Add parsing for conditionals (cont.)

Signed-off-by: Marcel Müller <neikos@neikos.email>

src/eval/mod.rs

@@ -13,6 +13,11 @@ pub enum EvaluationError {
     UnknownVariable(NomoInput),
     /// An explicit abort was requested
     ExplicitAbort,
+    /** The instruction pointer overflowed
+     **
+     **  This is an internal error and is a bug that should be reported
+     */
+    InstructionPointerOverflow,
 }
 
 pub fn execute(
@@ -23,7 +28,14 @@ pub fn execute(
 
     let mut scopes: HashMap<crate::emit::VariableSlot, serde_json::Value> = HashMap::new();
 
-    for instr in instructions {
+    let mut ip = 0;
+    loop {
+        if ip >= instructions.len() {
+            break;
+        }
+
+        let instr = instructions.get(ip).unwrap();
+
         match instr {
             Instruction::AppendContent { content } => output.push_str(content),
             Instruction::LoadFromContextToSlot { name, slot } => {
@@ -40,7 +52,24 @@ pub fn execute(
             }
             Instruction::PushScope { inherit_parent: _ } => todo!(),
             Instruction::Abort => return Err(EvaluationError::ExplicitAbort),
+            Instruction::JumpIfNotTrue { emit_slot, jump } => {
+                let dont_jump = scopes.get(emit_slot).unwrap().as_bool().unwrap();
+                if dont_jump {
+                    // We are done
+                } else {
+                    let (new_ip, overflow) = ip.overflowing_add_signed(*jump);
+
+                    if overflow {
+                        return Err(EvaluationError::InstructionPointerOverflow);
+                    } else {
+                        ip = new_ip;
+                        continue;
+                    }
+                }
+            }
         }
+
+        ip += 1;
     }
 
     Ok(output)