fix: get app_hash at proof_height instead of latest

[dangush]

Closes #58

Instead of getting the latest app hash, I extract the app_hash from the primary_block which was queried and used during proof generation.

Should be a simple change, but I'm not familiar with the library so not sure if there's something I missed.

[hu55a1n1]

This is the main change for the fix right @dangush?

[hu55a1n1]

I just confirmed that this is indeed the root cause of the bug we were seeing yesterday by adding this sleep before we get the status (and latest app hash) ->

$ git diff src/main.rs
diff --git a/utils/tm-prover/src/main.rs b/utils/tm-prover/src/main.rs
index 1225048..738d709 100644
--- a/utils/tm-prover/src/main.rs
+++ b/utils/tm-prover/src/main.rs
@@ -228,6 +228,9 @@ async fn main() -> Result<()> {
     )
     .await?;
 
+    let ten_secs = std::time::Duration::from_secs(10);
+    std::thread::sleep(ten_secs);
+
     let status = client.status().await?;
     let latest_app_hash = status.sync_info.latest_app_hash;

The old code (without the fix in this PR) always fails. Also just confirmed that the fix works even with this delay.
Only thing left to verify is that the verifier side can succesfully check the proof.json.

[hu55a1n1]

So the verifier was failing with this change. I solved this in a slightly different way by avoiding the extra status call altoghether ->

diff --git a/utils/tm-prover/src/main.rs b/utils/tm-prover/src/main.rs
index 1225048..d9fb05e 100644
--- a/utils/tm-prover/src/main.rs
+++ b/utils/tm-prover/src/main.rs
@@ -187,6 +187,7 @@ async fn main() -> Result<()> {
 
     let status = client.status().await?;
     let latest_height = status.sync_info.latest_block_height;
+    let latest_app_hash = status.sync_info.latest_app_hash;
 
     // `proof_height` is the height at which we want to query the blockchain's state
     // This is one less than than the `latest_height` because we want to verify the merkle-proof for
@@ -228,9 +229,6 @@ async fn main() -> Result<()> {
     )
     .await?;
 
-    let status = client.status().await?;
-    let latest_app_hash = status.sync_info.latest_app_hash;
-
     let path = WASM_STORE_KEY.to_owned();
     let data = CwAbciKey::new(args.contract_address, args.storage_key, None);

Will push soon. 🙏