add validity window checks on privacy preserving transactions

test_program_methods/guest/src/bin/validity_window.rs

@@ -0,0 +1,36 @@
+use nssa_core::program::{
+    AccountPostState, BlockId, ProgramInput, ProgramOutput, read_nssa_inputs,
+};
+
+type Instruction = (Option<BlockId>, Option<BlockId>);
+
+fn main() {
+    let (
+        ProgramInput {
+            pre_states,
+            instruction: (from_id, until_id),
+        },
+        instruction_words,
+    ) = read_nssa_inputs::<Instruction>();
+
+    let Ok([pre]) = <[_; 1]>::try_from(pre_states) else {
+        return;
+    };
+
+    let post = pre.account.clone();
+
+    let mut output = ProgramOutput::new(
+        instruction_words,
+        vec![pre],
+        vec![AccountPostState::new(post)],
+    );
+
+    if let Some(id) = from_id {
+        output = output.valid_from_id(id);
+    }
+    if let Some(id) = until_id {
+        output = output.valid_until_id(id);
+    }
+
+    output.write();
+}