Implement 'blockchain.transaction.id_from_pos'

src/query.rs

@@ -406,6 +406,30 @@ impl Query {
         Ok((branch, pos))
     }
 
+    pub fn get_id_from_pos(
+        &self,
+        height: usize,
+        tx_pos: usize,
+        want_merkle: bool,
+    ) -> Result<(Sha256dHash, Vec<Sha256dHash>)> {
+        let header_entry = self
+            .app
+            .index()
+            .get_header(height)
+            .chain_err(|| format!("missing block #{}", height))?;
+
+        let txids = self.app.daemon().getblocktxids(&header_entry.hash())?;
+        let txid = *txids
+            .get(tx_pos)
+            .chain_err(|| format!("No tx in position #{} in block #{}", tx_pos, height))?;
+
+        if want_merkle {
+            let (branches, _root) = create_merkle_branch_and_root(txids, tx_pos);
+            return Ok((txid, branches));
+        }
+        return Ok((txid, [].to_vec()));
+    }
+
     pub fn broadcast(&self, txn: &Transaction) -> Result<Sha256dHash> {
         self.app.daemon().broadcast(txn)
     }

src/rpc.rs

@@ -33,6 +33,12 @@ fn usize_from_value(val: Option<&Value>, name: &str) -> Result<usize> {
     Ok(val as usize)
 }
 
+fn bool_from_value(val: Option<&Value>, name: &str) -> Result<bool> {
+    let val = val.chain_err(|| format!("missing {}", name))?;
+    let val = val.as_bool().chain_err(|| format!("not a bool {}", name))?;
+    Ok(val as bool)
+}
+
 fn unspent_from_status(status: &Status) -> Value {
     json!(Value::Array(
         status
@@ -283,6 +289,30 @@ impl Connection {
                 "pos": pos}))
     }
 
+    fn blockchain_transaction_id_from_pos(&self, params: &[Value]) -> Result<Value> {
+        let height = usize_from_value(params.get(0), "height")?;
+        let tx_pos = usize_from_value(params.get(1), "tx_pos")?;
+        let mut want_merkle = false;
+        if params.len() > 2 {
+            want_merkle = bool_from_value(params.get(2), "merkle")?;
+        }
+
+        let (txid, merkle) = self.query.get_id_from_pos(height, tx_pos, want_merkle)?;
+
+        if !want_merkle {
+            return Ok(json!(txid.be_hex_string()));
+        }
+
+        let merkle_vec: Vec<String> = merkle
+            .into_iter()
+            .map(|entry| entry.be_hex_string())
+            .collect();
+
+        Ok(json!({
+            "tx_id" : txid.be_hex_string(),
+            "merkle" : merkle_vec}))
+    }
+
     fn handle_command(&mut self, method: &str, params: &[Value], id: &Number) -> Result<Value> {
         let timer = self
             .stats
@@ -307,6 +337,9 @@ impl Connection {
             "blockchain.transaction.broadcast" => self.blockchain_transaction_broadcast(&params),
             "blockchain.transaction.get" => self.blockchain_transaction_get(&params),
             "blockchain.transaction.get_merkle" => self.blockchain_transaction_get_merkle(&params),
+            "blockchain.transaction.id_from_pos" => {
+                self.blockchain_transaction_id_from_pos(&params)
+            }
             "mempool.get_fee_histogram" => self.mempool_get_fee_histogram(),
             "server.banner" => self.server_banner(),
             "server.donation_address" => self.server_donation_address(),