Remove stack, just use state machine

src/commit_request.cpp

@@ -75,23 +75,18 @@ void CommitRequest::on_begin_object(void *userdata) {
   if (ctx.parse_error)
     return;
 
-  if (ctx.state_stack.empty()) {
-    ctx.parse_error = "Unexpected object start - empty state stack";
-    return;
-  }
-
-  ParseState current_state = ctx.state_stack.top();
+  ParseState current_state = ctx.current_state;
 
   switch (current_state) {
   case ParseState::Root:
     // Expected - this is the main object
     break;
   case ParseState::PreconditionsArray:
-    ctx.state_stack.push(ParseState::PreconditionObject);
+    ctx.current_state = ParseState::PreconditionObject;
     ctx.current_precondition = PreconditionParseState{};
     break;
   case ParseState::OperationsArray:
-    ctx.state_stack.push(ParseState::OperationObject);
+    ctx.current_state = ParseState::OperationObject;
     ctx.current_operation = OperationParseState{};
     break;
   default:
@@ -104,15 +99,18 @@ void CommitRequest::on_end_object(void *userdata) {
   auto *self = static_cast<CommitRequest *>(userdata);
   auto &ctx = self->parser_context_;
 
-  if (ctx.parse_error || ctx.state_stack.empty()) {
-    if (!ctx.parse_error) {
-      ctx.parse_error = "Unexpected object end - empty state stack";
-    }
+  if (ctx.parse_error) {
     return;
   }
 
-  ParseState current_state = ctx.state_stack.top();
-  ctx.state_stack.pop();
+  ParseState current_state = ctx.current_state;
+  
+  // Handle state transitions on object end
+  if (current_state == ParseState::PreconditionObject) {
+    ctx.current_state = ParseState::PreconditionsArray;
+  } else if (current_state == ParseState::OperationObject) {
+    ctx.current_state = ParseState::OperationsArray;
+  }
 
   switch (current_state) {
   case ParseState::Root:
@@ -227,10 +225,10 @@ void CommitRequest::on_begin_array(void *userdata) {
 
   if (ctx.current_key == "preconditions") {
     ctx.current_key.clear();
-    ctx.state_stack.push(ParseState::PreconditionsArray);
+    ctx.current_state = ParseState::PreconditionsArray;
   } else if (ctx.current_key == "operations") {
     ctx.current_key.clear();
-    ctx.state_stack.push(ParseState::OperationsArray);
+    ctx.current_state = ParseState::OperationsArray;
   } else {
     ctx.parse_error = "Invalid array field - only 'preconditions' and "
                       "'operations' arrays are allowed";
@@ -241,14 +239,15 @@ void CommitRequest::on_end_array(void *userdata) {
   auto *self = static_cast<CommitRequest *>(userdata);
   auto &ctx = self->parser_context_;
 
-  if (ctx.parse_error || ctx.state_stack.empty()) {
-    if (!ctx.parse_error) {
-      ctx.parse_error = "Unexpected array end - empty state stack";
-    }
+  if (ctx.parse_error) {
     return;
   }
 
-  ctx.state_stack.pop();
+  // Transition back to Root state when arrays end
+  if (ctx.current_state == ParseState::PreconditionsArray || 
+      ctx.current_state == ParseState::OperationsArray) {
+    ctx.current_state = ParseState::Root;
+  }
 }
 
 void CommitRequest::on_number_data(void *userdata, const char *buf, int len,
@@ -285,12 +284,7 @@ void CommitRequest::on_null_literal(void *) {
 void CommitRequest::handle_completed_string(std::string_view s) {
   auto &ctx = parser_context_;
 
-  if (ctx.state_stack.empty()) {
-    ctx.parse_error = "String value received with empty state stack";
-    return;
-  }
-
-  ParseState current_state = ctx.state_stack.top();
+  ParseState current_state = ctx.current_state;
 
   switch (current_state) {
   case ParseState::Root:
@@ -363,12 +357,7 @@ void CommitRequest::handle_completed_string(std::string_view s) {
 void CommitRequest::handle_completed_number(std::string_view s) {
   auto &ctx = parser_context_;
 
-  if (ctx.state_stack.empty()) {
-    ctx.parse_error = "Number value received with empty state stack";
-    return;
-  }
-
-  ParseState current_state = ctx.state_stack.top();
+  ParseState current_state = ctx.current_state;
 
   switch (current_state) {
   case ParseState::Root:

src/commit_request.hpp

@@ -64,9 +64,6 @@ public:
   // Parser state
   enum class ParseState {
     Root,
-    RequestId,
-    LeaderId,
-    ReadVersion,
     PreconditionsArray,
     PreconditionObject,
     OperationsArray,
@@ -82,12 +79,9 @@ public:
   struct ParserContext {
     using ArenaString = std::basic_string<char, std::char_traits<char>,
                                           ArenaStlAllocator<char>>;
-    using ArenaStateStack =
-        std::stack<ParseState,
-                   std::vector<ParseState, ArenaStlAllocator<ParseState>>>;
     ArenaAllocator arena;
 
-    ArenaStateStack state_stack;
+    ParseState current_state = ParseState::Root;
     ArenaString current_key;
     ArenaString current_string;
     ArenaString current_number;
@@ -105,8 +99,7 @@ public:
 
     // Constructor to initialize arena-allocated containers
     explicit ParserContext()
-        : state_stack(ArenaStateStack::container_type(
-              ArenaStlAllocator<ParseState>(&arena))),
+        :
           current_key(ArenaStlAllocator<char>(&arena)),
           current_string(ArenaStlAllocator<char>(&arena)),
           current_number(ArenaStlAllocator<char>(&arena)),
@@ -122,8 +115,7 @@ public:
       current_operation = {};
       precondition_type = ArenaString{ArenaStlAllocator<char>(&arena)};
       operation_type = ArenaString{ArenaStlAllocator<char>(&arena)};
-      state_stack = ArenaStateStack{ArenaStateStack::container_type(
-          ArenaStlAllocator<ParseState>(&arena))};
+      current_state = ParseState::Root;
     }
   };
 
@@ -313,7 +305,7 @@ public:
       WeaselJsonParser_reset(json_parser_);
     }
     parser_context_.reset_arena_memory();
-    parser_context_.state_stack.push(ParseState::Root);
+    parser_context_.current_state = ParseState::Root;
     parser_context_.parse_error = nullptr;
     parser_context_.parse_complete = false;
   }