[iOS] Add metric for primary language

ios/brave-ios/App/iOS/Delegates/AppDelegate.swift

@@ -271,6 +271,8 @@ class AppDelegate: UIResponder, UIApplicationDelegate {
       )
     }
 
+    LanguageMetrics.recordPrimaryLanguageP3A()
+
     Task(priority: .low) {
       await self.cleanUpLargeTemporaryDirectory()
     }

ios/brave-ios/Package.swift

@@ -107,6 +107,7 @@ var package = Package(
       name: "Growth",
       dependencies: [
         "BraveVPN", "Shared", "BraveShared", "Strings", "SnapKit", "CertificateUtilities",
+        .product(name: "OrderedCollections", package: "swift-collections"),
       ],
       plugins: ["LoggerPlugin"]
     ),

ios/brave-ios/Sources/Growth/LanguageMetrics.swift

@@ -0,0 +1,225 @@
+// Copyright (c) 2024 The Brave Authors. All rights reserved.
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this file,
+// You can obtain one at https://mozilla.org/MPL/2.0/.
+
+import BraveCore
+import Foundation
+import OrderedCollections
+
+public class LanguageMetrics {
+
+  // This list is copied from //brave/components/misc_metrics/language_metrics.cc
+  static let acceptedLanguages: OrderedSet<String> = [
+    "aa",  // Afar
+    "ab",  // Abkhazian
+    "ae",  // Avestan
+    "af",  // Afrikaans
+    "ak",  // Akan
+    "am",  // Amharic
+    "an",  // Aragonese
+    "ar",  // Arabic
+    "as",  // Assamese
+    "av",  // Avaric
+    "ay",  // Aymara
+    "az",  // Azerbaijani
+    "ba",  // Bashkir
+    "be",  // Belarusian
+    "bg",  // Bulgarian
+    "bh",  // Bihari languages
+    "bi",  // Bislama
+    "bm",  // Bambara
+    "bn",  // Bengali
+    "bo",  // Tibetan
+    "br",  // Breton
+    "bs",  // Bosnian
+    "ca",  // Catalan; Valencian
+    "ce",  // Chechen
+    "ch",  // Chamorro
+    "co",  // Corsican
+    "cr",  // Cree
+    "cs",  // Czech
+    "cu",  // Church Slavic; Old Slavonic; Church Slavonic; Old Bulgarian; // Old Church Slavonic
+    "cv",  // Chuvash
+    "cy",  // Welsh
+    "da",  // Danish
+    "de",  // German
+    "dv",  // Divehi; Dhivehi; Maldivian
+    "dz",  // Dzongkha
+    "ee",  // Ewe
+    "el",  // "Greek, Modern (1453-)"
+    "en",  // English
+    "eo",  // Esperanto
+    "es",  // Spanish; Castilian
+    "et",  // Estonian
+    "eu",  // Basque
+    "fa",  // Persian
+    "ff",  // Fulah
+    "fi",  // Finnish
+    "fj",  // Fijian
+    "fo",  // Faroese
+    "fr",  // French
+    "fy",  // Western Frisian
+    "ga",  // Irish
+    "gd",  // Gaelic; Scottish Gaelic
+    "gl",  // Galician
+    "gn",  // Guarani
+    "gu",  // Gujarati
+    "gv",  // Manx
+    "ha",  // Hausa
+    "he",  // Hebrew
+    "hi",  // Hindi
+    "ho",  // Hiri Motu
+    "hr",  // Croatian
+    "ht",  // Haitian; Haitian Creole
+    "hu",  // Hungarian
+    "hy",  // Armenian
+    "hz",  // Herero
+    "ia",  // Interlingua (International Auxiliary Language Association)
+    "id",  // Indonesian
+    "ie",  // Interlingue; Occidental
+    "ig",  // Igbo
+    "ii",  // Sichuan Yi; Nuosu
+    "ik",  // Inupiaq
+    "io",  // Ido
+    "is",  // Icelandic
+    "it",  // Italian
+    "iu",  // Inuktitut
+    "ja",  // Japanese
+    "jv",  // Javanese
+    "ka",  // Georgian
+    "kg",  // Kongo
+    "ki",  // Kikuyu; Gikuyu
+    "kj",  // Kuanyama; Kwanyama
+    "kk",  // Kazakh
+    "kl",  // Kalaallisut; Greenlandic
+    "km",  // Central Khmer
+    "kn",  // Kannada
+    "ko",  // Korean
+    "kr",  // Kanuri
+    "ks",  // Kashmiri
+    "ku",  // Kurdish
+    "kv",  // Komi
+    "kw",  // Cornish
+    "ky",  // Kirghiz; Kyrgyz
+    "la",  // Latin
+    "lb",  // Luxembourgish; Letzeburgesch
+    "lg",  // Ganda
+    "li",  // Limburgan; Limburger; Limburgish
+    "ln",  // Lingala
+    "lo",  // Lao
+    "lt",  // Lithuanian
+    "lu",  // Luba-Katanga
+    "lv",  // Latvian
+    "mg",  // Malagasy
+    "mh",  // Marshallese
+    "mi",  // Maori
+    "mk",  // Macedonian
+    "ml",  // Malayalam
+    "mn",  // Mongolian
+    "mr",  // Marathi
+    "ms",  // Malay
+    "mt",  // Maltese
+    "my",  // Burmese
+    "na",  // Nauru
+    "nb",  // "Bokmål, Norwegian; Norwegian Bokmål"
+    "nd",  // "Ndebele, North; North Ndebele"
+    "ne",  // Nepali
+    "ng",  // Ndonga
+    "nl",  // Dutch; Flemish
+    "nn",  // "Norwegian Nynorsk; Nynorsk, Norwegian"
+    "no",  // Norwegian
+    "nr",  // "Ndebele, South; South Ndebele"
+    "nv",  // Navajo; Navaho
+    "ny",  // Chichewa; Chewa; Nyanja
+    "oc",  // Occitan (post 1500)
+    "oj",  // Ojibwa
+    "om",  // Oromo
+    "or",  // Oriya
+    "os",  // Ossetian; Ossetic
+    "pa",  // Panjabi; Punjabi
+    "pi",  // Pali
+    "pl",  // Polish
+    "ps",  // Pushto; Pashto
+    "pt",  // Portuguese
+    "qu",  // Quechua
+    "rm",  // Romansh
+    "rn",  // Rundi
+    "ro",  // Romanian; Moldavian; Moldovan
+    "ru",  // Russian
+    "rw",  // Kinyarwanda
+    "sa",  // Sanskrit
+    "sc",  // Sardinian
+    "sd",  // Sindhi
+    "se",  // Northern Sami
+    "sg",  // Sango
+    "si",  // Sinhala; Sinhalese
+    "sk",  // Slovak
+    "sl",  // Slovenian
+    "sm",  // Samoan
+    "sn",  // Shona
+    "so",  // Somali
+    "sq",  // Albanian
+    "sr",  // Serbian
+    "ss",  // Swati
+    "st",  // "Sotho, Southern"
+    "su",  // Sundanese
+    "sv",  // Swedish
+    "sw",  // Swahili
+    "ta",  // Tamil
+    "te",  // Telugu
+    "tg",  // Tajik
+    "th",  // Thai
+    "ti",  // Tigrinya
+    "tk",  // Turkmen
+    "tl",  // Tagalog
+    "tn",  // Tswana
+    "to",  // Tonga (Tonga Islands)
+    "tr",  // Turkish
+    "ts",  // Tsonga
+    "tt",  // Tatar
+    "tw",  // Twi
+    "ty",  // Tahitian
+    "ug",  // Uighur; Uyghur
+    "uk",  // Ukrainian
+    "ur",  // Urdu
+    "uz",  // Uzbek
+    "ve",  // Venda
+    "vi",  // Vietnamese
+    "vo",  // Volapük
+    "wa",  // Walloon
+    "wo",  // Wolof
+    "xh",  // Xhosa
+    "yi",  // Yiddish
+    "yo",  // Yoruba
+    "za",  // Zhuang; Chuang
+    "zh",  // Chinese
+    "zu",  // Zulu
+  ]
+
+  static let languageSynonyms: [String: String] = [
+    "in": "id",
+    "iw": "he",
+    "ji": "yi",
+    "jw": "jv",
+    "mo": "ro",
+  ]
+
+  static func answerForLangaugeCode(_ languageCode: String?) -> Int {
+    let suspendedMetricValue = Int.max - 1
+    guard let languageCode = languageCode,
+      case let primaryLanguage = languageSynonyms[languageCode, default: languageCode],
+      let answer = acceptedLanguages.firstIndex(of: primaryLanguage)
+    else {
+      // Suspend metric if primary language not detected or language isn't accepted
+      return suspendedMetricValue
+    }
+    return answer
+  }
+
+  public static func recordPrimaryLanguageP3A() {
+    let primaryLanguageHistogramName = "Brave.Core.PrimaryLang"
+    let answer = answerForLangaugeCode(Locale.current.languageCode)
+    UmaHistogramExactLinear(primaryLanguageHistogramName, answer, acceptedLanguages.count)
+  }
+}

ios/brave-ios/Tests/GrowthTests/LangaugeMetricsTests.swift

@@ -0,0 +1,29 @@
+// Copyright (c) 2024 The Brave Authors. All rights reserved.
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this file,
+// You can obtain one at https://mozilla.org/MPL/2.0/.
+
+import Foundation
+import XCTest
+
+@testable import Growth
+
+class LanguageMetricsTests: XCTestCase {
+  func testInvalidLanguageCodes() {
+    let expectedValue = Int.max - 1
+    XCTAssertEqual(LanguageMetrics.answerForLangaugeCode(nil), expectedValue)
+    XCTAssertEqual(LanguageMetrics.answerForLangaugeCode("notalangugage"), expectedValue)
+  }
+
+  func testValidLanguageCodes() {
+    for (index, languageCode) in LanguageMetrics.acceptedLanguages.enumerated() {
+      XCTAssertEqual(LanguageMetrics.answerForLangaugeCode(languageCode), index)
+    }
+  }
+
+  func testLanguageSynonyms() {
+    let (deprecated, active) = ("in", "id")
+    let expectedAnswer = LanguageMetrics.answerForLangaugeCode(active)
+    XCTAssertEqual(LanguageMetrics.answerForLangaugeCode(deprecated), expectedAnswer)
+  }
+}