bootstat: Allow regex matches for boot reasons

If the matching string contains a [, \ or *, then it is also checked
with a regex match.  Exact match is always tried firsts.  If we do
not find an exact string match, switch to iterate through the entire
list for regex strings to find a match.

This allows us to scale with details without consuming a large
number of enums, permitting details that we do not necessarily want
resolution on to propagate to TRON.  The hierarchical nature of the
boot reason <reason>,<subreason>,<detail>... can cause scenarios
where the <detail> does not matter to TRON, but does matter to
bugreport collection.

Add a bootstat --boot_reason_enum function to expose and test the
kBootReasonMap matchihg algorithm.

Add a kBootReasonMap test that exhaustively tests all built-in
entries, and an example of one regex entry.  New regex entries added
to bootstat.cpp will need a series of exact match examples added into
filter_kBootReasonMap() function.

Test: boot_reason_test.sh kBootReasonMap (or all tests)
Bug: 116838876
Bug: 128929506
Change-Id: I3f7b5de22f99195b7ce99672a212174365960b3f
diff --git a/bootstat/bootstat.cpp b/bootstat/bootstat.cpp
index 1ce0ec4..617ea4f 100644
--- a/bootstat/bootstat.cpp
+++ b/bootstat/bootstat.cpp
@@ -89,7 +89,7 @@
 }
 
 void ShowHelp(const char* cmd) {
-  fprintf(stderr, "Usage: %s [options]\n", cmd);
+  fprintf(stderr, "Usage: %s [options]...\n", cmd);
   fprintf(stderr,
           "options include:\n"
           "  -h, --help              Show this help\n"
@@ -99,7 +99,8 @@
           "  --value                 Optional value to associate with the boot event\n"
           "  --record_boot_complete  Record metrics related to the time for the device boot\n"
           "  --record_boot_reason    Record the reason why the device booted\n"
-          "  --record_time_since_factory_reset Record the time since the device was reset\n");
+          "  --record_time_since_factory_reset  Record the time since the device was reset\n"
+          "  --boot_reason_enum=<reason>  Report the match to the kBootReasonMap table\n");
 }
 
 // Constructs a readable, printable string from the givencommand line
@@ -120,9 +121,10 @@
 // A mapping from boot reason string, as read from the ro.boot.bootreason
 // system property, to a unique integer ID. Viewers of log data dashboards for
 // the boot_reason metric may refer to this mapping to discern the histogram
-// values.
+// values.  Regex matching, to manage the scale, as a minimum require either
+// [, \ or * to be present in the string to switch to checking.
 const std::map<std::string, int32_t> kBootReasonMap = {
-    {"empty", kEmptyBootReason},
+    {"reboot,[empty]", kEmptyBootReason},
     {"__BOOTSTAT_UNKNOWN__", kUnknownBootReason},
     {"normal", 2},
     {"recovery", 3},
@@ -314,6 +316,16 @@
     return kEmptyBootReason;
   }
 
+  for (const auto& [match, id] : kBootReasonMap) {
+    // Regex matches as a minimum require either [, \ or * to be present.
+    if (match.find_first_of("[\\*") == match.npos) continue;
+    // enforce match from beginning to end
+    auto exact = match;
+    if (exact[0] != '^') exact = "^" + exact;
+    if (exact[exact.size() - 1] != '$') exact = exact + "$";
+    if (std::regex_search(boot_reason, std::regex(exact))) return id;
+  }
+
   LOG(INFO) << "Unknown boot reason: " << boot_reason;
   return kUnknownBootReason;
 }
@@ -1266,6 +1278,19 @@
   boot_event_store.AddBootEventWithValue("time_since_factory_reset", time_since_factory_reset);
 }
 
+// List the associated boot reason(s), if arg is nullptr then all.
+void PrintBootReasonEnum(const char* arg) {
+  int value = -1;
+  if (arg != nullptr) {
+    value = BootReasonStrToEnum(arg);
+  }
+  for (const auto& [match, id] : kBootReasonMap) {
+    if ((value < 0) || (value == id)) {
+      printf("%u\t%s\n", id, match.c_str());
+    }
+  }
+}
+
 }  // namespace
 
 int main(int argc, char** argv) {
@@ -1280,6 +1305,7 @@
   static const char boot_complete_str[] = "record_boot_complete";
   static const char boot_reason_str[] = "record_boot_reason";
   static const char factory_reset_str[] = "record_time_since_factory_reset";
+  static const char boot_reason_enum_str[] = "boot_reason_enum";
   static const struct option long_options[] = {
       // clang-format off
       { "help",                 no_argument,       NULL,   'h' },
@@ -1291,6 +1317,7 @@
       { boot_complete_str,      no_argument,       NULL,   0 },
       { boot_reason_str,        no_argument,       NULL,   0 },
       { factory_reset_str,      no_argument,       NULL,   0 },
+      { boot_reason_enum_str,   optional_argument, NULL,   0 },
       { NULL,                   0,                 NULL,   0 }
       // clang-format on
   };
@@ -1315,6 +1342,8 @@
           RecordBootReason();
         } else if (option_name == factory_reset_str) {
           RecordFactoryReset();
+        } else if (option_name == boot_reason_enum_str) {
+          PrintBootReasonEnum(optarg);
         } else {
           LOG(ERROR) << "Invalid option: " << option_name;
         }