From 6e9f1ae51734d583d949375a7c0fefd291b3c456 Mon Sep 17 00:00:00 2001
From: Alexander Batalov <alex.batalov@gmail.com>
Date: Sun, 3 Sep 2023 18:23:19 +0300
Subject: [PATCH] Add op_set_self

---
 src/interpreter_extra.cc | 23 +++++++++++++++++++++--
 src/scripts.cc           |  2 ++
 src/scripts.h            |  2 ++
 src/sfall_opcodes.cc     | 14 ++++++++++++++
 4 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/src/interpreter_extra.cc b/src/interpreter_extra.cc
index b2d3295..ca3e5e0 100644
--- a/src/interpreter_extra.cc
+++ b/src/interpreter_extra.cc
@@ -1580,12 +1580,22 @@ static void opPickup(Program* program)
         return;
     }
 
-    if (script->target == NULL) {
+    Object* self = script->target;
+
+    // SFALL: Override `self` via `op_set_self`.
+    // CE: Implementation is different. Sfall integrates via `scriptGetSid` by
+    // returning fake script with overridden `self` (and `target` in this case).
+    if (script->overriddenSelf != nullptr) {
+        self = script->overriddenSelf;
+        script->overriddenSelf = nullptr;
+    }
+
+    if (self == NULL) {
         scriptPredefinedError(program, "pickup_obj", SCRIPT_ERROR_OBJECT_IS_NULL);
         return;
     }
 
-    actionPickUp(script->target, object);
+    actionPickUp(self, object);
 }
 
 // drop_obj
@@ -4548,6 +4558,15 @@ static void opUseObjectOnObject(Program* program)
     }
 
     Object* self = scriptGetSelf(program);
+
+    // SFALL: Override `self` via `op_set_self`.
+    // CE: Implementation is different. Sfall integrates via `scriptGetSid` by
+    // returning fake script with overridden `self`.
+    if (script->overriddenSelf != nullptr) {
+        self = script->overriddenSelf;
+        script->overriddenSelf = nullptr;
+    }
+
     if (PID_TYPE(self->pid) == OBJ_TYPE_CRITTER) {
         _action_use_an_item_on_object(self, target, item);
     } else {
diff --git a/src/scripts.cc b/src/scripts.cc
index 58dab5d..1485fff 100644
--- a/src/scripts.cc
+++ b/src/scripts.cc
@@ -2214,6 +2214,8 @@ int scriptAdd(int* sidPtr, int scriptType)
         scr->procs[index] = SCRIPT_PROC_NO_PROC;
     }
 
+    scr->overriddenSelf = nullptr;
+
     scriptListExtent->length++;
 
     return 0;
diff --git a/src/scripts.h b/src/scripts.h
index 5cc3220..782591c 100644
--- a/src/scripts.h
+++ b/src/scripts.h
@@ -143,6 +143,8 @@ typedef struct Script {
     int field_D4;
     int field_D8;
     int field_DC;
+
+    Object* overriddenSelf;
 } Script;
 
 extern const char* gScriptProcNames[SCRIPT_PROC_COUNT];
diff --git a/src/sfall_opcodes.cc b/src/sfall_opcodes.cc
index d070539..d202c1b 100644
--- a/src/sfall_opcodes.cc
+++ b/src/sfall_opcodes.cc
@@ -345,6 +345,19 @@ static void op_set_proto_data(Program* program)
     *reinterpret_cast<int*>(reinterpret_cast<unsigned char*>(proto) + offset) = value;
 }
 
+// set_self
+static void op_set_self(Program* program)
+{
+    Object* obj = static_cast<Object*>(programStackPopPointer(program));
+
+    int sid = scriptGetSid(program);
+
+    Script* scr;
+    if (scriptGetScript(sid, &scr) == 0) {
+        scr->overriddenSelf = obj;
+    }
+}
+
 // list_begin
 static void opListBegin(Program* program)
 {
@@ -1055,6 +1068,7 @@ void sfallOpcodesInit()
     interpreterRegisterOpcode(0x81F5, op_get_script);
     interpreterRegisterOpcode(0x8204, op_get_proto_data);
     interpreterRegisterOpcode(0x8205, op_set_proto_data);
+    interpreterRegisterOpcode(0x8206, op_set_self);
     interpreterRegisterOpcode(0x820D, opListBegin);
     interpreterRegisterOpcode(0x820E, opListNext);
     interpreterRegisterOpcode(0x820F, opListEnd);