From 5c339d459794dc97741a58f7951a060ed0c448e0 Mon Sep 17 00:00:00 2001
From: Oxan van Leeuwen <oxan@oxanvanleeuwen.nl>
Date: Thu, 6 Jan 2022 12:56:10 +0100
Subject: [PATCH] Convert clamp() helper to backport of std::clamp() (#3010)

---
 esphome/core/helpers.cpp | 11 -----------
 esphome/core/helpers.h   | 21 ++++++++++++---------
 2 files changed, 12 insertions(+), 20 deletions(-)

diff --git a/esphome/core/helpers.cpp b/esphome/core/helpers.cpp
index c70aa2d6dd..457c8ef37f 100644
--- a/esphome/core/helpers.cpp
+++ b/esphome/core/helpers.cpp
@@ -215,17 +215,6 @@ void HighFrequencyLoopRequester::stop() {
 }
 bool HighFrequencyLoopRequester::is_high_frequency() { return high_freq_num_requests > 0; }
 
-template<typename T> T clamp(const T val, const T min, const T max) {
-  if (val < min)
-    return min;
-  if (val > max)
-    return max;
-  return val;
-}
-template uint8_t clamp(uint8_t, uint8_t, uint8_t);
-template float clamp(float, float, float);
-template int clamp(int, int, int);
-
 float lerp(float completion, float start, float end) { return start + (end - start) * completion; }
 
 bool str_startswith(const std::string &full, const std::string &start) { return full.rfind(start, 0) == 0; }
diff --git a/esphome/core/helpers.h b/esphome/core/helpers.h
index 4699e8071c..bbe6b49827 100644
--- a/esphome/core/helpers.h
+++ b/esphome/core/helpers.h
@@ -58,15 +58,6 @@ class HighFrequencyLoopRequester {
   bool started_{false};
 };
 
-/** Clamp the value between min and max.
- *
- * @param val The value.
- * @param min The minimum value.
- * @param max The maximum value.
- * @return val clamped in between min and max.
- */
-template<typename T> T clamp(T val, T min, T max);
-
 /** Linearly interpolate between end start and end by completion.
  *
  * @tparam T The input/output typename.
@@ -277,6 +268,18 @@ using std::is_trivially_copyable;
 template<typename T> struct is_trivially_copyable : public std::integral_constant<bool, true> {};
 #endif
 
+// std::clamp from C++17
+#if __cpp_lib_clamp >= 201603
+using std::clamp;
+#else
+template<typename T, typename Compare> constexpr const T &clamp(const T &v, const T &lo, const T &hi, Compare comp) {
+  return comp(v, lo) ? lo : comp(hi, v) ? hi : v;
+}
+template<typename T> constexpr const T &clamp(const T &v, const T &lo, const T &hi) {
+  return clamp(v, lo, hi, std::less<T>{});
+}
+#endif
+
 // std::bit_cast from C++20
 #if __cpp_lib_bit_cast >= 201806
 using std::bit_cast;