[App] Run terminal processes (#3)

This PR contains the work done to run terminal processes within the context of the app, conforming to Swift concurrency.

Reviewed-on: #3
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>
Co-committed-by: Javier Cicchelli <javier@rock-n-code.com>

Piper.xcodeproj/project.pbxproj

@@ -35,6 +35,7 @@
 			membershipExceptions = (
 				UITests/UITests.swift,
 				UITests/UITestsLaunchTests.swift,
+				UnitTests/Tests/UseCases/RunProcessUseCaseTests.swift,
 				UnitTests/UnitTests.swift,
 			);
 			target = 46D4BE762CB06ED300FCFB84 /* Piper */;
@@ -42,6 +43,7 @@
 		46D4BEF72CB07CCB00FCFB84 /* Exceptions for "Tests" folder in "UnitTests" target */ = {
 			isa = PBXFileSystemSynchronizedBuildFileExceptionSet;
 			membershipExceptions = (
+				UnitTests/Tests/UseCases/RunProcessUseCaseTests.swift,
 				UnitTests/UnitTests.swift,
 			);
 			target = 46D4BED32CB07C7A00FCFB84 /* UnitTests */;
@@ -492,6 +494,7 @@
 				CURRENT_PROJECT_VERSION = 1;
 				DEVELOPMENT_TEAM = 7FMNM89WKG;
 				GENERATE_INFOPLIST_FILE = YES;
+				MACOSX_DEPLOYMENT_TARGET = 14.6;
 				MARKETING_VERSION = 1.0;
 				PRODUCT_BUNDLE_IDENTIFIER = "com.rock-n-code.piper.tests.unit";
 				PRODUCT_NAME = "$(TARGET_NAME)";
@@ -509,6 +512,7 @@
 				CURRENT_PROJECT_VERSION = 1;
 				DEVELOPMENT_TEAM = 7FMNM89WKG;
 				GENERATE_INFOPLIST_FILE = YES;
+				MACOSX_DEPLOYMENT_TARGET = 14.6;
 				MARKETING_VERSION = 1.0;
 				PRODUCT_BUNDLE_IDENTIFIER = "com.rock-n-code.piper.tests.unit";
 				PRODUCT_NAME = "$(TARGET_NAME)";

Piper/Sources/Logic/Extensions/Pipe+AsyncAvailableData.swift

@@ -0,0 +1,70 @@
+//
+//  Pipe+AsyncAvailableData.swift
+//  Piper ~ App
+//
+//  Created by Javier Cicchelli on 05/10/2024.
+//  Copyright © 2024 Röck+Cöde. All rights reserved.
+//
+
+import Foundation
+
+extension Pipe {
+    struct AsyncAvailableData {
+
+        // MARK: Properties
+        
+        private let pipe: Pipe
+        
+        // MARK: Initialisers
+        
+        init(_ pipe: Pipe) {
+            self.pipe = pipe
+        }
+        
+        // MARK: Functions
+        
+        func append() async -> Data {
+            var data = Data()
+
+            for await availableData in self {
+                data.append(availableData)
+            }
+
+            return data
+        }
+
+    }
+}
+
+// MARK: - AsyncSequence
+
+extension Pipe.AsyncAvailableData: AsyncSequence {
+    
+    // MARK: Type aliases
+    
+    typealias AsyncIterator = AsyncStream<Data>.Iterator
+    typealias Element = Data
+    
+    // MARK: Functions
+    
+    func makeAsyncIterator() -> AsyncIterator {
+        AsyncStream { continuation in
+            pipe.fileHandleForReading.readabilityHandler = { @Sendable handler in
+                let data = handler.availableData
+                
+                guard !data.isEmpty else {
+                    continuation.finish()
+                    return
+                }
+                
+                continuation.yield(data)
+            }
+            
+            continuation.onTermination = { _ in
+                pipe.fileHandleForReading.readabilityHandler = nil
+            }
+        }
+        .makeAsyncIterator()
+    }
+    
+}

Piper/Sources/Logic/Extensions/Pipe+Computed.swift

@@ -0,0 +1,17 @@
+//
+//  Pipe+Computed.swift
+//  Piper
+//
+//  Created by Javier Cicchelli on 05/10/2024.
+//  Copyright © 2024 Röck+Cöde. All rights reserved.
+//
+
+import Foundation
+
+extension Pipe {
+    
+    // MARK: Computed
+    
+    var availableData: AsyncAvailableData { .init(self) }
+    
+}

Piper/Sources/Logic/UseCases/RunProcessUseCase.swift

@@ -0,0 +1,87 @@
+//
+//  RunProcessUseCase.swift
+//  Piper ~ App
+//
+//  Created by Javier Cicchelli on 05/10/2024.
+//  Copyright © 2024 Röck+Cöde. All rights reserved.
+//
+
+import Foundation
+
+struct RunProcessUseCase {
+    
+    // MARK: Type aliases
+    
+    typealias Output = String
+    
+    // MARK: Properties
+    
+    private let path: String
+    private let arguments: [String]?
+    
+    // MARK: Initialisers
+    
+    init(
+        path: String,
+        arguments: [String] = []
+    ) {
+        self.path = path
+        self.arguments = arguments
+    }
+
+    // MARK: Functions
+    
+    func callAsFunction() async throws -> Output {
+        let process = Process()
+        
+        process.executableURL = URL(fileURLWithPath: path)
+        process.arguments = arguments
+        
+        let pipeError = Pipe()
+        let pipeOutput = Pipe()
+        
+        process.standardError = pipeError
+        process.standardOutput = pipeOutput
+        
+        async let streamOutput = pipeOutput.availableData.append()
+        async let streamError = pipeError.availableData.append()
+        
+        do {
+            try process.run()
+            
+            let dataOutput = await streamOutput
+            let dataError = await streamError
+            
+            guard dataError.isEmpty else {
+                guard let errorOutput = String(data: dataError, encoding: .utf8) else {
+                    throw RunProcessError.unexpected
+                }
+                
+                throw RunProcessError.output(errorOutput)
+            }
+            
+            guard let output = String(data: dataOutput, encoding: .utf8) else {
+                throw RunProcessError.unexpected
+            }
+
+            return await withCheckedContinuation { continuation in
+                process.terminationHandler = { _ in
+                    continuation.resume(returning: output)
+                }
+            }
+        } catch let error as RunProcessError {
+            throw error
+        } catch {
+            throw RunProcessError.captured(error)
+        }
+    }
+
+}
+
+// MARK: - Errors
+
+enum RunProcessError: Error {
+    case captured(_ error: Error)
+    case output(_ output: String)
+    case unexpected
+}

Tests/UnitTests/Tests/UseCases/RunProcessUseCaseTests.swift

@@ -0,0 +1,69 @@
+//
+//  RunProcessUseCaseTests.swift
+//  UnitTests
+//
+//  Created by Javier Cicchelli on 05/10/2024.
+//  Copyright © 2024 Röck+Cöde. All rights reserved.
+//
+
+import Testing
+
+@testable import Piper
+
+struct RunProcessUseCaseTests {
+    
+    // MARK: Functions tests
+    
+    @Test("Run a simple process without arguments")
+    func simpleCommand_withoutArguments() async throws {
+        // GIVEN
+        let useCase = RunProcessUseCase(path: .ls)
+        
+        // WHEN
+        let output = try await useCase()
+        
+        // THEN
+        #expect(output.isEmpty == false)
+    }
+    
+    @Test("Run a simple process with arguments")
+    func simpleCommand_withArguments() async throws {
+        // GIVEN
+        let useCase = RunProcessUseCase(
+            path: .ls,
+            arguments: ["-la", "."]
+        )
+
+        // WHEN
+        let output = try await useCase()
+        
+        // THEN
+        #expect(output.isEmpty == false)
+    }
+    
+    @Test("Run a simple command with arguments that throws an error")
+    func simpleCommand_withArguments_throwsError() async throws {
+        // GIVEN
+        let useCase = RunProcessUseCase(
+            path: .ls,
+            arguments: ["-la", "~"]
+        )
+        
+        // WHEN
+        // THEN
+        await #expect(throws: RunProcessError.self) {
+            try await useCase()
+        }
+    }
+    
+}
+
+// MARK: - String+Constants
+
+private extension String {
+    
+    // MARK: Constants
+    
+    static let ls = "/bin/ls"
+    
+}