Added fs.is_newer function to filesystem library

include/lua_filesystem.h

@@ -20,6 +20,11 @@ int lua_fs_forall_dir_next(lua_State* L);
 int lua_fs_foreach_dir_dtor(lua_State* L);
 int lua_fs_forall_dir_dtor(lua_State* L);
 
+// Returns true when a is newer than b. If b does not exist it returns true. If a does not exist it returns false
+// boolean | table<boolean> function fs.is_newer(path_a: string | number, path_b: string | table[string])
+int lua_fs_is_newer(lua_State* L);
+// table<string> | nil function fs.filter_newer(path_a: string | number, path_b: string | table[string])
+int lua_fs_filter_newer(lua_State* L);
 
 // number | nil function fs.last_modified(path: string)
 int lua_fs_last_modified(lua_State* L);

src/lua_filesystem.cpp

@@ -1,5 +1,6 @@
 #include "lua_filesystem.h"
 #include <filesystem>
+#include <chrono>
 
 int luaopen_filesystem(lua_State* L)
 {
@@ -18,6 +19,12 @@ int luaopen_filesystem(lua_State* L)
 	// Push functions
 	lua_newtable(L);
 
+	lua_pushcfunction(L, lua_fs_is_newer);
+	lua_setfield(L, -2, "is_newer");
+
+	lua_pushcfunction(L, lua_fs_filter_newer);
+	lua_setfield(L, -2, "filter_newer");
+
 	lua_pushcfunction(L, lua_fs_absolute);
 	lua_setfield(L, -2, "absolute");
 
@@ -251,11 +258,107 @@ int lua_fs_file_directory(lua_State* L)
 	return 0;
 }
 
+int lua_fs_is_newer(lua_State* L)
+{
+	luaL_argcheck(L, lua_type(L, 1) == LUA_TSTRING, 1, "Expected first argument to be a string representing a full file path");
+	const char* test_file = lua_tostring(L, 1);
+	if (!std::filesystem::exists(test_file))
+	{
+		lua_pushboolean(L, false);
+		return 1;
+	}
+
+	if (lua_type(L, 2) == LUA_TTABLE)
+	{
+		size_t tbl_len = lua_objlen(L, 2);
+		lua_newtable(L);
+		for (size_t i = 1; i <= tbl_len; ++i)
+		{
+			lua_rawgeti(L, 2, i);
+			if (lua_type(L, -1) != LUA_TSTRING) 
+				return luaL_error(L, "Expected second argument at index %llu to be a string, not %s\n",
+					i, lua_typename(L, lua_type(L, -1)));
+			const char* target = lua_tostring(L, 2);
+			lua_pushboolean(L,
+				std::filesystem::last_write_time(test_file) > std::filesystem::last_write_time(target));
+			lua_rawseti(L, -2, i);
+			lua_pop(L, 1);
+		}
+		return 1;
+	}
+	else if (lua_type(L, 2) == LUA_TSTRING)
+	{
+		const char* target = lua_tostring(L, 2);
+		if (!std::filesystem::exists(target))
+		{
+			lua_pushboolean(L, true);
+			return 1;
+		}
+		lua_pushboolean(L,
+			std::filesystem::last_write_time(test_file) > std::filesystem::last_write_time(target));
+		return 1;
+	}
+	else return luaL_error(L, "Expected second argument to be a string or table of strings");
+}
+
+int lua_fs_filter_newer(lua_State* L)
+{
+	luaL_argcheck(L, lua_type(L, 1) == LUA_TSTRING, 1, "Expected first argument to be a string representing a full file path");
+	const char* test_file = lua_tostring(L, 1);
+	if (!std::filesystem::exists(test_file))
+	{
+		lua_pushnil(L);
+		return 1;
+	}
+
+	if (lua_type(L, 2) == LUA_TTABLE)
+	{
+		size_t tbl_len = lua_objlen(L, 2);
+		lua_newtable(L);
+		for (size_t i = 1; i <= tbl_len; ++i)
+		{
+			lua_rawgeti(L, 2, i);
+			if (lua_type(L, -1) != LUA_TSTRING)
+				return luaL_error(L, "Expected second argument at index %llu to be a string, not %s\n",
+					i, lua_typename(L, lua_type(L, -1)));
+			const char* target = lua_tostring(L, 2);
+			if (std::filesystem::last_write_time(test_file) > std::filesystem::last_write_time(target))
+			{
+				lua_pushvalue(L, -1);
+				lua_rawseti(L, -2, lua_objlen(L, -2)+1);
+			}
+			lua_pop(L, 1);
+		}
+		return 1;
+	}
+	else if (lua_type(L, 2) == LUA_TSTRING)
+	{
+		const char* target = lua_tostring(L, 2);
+		if (!std::filesystem::exists(target))
+		{
+			lua_pushvalue(L, 2);
+			return 1;
+		}
+		
+		if (std::filesystem::last_write_time(test_file) > std::filesystem::last_write_time(target))
+			lua_pushvalue(L, 2);
+		else lua_pushnil(L);
+
+		return 1;
+	}
+	else return luaL_error(L, "Expected second argument to be a string or table of strings");
+}
+
 int lua_fs_last_modified(lua_State* L)
 {
 	luaL_argcheck(L, lua_type(L, 1) == LUA_TSTRING, 1, "Expected first argument to be a string representing a full file path");
 	try {
-		lua_pushinteger(L, std::filesystem::last_write_time(std::filesystem::path(lua_tostring(L, 1))).time_since_epoch().count());
+		const uint64_t file_last_write = std::chrono::duration_cast<std::chrono::milliseconds>(
+			std::chrono::clock_cast<std::chrono::system_clock>(
+				std::filesystem::last_write_time(lua_tostring(L, 1))
+			).time_since_epoch()
+		).count();
+		lua_pushinteger(L, file_last_write);
 		return 1;
 	} catch (const std::exception& e)
 	{