Adds `with_sapling_hrps()` method and uses it to set the Regtest HRPs in `new_regtest()`.

Adds a test for Sapling HRP validation

zebra-chain/src/parameters/network/testnet.rs

@@ -24,6 +24,9 @@ pub const RESERVED_NETWORK_NAMES: [&str; 6] = [
 /// Maximum length for a configured network name.
 pub const MAX_NETWORK_NAME_LENGTH: usize = 30;
 
+/// Maximum length for a configured human-readable prefix.
+pub const MAX_HRP_LENGTH: usize = 30;
+
 /// Configurable activation heights for Regtest and configured Testnets.
 #[derive(Deserialize, Default)]
 #[serde(rename_all = "PascalCase")]
@@ -103,6 +106,44 @@ impl ParametersBuilder {
         self
     }
 
+    /// Checks that the provided Sapling human-readable prefixes (HRPs) are valid and unique, then
+    /// sets the Sapling HRPs to be used in the [`Parameters`] being built.
+    pub fn with_sapling_hrps(
+        mut self,
+        hrp_sapling_extended_spending_key: impl fmt::Display,
+        hrp_sapling_extended_full_viewing_key: impl fmt::Display,
+        hrp_sapling_payment_address: impl fmt::Display,
+    ) -> Self {
+        self.hrp_sapling_extended_spending_key = hrp_sapling_extended_spending_key.to_string();
+        self.hrp_sapling_extended_full_viewing_key =
+            hrp_sapling_extended_full_viewing_key.to_string();
+        self.hrp_sapling_payment_address = hrp_sapling_payment_address.to_string();
+
+        let sapling_hrps = [
+            &self.hrp_sapling_extended_spending_key,
+            &self.hrp_sapling_extended_full_viewing_key,
+            &self.hrp_sapling_payment_address,
+        ];
+
+        for sapling_hrp in sapling_hrps {
+            assert!(sapling_hrp.len() <= MAX_HRP_LENGTH, "Sapling human-readable prefix {sapling_hrp} is too long, must be {MAX_HRP_LENGTH} characters or less");
+            assert!(
+                sapling_hrp.chars().all(|c| c.is_ascii_lowercase() || c == '-'),
+                "human-readable prefixes should contain only lowercase ASCII characters and dashes, hrp: {sapling_hrp}"
+            );
+            assert_eq!(
+                sapling_hrps
+                    .iter()
+                    .filter(|&&hrp| hrp == sapling_hrp)
+                    .count(),
+                1,
+                "Sapling human-readable prefixes must be unique, repeated Sapling HRP: {sapling_hrp}"
+            );
+        }
+
+        self
+    }
+
     /// Checks that the provided network upgrade activation heights are in the correct order, then
     /// sets them as the new network upgrade activation heights.
     pub fn with_activation_heights(
@@ -233,7 +274,13 @@ impl Parameters {
         Self {
             network_name: "Regtest".to_string(),
             ..Self::build()
-                // Removes default Testnet activation heights, most network upgrades are disabled by default for Regtest
+                .with_sapling_hrps(
+                    zp_constants::regtest::HRP_SAPLING_EXTENDED_SPENDING_KEY,
+                    zp_constants::regtest::HRP_SAPLING_EXTENDED_FULL_VIEWING_KEY,
+                    zp_constants::regtest::HRP_SAPLING_PAYMENT_ADDRESS,
+                )
+                // Removes default Testnet activation heights if not configured,
+                // most network upgrades are disabled by default for Regtest in zcashd
                 .with_activation_heights(activation_heights)
                 .finish()
         }

zebra-chain/src/parameters/network/tests/vectors.rs

@@ -151,7 +151,7 @@ fn activates_network_upgrades_correctly() {
 
 /// Checks that configured testnet names are validated and used correctly.
 #[test]
-fn check_network_name() {
+fn check_configured_network_name() {
     // Sets a no-op panic hook to avoid long output.
     std::panic::set_hook(Box::new(|_| {}));
 
@@ -206,3 +206,64 @@ fn check_network_name() {
         "network must be displayed as configured network name"
     );
 }
+
+/// Checks that configured Sapling human-readable prefixes (HRPs) are validated and used correctly.
+#[test]
+fn check_configured_sapling_hrps() {
+    // Sets a no-op panic hook to avoid long output.
+    std::panic::set_hook(Box::new(|_| {}));
+
+    // Check that configured Sapling HRPs must be unique.
+    std::panic::catch_unwind(|| {
+        testnet::Parameters::build().with_sapling_hrps("", "", "");
+    })
+    .expect_err("should panic when setting non-unique Sapling HRPs");
+
+    // Check that max length is enforced, and that network names may only contain lowecase ASCII characters and dashes.
+    for invalid_hrp in [
+        "a".repeat(MAX_NETWORK_NAME_LENGTH + 1),
+        "!!!!non-alphabetical-name".to_string(),
+        "A".to_string(),
+    ] {
+        std::panic::catch_unwind(|| {
+            testnet::Parameters::build().with_sapling_hrps(invalid_hrp, "dummy-hrp-a", "dummy-hrp-b");
+        })
+        .expect_err("should panic when setting Sapling HRPs that are too long or contain non-alphanumeric characters (except '-')");
+    }
+
+    // Check that Sapling HRPs can contain lowercase ascii characters and dashes.
+    let expected_hrp_sapling_extended_spending_key = "sapling-hrp-a";
+    let expected_hrp_sapling_extended_full_viewing_key = "sapling-hrp-b";
+    let expected_hrp_sapling_payment_address = "sapling-hrp-c";
+
+    let network = testnet::Parameters::build()
+        // Check that Sapling HRPs can contain `MAX_NETWORK_NAME_LENGTH` characters
+        .with_sapling_hrps(
+            "a".repeat(MAX_NETWORK_NAME_LENGTH),
+            "dummy-hrp-a",
+            "dummy-hrp-b",
+        )
+        .with_sapling_hrps(
+            expected_hrp_sapling_extended_spending_key,
+            expected_hrp_sapling_extended_full_viewing_key,
+            expected_hrp_sapling_payment_address,
+        )
+        .to_network();
+
+    // Check that configured Sapling HRPs are returned by `Parameters` trait methods
+    assert_eq!(
+        network.hrp_sapling_extended_spending_key(),
+        expected_hrp_sapling_extended_spending_key,
+        "should return expected Sapling extended spending key HRP"
+    );
+    assert_eq!(
+        network.hrp_sapling_extended_full_viewing_key(),
+        expected_hrp_sapling_extended_full_viewing_key,
+        "should return expected Sapling EFVK HRP"
+    );
+    assert_eq!(
+        network.hrp_sapling_payment_address(),
+        expected_hrp_sapling_payment_address,
+        "should return expected Sapling payment address HRP"
+    );
+}