Adds basic implementation of Consolidatable for reuse in other projects

Author: SoftwareEngineerChris

.gitignore

@@ -35,10 +35,13 @@ playground.xcworkspace
 # Swift Package Manager
 #
 # Add this line if you want to avoid checking in source code from Swift Package Manager dependencies.
-# Packages/
-# Package.pins
-# Package.resolved
+Packages/
+Package.pins
+Package.resolved
 .build/
+.DS_Store
+/*.xcodeproj
+.swiftpm
 
 # CocoaPods
 #

Package.swift

@@ -0,0 +1,23 @@
+// swift-tools-version:5.0
+// The swift-tools-version declares the minimum version of Swift required to build this package.
+
+import PackageDescription
+
+let package = Package(
+    name: "Consolidate",
+    products: [
+        .library(
+            name: "Consolidate",
+            type: .static,
+            targets: ["Consolidate"]),
+    ],
+    dependencies: [],
+    targets: [
+        .target(
+            name: "Consolidate",
+            dependencies: []),
+        .testTarget(
+            name: "ConsolidateTests",
+            dependencies: ["Consolidate"]),
+    ]
+)

Sources/Consolidate/Consolidatable.swift

@@ -0,0 +1,37 @@
+//
+//  Consolidatable.swift
+//  Consolidate
+//
+//  Created by Chris Hargreaves on 28/09/2019.
+//  Copyright © 2019 Software Engineering Limited. All rights reserved.
+//
+
+import Foundation
+
+protocol Consolidatable {
+    
+    var consolidationGroup: AnyHashable { get }
+    
+    func consolidate(with other: Self) -> Self
+    
+}
+
+extension Array where Element: Consolidatable {
+    
+    func consolidated() -> Self {
+        
+        return reduce([]) { (result, element) -> [Element] in
+            
+            if let existingGroupIndex = result.firstIndex(where: { $0.consolidationGroup == element.consolidationGroup }) {
+                
+                var mutableResult = result
+                
+                mutableResult[existingGroupIndex] = result[existingGroupIndex].consolidate(with: element)
+                
+                return mutableResult
+            }
+            
+            return result + [element]
+        }
+    }
+}

Tests/ConsolidateTests/ConsolidatableTests.swift

@@ -0,0 +1,83 @@
+//
+//  ConsolidatableTests.swift
+//  Consolidate
+//
+//  Created by Chris Hargreaves on 28/09/2019.
+//  Copyright © 2019 Software Engineering Limited. All rights reserved.
+//
+
+import XCTest
+@testable import Consolidate
+
+final class ConsolidatableTests: XCTestCase {
+    
+    func test_emptyArray_returnsEmptyArray() {
+    
+        let consolidatedTaxes: [TaxAmount] = [].consolidated()
+        
+        XCTAssertEqual(consolidatedTaxes, [])
+    }
+    
+    func test_noConsolidabaleValues_doesNotConsolidate() {
+    
+        let importTax = TaxAmount(tax: "Import Tax", amount: 3.00)
+        let salesTax = TaxAmount(tax: "Sales Tax", amount: 1.75)
+        let exportTax = TaxAmount(tax: "Export Tax", amount: 2.30)
+        let incomeTax = TaxAmount(tax: "Income Tax", amount: 2.35)
+        
+        let consolidatedTaxes = [
+            importTax,
+            salesTax,
+            exportTax,
+            incomeTax
+        ].consolidated()
+        
+        XCTAssertEqual(consolidatedTaxes, [
+            TaxAmount(tax: "Import Tax", amount: 3.00),
+            TaxAmount(tax: "Sales Tax", amount: 1.75),
+            TaxAmount(tax: "Export Tax", amount: 2.30),
+            TaxAmount(tax: "Income Tax", amount: 2.35)
+        ])
+    }
+    
+    func test_multipleConsolidabaleValues_consolidates() {
+    
+        let importTaxA = TaxAmount(tax: "Import Tax", amount: 3.00)
+        let salesTaxA = TaxAmount(tax: "Sales Tax", amount: 1.75)
+        let importTaxB = TaxAmount(tax: "Import Tax", amount: 2.30)
+        let salesTaxB = TaxAmount(tax: "Sales Tax", amount: 2.35)
+        
+        let consolidatedTaxes = [
+            importTaxA,
+            salesTaxA,
+            importTaxB,
+            salesTaxB
+        ].consolidated()
+        
+        XCTAssertEqual(consolidatedTaxes, [
+            TaxAmount(tax: "Import Tax", amount: 5.30),
+            TaxAmount(tax: "Sales Tax", amount: 4.10)
+        ])
+    }
+
+    static var allTests = [
+        ("test_noConsolidabaleValues_doesNotConsolidate", test_noConsolidabaleValues_doesNotConsolidate),
+        ("test_multipleConsolidabaleValues_consolidates", test_multipleConsolidabaleValues_consolidates),
+    ]
+}
+
+// MARK: Test Fixtures
+
+struct TaxAmount: Equatable, Consolidatable {
+    
+    let tax: String
+    let amount: Decimal
+    
+    var consolidationGroup: AnyHashable {
+        return tax
+    }
+    
+    func consolidate(with other: Self) -> Self {
+        return .init(tax: tax, amount: amount + other.amount)
+    }
+}

Tests/ConsolidateTests/XCTestManifests.swift

@@ -0,0 +1,9 @@
+import XCTest
+
+#if !canImport(ObjectiveC)
+public func allTests() -> [XCTestCaseEntry] {
+    return [
+        testCase(ConsolidatableTests.allTests),
+    ]
+}
+#endif

Tests/LinuxMain.swift

@@ -0,0 +1,7 @@
+import XCTest
+
+import ConsolidateTests
+
+var tests = [XCTestCaseEntry]()
+tests += ConsolidateTests.allTests()
+XCTMain(tests)