Adapt vote reset code into fast campaign resetting

This is kind of a breaking change but the other code was obviously never
released or relied on by anyone - it will be pushed at the same time as
this in fact. It still seems worth having the original committed
separately to show the progression of development of the feature,
however. Technically the standalone vote cooldown resetting could also
be added back if ever desired however there doesn't seem to be that much
of a use case for that at the moment.

This feature ought to be a lot more convenient now as it allows for
resetting back to a set starting point no matter where the player is in
a run. It isn't universally useful as All Campaigns Legacy solo runs
require switching to a different type of server and Main Campaigns co-op
runs require restarting the game after Swamp Fever to work around the
god mode bug, however it is still useful in a good few situations.

Unfortunately this turned out to be pretty complex to implement, first
requiring a bunch of interop with valve's rather wacky KeyValues stuff,
and then requiring a bunch of especially difficult reverse engineering
of L4D1 v1.0.0.5 because it doesn't use said KeyValues stuff and does
something else completely different instead.

A side effect of all this work is that the nag removal hack is now part
of the KeyValues stuff in kvsys.c, which is kind of a comfier place for
it than just kind of dumped in the middle of sst.c.

1 files changed, 134 insertions, 0 deletions

diff --git a/src/l4dmm.c b/src/l4dmm.c
new file mode 100644
index 0000000..8394038
--- /dev/null
+++ b/src/l4dmm.c
@@ -0,0 +1,134 @@
+/*
+ * Copyright © 2023 Michael Smith <mikesmiffy128@gmail.com>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED “AS IS” AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+ * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+ * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+ * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+ * OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+ * PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <string.h>
+
+#include "engineapi.h"
+#include "errmsg.h"
+#include "feature.h"
+#include "gamedata.h"
+#include "gametype.h"
+#include "kvsys.h"
+#include "mem.h"
+#include "os.h"
+#include "vcall.h"
+
+FEATURE()
+REQUIRE(kvsys)
+REQUIRE_GAMEDATA(vtidx_GetMatchNetworkMsgController)
+REQUIRE_GAMEDATA(vtidx_GetActiveGameServerDetails)
+
+DECL_VFUNC_DYN(void *, GetMatchNetworkMsgController)
+DECL_VFUNC_DYN(struct KeyValues *, GetActiveGameServerDetails,
+		struct KeyValues *)
+
+// Old L4D1 uses a heavily modified version of the CMatchmaking in Source 2007.
+// None of it is publicly documented or well-understood but I was able to figure
+// out that this random function does something *close enough* to what we want.
+struct contextval {
+	const char *name;
+	int _unknown[8];
+	const char *val;
+	/* other stuff unknown */
+};
+DECL_VFUNC(struct contextval *, unknown_contextlookup, 67, const char *)
+
+static void *matchfwk;
+static union { // space saving
+	struct { int sym_game, sym_campaign; }; // "game/campaign" KV lookup
+	void *oldmmiface; // old L4D1 interface
+} U;
+#define oldmmiface U.oldmmiface
+#define sym_game U.sym_game
+#define sym_campaign U.sym_campaign
+static char campaignbuf[32];
+
+const char *l4dmm_curcampaign(void) {
+#ifdef _WIN32
+	if (!matchfwk) { // we must have oldmmiface, then
+		struct contextval *ctxt = unknown_contextlookup(oldmmiface,
+				"CONTEXT_L4D_CAMPAIGN");
+		if (ctxt) {
+			// HACK: since this context symbol stuff was the best that was found
+			// for this old MM interface, just map things back to their names
+			// manually. bit stupid, but it gets the (rather difficult) job done
+			if (strncmp(ctxt->val, "CONTEXT_L4D_CAMPAIGN_", 21)) return 0;
+			if (!strcmp(ctxt->val + 21, "APARTMENTS")) return "Hospital";
+			if (!strcmp(ctxt->val + 21, "CAVES")) return "SmallTown";
+			if (!strcmp(ctxt->val + 21, "GREENHOUSE")) return "Airport";
+			if (!strcmp(ctxt->val + 21, "HILLTOP")) return "Farm";
+		}
+		return 0;
+	}
+#endif
+	void *ctrlr = GetMatchNetworkMsgController(matchfwk);
+	struct KeyValues *kv = GetActiveGameServerDetails(ctrlr, 0);
+	if (!kv) return 0; // not in server, probably
+	const char *ret = 0;
+	struct KeyValues *subkey = kvsys_getsubkey(kv, sym_game);
+	if (subkey) subkey = kvsys_getsubkey(subkey, sym_campaign);
+	if (subkey) ret = kvsys_getstrval(subkey);
+	if (ret) {
+		// ugh, we have to free all the memory allocated by the engine, so copy
+		// this glorified global state to a buffer so the caller doesn't have to
+		// deal with freeing. this necessitates a length cap but it's hopefully
+		// reasonable...
+		int len = strlen(ret);
+		if (len > sizeof(campaignbuf) - 1) ret = 0;
+		else ret = memcpy(campaignbuf, ret, len + 1);
+	}
+	kvsys_free(kv);
+	return ret;
+}
+
+INIT {
+	// ugh, we NEED to centralise the library stuff at some point, this sucks
+#ifdef _WIN32
+	void *mmlib = GetModuleHandleW(L"matchmaking.dll");
+#else
+	void *mmlib = dlopen("matchmaking.so", RTLD_NOW | RTLD_NOLOAD);
+	if (mmlib) dlclose(mmlib);
+#endif
+	if (mmlib) {
+		ifacefactory factory = (ifacefactory)os_dlsym(mmlib, "CreateInterface");
+		if (!factory) {
+			errmsg_errordl("couldn't get matchmaking interface factory");
+			return false;
+		}
+		matchfwk = factory("MATCHFRAMEWORK_001", 0);
+		if (!matchfwk) {
+			errmsg_errorx("couldn't get IMatchFramework interface");
+			return false;
+		}
+		sym_game = kvsys_strtosym("game");
+		sym_campaign = kvsys_strtosym("campaign");
+	}
+	else {
+#ifdef _WIN32
+		oldmmiface = factory_engine("VENGINE_MATCHMAKING_VERSION001", 0);
+		if (!oldmmiface) {
+			errmsg_errorx("couldn't get IMatchmaking interface");
+			return false;
+		}
+#else // Linux L4D1 has always used the separate matchmaking library
+		errmsg_errordl("couldn't get matchmaking library");
+		return false;
+#endif
+	}
+	return true;
+}
+
+// vi: sw=4 ts=4 noet tw=80 cc=80