From e13b220be977375376d419d3378d690dcade7c39 Mon Sep 17 00:00:00 2001
From: Martin Michelsen <fuzziqersoftware+g@gmail.com>
Date: Wed, 3 Jan 2024 23:27:06 -0800
Subject: [PATCH] support non-BB rare enemy generation logic

---
 TODO.md      |  1 +
 src/Lobby.cc |  2 +-
 src/Map.cc   | 26 ++++++++++++++++++++++----
 src/Map.hh   |  3 ++-
 4 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/TODO.md b/TODO.md
index 0f9eaa4e..424c522c 100644
--- a/TODO.md
+++ b/TODO.md
@@ -5,6 +5,7 @@
 - Make UI strings localizable (e.g. entries in menus, welcome message, etc.)
 - Add an idle connection timeout for proxy sessions
 - Look into JP heart symbol bug on Linux
+- Check server's rare enemy logic against GC's logic
 
 ## Episode 3
 
diff --git a/src/Lobby.cc b/src/Lobby.cc
index 334f7070..8a2857d3 100644
--- a/src/Lobby.cc
+++ b/src/Lobby.cc
@@ -262,7 +262,7 @@ void Lobby::create_item_creator() {
 }
 
 void Lobby::load_maps() {
-  this->map = make_shared<Map>(this->lobby_id, this->random_crypt);
+  this->map = make_shared<Map>(this->base_version, this->lobby_id, this->random_crypt);
 
   auto rare_rates = ((this->base_version == Version::BB_V4) && this->rare_enemy_rates)
       ? this->rare_enemy_rates
diff --git a/src/Map.cc b/src/Map.cc
index 11e63608..a7347805 100644
--- a/src/Map.cc
+++ b/src/Map.cc
@@ -683,8 +683,9 @@ string Map::Object::str() const {
       this->item_drop_checked ? "true" : "false");
 }
 
-Map::Map(uint32_t lobby_id, std::shared_ptr<PSOLFGEncryption> random_crypt)
+Map::Map(Version version, uint32_t lobby_id, std::shared_ptr<PSOLFGEncryption> random_crypt)
     : log(string_printf("[Lobby:%08" PRIX32 ":map] ", lobby_id), lobby_log.min_level),
+      version(version),
       random_crypt(random_crypt) {}
 
 void Map::clear() {
@@ -722,10 +723,27 @@ bool Map::check_and_log_rare_enemy(bool default_is_rare, uint32_t rare_rate) {
   if (default_is_rare) {
     return true;
   }
-  if ((this->rare_enemy_indexes.size() < 0x10) && (this->random_crypt->next() < rare_rate)) {
-    this->rare_enemy_indexes.emplace_back(this->enemies.size());
-    return true;
+
+  // On BB, rare enemy indexes are generated by the server and sent to the
+  // client, so we can use any method we want to choose rares. On other
+  // versions, we must match the client's logic, even though it's more
+  // computationally expensive.
+  if (this->version == Version::BB_V4) {
+    if ((this->rare_enemy_indexes.size() < 0x10) && (this->random_crypt->next() < rare_rate)) {
+      this->rare_enemy_indexes.emplace_back(this->enemies.size());
+      return true;
+    }
+
+  } else {
+    // TODO: We only need the first value from this crypt, so it's unfortunate
+    // that we have to initialize the entire thing. Find a way to make this
+    // faster.
+    PSOV2Encryption crypt(this->random_crypt->seed());
+    if ((static_cast<float>((crypt.next() >> 16) & 0xFFFF) / 65536.0f) < 0.002f) {
+      return true;
+    }
   }
+
   return false;
 }
 
diff --git a/src/Map.hh b/src/Map.hh
index e92081e4..28b44782 100644
--- a/src/Map.hh
+++ b/src/Map.hh
@@ -256,7 +256,7 @@ struct Map {
     void generate_shuffled_location_table(const Map::RandomEnemyLocationsHeader& header, StringReader r, uint16_t section);
   };
 
-  Map(uint32_t lobby_id, std::shared_ptr<PSOLFGEncryption> random_crypt);
+  Map(Version version, uint32_t lobby_id, std::shared_ptr<PSOLFGEncryption> random_crypt);
   ~Map() = default;
 
   void clear();
@@ -315,6 +315,7 @@ struct Map {
   static std::string disassemble_quest_data(const void* data, size_t size);
 
   PrefixedLogger log;
+  Version version;
   std::shared_ptr<PSOLFGEncryption> random_crypt;
   std::vector<Object> objects;
   std::vector<Enemy> enemies;