Add NetworkKind

Add a new type `NetworkKind` the describes the kind of network we are
on, ether mainnet or one of the test nets (testnet, regtest, signet).

Do not use the type yet.

bitcoin/src/lib.rs

@@ -129,7 +129,7 @@ pub use crate::{
     crypto::key::{self, PrivateKey, PubkeyHash, PublicKey, CompressedPublicKey, WPubkeyHash, XOnlyPublicKey},
     crypto::sighash::{self, LegacySighash, SegwitV0Sighash, TapSighash, TapSighashTag},
     merkle_tree::MerkleBlock,
-    network::Network,
+    network::{Network, NetworkKind},
     pow::{CompactTarget, Target, Work},
     psbt::Psbt,
     sighash::{EcdsaSighashType, TapSighashType},

bitcoin/src/network.rs

@@ -31,6 +31,33 @@ use crate::constants::ChainHash;
 use crate::p2p::Magic;
 use crate::prelude::{String, ToOwned};
 
+/// What kind of network we are on.
+#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub enum NetworkKind {
+    /// The Bitcoin mainnet network.
+    Main,
+    /// Some kind of testnet network.
+    Test,
+}
+
+// We explicitly do not provide `is_testnet`, using `!network.is_mainnet()` is less
+// ambiguous due to confusion caused by signet/testnet/regtest.
+impl NetworkKind {
+    /// Returns true if this is real mainnet bitcoin.
+    pub fn is_mainnet(&self) -> bool { *self == NetworkKind::Main }
+}
+
+impl From<Network> for NetworkKind {
+    fn from(n: Network) -> Self {
+        use Network::*;
+
+        match n {
+            Bitcoin => NetworkKind::Main,
+            Testnet | Signet | Regtest => NetworkKind::Test,
+        }
+    }
+}
+
 /// The cryptocurrency network to act on.
 #[derive(Copy, PartialEq, Eq, PartialOrd, Ord, Clone, Hash, Debug)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]