feat!: Add Electrum protocol v1.6 method support

src/custom_serde.rs

@@ -19,23 +19,44 @@ where
     deserialize_hex(&hex_str).map_err(serde::de::Error::custom)
 }
 
-pub fn from_cancat_consensus_hex<'de, T, D>(deserializer: D) -> Result<Vec<T>, D::Error>
+/// Deserializes headers from either:
+/// - A single concatenated hex string (pre-1.6: `"hex"` field)
+/// - An array of individual hex strings (v1.6+: `"headers"` field)
+pub fn headers_from_hex_or_list<'de, T, D>(deserializer: D) -> Result<Vec<T>, D::Error>
 where
     T: bitcoin::consensus::encode::Decodable,
     D: Deserializer<'de>,
 {
-    let hex_str = String::deserialize(deserializer)?;
-    let data = Vec::<u8>::from_hex(&hex_str).map_err(serde::de::Error::custom)?;
-
-    let mut items = Vec::<T>::new();
-    let mut read_start = 0_usize;
-    while read_start < data.len() {
-        let (item, read_count) =
-            deserialize_partial::<T>(&data[read_start..]).map_err(serde::de::Error::custom)?;
-        read_start += read_count;
-        items.push(item);
+    let value = Value::deserialize(deserializer)?;
+    match value {
+        Value::String(hex_str) => {
+            // Pre-1.6: single concatenated hex string
+            let data = Vec::<u8>::from_hex(&hex_str).map_err(serde::de::Error::custom)?;
+            let mut items = Vec::<T>::new();
+            let mut read_start = 0_usize;
+            while read_start < data.len() {
+                let (item, read_count) = deserialize_partial::<T>(&data[read_start..])
+                    .map_err(serde::de::Error::custom)?;
+                read_start += read_count;
+                items.push(item);
+            }
+            Ok(items)
+        }
+        Value::Array(arr) => {
+            // v1.6: array of hex strings
+            arr.into_iter()
+                .map(|v| {
+                    let hex_str = v.as_str().ok_or_else(|| {
+                        serde::de::Error::custom("expected hex string in headers array")
+                    })?;
+                    deserialize_hex(hex_str).map_err(serde::de::Error::custom)
+                })
+                .collect()
+        }
+        _ => Err(serde::de::Error::custom(
+            "expected a hex string or array of hex strings for headers",
+        )),
     }
-    Ok(items)
 }
 
 pub fn feerate_opt_from_btc_per_kb<'de, D>(
@@ -137,3 +158,34 @@ where
     }
     Ok(Version)
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[derive(Deserialize)]
+    struct Wrapper {
+        #[serde(deserialize_with = "headers_from_hex_or_list")]
+        headers: Vec<bitcoin::block::Header>,
+    }
+
+    #[test]
+    fn headers_from_hex_or_list_accepts_both_formats() {
+        // Any 80 bytes parse as a Header structurally; the test just checks both paths agree.
+        let h0 = "00".repeat(80);
+        let h1 = "ff".repeat(80);
+
+        let concatenated: Wrapper =
+            serde_json::from_value(serde_json::json!({ "headers": format!("{h0}{h1}") })).unwrap();
+        let array: Wrapper =
+            serde_json::from_value(serde_json::json!({ "headers": [h0, h1] })).unwrap();
+
+        assert_eq!(concatenated.headers.len(), 2);
+        assert_eq!(concatenated.headers, array.headers);
+    }
+
+    #[test]
+    fn headers_from_hex_or_list_rejects_other_types() {
+        assert!(serde_json::from_value::<Wrapper>(serde_json::json!({ "headers": 42 })).is_err());
+    }
+}

src/pending_request.rs

@@ -97,11 +97,15 @@ gen_pending_request_types! {
     ScriptHashSubscribe,
     ScriptHashUnsubscribe,
     BroadcastTx,
+    BroadcastPackage,
     GetTx,
     GetTxMerkle,
     GetTxidFromPos,
     GetFeeHistogram,
+    GetMempoolInfo,
+    ServerVersion,
     Banner,
+    Features,
     Ping,
     Custom
 }

src/request.rs

@@ -235,17 +235,50 @@ impl Request for HeadersWithCheckpoint {
 /// fee rate (in BTC per kilobyte) required to be included within the specified number of blocks.
 ///
 /// See: <https://electrum-protocol.readthedocs.io/en/latest/protocol-methods.html#blockchain-estimatefee>
+/// The fee estimation mode passed to the server's `estimatesmartfee` RPC.
+///
+/// Added in Electrum protocol v1.6.
+///
+/// See: <https://electrum-protocol.readthedocs.io/en/latest/protocol-methods.html#blockchain-estimatefee>
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum EstimateFeeMode {
+    /// Conservative fee estimation (less likely to underestimate).
+    Conservative,
+    /// Economical fee estimation (may underestimate for faster inclusion).
+    Economical,
+}
+
+impl EstimateFeeMode {
+    fn as_str(&self) -> &'static str {
+        match self {
+            Self::Conservative => "CONSERVATIVE",
+            Self::Economical => "ECONOMICAL",
+        }
+    }
+}
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub struct EstimateFee {
     /// The number of blocks to target for confirmation.
     pub number: usize,
+
+    /// An optional estimation mode passed to the server's `estimatesmartfee` RPC.
+    ///
+    /// If `None`, the server uses its default mode.
+    ///
+    /// Added in Electrum protocol v1.6.
+    pub mode: Option<EstimateFeeMode>,
 }
 
 impl Request for EstimateFee {
     type Response = response::EstimateFeeResp;
 
     fn to_method_and_params(&self) -> MethodAndParams {
-        ("blockchain.estimatefee".into(), vec![self.number.into()])
+        let mut params: Vec<serde_json::Value> = vec![self.number.into()];
+        if let Some(mode) = &self.mode {
+            params.push(mode.as_str().into());
+        }
+        ("blockchain.estimatefee".into(), params)
     }
 }
 
@@ -271,6 +304,9 @@ impl Request for HeadersSubscribe {
 /// This corresponds to the `"server.relayfee"` Electrum RPC method. It returns the minimum
 /// fee rate (in BTC per kilobyte) that the server will accept for relaying transactions.
 ///
+/// Removed in Electrum protocol v1.6 — use [`GetMempoolInfo`] (`mempool.get_info`) when
+/// targeting v1.6+ servers.
+///
 /// See: <https://electrum-protocol.readthedocs.io/en/latest/protocol-methods.html#server-relayfee>
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub struct RelayFee;
@@ -589,6 +625,37 @@ impl Request for GetTxidFromPos {
     }
 }
 
+/// A request to broadcast a package of transactions to the network.
+///
+/// This corresponds to the `"blockchain.transaction.broadcast_package"` Electrum RPC method,
+/// which submits a package of related transactions (e.g., for CPFP or package relay).
+///
+/// Added in Electrum protocol v1.6.
+///
+/// See: <https://electrum-protocol.readthedocs.io/en/latest/protocol-methods.html#blockchain-transaction-broadcast-package>
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct BroadcastPackage(pub Vec<bitcoin::Transaction>);
+
+impl Request for BroadcastPackage {
+    type Response = response::BroadcastPackageResp;
+
+    fn to_method_and_params(&self) -> MethodAndParams {
+        let txs: Vec<serde_json::Value> = self
+            .0
+            .iter()
+            .map(|tx| {
+                let mut tx_bytes = Vec::<u8>::new();
+                tx.consensus_encode(&mut tx_bytes).expect("must encode");
+                tx_bytes.to_lower_hex_string().into()
+            })
+            .collect();
+        (
+            "blockchain.transaction.broadcast_package".into(),
+            vec![txs.into()],
+        )
+    }
+}
+
 /// A request for the current mempool fee histogram.
 ///
 /// This corresponds to the `"mempool.get_fee_histogram"` Electrum RPC method. It returns a compact
@@ -607,6 +674,61 @@ impl Request for GetFeeHistogram {
     }
 }
 
+/// A request to negotiate the protocol version with the Electrum server.
+///
+/// This corresponds to the `"server.version"` Electrum RPC method. It identifies the client and
+/// negotiates a compatible protocol version with the server. According to the Electrum protocol
+/// specification, this should be the first message sent after connecting.
+///
+/// The server will select the highest protocol version that both client and server support.
+///
+/// See: <https://electrum-protocol.readthedocs.io/en/latest/protocol-methods.html#server-version>
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct ServerVersion {
+    /// A string identifying the client software (e.g., `"electrum_streaming_client/0.5"`).
+    pub client_name: CowStr,
+
+    /// The protocol version or version range the client supports.
+    ///
+    /// Can be a single version string (e.g., `"1.6"`) or an array-style string for a range.
+    pub protocol_version: CowStr,
+}
+
+impl Request for ServerVersion {
+    type Response = response::ServerVersionResp;
+
+    fn to_method_and_params(&self) -> MethodAndParams {
+        (
+            "server.version".into(),
+            vec![
+                self.client_name.as_ref().into(),
+                self.protocol_version.as_ref().into(),
+            ],
+        )
+    }
+}
+
+/// A request for general mempool information from the Electrum server.
+///
+/// This corresponds to the `"mempool.get_info"` Electrum RPC method. It returns fee-related
+/// parameters including `mempoolminfee`, `minrelaytxfee`, and `incrementalrelayfee`.
+///
+/// This replaces the `blockchain.relayfee` method, which was removed in v1.6.
+///
+/// Added in Electrum protocol v1.6.
+///
+/// See: <https://electrum-protocol.readthedocs.io/en/latest/protocol-methods.html#mempool-get-info>
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct GetMempoolInfo;
+
+impl Request for GetMempoolInfo {
+    type Response = response::MempoolInfoResp;
+
+    fn to_method_and_params(&self) -> MethodAndParams {
+        ("mempool.get_info".into(), vec![])
+    }
+}
+
 /// A request for the Electrum server's banner message.
 ///
 /// This corresponds to the `"server.banner"` Electrum RPC method, which returns a server-defined

src/response.rs

@@ -14,6 +14,20 @@ use bitcoin::{
 
 use crate::DoubleSHA;
 
+/// Response to the `"server.version"` method.
+///
+/// Returns the server's software version and the negotiated protocol version.
+///
+/// See: <https://electrum-protocol.readthedocs.io/en/latest/protocol-methods.html#server-version>
+#[derive(Debug, Clone, serde::Deserialize)]
+pub struct ServerVersionResp {
+    /// The server's software version string.
+    pub server_software: String,
+
+    /// The negotiated protocol version string.
+    pub protocol_version: String,
+}
+
 /// Response to the `"blockchain.block.header"` method (without checkpoint).
 #[derive(Debug, Clone, serde::Deserialize, PartialEq, Eq)]
 #[serde(transparent)]
@@ -38,36 +52,44 @@ pub struct HeaderWithProofResp {
 }
 
 /// Response to the `"blockchain.block.headers"` method (without checkpoint).
+///
+/// Supports both the pre-1.6 format (concatenated hex in `"hex"` field) and the v1.6 format
+/// (array of hex strings in `"headers"` field).
 #[derive(Debug, Clone, serde::Deserialize)]
 pub struct HeadersResp {
     /// The number of headers returned.
     pub count: usize,
 
     /// The deserialized headers returned by the server.
     #[serde(
-        rename = "hex",
-        deserialize_with = "crate::custom_serde::from_cancat_consensus_hex"
+        alias = "hex",
+        alias = "headers",
+        deserialize_with = "crate::custom_serde::headers_from_hex_or_list"
     )]
     pub headers: Vec<bitcoin::block::Header>,
 
-    /// The server’s maximum allowed headers per request.
+    /// The server's maximum allowed headers per request.
     pub max: usize,
 }
 
 /// Response to the `"blockchain.block.headers"` method with a `cp_height` parameter.
+///
+/// Supports both the pre-1.6 format (concatenated hex in `"hex"` field) and the v1.6 format
+/// (array of hex strings in `"headers"` field).
 #[derive(Debug, Clone, serde::Deserialize)]
 pub struct HeadersWithCheckpointResp {
     /// The number of headers returned.
     pub count: usize,
 
     /// The deserialized headers returned by the server.
     #[serde(
-        rename = "hex",
-        deserialize_with = "crate::custom_serde::from_cancat_consensus_hex"
+        alias = "hex",
+        alias = "headers",
+        deserialize_with = "crate::custom_serde::headers_from_hex_or_list"
     )]
     pub headers: Vec<bitcoin::block::Header>,
 
-    /// The server’s maximum allowed headers per request.
+    /// The server's maximum allowed headers per request.
     pub max: usize,
 
     /// The Merkle root of all headers up to the checkpoint height.
@@ -281,6 +303,35 @@ pub struct FeePair {
     pub weight: bitcoin::Weight,
 }
 
+/// Response to the `"blockchain.transaction.broadcast_package"` method (non-verbose mode).
+///
+/// See: <https://electrum-protocol.readthedocs.io/en/latest/protocol-methods.html#blockchain-transaction-broadcast-package>
+#[derive(Debug, Clone, serde::Deserialize)]
+pub struct BroadcastPackageResp {
+    /// Whether the package was accepted by the server.
+    pub success: bool,
+}
+
+/// Response to the `"mempool.get_info"` method.
+///
+/// Provides fee-related information about the server's mempool. All fee rates are in BTC/kvB.
+///
+/// See: <https://electrum-protocol.readthedocs.io/en/latest/protocol-methods.html#mempool-get-info>
+#[derive(Debug, Clone, serde::Deserialize)]
+pub struct MempoolInfoResp {
+    /// The minimum fee rate (BTC/kvB) for a transaction to be accepted into the mempool.
+    #[serde(deserialize_with = "crate::custom_serde::feerate_opt_from_btc_per_kb")]
+    pub mempoolminfee: Option<bitcoin::FeeRate>,
+
+    /// The minimum relay fee rate (BTC/kvB).
+    #[serde(deserialize_with = "crate::custom_serde::feerate_opt_from_btc_per_kb")]
+    pub minrelaytxfee: Option<bitcoin::FeeRate>,
+
+    /// The incremental relay fee rate (BTC/kvB).
+    #[serde(deserialize_with = "crate::custom_serde::feerate_opt_from_btc_per_kb")]
+    pub incrementalrelayfee: Option<bitcoin::FeeRate>,
+}
+
 /// Response to the `"server.features"` method.
 #[derive(Debug, Clone, serde::Deserialize)]
 pub struct ServerFeatures {