fix(lightning): closed channel short channel ID

Bitkit/Extensions/ShortChannelId.swift

@@ -11,3 +11,28 @@ extension UInt64 {
         return "\(blockHeight)x\(txIndex)x\(outputIndex)"
     }
 }
+
+/// Whether the string is a Core Lightning `block x tx x output` short channel id (e.g. `792906x599x1`):
+/// exactly three non-empty, all-digit components separated by `x`.
+private func isClnShortChannelId(_ value: String) -> Bool {
+    let parts = value.split(separator: "x", omittingEmptySubsequences: false)
+    return parts.count == 3 && parts.allSatisfy { !$0.isEmpty && $0.allSatisfy { $0.isASCII && $0.isNumber } }
+}
+
+/// Resolves the short channel id to display, formatted as `block x tx x output`. Uses the channel's
+/// own scid (open channels, a numeric BOLT scid) and, for closed channels which carry none, the scid
+/// from the confidently-linked Blocktank order. Blocktank delivers it already in `block x tx x output`
+/// form, so an `x`-formatted value is kept as-is and only a numeric value is decoded. Nil when unavailable.
+func resolveDisplayShortChannelId(channelScid: UInt64?, linkedOrderScid: String?) -> String? {
+    if let channelScid {
+        return channelScid.formattedAsShortChannelId
+    }
+
+    guard let orderScid = linkedOrderScid, !orderScid.isEmpty else { return nil }
+
+    if let numeric = UInt64(orderScid) {
+        return numeric.formattedAsShortChannelId
+    }
+
+    return isClnShortChannelId(orderScid) ? orderScid : nil
+}

Bitkit/ViewModels/ChannelDetailsViewModel.swift

@@ -76,13 +76,8 @@ class ChannelDetailsViewModel: ObservableObject {
     /// scid (open channels) and, for closed channels (which are not stored with one), the scid from
     /// a confidently linked Blocktank order. Hidden otherwise rather than showing a guessed value.
     var displayShortChannelId: String? {
-        if let scid = foundChannel?.shortChannelIdValue {
-            return scid.formattedAsShortChannelId
-        }
-        if isLinkedOrderConfident, let scidString = linkedOrder?.channel?.shortChannelId, let scid = UInt64(scidString) {
-            return scid.formattedAsShortChannelId
-        }
-        return nil
+        let linkedOrderScid = isLinkedOrderConfident ? linkedOrder?.channel?.shortChannelId : nil
+        return resolveDisplayShortChannelId(channelScid: foundChannel?.shortChannelIdValue, linkedOrderScid: linkedOrderScid)
     }
 
     /// Find a channel by ID, checking open channels, pending channels, pending orders, then closed channels

BitkitTests/ChannelDetailsViewModelTests.swift

@@ -48,6 +48,20 @@ final class ChannelDetailsViewModelTests: XCTestCase {
         XCTAssertEqual(vm.displayShortChannelId, "777477x916x0")
     }
 
+    @MainActor
+    func testDisplayShortChannelIdKeepsClnFormLinkedOrderScidForClosedChannel() {
+        let vm = ChannelDetailsViewModel.shared
+        // Blocktank delivers the order scid already in `block x tx x output` form; it is kept as-is.
+        vm.foundChannel = makeClosedChannel(fundingTxoTxid: "fundingtxid")
+        var channel = IBtChannel.mock()
+        channel.fundingTx = FundingTx(id: "fundingtxid", vout: 0)
+        channel.shortChannelId = "792906x599x1"
+        vm.linkedOrder = IBtOrder.mock(channel: channel)
+        defer { resetDisplayState(vm) }
+
+        XCTAssertEqual(vm.displayShortChannelId, "792906x599x1")
+    }
+
     @MainActor
     func testDisplayIgnoresWeaklyLinkedOrder() {
         let vm = ChannelDetailsViewModel.shared

BitkitTests/ShortChannelIdTests.swift

@@ -21,4 +21,30 @@ final class ShortChannelIdTests: XCTestCase {
         let scid = (UInt64(0xFFFFFF) << 40) | (UInt64(0xFFFFFF) << 16) | UInt64(0xFFFF)
         XCTAssertEqual(scid.formattedAsShortChannelId, "16777215x16777215x65535")
     }
+
+    func testResolveDisplayShortChannelIdDecodesOpenChannelScid() {
+        XCTAssertEqual(resolveDisplayShortChannelId(channelScid: 854_845_001_888_432_128, linkedOrderScid: nil), "777477x916x0")
+    }
+
+    func testResolveDisplayShortChannelIdKeepsClnFormLinkedOrderScidForClosedChannel() {
+        // Blocktank delivers the order scid already in `block x tx x output` form.
+        XCTAssertEqual(resolveDisplayShortChannelId(channelScid: nil, linkedOrderScid: "792906x599x1"), "792906x599x1")
+    }
+
+    func testResolveDisplayShortChannelIdDecodesNumericLinkedOrderScid() {
+        XCTAssertEqual(resolveDisplayShortChannelId(channelScid: nil, linkedOrderScid: "854845001888432128"), "777477x916x0")
+    }
+
+    func testResolveDisplayShortChannelIdReturnsNilWhenBothUnavailable() {
+        XCTAssertNil(resolveDisplayShortChannelId(channelScid: nil, linkedOrderScid: nil))
+        XCTAssertNil(resolveDisplayShortChannelId(channelScid: nil, linkedOrderScid: ""))
+    }
+
+    func testResolveDisplayShortChannelIdReturnsNilForMalformedOrderScid() {
+        XCTAssertNil(resolveDisplayShortChannelId(channelScid: nil, linkedOrderScid: "not-a-scid"))
+        XCTAssertNil(resolveDisplayShortChannelId(channelScid: nil, linkedOrderScid: "792906x599"))
+        XCTAssertNil(resolveDisplayShortChannelId(channelScid: nil, linkedOrderScid: "792906xx1"))
+        // Non-ASCII numeric glyphs (e.g. superscripts) are not valid scid digits.
+        XCTAssertNil(resolveDisplayShortChannelId(channelScid: nil, linkedOrderScid: "²x³x¹"))
+    }
 }