Add ParseTime (strptime) native (#1697)

* Add GetTimeStamp (strptime) native

* Fix description

* Fix typos

* Fix issues

* Rewrite ParseTime

* Fix docstrings

* Fix ParseTime

* Clarify docs

core/logic/smn_core.cpp

@@ -32,6 +32,8 @@
 #include <time.h>
 #include <string.h>
 #include <stdlib.h>
+#include <iomanip>
+#include <sstream>
 #include <list>
 #include "common_logic.h"
 #include "Logger.h"
@@ -273,6 +275,49 @@ static cell_t FormatTime(IPluginContext *pContext, const cell_t *params)
 	return 1;
 }
 
+static int ParseTime(IPluginContext *pContext, const cell_t *params)
+{
+	char *datetime;
+	char *format;
+	pContext->LocalToStringNULL(params[1], &datetime);
+	pContext->LocalToStringNULL(params[2], &format);
+
+	if (format == NULL)
+	{
+		format = const_cast<char *>(bridge->GetCvarString(g_datetime_format));
+	}
+	else if (!format[0])
+	{
+		return pContext->ThrowNativeError("Time format string cannot be empty.");
+	}
+	if (!datetime || !datetime[0])
+	{
+		return pContext->ThrowNativeError("Date/time string cannot be empty.");
+	}
+
+	// https://stackoverflow.com/a/33542189
+	std::tm t{};
+	std::istringstream input(datetime);
+
+	auto previousLocale = input.imbue(std::locale::classic());
+	input >> std::get_time(&t, format);
+	bool failed = input.fail();
+	input.imbue(previousLocale);
+
+	if (failed)
+	{
+		return pContext->ThrowNativeError("Invalid date/time string or time format.");
+	}
+
+#if defined PLATFORM_WINDOWS
+	return _mkgmtime(&t);
+#elif defined PLATFORM_LINUX || defined PLATFORM_APPLE
+	return timegm(&t);
+#else
+	return pContext->ThrowNativeError("Platform has no implemented UTC conversion for std::tm to std::time_t");
+#endif
+}
+
 static cell_t GetPluginIterator(IPluginContext *pContext, const cell_t *params)
 {
 	IPluginIterator *iter = scripts->GetPluginIterator();
@@ -1088,6 +1133,7 @@ REGISTER_NATIVES(coreNatives)
 	{"ThrowError",				ThrowError},
 	{"GetTime",					GetTime},
 	{"FormatTime",				FormatTime},
+	{"ParseTime",				ParseTime},
 	{"GetPluginIterator",		GetPluginIterator},
 	{"MorePlugins",				MorePlugins},
 	{"ReadPlugin", 				ReadPlugin},

plugins/include/sourcemod.inc

@@ -412,6 +412,24 @@ native int GetTime(int bigStamp[2]={0,0});
  */
 native void FormatTime(char[] buffer, int maxlength, const char[] format, int stamp=-1);
 
+/**
+ * Parses a string representing a date and/or time into a unix timestamp.
+ * The timezone is always interpreted as UTC/GMT.
+ *
+ * See this URL for valid parameters:
+ * https://en.cppreference.com/w/cpp/io/manip/get_time
+ *
+ * Note that available parameters depends on support from your operating system.
+ * In particular, ones highlighted in yellow on that page are not currently
+ * available on Windows and should be avoided for portable plugins.
+ *
+ * @param dateTime     Date and/or time string.
+ * @param format       Formatting rules (passing NULL_STRING will use the rules defined in sm_datetime_format).
+ * @return             32bit timestamp (number of seconds since unix epoch).
+ * @error              Invalid date/time string or time format.
+ */
+native int ParseTime(const char[] dateTime, const char[] format);
+
 /**
  * Loads a game config file.
  *