();
}

bool GnssSession::isInRequestedState(
    bool requestedState, Milliseconds minInterval, bool nanoappHasRequest)
    const {
  bool inTargetState = (requestedState == isEnabled());
  bool meetsMinInterval = (minInterval >= mCurrentInterval);
  bool hasMoreThanOneRequest = (mRequests.size() > 1);
  return ((inTargetState && (!requestedState || meetsMinInterval))
      || (!requestedState && (!nanoappHasRequest || hasMoreThanOneRequest)));
}

bool GnssSession::stateTransitionIsRequired(
    bool requestedState, Milliseconds minInterval, bool nanoappHasRequest,
    size_t requestIndex) const {
  bool requestToEnable = (requestedState && !isEnabled());
  bool requestToIncreaseRate = (requestedState && isEnabled()
      && minInterval < mCurrentInterval);
  bool requestToDisable = (!requestedState && nanoappHasRequest
                           && mRequests.size() == 1);

  // An effective rate decrease for the session can only occur if the nanoapp
  // has an existing request.
  bool requestToDecreaseRate = false;
  if (nanoappHasRequest) {
    // The nanoapp has an existing request. Check that the request does not
    // result in a rate decrease by checking if no other nanoapps have the
    // same request, the nanoapp's existing request is not equal to the current
    // requested interval and the new request is slower than the current
    // requested rate.
    size_t requestCount = 0;
    const auto& currentRequest = mRequests[requestIndex];
    for (size_t i = 0; i < mRequests.size(); i++) {
      const Request& request = mRequests[i];
      if (i != requestIndex
          && request.minInterval == currentRequest.minInterval) {
        requestCount++;
      }
    }

    requestToDecreaseRate = (minInterval > mCurrentInterval
        && currentRequest.minInterval == mCurrentInterval && requestCount == 0);
  }

  return (requestToEnable || requestToDisable || requestToIncreaseRate
          || requestToDecreaseRate);
}

bool GnssSession::updateRequests(
    bool enable, Milliseconds minInterval, uint32_t instanceId) {
  bool success = true;
  Nanoapp *nanoapp = EventLoopManagerSingleton::get()->getEventLoop()
      .findNanoappByInstanceId(instanceId);
  if (nanoapp == nullptr) {
    LOGW("Failed to update GNSS session request list for non-existent nanoapp");
  } else {
    size_t requestIndex;
    bool hasExistingRequest = nanoappHasRequest(instanceId, &requestIndex);
    if (enable) {
      if (hasExistingRequest) {
        // If the nanoapp has an open request ensure that the minInterval is
        // kept up to date.
        mRequests[requestIndex].minInterval = minInterval;
      } else {
        // The GNSS session was successfully enabled for this nanoapp and
        // there is no existing request. Add it to the list of GNSS session
        // nanoapps.
        Request request;
        request.nanoappInstanceId = instanceId;
        request.minInterval = minInterval;
        success = mRequests.push_back(request);
        if (!success) {
          LOGE("Failed to add nanoapp to the list of GNSS session nanoapps");
        } else {
          nanoapp->registerForBroadcastEvent(mReportEventType);
        }
      }
    } else {
      if (!hasExistingRequest) {
        success = false;
        LOGE("Received a GNSS session state change for a non-existent nanoapp");
      } else {
        // The session was successfully disabled for a previously enabled
        // nanoapp. Remove it from the list of requests.
        mRequests.erase(requestIndex);
        nanoapp->unregisterForBroadcastEvent(mReportEventType);
      }
    }
  }

  return success;
}

bool GnssSession::postAsyncResultEvent(
    uint32_t instanceId, bool success, bool enable, Milliseconds minInterval,
    uint8_t errorCode, const void *cookie) {
  bool eventPosted = false;
  if (!success || updateRequests(enable, minInterval, instanceId)) {
    chreAsyncResult *event = memoryAlloc<chreAsyncResult>();
    if (event == nullptr) {
      LOGE("Failed to allocate GNSS session async result event");
    } else {
      event->requestType = enable ? mStartRequestType : mStopRequestType;
      event->success = success;
      event->errorCode = errorCode;
      event->reserved = 0;
      event->cookie = cookie;

      eventPosted = EventLoopManagerSingleton::get()->getEventLoop()
          .postEvent(CHRE_EVENT_GNSS_ASYNC_RESULT, event, freeEventDataCallback,
                     kSystemInstanceId, instanceId);

      if (!eventPosted) {
        memoryFree(event);
      }
    }
  }

  return eventPosted;
}

void GnssSession::postAsyncResultEventFatal(
    uint32_t instanceId, bool success, bool enable, Milliseconds minInterval,
    uint8_t errorCode, const void *cookie) {
  if (!postAsyncResultEvent(instanceId, success, enable, minInterval, errorCode,
                            cookie)) {
    FATAL_ERROR("Failed to send GNSS session request async result event");
  }
}

void GnssSession::handleStatusChangeSync(bool enabled, uint8_t errorCode) {
  bool success = (errorCode == CHRE_ERROR_NONE);

  CHRE_ASSERT_LOG(!mStateTransitions.empty(),
                  "handleStatusChangeSync called with no transitions");
  if (!mStateTransitions.empty()) {
    const auto& stateTransition = mStateTransitions.front();

    if (success) {
      mCurrentInterval = stateTransition.minInterval;
    }

    success &= (stateTransition.enable == enabled);
    postAsyncResultEventFatal(stateTransition.nanoappInstanceId, success,
                              stateTransition.enable,
                              stateTransition.minInterval,
                              errorCode, stateTransition.cookie);
    mStateTransitions.pop();
  }

  while (!mStateTransitions.empty()) {
    const auto& stateTransition = mStateTransitions.front();

    size_t requestIndex;
    bool hasRequest = nanoappHasRequest(
        stateTransition.nanoappInstanceId, &requestIndex);

    if (stateTransitionIsRequired(stateTransition.enable,
                                  stateTransition.minInterval,
                                  hasRequest, requestIndex)) {
      if (controlPlatform(stateTransition.enable, stateTransition.minInterval,
                          Milliseconds(0))) {
        break;
      } else {
        LOGE("Failed to enable a GNSS session for nanoapp instance %" PRIu32,
             stateTransition.nanoappInstanceId);
        postAsyncResultEventFatal(
            stateTransition.nanoappInstanceId, false /* success */,
            stateTransition.enable, stateTransition.minInterval,
            CHRE_ERROR, stateTransition.cookie);
        mStateTransitions.pop();
      }
    } else {
      postAsyncResultEventFatal(
          stateTransition.nanoappInstanceId, true /* success */,
          stateTransition.enable, stateTransition.minInterval,
          errorCode, stateTransition.cookie);
      mStateTransitions.pop();
    }
  }
}

void GnssSession::freeReportEventCallback(uint16_t eventType, void *eventData) {
  switch (eventType) {
    case CHRE_EVENT_GNSS_LOCATION:
      EventLoopManagerSingleton::get()->getGnssManager().mPlatformGnss
          .releaseLocationEvent(
              static_cast<chreGnssLocationEvent *>(eventData));
      break;

    case CHRE_EVENT_GNSS_DATA:
      EventLoopManagerSingleton::get()->getGnssManager().mPlatformGnss
          .releaseMeasurementDataEvent(
              static_cast<chreGnssDataEvent *>(eventData));
      break;

    default:
      CHRE_ASSERT_LOG(false, "Unhandled event type %" PRIu16, eventType);
  }
}

bool GnssSession::controlPlatform(
    bool enable, Milliseconds minInterval, Milliseconds /* minTimeToNext */) {
  bool success = false;

  switch (mReportEventType) {
    case CHRE_EVENT_GNSS_LOCATION:
      // TODO: Provide support for min time to next report. It is currently sent
      // to the platform as zero.
      success = EventLoopManagerSingleton::get()->getGnssManager().mPlatformGnss
          .controlLocationSession(enable, minInterval, Milliseconds(0));
      break;

    case CHRE_EVENT_GNSS_DATA:
      success = EventLoopManagerSingleton::get()->getGnssManager().mPlatformGnss
          .controlMeasurementSession(enable, minInterval);
      break;

    default:
      CHRE_ASSERT_LOG(false, "Unhandled event type %" PRIu16, mReportEventType);
  }
  return success;
}

}  // namespace chre