DRAFT: add unstreamedETHForNoun

packages/nouns-contracts/contracts/StreamEscrow.sol

@@ -245,6 +245,22 @@ contract StreamEscrow is IStreamEscrow {
         return !streams[nounId].canceled && streams[nounId].lastTick > currentTick;
     }
 
+    /**
+     * @notice Returns the amount of ETH that was not yet streamed for a specific Noun token.
+     * Returns zero for inactive streams.
+     * @param nounId The ID of the Noun token to check the stream for.
+     */
+    function unstreamedETHForNoun(uint256 nounId) public view returns (uint256) {
+        Stream memory stream = streams[nounId];
+        uint32 currentTick_ = currentTick;
+        if (!isStreamActive(stream, currentTick_)) {
+            return 0;
+        }
+
+        uint256 ticksLeft = stream.lastTick - currentTick_;
+        return ticksLeft * stream.ethPerTick;
+    }
+
     function isStreamActive(Stream memory stream, uint32 tick) internal pure returns (bool) {
         return !stream.canceled && stream.lastTick > tick;
     }

packages/nouns-contracts/test/foundry/StreamEscrow.t.sol

@@ -717,6 +717,65 @@ contract RescueTokensTest is BaseStreamEscrowTest {
     }
 }
 
+contract UnstreamedETHTest is BaseStreamEscrowTest {
+    function test_unstreamedETHForNoun() public {
+        vm.prank(streamCreator);
+        escrow.forwardAllAndCreateStream{ value: 1 ether }({ nounId: 1, streamLengthInTicks: 20 });
+
+        // 1 ether / 20 = 0.05 eth per tick
+        assertEq(escrow.unstreamedETHForNoun(1), 1 ether);
+
+        // forward 5 ticks
+        for (uint i; i < 5; i++) {
+            forwardOneDay();
+        }
+        // check unstreamed eth
+        assertEq(escrow.unstreamedETHForNoun(1), 0.75 ether);
+
+        // forward 15 more ticks
+        for (uint i; i < 15; i++) {
+            forwardOneDay();
+        }
+        // check unstreamed eth
+        assertEq(escrow.unstreamedETHForNoun(1), 0 ether);
+    }
+
+    function test_unstreamedETHForNoun_canceledStream() public {
+        vm.prank(streamCreator);
+        escrow.forwardAllAndCreateStream{ value: 1 ether }({ nounId: 1, streamLengthInTicks: 20 });
+
+        // 1 ether / 20 = 0.05 eth per tick
+        assertEq(escrow.unstreamedETHForNoun(1), 1 ether);
+
+        // forward 5 ticks
+        for (uint i; i < 5; i++) {
+            forwardOneDay();
+        }
+        // check unstreamed eth
+        assertEq(escrow.unstreamedETHForNoun(1), 0.75 ether);
+
+        // cancel stream
+        vm.prank(streamCreator);
+        nounsToken.approve(address(escrow), 1);
+        vm.prank(streamCreator);
+        escrow.cancelStream(1);
+
+        // check unstreamed eth is zero
+        assertEq(escrow.unstreamedETHForNoun(1), 0 ether);
+    }
+
+    function test_unstreamedETHForNoun_returnsZeroForNonExistentStream() public {
+        assertEq(escrow.unstreamedETHForNoun(1), 0 ether);
+
+        // forward 5 ticks
+        for (uint i; i < 5; i++) {
+            forwardOneDay();
+        }
+
+        assertEq(escrow.unstreamedETHForNoun(3), 0 ether);
+    }
+}
+
 contract StreamEscrowGasTest is BaseStreamEscrowTest {
     function setUp() public virtual override {
         super.setUp();