Allow specifying relative DFS index for focus command

Sources/AppBundle/command/impl/FocusCommand.swift

@@ -32,10 +32,23 @@
                     return io.err("Can't find window with ID \(windowId)")
                 }
             case .dfsIndex(let dfsIndex):
-                if let windowToFocus = target.workspace.rootTilingContainer.allLeafWindowsRecursive.getOrNil(atIndex: Int(dfsIndex)) {
+                guard let window = target.windowOrNil else {
+                    return io.err("Can't focus window by DFS index without a window")
+                }
+
+                let allWindows = target.workspace.rootTilingContainer.allLeafWindowsRecursive
+
+                guard let dfsAbsoluteIndex = switch dfsIndex {
+                    case .absolute(let index): index
+                    case .relative(let index): allWindows.firstIndex(of: window).map { $0 + index }
+                } else {
+                    return io.err("Can't find window in allLeafWindowsRecursive")
+                }
+
+                if let windowToFocus = allWindows.get(wrappingIndex: dfsAbsoluteIndex) {
                     return windowToFocus.focusWindow()
                 } else {
-                    return io.err("Can't find window with DFS index \(dfsIndex)")
+                    return io.err("Can't find window with DFS index \(dfsAbsoluteIndex)")
                 }
         }
     }

Sources/Common/cmdArgs/cmdArgsStringArrayEx.swift

@@ -7,6 +7,10 @@ extension [String] {
         first?.starts(with: "-") == true ? nil : nextOrNil()
     }
 
+    mutating func nextNonFullFlagOrNil() -> String? {
+        first?.starts(with: "--") == true ? nil : nextOrNil()
+    }
+
     mutating func allNextNonFlagArgs() -> [String] {
         var args: [String] = []
         while let nextArg = nextNonFlagOrNil() {

Sources/Common/cmdArgs/impl/FocusCmdArgs.swift

@@ -1,5 +1,6 @@
 private let boundar = "<boundary>"
 private let actio = "<action>"
+private let dfsinde = "<dfs index>"
 
 public struct FocusCmdArgs: CmdArgs {
     public let rawArgs: EquatableNoop<[String]>
@@ -13,14 +14,14 @@ public struct FocusCmdArgs: CmdArgs {
             "--boundaries": ArgParser(\.rawBoundaries, upcastArgParserFun(parseBoundaries)),
             "--boundaries-action": ArgParser(\.rawBoundariesAction, upcastArgParserFun(parseBoundariesAction)),
             "--window-id": ArgParser(\.windowId, upcastArgParserFun(parseArgWithUInt32)),
-            "--dfs-index": ArgParser(\.dfsIndex, upcastArgParserFun(parseArgWithUInt32)),
+            "--dfs-index": ArgParser(\.dfsIndex, upcastArgParserFun(parseDfsIndex)),
         ],
         arguments: [ArgParser(\.direction, upcastArgParserFun(parseCardinalDirectionArg))]
     )
 
     public var rawBoundaries: Boundaries? = nil // todo cover boundaries wrapping with tests
     public var rawBoundariesAction: WhenBoundariesCrossed? = nil
-    public var dfsIndex: UInt32? = nil
+    public var dfsIndex: DfsIndex? = nil
     public var direction: CardinalDirection? = nil
     public var floatingAsTiling: Bool = true
     public var windowId: UInt32?
@@ -36,7 +37,7 @@ public struct FocusCmdArgs: CmdArgs {
         self.windowId = windowId
     }
 
-    public init(rawArgs: [String], dfsIndex: UInt32) {
+    public init(rawArgs: [String], dfsIndex: DfsIndex) {
         self.rawArgs = .init(rawArgs)
         self.dfsIndex = dfsIndex
     }
@@ -55,7 +56,7 @@ public struct FocusCmdArgs: CmdArgs {
 public enum FocusCmdTarget {
     case direction(CardinalDirection)
     case windowId(UInt32)
-    case dfsIndex(UInt32)
+    case dfsIndex(DfsIndex)
 }
 
 public extension FocusCmdArgs {
@@ -109,3 +110,23 @@ private func parseBoundaries(arg: String, nextArgs: inout [String]) -> Parsed<Fo
         return .failure("\(boundar) is mandatory")
     }
 }
+
+private func parseDfsIndex(arg: String, nextArgs: inout [String]) -> Parsed<DfsIndex> {
+    guard let arg = nextArgs.nextNonFullFlagOrNil() else {
+        return .failure("\(dfsinde) is mandatory")
+    }
+
+    // Handle relative indices with + or - prefix
+    if arg.hasPrefix("+") || arg.hasPrefix("-") {
+        if let value = Int(arg) {
+            return .success(.relative(value))
+        }
+        return .failure("Invalid relative DFS index format")
+    }
+
+    // Handle absolute indices (no prefix)
+    if let value = Int(arg) {
+        return .success(.absolute(value))
+    }
+    return .failure("Invalid DFS index format")
+}

Sources/Common/model/dfsIndex.swift

@@ -0,0 +1,4 @@
+public enum DfsIndex: Equatable {
+    case absolute(Int)
+    case relative(Int)
+}