From f92ffcecbdbf46b6570ae4aa945d60b5d3b5d211 Mon Sep 17 00:00:00 2001
From: cpunch <sethtstubbs@gmail.com>
Date: Sat, 20 Feb 2021 12:42:13 -0600
Subject: [PATCH] Added '__equal' metamethod, slightly refactored cosmoO_equal

- ISTRING_EQUAL has been added
---
 src/cobj.c   | 35 +++++++++++++++++++++++++++++++----
 src/cstate.c |  1 +
 src/cstate.h |  1 +
 3 files changed, 33 insertions(+), 4 deletions(-)

diff --git a/src/cobj.c b/src/cobj.c
index 95550c5..1b4fcfc 100644
--- a/src/cobj.c
+++ b/src/cobj.c
@@ -35,7 +35,7 @@ CObj *cosmoO_allocateBase(CState *state, size_t sz, CObjType type) {
     return obj;
 }
 
-void cosmoO_free(CState *state, CObj* obj) {
+void cosmoO_free(CState *state, CObj *obj) {
 #ifdef GC_DEBUG
     printf("freeing %p [", obj);
     printObject(obj);
@@ -95,10 +95,14 @@ void cosmoO_free(CState *state, CObj* obj) {
     }
 }
 
-bool cosmoO_equal(CState *state, CObj* obj1, CObj* obj2) {
-    if (obj1 == obj2) // its the same object, this compares strings for us since they're interned anyways :)
+bool cosmoO_equal(CState *state, CObj *obj1, CObj *obj2) {
+    CObjObject *proto1, *proto2;
+    CValue eq1, eq2;
+
+    if (obj1 == obj2) // its the same reference, this compares strings for us since they're interned anyways :)
         return true;
 
+    // its not the same type, maybe both <ref>'s have the same '__equal' metamethod in their protos?
     if (obj1->type != obj2->type)
         goto _eqFail;
 
@@ -130,7 +134,30 @@ bool cosmoO_equal(CState *state, CObj* obj1, CObj* obj2) {
     }
 
 _eqFail:
-    // TODO: add support for an '__equal' metamethod
+    // this is pretty expensive (bad lookup caching helps a lot), but it only all gets run if both objects have protos & both have the `__equal` metamethod defined so...
+    // it should stay light for the majority of cases
+    if ((proto1 = cosmoO_grabProto(obj1)) != NULL && (proto2 = cosmoO_grabProto(obj2)) != NULL && // make sure both protos exist
+        cosmoO_getIString(state, proto1, ISTRING_EQUAL, &eq1) && // grab the `__equal` metamethod from the first proto, if fail abort
+        cosmoO_getIString(state, proto2, ISTRING_EQUAL, &eq2) && // grab the `__equal` metamethod from the second proto, if fail abort
+        cosmoV_equal(state, eq1, eq2)) { // compare the two `__equal` metamethods
+
+        // now finally, call the `__equal` metamethod (<object>, <object>)
+        cosmoV_pushValue(state, eq1);
+        cosmoV_pushRef(state, obj1);
+        cosmoV_pushRef(state, obj2);
+        if (cosmoV_call(state, 2, 1) != COSMOVM_OK)
+            return false;
+
+        // check return value and make sure it's a boolean
+        if (!IS_BOOLEAN(*cosmoV_getTop(state, 0))) {
+            cosmoV_error(state, "__equal expected to return <boolean>, got %s!", cosmoV_typeStr(*cosmoV_pop(state)));
+            return false;
+        }
+
+        // return the result
+        return cosmoV_readBoolean(*cosmoV_pop(state));
+    }
+
     return false;
 }
 
diff --git a/src/cstate.c b/src/cstate.c
index 5f60be2..ebbfbc6 100644
--- a/src/cstate.c
+++ b/src/cstate.c
@@ -50,6 +50,7 @@ CState *cosmoV_newState() {
     state->iStrings[ISTRING_TOSTRING] = cosmoO_copyString(state, "__tostring", 10);
     state->iStrings[ISTRING_TONUMBER] = cosmoO_copyString(state, "__tonumber", 10);
     state->iStrings[ISTRING_INDEX] = cosmoO_copyString(state, "__index", 7);
+    state->iStrings[ISTRING_EQUAL] = cosmoO_copyString(state, "__equal", 7);
     state->iStrings[ISTRING_NEWINDEX] = cosmoO_copyString(state, "__newindex", 10);
     state->iStrings[ISTRING_COUNT] = cosmoO_copyString(state, "__count", 7);
 
diff --git a/src/cstate.h b/src/cstate.h
index 353a066..a2f71ac 100644
--- a/src/cstate.h
+++ b/src/cstate.h
@@ -16,6 +16,7 @@ typedef enum IStringEnum {
     ISTRING_INIT,       // __init
     ISTRING_TOSTRING,   // __tostring
     ISTRING_TONUMBER,   // __tonumber
+    ISTRING_EQUAL,      // __equals
     ISTRING_INDEX,      // __index
     ISTRING_NEWINDEX,   // __newindex
     ISTRING_COUNT,      // __count