reactivate headers.subscribe endpoint

src/index.rs

@@ -342,6 +342,11 @@ impl Index {
         *headers = read_indexed_headers(store);
     }
 
+    pub fn best_header(&self) -> Option<HeaderEntry> {
+        let headers = self.headers.read().unwrap();
+        headers.header_by_blockhash(&headers.tip()).cloned()
+    }
+
     pub fn get_header(&self, height: usize) -> Option<HeaderEntry> {
         self.headers
             .read()

src/query.rs

@@ -7,7 +7,7 @@ use crate::errors::*;
 use crate::index::{TxInRow, TxOutRow, TxRow};
 use crate::mempool::Tracker;
 use crate::store::ReadStore;
-use crate::util::HashPrefix;
+use crate::util::{HashPrefix, HeaderEntry};
 
 //
 // Output of a Transaction
@@ -246,6 +246,11 @@ impl Query {
         Ok(Status { confirmed, mempool })
     }
 
+    pub fn get_best_header(&self) -> Result<HeaderEntry> {
+        let last_header = self.app.index().best_header();
+        Ok(last_header.chain_err(|| "no headers indexed")?)
+    }
+
     pub fn update_mempool(&self) -> Result<()> {
         self.tracker.write().unwrap().update(self.app.daemon())
     }

src/rpc.rs

+use bitcoin::consensus::encode::serialize;
 use bitcoin_hashes::hex::{FromHex, ToHex};
 use bitcoin_hashes::sha256d::Hash as Sha256dHash;
 use error_chain::ChainedError;
@@ -60,6 +61,13 @@ impl Connection {
         ]))
     }
 
+    fn blockchain_headers_subscribe(&mut self) -> Result<Value> {
+        let entry = self.query.get_best_header()?;
+        let hex_header = hex::encode(serialize(entry.header()));
+        let result = json!({"hex": hex_header, "height": entry.height()});
+        Ok(result)
+    }
+
     fn blockchain_scripthash_get_balance(&self, _params: &[Value]) -> Result<Value> {
         Ok(
             json!({ "confirmed": null, "unconfirmed": null }),
@@ -80,6 +88,7 @@ impl Connection {
 
     fn handle_command(&mut self, method: &str, params: &[Value], id: &Value) -> Result<Value> {
         let result = match method {
+            "blockchain.headers.subscribe" => self.blockchain_headers_subscribe(),
             "blockchain.scripthash.get_balance" => self.blockchain_scripthash_get_balance(&params),
             "blockchain.scripthash.get_history" => self.blockchain_scripthash_get_history(&params),
             "server.ping" => Ok(Value::Null),