init

Sources/Chain/Chain.swift

@@ -1,3 +1,40 @@
-struct Chain {
-    var text = "Hello, World!"
+import Foundation
+
+public typealias ChainAction = () -> Void
+
+public indirect enum Chain {
+    case end
+    case complete(ChainAction?)
+    case link(ChainAction, Chain)
+    case background(ChainAction, Chain)
+    case multi([Chain])
+}
+
+public extension Chain {
+    func run() {
+        switch self {
+        case .end:
+            print("[\(Date())] Chain: End")
+        case .complete(let completion):
+            print("[\(Date())] Chain: Complete")
+            completion?()
+        case .link(let action,
+                   let next):
+            print("[\(Date())] Chain: Link")
+            action()
+            next.run()
+        case .background(let action,
+                         let next):
+            print("[\(Date())] Chain: Background")
+            DispatchQueue.global().async {
+                action()
+                DispatchQueue.main.async {
+                    next.run()
+                }
+            }
+        case .multi(let links):
+            print("[\(Date())] Chain: Multi")
+            links.forEach { $0.run() }
+        }
+    }
 }

Tests/ChainTests/ChainTests.swift

@@ -3,12 +3,48 @@ import XCTest
 
 final class ChainTests: XCTestCase {
     func testExample() {
-        // This is an example of a functional test case.
-        // Use XCTAssert and related functions to verify your tests produce the correct
-        // results.
-        XCTAssertEqual(Chain().text, "Hello, World!")
+        var isLooping = true
+
+        var text = ""
+
+
+        Chain.link(
+            { print(0) },
+            .link(
+                { print(1) },
+                .background(
+                    { print(2)
+                        sleep(3)
+                    },
+                    .link(
+                        { print(3) },
+                          .complete {
+                            text = "Hello, World?"
+                          }
+                    )
+                )
+            )
+        )
+        .run()
+
+        Chain.background(
+            {
+                sleep(5)
+            },
+            .link(
+                {
+                    XCTAssertEqual(text, "Hello, World!")
+                },
+                .complete {
+                        isLooping = false
+                }
+            )
+        )
+        .run()
+
+        while isLooping { }
     }
-
+    
     static var allTests = [
         ("testExample", testExample),
     ]