pebble/src/fw/services/normal/activity/activity_sessions.c

/*
 * Copyright 2024 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
 *
 *     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 "applib/data_logging.h"
#include "applib/health_service.h"
#include "kernel/events.h"
#include "kernel/pbl_malloc.h"
#include "os/mutex.h"
#include "os/tick.h"
#include "services/common/analytics/analytics_event.h"
#include "services/normal/alarms/alarm.h"
#include "syscall/syscall.h"
#include "syscall/syscall_internal.h"
#include "system/passert.h"
#include "util/size.h"

#include <pebbleos/cron.h>

#include "activity.h"
#include "activity_algorithm.h"
#include "activity_insights.h"
#include "activity_private.h"


// ------------------------------------------------------------------------------------
// Figure out the cutoff times for sleep and step activities for today given the current time
static void prv_get_earliest_end_times_utc(time_t utc_sec, time_t *sleep_earliest_end_utc,
                                           time_t *step_earliest_end_utc) {
  time_t start_of_today_utc = time_util_get_midnight_of(utc_sec);
  int last_sleep_second_of_day = ACTIVITY_LAST_SLEEP_MINUTE_OF_DAY * SECONDS_PER_MINUTE;
  *sleep_earliest_end_utc = start_of_today_utc - (SECONDS_PER_DAY - last_sleep_second_of_day);
  *step_earliest_end_utc = start_of_today_utc;
}


// ------------------------------------------------------------------------------------
// Remove all activity sessions that are older than "today", those that are invalid because they
// are in the future, and optionally those that are still ongoing.
void activity_sessions_prv_remove_out_of_range_activity_sessions(time_t utc_sec,
                                                                 bool remove_ongoing) {
  ActivityState *state = activity_private_state();
  uint16_t num_sessions_to_clear = 0;
  uint16_t *session_entries = &state->activity_sessions_count;
  ActivitySession *sessions = state->activity_sessions;

  // Figure out the cutoff times for sleep and step activities
  time_t sleep_earliest_end_utc;
  time_t step_earliest_end_utc;
  prv_get_earliest_end_times_utc(utc_sec, &sleep_earliest_end_utc, &step_earliest_end_utc);

  for (uint32_t i = 0; i < *session_entries; i++) {
    time_t end_utc;
    if (activity_sessions_prv_is_sleep_activity(sessions[i].type)) {
      end_utc = sleep_earliest_end_utc;
    } else {
      end_utc = step_earliest_end_utc;
    }

    // See if we should keep this activity
    time_t end_time = sessions[i].start_utc + (sessions[i].length_min * SECONDS_PER_MINUTE);
    if ((end_time >= end_utc) && (end_time <= utc_sec)
        && (!remove_ongoing || !sessions[i].ongoing)) {
      // Keep it
      continue;
    }

    // This one needs to be removed
    uint32_t remaining = *session_entries - i - 1;
    memcpy(&sessions[i], &sessions[i + 1], remaining * sizeof(*sessions));
    (*session_entries)--;
    num_sessions_to_clear++;
    i--;
  }

  // Zero out unused sessions at end. This is important because when we re-init from stored
  // settings, we detect the number of sessions we have by checking for non-zero ones
  memset(&sessions[*session_entries], 0, num_sessions_to_clear * sizeof(ActivitySession));
}


// ------------------------------------------------------------------------------------
// Return true if the given activity type is a sleep activity
bool activity_sessions_prv_is_sleep_activity(ActivitySessionType activity_type) {
  switch (activity_type) {
    case ActivitySessionType_Sleep:
    case ActivitySessionType_RestfulSleep:
    case ActivitySessionType_Nap:
    case ActivitySessionType_RestfulNap:
      return true;
    case ActivitySessionType_Walk:
    case ActivitySessionType_Run:
    case ActivitySessionType_Open:
      return false;
    case ActivitySessionType_None:
    case ActivitySessionTypeCount:
      break;
  }
  WTF;
}


// ------------------------------------------------------------------------------------
// Return true if this is a valid activity session
static bool prv_is_valid_activity_session(ActivitySession *session) {
  // Make sure the type is valid
  switch (session->type) {
    case ActivitySessionType_Sleep:
    case ActivitySessionType_RestfulSleep:
    case ActivitySessionType_Nap:
    case ActivitySessionType_RestfulNap:
    case ActivitySessionType_Walk:
    case ActivitySessionType_Run:
    case ActivitySessionType_Open:
      break;
    case ActivitySessionType_None:
    case ActivitySessionTypeCount:
      PBL_LOG(LOG_LEVEL_WARNING, "Invalid activity type: %d", (int)session->type);
      return false;
  }

  // The length must be reasonable
  if (session->length_min > ACTIVITY_SESSION_MAX_LENGTH_MIN) {
    PBL_LOG(LOG_LEVEL_WARNING, "Invalid duration: %"PRIu16" ", session->length_min);
    return false;
  }

  // The flags must be valid
  if (session->reserved != 0) {
    PBL_LOG(LOG_LEVEL_WARNING, "Invalid flags: %d", (int)session->reserved);
    return false;
  }

  return true;
}


// ------------------------------------------------------------------------------------
// Return true if two activity sessions are equal in their type and start time
// @param[in] session_a ptr to first session
// @param[in] session_b ptr to second session
// @param[in] any_sleep if true, a match occurs if session_a and session_b are both sleep
//              activities, even if they are different types of sleep
static bool prv_activity_sessions_equal(ActivitySession *session_a, ActivitySession *session_b,
                                        bool any_sleep) {
  bool type_matches;

  const bool a_is_sleep = activity_sessions_prv_is_sleep_activity(session_a->type);
  const bool b_is_sleep = activity_sessions_prv_is_sleep_activity(session_b->type);

  if (any_sleep && a_is_sleep && b_is_sleep) {
    type_matches = true;
  } else {
    type_matches = (session_a->type == session_b->type);
  }

  return type_matches && (session_a->start_utc == session_b->start_utc);
}


// ------------------------------------------------------------------------------------
// Register a new activity. Called by the algorithm code when it detects a new activity.
// If we already have this activity registered, it is updated.
void activity_sessions_prv_add_activity_session(ActivitySession *session) {
  ActivityState *state = activity_private_state();
  mutex_lock_recursive(state->mutex);
  {
    if (!session->ongoing) {
      state->need_activities_saved = true;
    }

    // Modifying a sleep session?
    if (activity_sessions_prv_is_sleep_activity(session->type)) {
      state->sleep_sessions_modified = true;
    }

    // If this is an existing activity, update it
    ActivitySession *stored_session = state->activity_sessions;
    for (uint16_t i = 0; i < state->activity_sessions_count; i++, stored_session++) {
      if (prv_activity_sessions_equal(session, stored_session, true /*any_sleep*/)) {
        state->activity_sessions[i] = *session;
        goto unlock;
      }
    }

    // If no more room, fail
    if (state->activity_sessions_count >= ACTIVITY_MAX_ACTIVITY_SESSIONS_COUNT) {
      PBL_LOG(LOG_LEVEL_WARNING, "No more room for additional activities");
      goto unlock;
    }

    // Add this activity in
    PBL_LOG(LOG_LEVEL_INFO, "Adding activity session %d, start_time: %"PRIu32,
            (int)session->type, (uint32_t)session->start_utc);
    state->activity_sessions[state->activity_sessions_count++] = *session;
  }
unlock:
  mutex_unlock_recursive(state->mutex);
}


// ------------------------------------------------------------------------------------
// Delete an ongoing activity. Called by the algorithm code when it decides that an activity
// that was previously ongoing should not be registered after all.
void activity_sessions_prv_delete_activity_session(ActivitySession *session) {
  ActivityState *state = activity_private_state();
  mutex_lock_recursive(state->mutex);
  {
    // Look for this activity
    int found_session_idx = -1;
    ActivitySession *stored_session = state->activity_sessions;
    for (uint16_t i = 0; i < state->activity_sessions_count; i++, stored_session++) {
      if (prv_activity_sessions_equal(session, stored_session, false /*any_sleep*/)) {
        found_session_idx = i;
        break;
      }
    }

    // If session not found, do nothing
    if (found_session_idx < 0) {
      PBL_LOG(LOG_LEVEL_WARNING, "Session to delete not found");
      goto unlock;
    }

    // The session we are deleting must be ongoing
    PBL_ASSERT(stored_session->ongoing, "Only ongoing sessions can be deleted");

    // Remove this session
    int num_to_move = state->activity_sessions_count - found_session_idx - 1;
    PBL_ASSERTN(num_to_move >= 0);
    if (num_to_move == 0) {
      memset(&state->activity_sessions[found_session_idx], 0, sizeof(ActivitySession));
    } else {
      memmove(&state->activity_sessions[found_session_idx],
              &state->activity_sessions[found_session_idx + 1],
              num_to_move * sizeof(ActivitySession));
    }
    state->activity_sessions_count--;
  }
unlock:
  mutex_unlock_recursive(state->mutex);
}



// --------------------------------------------------------------------------------------------
// Compute the total number of restful sleep seconds within a range of time
static uint32_t prv_sleep_restful_seconds(uint32_t num_sessions, ActivitySession *sessions,
                                          time_t start_utc, time_t end_utc) {
  // Iterate through the sleep sessions, accumulating the total restful seconds seen between
  // start_utc and end_utc
  ActivitySession *session = sessions;
  uint32_t restful_sec = 0;
  for (uint32_t i = 0; i < num_sessions; i++, session++) {
    if ((session->type != ActivitySessionType_RestfulSleep)
        && (session->type != ActivitySessionType_RestfulNap)) {
      continue;
    }
    if ((session->start_utc >= start_utc)
        && ((time_t)(session->start_utc + (session->length_min * SECONDS_PER_MINUTE)) <= end_utc)) {
      restful_sec += session->length_min * SECONDS_PER_MINUTE;
    }
  }
  return restful_sec;
}


// --------------------------------------------------------------------------------------------
// Send an activity session (including sleep sessions) to data logging
void activity_sessions_prv_send_activity_session_to_data_logging(ActivitySession *session) {
  ActivityState *state = activity_private_state();
  time_t start_local = time_utc_to_local(session->start_utc);
  ActivitySessionDataLoggingRecord dls_record = {
    .version = ACTIVITY_SESSION_LOGGING_VERSION,
    .size = sizeof(ActivitySessionDataLoggingRecord),
    .activity = session->type,
    .utc_to_local = start_local - session->start_utc,
    .start_utc = (uint32_t)session->start_utc,
    .elapsed_sec = session->length_min * SECONDS_PER_MINUTE,
  };
  if (activity_sessions_prv_is_sleep_activity(session->type)) {
    dls_record.sleep_data = session->sleep_data;
  } else {
    dls_record.step_data = session->step_data;
  }

  if (state->activity_dls_session == NULL) {
    // We don't need to be buffered since we are logging from the KernelBG task and this
    // saves having to allocate another buffer from the kernel heap.
    const bool buffered = false;
    const bool resume = false;
    Uuid system_uuid = UUID_SYSTEM;
    state->activity_dls_session = dls_create(
        DlsSystemTagActivitySession, DATA_LOGGING_BYTE_ARRAY, sizeof(dls_record),
        buffered, resume, &system_uuid);
    if (!state->activity_dls_session) {
      PBL_LOG(LOG_LEVEL_WARNING, "Error creating activity DLS session");
      return;
    }
  }

  // Log the record
  DataLoggingResult result = dls_log(state->activity_dls_session, &dls_record, 1);
  if (result != DATA_LOGGING_SUCCESS) {
    PBL_LOG(LOG_LEVEL_WARNING, "Error %"PRIi32" while logging activity to DLS", (int32_t)result);
  }
  PBL_LOG(LOG_LEVEL_INFO, "Logging activity event %d, start_time: %"PRIu32", "
          "elapsed_min: %"PRIu16", end_time: %"PRIu32" ",
          (int)session->type, (uint32_t)session->start_utc, session->length_min,
          (uint32_t)session->start_utc + (session->length_min * SECONDS_PER_MINUTE));
}


// This structre holds stats we collected from going through a list of sleep sessions. It is
// filled in by prv_compute_sleep_stats
typedef struct {
  ActivityScalarStore total_minutes;
  ActivityScalarStore restful_minutes;
  time_t enter_utc;           // When we entered sleep
  time_t today_exit_utc;      // last exit time for today, for regular sleep only
  time_t last_exit_utc;       // last exit time (sleep or nap, ignoring "today" boundary)
  time_t last_deep_exit_utc;  // last deep sleep exit time (sleep or nap, ignoring "today" boundary)
  uint32_t last_session_len_sec;
} ActivitySleepStats;

// --------------------------------------------------------------------------------------------
// Goes through a list of activity sessions and collect sleep stats
// @param[in] now_utc the UTC time when the activity sessions were computed
// @param[in] min_end_utc Only include sleep sessions that end AFTER this time
// @param[in] max_end_utc Only include sleep sessions that end BEFORE this time
// @param[in] last_processed_utc When activity sessions were computed, this is the UTC of the
//        most recent minute we had access to when activities were computed.
// @param[out] stats this structure is filled in with the sleep stats
// @return True if there were sleep session, False if not
static bool prv_compute_sleep_stats(time_t now_utc, time_t min_end_utc, time_t max_end_utc,
                                    ActivitySleepStats *stats) {
  ActivityState *state = activity_private_state();
  *stats = (ActivitySleepStats) { };

  bool rv = false;

  // Iterate through the sleep sessions, accumulating the total sleep minutes, total
  // restful minutes, sleep enter time, and sleep exit time.
  ActivitySession *session = state->activity_sessions;
  for (uint32_t i = 0; i < state->activity_sessions_count; i++, session++) {
    // Get info on this session
    stats->last_session_len_sec = session->length_min * SECONDS_PER_MINUTE;
    time_t session_exit_utc = session->start_utc + stats->last_session_len_sec;

    // Skip if it ended too early
    if (session_exit_utc < min_end_utc) {
      continue;
    }

    if ((session->type == ActivitySessionType_Sleep)
      || (session->type == ActivitySessionType_Nap)) {
      rv = true;
      // Accumulate sleep container stats
      if (session_exit_utc <= max_end_utc) {
        stats->total_minutes += session->length_min;
      }
      // Only regular sleep (not naps) should affect the enter and exit times
      if (session->type == ActivitySessionType_Sleep) {
        stats->enter_utc = (stats->enter_utc != 0) ? MIN(session->start_utc, stats->enter_utc)
                                                   : session->start_utc;
        if ((session_exit_utc > stats->today_exit_utc) && (session_exit_utc <= max_end_utc)) {
          stats->today_exit_utc = session_exit_utc;
        }
      }
      stats->last_exit_utc = MAX(session_exit_utc, stats->last_exit_utc);
    } else if ((session->type == ActivitySessionType_RestfulSleep)
      || (session->type == ActivitySessionType_RestfulNap)) {
      if (session_exit_utc <= max_end_utc) {
        // Accumulate restful sleep stats
        stats->restful_minutes += session->length_min;
      }
      stats->last_deep_exit_utc = MAX(stats->last_deep_exit_utc, session_exit_utc);
    }
  }

  return rv;
}


// --------------------------------------------------------------------------------------------
// Goes through a list of activity sessions and updates our sleep totals in the metrics
// accordingly. We also take this opportunity to post a sleep metric changed event for the SDK
// if the sleep totals have changed.
// @param num_sessions the number of sessions in the sessions array
// @param sessions array of activity sessions
// @param now_utc the UTC time when the activity sessions were computed
// @param max_end_utc Only include sleep sessions that end BEFORE this time
// @param last_processed_utc When activity sessions were computed, this is the UTC of the
//        most recent minute we had access to when activities were computed.
static void prv_update_sleep_metrics(time_t now_utc, time_t max_end_utc,
                                     time_t last_processed_utc) {
  ActivityState *state = activity_private_state();
  mutex_lock_recursive(state->mutex);
  {
    // We will be filling in this structure based on the sleep sessions
    ActivitySleepData *sleep_data = &state->sleep_data;

    // If we detect a change in the sleep metrics, we want to post a health event
    ActivitySleepData prev_sleep_data = *sleep_data;

    // Collect stats on sleep
    ActivitySleepStats stats;
    if (!prv_compute_sleep_stats(now_utc, 0 /*min_end_utc*/, max_end_utc, &stats)) {
      // We didn't have any sleep data exit early
      goto unlock;
    }

    // Update our sleep metrics
    sleep_data->total_minutes = stats.total_minutes;
    sleep_data->restful_minutes = stats.restful_minutes;

    // Fill in the enter and exit minute
    uint16_t enter_minute = time_util_get_minute_of_day(stats.enter_utc);
    uint16_t exit_minute = time_util_get_minute_of_day(stats.today_exit_utc);
    sleep_data->enter_at_minute = enter_minute;
    sleep_data->exit_at_minute = exit_minute;

    // Fill in the rest of the sleep data metrics: the current state, and how long we have been
    // in the current state
    uint32_t delta_min = abs((int32_t)(last_processed_utc - stats.last_exit_utc))
                         / SECONDS_PER_MINUTE;

    // Figure out our current state
    if (delta_min > 1) {
      // We are awake
      sleep_data->cur_state = ActivitySleepStateAwake;
      if (stats.last_exit_utc != 0) {
        sleep_data->cur_state_elapsed_minutes = (now_utc - stats.last_exit_utc)
                                                / SECONDS_PER_MINUTE;
      } else {
        sleep_data->cur_state_elapsed_minutes = MINUTES_PER_DAY;
      }
    } else {
      // We are still sleeping
      if (stats.last_deep_exit_utc == stats.last_exit_utc) {
        sleep_data->cur_state = ActivitySleepStateRestfulSleep;
      } else {
        sleep_data->cur_state = ActivitySleepStateLightSleep;
      }
      sleep_data->cur_state_elapsed_minutes = (stats.last_session_len_sec + now_utc
                                               - stats.last_exit_utc) / SECONDS_PER_MINUTE;
    }

    // If the info that is part of a health sleep event has changed, send out a notification event
    if ((sleep_data->total_minutes != prev_sleep_data.total_minutes)
        || (sleep_data->restful_minutes != prev_sleep_data.restful_minutes)) {
      // Post a sleep changed event
      PebbleEvent e = {
        .type = PEBBLE_HEALTH_SERVICE_EVENT,
        .health_event = {
          .type = HealthEventSleepUpdate,
          .data.sleep_update = {
            .total_seconds = sleep_data->total_minutes * SECONDS_PER_MINUTE,
            .total_restful_seconds = sleep_data->restful_minutes * SECONDS_PER_MINUTE,
          },
        },
      };
      event_put(&e);
    }

    if (sleep_data->cur_state != prev_sleep_data.cur_state) {
      // Debug logging
      ACTIVITY_LOG_DEBUG("total_min: %"PRIu16", deep_min: %"PRIu16", state: %"PRIu16", "
                         "state_min: %"PRIu16"",
                         sleep_data->total_minutes,
                         sleep_data->restful_minutes,
                         sleep_data->cur_state,
                         sleep_data->cur_state_elapsed_minutes);
    }
  }
unlock:
  mutex_unlock_recursive(state->mutex);
}


// --------------------------------------------------------------------------------------------
void activity_sessions_prv_get_sleep_bounds_utc(time_t now_utc, time_t *enter_utc,
                                                time_t *exit_utc) {
  // Get useful UTC times
  time_t start_of_today_utc = time_util_get_midnight_of(now_utc);
  int minute_of_day = time_util_get_minute_of_day(now_utc);
  int last_sleep_second_of_day = ACTIVITY_LAST_SLEEP_MINUTE_OF_DAY * SECONDS_PER_MINUTE;

  int first_sleep_utc;
  if (minute_of_day < ACTIVITY_LAST_SLEEP_MINUTE_OF_DAY) {
    // It is before the ACTIVITY_LAST_SLEEP_MINUTE_OF_DAY (currently 9pm) cutoff, so use
    // the previous day's cutoff
    first_sleep_utc = start_of_today_utc - (SECONDS_PER_DAY - last_sleep_second_of_day);
  } else {
    // It is after 9pm, so use the 9pm cutoff
    first_sleep_utc = start_of_today_utc + last_sleep_second_of_day;
  }

  // Compute stats for today
  ActivitySleepStats stats;
  prv_compute_sleep_stats(now_utc, first_sleep_utc /*min_utc*/, now_utc /*max_utc*/, &stats);
  *enter_utc = stats.enter_utc;
  *exit_utc = stats.today_exit_utc;
}


// --------------------------------------------------------------------------------------------
// Goes through a list of activity sessions and logs new ones to data logging
static void prv_log_activities(time_t now_utc) {
  ActivityState *state = activity_private_state();
  // Activity classes. All of the activities in a class share the same "_exit_at_utc" state in
  // the globals and the same settings key to persist it.
  enum {
    // for ActivitySessionType_Sleep, ActivitySessionType_Nap
    ActivityClass_Sleep = 0,
    // for ActivitySessionType_RestfulSleep, ActivitySessionType_RestfulNap
    ActivityClass_RestfulSleep = 1,
    // for ActivitySessionType_Walk, ActivitySessionType_Run, ActivitySessionType_Open
    ActivityClass_Step = 2,

    // Leave at end
    ActivityClassCount,
  };

  // List of event classes and info on each
  typedef struct {
    ActivitySettingsKey key;  // settings key used to store last UTC time for this activity class
    time_t *exit_utc;         // pointer to last UTC time in our globals
    bool modified;            // true if we need to update it.
  } ActivityClassParams;

  ActivityClassParams class_settings[ActivityClassCount] = {
    {ActivitySettingsKeyLastSleepActivityUTC,
     &state->logged_sleep_activity_exit_at_utc, false},

    {ActivitySettingsKeyLastRestfulSleepActivityUTC,
     &state->logged_restful_sleep_activity_exit_at_utc, false},

    {ActivitySettingsKeyLastStepActivityUTC,
     &state->logged_step_activity_exit_at_utc, false},
  };

  bool logged_event = false;
  ActivitySession *session = state->activity_sessions;
  for (uint32_t i = 0; i < state->activity_sessions_count; i++, session++) {
    // Get info on this activity
    uint32_t session_len_sec = session->length_min * SECONDS_PER_MINUTE;
    time_t session_exit_utc = session->start_utc + session_len_sec;

    ActivityClassParams *params = NULL;
    switch (session->type) {
      case ActivitySessionType_Sleep:
      case ActivitySessionType_Nap:
        params = &class_settings[ActivityClass_Sleep];
        break;

      case ActivitySessionType_RestfulSleep:
      case ActivitySessionType_RestfulNap:
        params = &class_settings[ActivityClass_RestfulSleep];
        break;

      case ActivitySessionType_Walk:
      case ActivitySessionType_Run:
      case ActivitySessionType_Open:
        params = &class_settings[ActivityClass_Step];
        break;
      case ActivitySessionType_None:
      case ActivitySessionTypeCount:
        WTF;
        break;
    }
    PBL_ASSERTN(params);

    // If this is an event we already logged, or it's still ongoing, don't log it
    if (session->ongoing || (session_exit_utc <= *params->exit_utc)) {
      continue;
    }

    // Don't log *any* sleep events until we know for sure we are awake. For restful sessions
    // in particular, even if the session ended, it might later be converted to a restful nap
    // session (after the container sleep session it is in finally ends).
    if (activity_sessions_prv_is_sleep_activity(session->type)) {
      if (state->sleep_data.cur_state != ActivitySleepStateAwake) {
        continue;
      }
    }

    // Log this event
    activity_sessions_prv_send_activity_session_to_data_logging(session);
    *params->exit_utc = session_exit_utc;
    params->modified = true;
    logged_event = true;
  }

  // Update settings file if any events were logged
  if (logged_event) {
    mutex_lock_recursive(state->mutex);
    SettingsFile *file = activity_private_settings_open();
    if (file) {
      for (int i = 0; i < ActivityClassCount; i++) {
        ActivityClassParams *params = &class_settings[i];
        status_t result = settings_file_set(file, &params->key, sizeof(params->key),
                                            params->exit_utc, sizeof(*params->exit_utc));
        if (result != S_SUCCESS) {
          PBL_LOG(LOG_LEVEL_ERROR, "Error saving last event time");
        }
      }
      activity_private_settings_close(file);
    }
    mutex_unlock_recursive(state->mutex);
  }
}


// ------------------------------------------------------------------------------------------------
// Load in the stored activities from our settings file
void activity_sessions_prv_init(SettingsFile *file, time_t utc_now) {
  ActivityState *state = activity_private_state();
  ActivitySettingsKey key = ActivitySettingsKeyStoredActivities;

  // Check the length first. The settings_file_get() call will not return an error if we ask
  // for less than the value size
  int stored_len = settings_file_get_len(file, &key, sizeof(key));
  if (stored_len != sizeof(state->activity_sessions)) {
    PBL_LOG(LOG_LEVEL_WARNING, "Stored activities not found or incompatible");
    return;
  }

  // Read in the stored activities
  status_t result = settings_file_get(file, &key, sizeof(key), state->activity_sessions,
                                      sizeof(state->activity_sessions));
  if (result != S_SUCCESS) {
    return;
  }

  // Scan to see how many valid activities we have.
  ActivitySession *session = state->activity_sessions;
  ActivitySession null_session = {};
  for (unsigned i = 0; i < ARRAY_LENGTH(state->activity_sessions); i++, session++) {
    if (!memcmp(session, &null_session, sizeof(null_session))) {
      // Empty session detected, we are done
      break;
    }
    if (!prv_is_valid_activity_session(session)) {
      // NOTE: We check for full validity as well as we can (rather than just checking for a
      // non-null activity start time for example) because there have been cases where
      // flash got corrupted, as in PBL-37848
      PBL_HEXDUMP(LOG_LEVEL_INFO, (void *)state->activity_sessions,
                  sizeof(state->activity_sessions));
      PBL_LOG(LOG_LEVEL_ERROR, "Invalid activity session detected - could be flash corruption");

      // Zero out flash so that we don't get into a reboot loop
      memset(state->activity_sessions, 0, sizeof(state->activity_sessions));
      settings_file_set(file, &key, sizeof(key), state->activity_sessions,
                                          sizeof(state->activity_sessions));
      WTF;
    }
    state->activity_sessions_count++;
  }

  // Remove any activities that don't belong to "today" or that are ongoing
  activity_sessions_prv_remove_out_of_range_activity_sessions(utc_now, true /*remove_ongoing*/);

  PBL_LOG(LOG_LEVEL_INFO, "Restored %"PRIu16" activities from storage",
          state->activity_sessions_count);
}


// --------------------------------------------------------------------------------------
void NOINLINE activity_sessions_prv_minute_handler(time_t utc_sec) {
  ActivityState *state = activity_private_state();
  time_t last_sleep_processed_utc = activity_algorithm_get_last_sleep_utc();

  // Post process sleep sessions if we got any new sleep sessions that showed up
  if (state->sleep_sessions_modified) {
    // Post-process the sleep activities. This is where we relabel sleep sessions as nap
    // sessions, depending on time and length heuristics.
    activity_algorithm_post_process_sleep_sessions(state->activity_sessions_count,
                                                   state->activity_sessions);
    state->sleep_sessions_modified = false;
  }

  // Update sleep metrics
  // For today's metrics, we include sleep sessions that end between
  // ACTIVITY_LAST_SLEEP_MINUTE_OF_DAY the previous day and ACTIVITY_LAST_SLEEP_MINUTE_OF_DAY
  // today. activity_algorithm_get_activity_sessions() insures that we only get sessions
  // that end after ACTIVITY_LAST_SLEEP_MINUTE_OF_DAY the previous day, so we just need to insure
  // that the end BEFORE ACTIVITY_LAST_SLEEP_MINUTE_OF_DAY today.
  int last_sleep_utc_of_day = time_util_get_midnight_of(utc_sec)
    + ACTIVITY_LAST_SLEEP_MINUTE_OF_DAY * SECONDS_PER_MINUTE;
  prv_update_sleep_metrics(utc_sec, last_sleep_utc_of_day,
                                             last_sleep_processed_utc);

  // Log any new activities we detected to the phone
  prv_log_activities(utc_sec);
}


// ------------------------------------------------------------------------------------------------
bool activity_sessions_is_session_type_ongoing(ActivitySessionType type) {
  ActivityState *state = activity_private_state();
  bool rv = false;

  mutex_lock_recursive(state->mutex);
  {
    for (int i = 0; i < state->activity_sessions_count; i++) {
      const ActivitySession *session = &state->activity_sessions[i];
      if (session->type == type && session->ongoing) {
        rv = true;
        break;
      }
    }
  }
  mutex_unlock_recursive(state->mutex);
  return rv;
}

// ------------------------------------------------------------------------------------------------
DEFINE_SYSCALL(bool, sys_activity_sessions_is_session_type_ongoing, ActivitySessionType type) {
  return activity_sessions_is_session_type_ongoing(type);
}