From 0148ebcaa604f929aba06b6722697bb1b6e4c83c Mon Sep 17 00:00:00 2001
From: Jesse Hills <3060199+jesserockz@users.noreply.github.com>
Date: Thu, 4 Apr 2024 13:41:41 +1300
Subject: [PATCH] Replace std::regex with sscanf calls (#6468)

* Replace std::regex with sscanf calls

* Fix CI

* Use regular formatting placeholders

* Fix
---
 esphome/core/time.cpp | 77 +++++++++++++++++++++----------------------
 esphome/core/time.h   |  4 ---
 2 files changed, 37 insertions(+), 44 deletions(-)

diff --git a/esphome/core/time.cpp b/esphome/core/time.cpp
index ae4fabac52..0004fc7e8e 100644
--- a/esphome/core/time.cpp
+++ b/esphome/core/time.cpp
@@ -1,9 +1,7 @@
-#ifdef USE_DATETIME
-#include <regex>
-#endif
-
-#include "helpers.h"
 #include "time.h"  // NOLINT
+#include "helpers.h"
+
+#include <cinttypes>
 
 namespace esphome {
 
@@ -66,48 +64,47 @@ std::string ESPTime::strftime(const std::string &format) {
   return timestr;
 }
 
-#ifdef USE_DATETIME
-
 bool ESPTime::strptime(const std::string &time_to_parse, ESPTime &esp_time) {
-  // clang-format off
-  std::regex dt_regex(R"(^
-    (
-      (\d{4})-(\d{1,2})-(\d{1,2})
-      (?:\s(?=.+))
-    )?
-    (
-      (\d{1,2}):(\d{2})
-      (?::(\d{2}))?
-    )?
-  $)");
-  // clang-format on
+  uint16_t year;
+  uint8_t month;
+  uint8_t day;
+  uint8_t hour;
+  uint8_t minute;
+  uint8_t second;
+  int num;
 
-  std::smatch match;
-  if (std::regex_match(time_to_parse, match, dt_regex) == 0)
+  if (sscanf(time_to_parse.c_str(), "%04hu-%02hhu-%02hhu %02hhu:%02hhu:%02hhu %n", &year, &month, &day,  // NOLINT
+             &hour,                                                                                      // NOLINT
+             &minute,                                                                                    // NOLINT
+             &second, &num) == 6 &&                                                                      // NOLINT
+      num == time_to_parse.size()) {
+    esp_time.year = year;
+    esp_time.month = month;
+    esp_time.day_of_month = day;
+    esp_time.hour = hour;
+    esp_time.minute = minute;
+    esp_time.second = second;
+  } else if (sscanf(time_to_parse.c_str(), "%02hhu:%02hhu:%02hhu %n", &hour, &minute, &second, &num) == 3 &&  // NOLINT
+             num == time_to_parse.size()) {
+    esp_time.hour = hour;
+    esp_time.minute = minute;
+    esp_time.second = second;
+  } else if (sscanf(time_to_parse.c_str(), "%02hhu:%02hhu %n", &hour, &minute, &num) == 2 &&  // NOLINT
+             num == time_to_parse.size()) {
+    esp_time.hour = hour;
+    esp_time.minute = minute;
+    esp_time.second = 0;
+  } else if (sscanf(time_to_parse.c_str(), "%04hu-%02hhu-%02hhu %n", &year, &month, &day, &num) == 3 &&  // NOLINT
+             num == time_to_parse.size()) {
+    esp_time.year = year;
+    esp_time.month = month;
+    esp_time.day_of_month = day;
+  } else {
     return false;
-
-  if (match[1].matched) {  // Has date parts
-
-    esp_time.year = parse_number<uint16_t>(match[2].str()).value_or(0);
-    esp_time.month = parse_number<uint8_t>(match[3].str()).value_or(0);
-    esp_time.day_of_month = parse_number<uint8_t>(match[4].str()).value_or(0);
   }
-  if (match[5].matched) {  // Has time parts
-
-    esp_time.hour = parse_number<uint8_t>(match[6].str()).value_or(0);
-    esp_time.minute = parse_number<uint8_t>(match[7].str()).value_or(0);
-    if (match[8].matched) {
-      esp_time.second = parse_number<uint8_t>(match[8].str()).value_or(0);
-    } else {
-      esp_time.second = 0;
-    }
-  }
-
   return true;
 }
 
-#endif
-
 void ESPTime::increment_second() {
   this->timestamp++;
   if (!increment_time_value(this->second, 0, 60))
diff --git a/esphome/core/time.h b/esphome/core/time.h
index 738a0261c7..4300cf26b7 100644
--- a/esphome/core/time.h
+++ b/esphome/core/time.h
@@ -67,8 +67,6 @@ struct ESPTime {
            this->day_of_year < 367 && this->month > 0 && this->month < 13;
   }
 
-#ifdef USE_DATETIME
-
   /** Convert a string to ESPTime struct as specified by the format argument.
    * @param time_to_parse null-terminated c string formatet like this: 2020-08-25 05:30:00.
    * @param esp_time an instance of a ESPTime struct
@@ -76,8 +74,6 @@ struct ESPTime {
    */
   static bool strptime(const std::string &time_to_parse, ESPTime &esp_time);
 
-#endif
-
   /// Convert a C tm struct instance with a C unix epoch timestamp to an ESPTime instance.
   static ESPTime from_c_tm(struct tm *c_tm, time_t c_time);