Adds an unused lockbox_input_value() fn for checking the expected i…

…nput value by a certain block height.

zebra-consensus/src/block/subsidy/general.rs

@@ -7,7 +7,10 @@ use std::collections::HashSet;
 use zebra_chain::{
     amount::{Amount, Error, NonNegative},
     block::{Height, HeightDiff},
-    parameters::{Network, NetworkUpgrade::*},
+    parameters::{
+        Network,
+        NetworkUpgrade::{self, *},
+    },
     transaction::Transaction,
 };
 
@@ -108,6 +111,43 @@ pub fn miner_subsidy(height: Height, network: &Network) -> Result<Amount<NonNega
     block_subsidy(height, network)? - total_funding_stream_amount?
 }
 
+/// Lockbox funding stream total input value for a block height.
+///
+/// Assumes a constant funding stream amount per block.
+// TODO: Cache the lockbox value balance in zebra-state (will be required for tracking lockbox
+//       value balance after ZSF ZIPs or after a ZIP for spending from the deferred pool)
+#[allow(dead_code)]
+fn lockbox_input_value(network: &Network, height: Height) -> Amount<NonNegative> {
+    let Some(nu5_activation_height) = NetworkUpgrade::Nu5.activation_height(network) else {
+        return Amount::zero();
+    };
+
+    // TODO: Use NU6 directly once it's been added.
+    let Some(nu6_activation_height) = NetworkUpgrade::Nu5
+        .next_upgrade()
+        .and_then(|nu6| nu6.activation_height(network))
+    else {
+        return Amount::zero();
+    };
+
+    let &deferred_amount_per_block = funding_stream_values(nu6_activation_height, network)
+        .expect("we always expect a funding stream hashmap response even if empty")
+        .get(&FundingStreamReceiver::Deferred)
+        .expect("we expect a lockbox funding stream after NU5");
+
+    let funding_stream_height_range = FUNDING_STREAM_HEIGHT_RANGES
+        .get(&network.kind())
+        .expect("must have funding stream height range on all networks");
+
+    let num_blocks_with_lockbox_output =
+        height.min(funding_stream_height_range.end) - nu5_activation_height;
+
+    (deferred_amount_per_block
+        * u64::try_from(num_blocks_with_lockbox_output)
+            .expect("num blocks with lockbox funding stream should fit in u64"))
+    .expect("lockbox input value should fit in Amount")
+}
+
 /// Returns all output amounts in `Transaction`.
 pub fn output_amounts(transaction: &Transaction) -> HashSet<Amount<NonNegative>> {
     transaction