[Library] Word filtering in Foundation library (#6)

This PR contains the work done to Implemented the `FilterWordsUseCase` use case in the Foundation library, which will be used to filter the content of the reviews.

Reviewed-on: #6
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>
Co-committed-by: Javier Cicchelli <javier@rock-n-code.com>

Libraries/Foundation/Kit/Sources/Use Cases/FilterWordsUseCase.swift

@@ -0,0 +1,120 @@
+//
+//  FilterWordsUseCase.swift
+//  ReviewsParserKit
+//
+//  Created by Javier Cicchelli on 17/03/2024.
+//  Copyright © 2024 Röck+Cöde VoF. All rights reserved.
+//
+
+import Foundation
+
+public struct FilterWordsUseCase {
+    
+    // MARK: Type aliases
+    public typealias Input = String
+    public typealias Output = [Tuple]
+    
+    // MARK: Initialisers
+    public init() {}
+    
+    // MARK: Functions
+    public func callAsFunction(_ input: Input) throws -> Output {
+        let regularExpression = try NSRegularExpression(
+            pattern: .Pattern.wordsLongerThan4Characters,
+            options: .caseInsensitive
+        )
+        
+        let matches = regularExpression.matches(
+            in: input,
+            options: [],
+            range: .init(input.startIndex..., in: input)
+        )
+        
+        guard !matches.isEmpty else { return [] }
+        
+        let wordsAll = matches.compactMap {
+            Range($0.range, in: input).map { String(input[$0]) }
+        }
+        
+        let wordsUnique = wordsAll
+            .reduce(into: [String]()) { partialResult, word in
+                guard partialResult
+                    .filter({ compareWords(word, $0) })
+                    .isEmpty
+                else { return }
+                
+                partialResult.append(
+                    word.folding(
+                        options: [
+                            .caseInsensitive,
+                            .diacriticInsensitive
+                        ],
+                        locale: .current
+                    )
+                    .capitalized
+                )
+            }
+        
+        return Dictionary(grouping: wordsUnique) { word in
+            wordsAll
+                .filter { compareWords(word, $0) }
+                .count
+        }
+        .flatMap { (key, values) -> Output in
+            values.map {
+                .init(word: $0, count: key)
+            }
+        }
+        .sorted {
+            guard $0.count != $1.count else {
+                return $0.word < $1.word
+            }
+            
+            return $0.count > $1.count
+        }
+    }
+    
+}
+
+// MARK: - Helpers
+private extension FilterWordsUseCase {
+    
+    // MARK: Functions
+    func compareWords(
+        _ lword: String,
+        _ rword: String
+    ) -> Bool {
+        lword.compare(rword, options: [
+            .caseInsensitive,
+            .diacriticInsensitive
+        ]) == .orderedSame
+    }
+    
+}
+
+// MARK: - Structs
+extension FilterWordsUseCase {
+    public struct Tuple: Equatable {
+        
+        // MARK: Constants
+        let word: String
+        let count: Int
+        
+        // MARK: Initialisers
+        public init(
+            word: String,
+            count: Int
+        ) {
+            self.word = word
+            self.count = count
+        }
+
+    }
+}
+
+// MARK: - String+Constants
+private extension String {
+    enum Pattern {
+        static let wordsLongerThan4Characters = "\\w{4,}"
+    }
+}

Libraries/Foundation/Test/Tests/Use Cases/FilterWordsUseCaseTests.swift

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+//
+//  FilterWordsUseCaseTests.swift
+//  ReviewsFoundationTest
+//
+//  Created by Javier Cicchelli on 18/03/2024.
+//  Copyright © 2024 Röck+Cöde VoF. All rights reserved.
+//
+
+import ReviewsFoundationKit
+import XCTest
+
+final class FilterWordsUseCaseTests: XCTestCase {
+
+    // MARK: Properties
+    private var input: FilterWordsUseCase.Input!
+    private var output: FilterWordsUseCase.Output!
+    private var sut: FilterWordsUseCase!
+
+    // MARK: Setup
+    override func setUp() async throws {
+        sut = .init()
+    }
+
+    // MARK: Function tests
+    func testCallAsFunction_withInput_hasSomeLongWords() throws {
+        // GIVEN
+        input = "one two three four five six seven eight nine ten"
+        
+        // WHEN
+        output = try sut(input)
+        
+        // THEN
+        XCTAssertFalse(output.isEmpty)
+        XCTAssertEqual(output, [
+            .init(word: "Eight", count: 1),
+            .init(word: "Five", count: 1),
+            .init(word: "Four", count: 1),
+            .init(word: "Nine", count: 1),
+            .init(word: "Seven", count: 1),
+            .init(word: "Three", count: 1),
+        ])
+    }
+    
+    func testCallAsFunction_withInput_hasSomeRepeatedLongWords() throws {
+        // GIVEN
+        input = "one two three three four five five six seven eight nine nine ten"
+        
+        // WHEN
+        output = try sut(input)
+        
+        // THEN
+        XCTAssertFalse(output.isEmpty)
+        XCTAssertEqual(output, [
+            .init(word: "Five", count: 2),
+            .init(word: "Nine", count: 2),
+            .init(word: "Three", count: 2),
+            .init(word: "Eight", count: 1),
+            .init(word: "Four", count: 1),
+            .init(word: "Seven", count: 1),
+        ])
+    }
+    
+    func testCallAsFunction_withInput_hasSomeRepeatedCaseSensitiveLongWords() throws {
+        // GIVEN
+        input = "one two three Three four Five five six seven eight nine nine ten"
+        
+        // WHEN
+        output = try sut(input)
+        
+        // THEN
+        XCTAssertFalse(output.isEmpty)
+        XCTAssertEqual(output, [
+            .init(word: "Five", count: 2),
+            .init(word: "Nine", count: 2),
+            .init(word: "Three", count: 2),
+            .init(word: "Eight", count: 1),
+            .init(word: "Four", count: 1),
+            .init(word: "Seven", count: 1),
+        ])
+    }
+    
+    func testCallAsFunction_withInput_hasSomeRepeatedDiacriticSensitiveLongWords() throws {
+        // GIVEN
+        input = "one two thrèé Three four Fíve fïve six Šëvêń seven eight niñe nine ten"
+        
+        // WHEN
+        output = try sut(input)
+        
+        // THEN
+        XCTAssertFalse(output.isEmpty)
+        XCTAssertEqual(output, [
+            .init(word: "Five", count: 2),
+            .init(word: "Nine", count: 2),
+            .init(word: "Seven", count: 2),
+            .init(word: "Three", count: 2),
+            .init(word: "Eight", count: 1),
+            .init(word: "Four", count: 1),
+        ])
+    }
+    
+    func testCallAsFunction_withInput_hasOnlyShortWords() throws {
+        // GIVEN
+        input = "no one is a two"
+        
+        // WHEN
+        output = try sut(input)
+        
+        // THEN
+        XCTAssertTrue(output.isEmpty)
+        XCTAssertEqual(output, [])
+    }
+
+    func testCallAsFunction_withEmptyInput() throws {
+        // GIVEN
+        input = .empty
+
+        // WHEN
+        output = try sut(input)
+
+        // THEN
+        XCTAssertTrue(output.isEmpty)
+        XCTAssertEqual(output, [])
+    }
+    
+}