Cassette loading stuff

monkestation/code/modules/cassettes/cassette_db/cassette_datum.dm

@@ -1,5 +1,6 @@
+#define BASE_CASSETTE_DIR "data/cassette_storage/"
 /// An associative list of cassette IDs to cassette datums.
-GLOBAL_LIST_EMPTY_TYPED(cassettes, /datum/cassette)
+GLOBAL_LIST_INIT_TYPED(cassettes, /datum/cassette, load_all_cassettes())
 
 /datum/cassette
 	/// The name of the cassette.
@@ -87,7 +88,7 @@ GLOBAL_LIST_EMPTY_TYPED(cassettes, /datum/cassette)
 /datum/cassette/proc/save()
 	if(!id)
 		CRASH("Attempted to save cassette without an ID to disk")
-	rustg_file_write(json_encode(export_old_format(), JSON_PRETTY_PRINT), "data/cassette_storage/[id].json")
+	rustg_file_write(json_encode(export_old_format(), JSON_PRETTY_PRINT), BASE_CASSETTE_DIR + "[id].json")
 
 /// Simple helper to get a side of the cassette.
 /// TRUE is front side, FALSE is back side.
@@ -129,12 +130,39 @@ GLOBAL_LIST_EMPTY_TYPED(cassettes, /datum/cassette)
 		return null
 	if(GLOB.cassettes[id])
 		return GLOB.cassettes[id]
-	var/cassette_file = "data/cassette_storage/[id].json"
+	var/datum/cassette/cassette_data = load_cassette_raw(id)
+	if(cassette_data)
+		GLOB.cassettes[id] = cassette_data
+		return cassette_data
+
+/// Loads the cassette with the given ID from a JSON in the `data/cassette_storage` folder.
+/// This does not check the GLOB.cassettes cache, and you should not use this - this is only used to initialize GLOB.cassettes
+/proc/load_cassette_raw(id) as /datum/cassette
+	RETURN_TYPE(/datum/cassette)
+	var/cassette_file = BASE_CASSETTE_DIR + "[id].json"
 	if(!rustg_file_exists(cassette_file))
 		return null
 	var/list/cassette_json = json_decode(rustg_file_read(cassette_file))
 	var/datum/cassette/cassette_data = new
 	cassette_data.import_old_format(cassette_json)
 	cassette_data.id = id
-	GLOB.cassettes[id] = cassette_data
 	return cassette_data
+
+/// Returns an associative list of id to cassette datums, of all existing saved cassettes.
+/proc/load_all_cassettes() as /list
+	RETURN_TYPE(/list)
+	. = list()
+	var/ids_file = BASE_CASSETTE_DIR + "ids.json"
+	if(!rustg_file_exists(ids_file))
+		return
+	var/list/ids = json_decode(rustg_file_read(ids_file))
+	for(var/id in ids)
+		if(!ids)
+			continue
+		var/datum/cassette/cassette_data = load_cassette_raw(id)
+		if(isnull(cassette_data))
+			stack_trace("Failed to load cassette [id]")
+			continue
+		.[id] = cassette_data
+
+#undef BASE_CASSETTE_DIR