Implement dependency wrapping & version spec

Sources/apk/Common/ApkVersionSpecification.swift

@@ -0,0 +1,46 @@
+// SPDX-License-Identifier: Apache-2.0
+
+enum ApkVersionSpecification: Equatable {
+  case any
+  case constraint(op: Operator, version: String)
+  case conflict
+}
+
+extension ApkVersionSpecification: CustomStringConvertible {
+  var description: String {
+    switch self {
+    case .any: ""
+    case .conflict: "!"
+    case .constraint(let op, let version): "\(op)\(version)"
+    }
+  }
+}
+
+extension ApkVersionSpecification {
+  enum Operator: Equatable {
+    case equals
+    case fuzzyEquals
+    case greater
+    case less
+    case greaterEqual
+    case lessEqual
+    case greaterFuzzy
+    case lessFuzzy
+  }
+}
+
+extension ApkVersionSpecification.Operator: CustomStringConvertible {
+  var description: String {
+    switch self {
+    //case .checksum:     "><"
+    case .lessEqual:    "<="
+    case .greaterEqual: ">="
+    case .lessFuzzy:    "<~"
+    case .greaterFuzzy: ">~"
+    case .equals:       "="
+    case .less:         "<"
+    case .greater:      ">"
+    case .fuzzyEquals:  "~"
+    }
+  }
+}