Added functionality to align display refreshes

TRMNL.cpp

@@ -1,6 +1,8 @@
 #include "TRMNL.h"
 #include "helpers.h"
 
+#include <time.h>
+
 using std::list;
 using std::map;
 using std::optional;
@@ -11,11 +13,13 @@ using nlohmann::json;
 TRMNL::TRMNL(const string& id,
 	const string& api_key,
 	const string& friendly_id,
-	int refresh_rate)
+	int refresh_rate,
+	bool is_refresh_aligned)
 : m_id(id),
 m_api_key(api_key),
 m_friendly_id(friendly_id),
 m_refresh_rate(refresh_rate),
+m_is_refresh_aligned(is_refresh_aligned),
 m_update_handler()
 {}
 
@@ -52,6 +56,65 @@ int TRMNL::refresh_rate() const
 	return m_refresh_rate;
 }
 
+bool TRMNL::is_refresh_aligned() const
+{
+	return m_is_refresh_aligned;
+}
+
+int TRMNL::get_next_refresh(int min_time, int offset) const
+{
+	if (!m_is_refresh_aligned)
+	{
+		return m_refresh_rate;
+	}
+
+	if (min_time > m_refresh_rate)
+	{
+		min_time = m_refresh_rate;
+	}
+
+	int result = 0;
+	time_t curr = time(nullptr);
+	struct tm* now = localtime(&curr);
+
+	int tmp_refresh = m_refresh_rate;
+	bool align_minutes = false;
+	bool align_hours = false;
+
+	if (0 == m_refresh_rate % 60)
+	{
+		align_minutes = true;
+		tmp_refresh /= 60;
+
+		if (0 == tmp_refresh % 60)
+		{
+			align_hours = true;
+			tmp_refresh /= 60;
+		}
+	}
+
+	if (align_minutes)
+	{
+		now->tm_sec = 0;
+		now->tm_min += 1;
+	}
+
+	if (align_hours)
+	{
+		now->tm_min = 0;
+		now->tm_hour += 1;
+	}
+
+	time_t next = mktime(now);
+	result = next - curr + offset;
+	while (result < min_time)
+	{
+		result += m_refresh_rate;
+	}
+
+	return result;
+}
+
 void TRMNL::id(const std::string& id)
 {
 	m_id = id;
@@ -88,6 +151,15 @@ void TRMNL::refresh_rate(int refresh_rate)
 	}
 }
 
+void TRMNL::is_refresh_aligned(bool to_align)
+{
+	m_is_refresh_aligned = to_align;
+	if (m_update_handler)
+	{
+		m_update_handler(*this);
+	}
+}
+
 void TRMNL::set_update_handler(std::function<void (const TRMNL& trmnl)> handler)
 {
 	m_update_handler = handler;

TRMNL.h

@@ -18,6 +18,7 @@ private:
 	std::string m_api_key;
 	std::string m_friendly_id;
 	int m_refresh_rate;
+	bool m_is_refresh_aligned;
 
 	std::function<void (const TRMNL& trmnl)> m_update_handler;
 
@@ -26,7 +27,8 @@ public:
 	TRMNL(const std::string& id = "",
 		const std::string& api_key = "",
 		const std::string& friendly_id = "",
-		int refresh_rate = DEFAULT_REFRESH_RATE);
+		int refresh_rate = DEFAULT_REFRESH_RATE,
+		bool is_refresh_aligned = true);
 
 	TRMNL(const nlohmann::json& j);
 
@@ -35,12 +37,24 @@ public:
 	const std::string& api_key() const;
 	const std::string& friendly_id() const;
 	int refresh_rate() const;
+	bool is_refresh_aligned() const;
+
+	// Uses the current time to return when next this device should refresh
+	// min_time
+	// - if calculated time is lower than this - increase by refresh rate until higher
+	// - Capped to the refresh rate
+	// offset
+	// - offset to apply to the refresh rate
+	// - Capped to the refresh rate
+	// - useful when generating images via cron and you want the refresh to happen a few seconds later
+	int get_next_refresh(int min_time = 0, int offset = 0) const;
 
 	// Setters
 	void id(const std::string& id);
 	void api_key(const std::string& api_key);
 	void friendly_id(const std::string& friendly_id);
 	void refresh_rate(int refresh_rate);
+	void is_refresh_aligned(bool to_align);
 
 	void set_update_handler(std::function<void (const TRMNL& trmnl)> handler);
 

config_example.json

@@ -8,5 +8,8 @@
 	"devices_filename": "devices.json",
 	"folder_images": "images",
 	"cert_file": "path/to/file",
-	"key_file": "path/to/file"
+	"key_file": "path/to/file",
+
+	"refresh_min": 60,
+	"refresh_offset": 15
 }

devices_example.json

@@ -6,6 +6,7 @@
 		// Auto managed
 		"api_key": "api key",
 		"friendly_id": "917F0B",
-		"refresh_rate": 600
+		"refresh_rate": 300,
+		"refresh_aligned": true
 	}
 ]

main.cpp

@@ -190,6 +190,9 @@ int main(int argc, char **argv)
 	string cert_file = "";
 	string key_file = "";
 
+	int refresh_min = 60;
+	int refresh_offset = 15;
+
 	shared_ptr<httplib::Server> server = nullptr;
 
 	bool ok;
@@ -219,6 +222,9 @@ int main(int argc, char **argv)
 	// json_extract(cfg, "cert_file", cert_file);
 	// json_extract(cfg, "key_file", cert_file);
 
+	json_extract(cfg, "refresh_min", refresh_min);
+	json_extract(cfg, "refresh_offset", refresh_offset);
+
 	if (host.empty())
 	{
 		cout << "host not provided" << endl;
@@ -335,7 +341,7 @@ int main(int argc, char **argv)
 		}
 	};
 
-	auto display_handler = [&container, &devices_filename, &folder_images, &base_url]
+	auto display_handler = [&container, &devices_filename, &folder_images, &base_url, refresh_min, refresh_offset]
 		(const httplib::Request& req, httplib::Response& res)
 	{
 		json response;
@@ -411,7 +417,7 @@ int main(int argc, char **argv)
 			response["filename"] = image_timestamp;
 		}
 
-		response["refresh_rate"] = to_string(trmnl->refresh_rate());
+		response["refresh_rate"] = to_string(trmnl->get_next_refresh(refresh_min, refresh_offset));
 
 		// TODO: Handle firmware updating
 		response["update_firmware"] = false;