Add helper for adjusting date-to-duration map.

The helper isn't used yet. The goal is to export this on /camera/<uuid>/ as
described in a TODO in design/api.md.

The next step is to keep MoonfireDatabase::CameraData::days up-to-date:

* Init: call on every recording (replacing the current aggregated query with
  a recording-by-recording query)
* InsertRecording, DeleteRecordings: call for added/removed recordings

then return it from GetCamera and pass it along to the client in
WebInterface::HandleJsonCameraDetail.

src/moonfire-db-test.cc

@@ -28,6 +28,8 @@
 //
 // moonfire-db-test.cc: tests of the moonfire-db.h interface.
 
+#include <time.h>
+
 #include <string>
 
 #include <gflags/gflags.h>
@@ -232,6 +234,63 @@ class MoonfireDbTest : public testing::Test {
   std::unique_ptr<MoonfireDatabase> mdb_;
 };
 
+TEST(AdjustDaysMapTest, Basic) {
+  std::map<std::string, int64_t> days;
+
+  // Create a day.
+  const int64_t kTestTime = INT64_C(130647162600000);  // 2015-12-31 23:59:00
+  moonfire_nvr::internal::AdjustDaysMap(
+      kTestTime, kTestTime + 60 * kTimeUnitsPerSecond, 1, &days);
+  EXPECT_THAT(days, testing::ElementsAre(std::make_pair(
+                        "2015-12-31", 60 * kTimeUnitsPerSecond)));
+
+  // Add to a day.
+  moonfire_nvr::internal::AdjustDaysMap(
+      kTestTime, kTestTime + 60 * kTimeUnitsPerSecond, 1, &days);
+  EXPECT_THAT(days, testing::ElementsAre(std::make_pair(
+                        "2015-12-31", 120 * kTimeUnitsPerSecond)));
+
+  // Subtract from a day.
+  moonfire_nvr::internal::AdjustDaysMap(
+      kTestTime, kTestTime + 60 * kTimeUnitsPerSecond, -1, &days);
+  EXPECT_THAT(days, testing::ElementsAre(std::make_pair(
+                        "2015-12-31", 60 * kTimeUnitsPerSecond)));
+
+  // Remove a day.
+  moonfire_nvr::internal::AdjustDaysMap(
+      kTestTime, kTestTime + 60 * kTimeUnitsPerSecond, -1, &days);
+  EXPECT_THAT(days, testing::ElementsAre());
+
+  // Create two days.
+  moonfire_nvr::internal::AdjustDaysMap(
+      kTestTime, kTestTime + 3 * 60 * kTimeUnitsPerSecond, 1, &days);
+  EXPECT_THAT(days,
+              testing::ElementsAre(
+                  std::make_pair("2015-12-31", 1 * 60 * kTimeUnitsPerSecond),
+                  std::make_pair("2016-01-01", 2 * 60 * kTimeUnitsPerSecond)));
+
+  // Add to two days.
+  moonfire_nvr::internal::AdjustDaysMap(
+      kTestTime, kTestTime + 3 * 60 * kTimeUnitsPerSecond, 1, &days);
+  EXPECT_THAT(days,
+              testing::ElementsAre(
+                  std::make_pair("2015-12-31", 2 * 60 * kTimeUnitsPerSecond),
+                  std::make_pair("2016-01-01", 4 * 60 * kTimeUnitsPerSecond)));
+
+  // Subtract from two days.
+  moonfire_nvr::internal::AdjustDaysMap(
+      kTestTime, kTestTime + 3 * 60 * kTimeUnitsPerSecond, -1, &days);
+  EXPECT_THAT(days,
+              testing::ElementsAre(
+                  std::make_pair("2015-12-31", 1 * 60 * kTimeUnitsPerSecond),
+                  std::make_pair("2016-01-01", 2 * 60 * kTimeUnitsPerSecond)));
+
+  // Remove two days.
+  moonfire_nvr::internal::AdjustDaysMap(
+      kTestTime, kTestTime + 3 * 60 * kTimeUnitsPerSecond, -1, &days);
+  EXPECT_THAT(days, testing::ElementsAre());
+}
+
 // Basic test of running some queries on an empty database.
 TEST_F(MoonfireDbTest, EmptyDatabase) {
   std::string error_message;
@@ -337,7 +396,6 @@ TEST_F(MoonfireDbTest, FullLifecycle) {
   EXPECT_TRUE(mdb_->ListReservedSampleFiles(&reserved, &error_message))
       << error_message;
   EXPECT_THAT(reserved, testing::UnorderedElementsAre(uuids[0], uuids[1]));
-  LOG(INFO) << "after delete";
   ExpectNoRecordings(camera_uuid);
 
   EXPECT_TRUE(mdb_->MarkSampleFilesDeleted(uuids, &error_message))
@@ -355,5 +413,10 @@ int main(int argc, char **argv) {
   google::ParseCommandLineFlags(&argc, &argv, true);
   testing::InitGoogleTest(&argc, argv);
   google::InitGoogleLogging(argv[0]);
+
+  // The calendar day math assumes this timezone.
+  CHECK_EQ(0, setenv("TZ", "America/Los_Angeles", 1)) << strerror(errno);
+  tzset();
+
   return RUN_ALL_TESTS();
 }

src/moonfire-db.cc

@@ -33,6 +33,8 @@
 
 #include "moonfire-db.h"
 
+#include <time.h>
+
 #include <string>
 
 #include <glog/logging.h>
@@ -43,6 +45,78 @@
 
 namespace moonfire_nvr {
 
+namespace {
+
+// Helper for AdjustDaysMap.
+void AdjustDay(const std::string &day, int64_t delta,
+               std::map<std::string, int64_t> *days) {
+  auto it = days->find(day);
+  if (it != days->end()) {
+    it->second += delta;
+    DCHECK_GE(it->second, 0) << day << ", " << delta;
+    if (it->second == 0) {
+      days->erase(it);
+    }
+  } else {
+    days->insert(it, std::make_pair(day, delta));
+  }
+}
+
+}  // namespace
+
+namespace internal {
+
+void AdjustDaysMap(int64_t start_time_90k, int64_t end_time_90k, int sign,
+                   std::map<std::string, int64_t> *days) {
+  // There will always be at most two days adjusted, because
+  // kMaxRecordingDuration is less than a day (even during spring forward).
+  DCHECK_LT(start_time_90k, end_time_90k);
+  DCHECK_LE(end_time_90k - start_time_90k, kMaxRecordingDuration);
+  static_assert(kMaxRecordingDuration <= 23 * 60 * kTimeUnitsPerSecond,
+                "max duration should be less than a (spring-forward) day");
+
+  // Fill |buf| with the first day.
+  struct tm mytm;
+  memset(&mytm, 0, sizeof(mytm));
+  time_t start_ts = start_time_90k / kTimeUnitsPerSecond;
+  localtime_r(&start_ts, &mytm);
+  const char kFmt[] = "%Y-%m-%d";
+  char buf[sizeof("YYYY-mm-DD")];
+  strftime(buf, sizeof(buf), kFmt, &mytm);
+
+  // Determine the start of the next day.
+  // Note that mktime(3) normalizes tm_mday, so this should work on the last
+  // day of the month/year.
+  mytm.tm_isdst = -1;
+  mytm.tm_hour = 0;
+  mytm.tm_min = 0;
+  mytm.tm_sec = 0;
+  ++mytm.tm_mday;
+  auto boundary_90k = kTimeUnitsPerSecond * static_cast<int64_t>(mktime(&mytm));
+
+  // Adjust the first day.
+  auto first_day_delta =
+      sign * (std::min(end_time_90k, boundary_90k) - start_time_90k);
+  DCHECK_NE(first_day_delta, 0) << "start=" << start_time_90k
+                                << ", end=" << end_time_90k;
+  AdjustDay(buf, first_day_delta, days);
+
+  if (end_time_90k <= boundary_90k) {
+    return;  // no second day.
+  }
+
+  // Fill |buf| with the second day.
+  strftime(buf, sizeof(buf), kFmt, &mytm);
+
+  // Adjust the second day.
+  auto second_day_delta = sign * (end_time_90k - boundary_90k);
+  DCHECK_NE(second_day_delta, 0) << "start=" << start_time_90k
+                                 << ", end=" << end_time_90k;
+  AdjustDay(buf, second_day_delta, days);
+}
+
+}  // namespace internal
+
 bool MoonfireDatabase::Init(Database *db, std::string *error_message) {
   CHECK(db_ == nullptr);
   db_ = db;

src/moonfire-db.h

@@ -225,6 +225,12 @@ class MoonfireDatabase {
     int64_t max_end_time_90k = -1;
     int64_t total_sample_file_bytes = -1;
     int64_t total_duration_90k = -1;
+
+    // A map of calendar days (in the local timezone, "YYYY-mm-DD") to the
+    // total duration (in 90k units) of recorded data in the day. A day is
+    // present in the map ff the value is non-zero.
+    // TODO: actually fill this.
+    std::map<std::string, int64_t> days;
   };
 
   enum class ReservationState { kWriting = 0, kDeleting = 1 };
@@ -253,6 +259,15 @@ class MoonfireDatabase {
   std::map<int64_t, VideoSampleEntry> video_sample_entries_;
 };
 
+namespace internal {
+
+// Adjust a day-to-duration map (see MoonfireDatabase::CameraData::days_)
+// to reflect a recording.
+void AdjustDaysMap(int64_t start_time_90k, int64_t end_time_90k, int sign,
+                   std::map<std::string, int64_t> *days);
+
+}  // namespace internal
+
 }  // namespace moonfire_nvr
 
 #endif  // MOONFIRE_NVR_MOONFIRE_DB_H