add tox friend faux offline message (still wonky) + small file copy error handling

src/tox_friend_faux_offline_messaging.hpp

@@ -0,0 +1,50 @@
+#pragma once
+
+#include <solanaceae/toxcore/tox_event_interface.hpp>
+#include <solanaceae/tox_contacts/tox_contact_model2.hpp>
+#include <solanaceae/contact/contact_model3.hpp>
+#include <solanaceae/message3/registry_message_model.hpp>
+
+// fwd
+struct ToxI;
+namespace Contact::Components {
+	struct ToxFriendEphemeral;
+}
+
+// resends unconfirmed messages.
+// timers get reset on connection changes, and send order is preserved.
+class ToxFriendFauxOfflineMessaging : public ToxEventI {
+	Contact3Registry& _cr;
+	RegistryMessageModel& _rmm;
+	ToxContactModel2& _tcm;
+	ToxI& _t;
+	ToxEventProviderI& _tep;
+
+	float _interval_timer{0.f};
+
+	// TODO: increase timer?
+	const float _delay_after_cc {4.5f};
+	const float _delay_inbetween {0.3f};
+	const float _delay_retry {10.f}; // retry sending after 10s
+
+	public:
+		ToxFriendFauxOfflineMessaging(
+			Contact3Registry& cr,
+			RegistryMessageModel& rmm,
+			ToxContactModel2& tcm,
+			ToxI& t,
+			ToxEventProviderI& tep
+		);
+
+		float tick(float time_delta);
+
+	private:
+		// only called for online friends
+		// returns true if a message was sent
+		// dont call this too often
+		bool doFriendMessageCheck(const Contact3 c, const Contact::Components::ToxFriendEphemeral& tfe);
+
+	protected:
+		bool onToxEvent(const Tox_Event_Friend_Connection_Status* e) override;
+};
+