Fix multilanguage ZIM listing and count, add unit tests

Model/Entities/Entities.swift

@@ -67,7 +67,8 @@ struct Language: Identifiable, Comparable {
     let count: Int
 
     init?(code: String, count: Int) {
-        guard let name = Locale.current.localizedString(forIdentifier: code) else { return nil }
+        guard let name = Locale.current.localizedString(forIdentifier: code),
+            count > 0 else { return nil }
         self.code = code
         self.name = name
         self.count = count

Model/LanguageCollector.swift

@@ -0,0 +1,44 @@
+// This file is part of Kiwix for iOS & macOS.
+//
+// Kiwix is free software; you can redistribute it and/or modify it
+// under the terms of the GNU General Public License as published by
+// the Free Software Foundation; either version 3 of the License, or
+// any later version.
+//
+// Kiwix is distributed in the hope that it will be useful, but
+// WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+// General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Kiwix; If not, see https://www.gnu.org/licenses/.
+
+import Foundation
+
+/// Helper to collect all language codes with counts,
+/// some of them are coma separated entries in the DB, such as "eng,spa,por"
+final class LanguageCollector {
+
+    private var items: [String: Int] = [:]
+
+    func addLanguages(codes: String, count: Int) {
+        Set(codes.split(separator: ",")).forEach { code in
+            addLanguage(code: String(code), count: count)
+        }
+    }
+
+    func languages() -> [Language] {
+        items.compactMap { (code: String, count: Int) -> Language? in
+            Language(code: code, count: count)
+        }.sorted()
+    }
+
+    private func addLanguage(code: String, count: Int) {
+        if let previousCount = items[code] {
+            items[code] = previousCount + count
+        } else {
+            items[code] = count
+        }
+    }
+
+}

Tests/LanguageCollectorTest.swift

@@ -0,0 +1,80 @@
+// This file is part of Kiwix for iOS & macOS.
+//
+// Kiwix is free software; you can redistribute it and/or modify it
+// under the terms of the GNU General Public License as published by
+// the Free Software Foundation; either version 3 of the License, or
+// any later version.
+//
+// Kiwix is distributed in the hope that it will be useful, but
+// WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+// General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Kiwix; If not, see https://www.gnu.org/licenses/.
+
+import XCTest
+@testable import Kiwix
+
+final class LanguageCollectorTest: XCTestCase {
+
+    func testEmpty() {
+        let collector = LanguageCollector()
+        XCTAssertTrue(collector.languages().isEmpty)
+    }
+
+    func testInvalidEntriesIgnored() {
+        let collector = LanguageCollector()
+        collector.addLanguages(codes: "invalid", count: 1)
+        XCTAssertTrue(collector.languages().isEmpty)
+        collector.addLanguages(codes: "more,invalid,entries", count: 2)
+        XCTAssertTrue(collector.languages().isEmpty)
+        collector.addLanguages(codes: "i_am,invalid,fra", count: 1)
+        XCTAssertEqual(collector.languages().count, 1)
+        XCTAssertEqual(collector.languages().first!.name, "French")
+    }
+
+    func testZeroAndNegativeCountsIgnored() {
+        let collector = LanguageCollector()
+        collector.addLanguages(codes: "eng", count: 0)
+        XCTAssertTrue(collector.languages().isEmpty)
+        collector.addLanguages(codes: "eng,fra", count: -1)
+        XCTAssertTrue(collector.languages().isEmpty)
+    }
+
+    func testAddingSingleLanguages() {
+        let collector = LanguageCollector()
+        collector.addLanguages(codes: "eng", count: 1)
+        XCTAssertEqual(collector.languages().count, 1)
+        XCTAssertEqual(collector.languages().first!.name, "English")
+        XCTAssertEqual(collector.languages().first!.code, "eng")
+        XCTAssertEqual(collector.languages().first!.count, 1)
+    }
+
+    func testRepeatedLanguagesCodesAreIgnored() {
+        let collector = LanguageCollector()
+        collector.addLanguages(codes: "eng,eng", count: 1)
+        XCTAssertEqual(collector.languages().count, 1)
+        XCTAssertEqual(collector.languages().first!.count, 1)
+    }
+
+    func testAddingMultipleLanguagesWithCountOne() {
+        let collector = LanguageCollector()
+        collector.addLanguages(codes: "fra,eng", count: 1)
+        XCTAssertEqual(collector.languages().count, 2)
+        XCTAssertEqual(collector.languages().map { $0.name }, ["English", "French"])
+    }
+
+    func testAddingMultiLanguagesWithVariousCounts() {
+        let collector = LanguageCollector()
+        collector.addLanguages(codes: "fra,eng", count: 1)
+        collector.addLanguages(codes: "spa,por,fra", count: 1)
+        XCTAssertEqual(collector.languages().count, 4)
+        XCTAssertEqual(collector.languages(), [
+            Language(code: "eng", count: 1)!,
+            Language(code: "fra", count: 2)!,
+            Language(code: "por", count: 1)!,
+            Language(code: "spa", count: 1)!
+        ])
+    }
+}

Views/Settings/LanguageSelector.swift

@@ -170,13 +170,15 @@ class Languages {
                     continuation.resume(returning: [])
                     return
                 }
-                let language: [Language] = results.compactMap { result in
-                    guard let result = result as? NSDictionary,
-                          let languageCode = result["languageCode"] as? String,
-                          let count = result["count"] as? Int else { return nil }
-                    return Language(code: languageCode, count: count)
+                let collector = LanguageCollector()
+                for result in results {
+                    if let result = result as? NSDictionary,
+                       let languageCodes = result["languageCode"] as? String,
+                       let count = result["count"] as? Int {
+                        collector.addLanguages(codes: languageCodes, count: count)
+                    }
                 }
-                continuation.resume(returning: language)
+                continuation.resume(returning: collector.languages())
             }
         }
         return languages