//
//  AppLocalization.swift
//  App for Indeed
//
//  English-first localization using Localizable.strings (same pattern as the LinkedIn app).
//  Add more locales by creating `<locale>.lproj/Localizable.strings` and extending AppLanguage.
//

import Foundation

enum AppLanguage: CaseIterable {
    case english
    case german
    case swedish
    case frenchCanada
    case french
    case arabic
    case chineseSimplified
    case chineseTraditional

    var localeIdentifier: String {
        switch self {
        case .english:
            return "en"
        case .german:
            return "de"
        case .swedish:
            return "sv"
        case .frenchCanada:
            return "fr-CA"
        case .french:
            return "fr"
        case .arabic:
            return "ar"
        case .chineseSimplified:
            return "zh-Hans"
        case .chineseTraditional:
            return "zh-Hant"
        }
    }

    static var systemLanguage: AppLanguage {
        let preferred = Locale.preferredLanguages.first ?? "en"
        let lower = preferred.lowercased()
        if lower.hasPrefix("zh-hant")
            || lower.hasPrefix("zh-tw")
            || lower.hasPrefix("zh-hk")
            || lower.hasPrefix("zh-mo")
            || lower.contains("-hant") {
            return .chineseTraditional
        }
        if lower.hasPrefix("zh") {
            return .chineseSimplified
        }
        if lower.hasPrefix("de") {
            return .german
        }
        if lower.hasPrefix("sv") {
            return .swedish
        }
        if lower.hasPrefix("en") {
            return .english
        }
        if lower.hasPrefix("fr-ca") {
            return .frenchCanada
        }
        if lower.hasPrefix("fr") {
            return .french
        }
        if lower.hasPrefix("ar") {
            return .arabic
        }
        for language in AppLanguage.allCases where preferred.hasPrefix(language.localeIdentifier) {
            return language
        }
        return .english
    }

    /// Settings language picker labels — fixed English names, not localized.
    var localizedDisplayName: String {
        switch self {
        case .english:
            return "English"
        case .german:
            return "German"
        case .swedish:
            return "Swedish"
        case .frenchCanada:
            return "French (Canada)"
        case .french:
            return "French"
        case .arabic:
            return "Arabic"
        case .chineseSimplified:
            return "Chinese (Simplified)"
        case .chineseTraditional:
            return "Chinese (Traditional)"
        }
    }
}

func appLocalized(_ key: String, language: AppLanguage) -> String {
    guard let path = Bundle.main.path(forResource: language.localeIdentifier, ofType: "lproj"),
          let bundle = Bundle(path: path) else {
        return key
    }
    let value = bundle.localizedString(forKey: key, value: key, table: nil)
    return value.isEmpty ? key : value
}

func currentAppLanguage() -> AppLanguage {
    AppLanguageManager.resolvedLanguage
}

/// Resolves copy for the user’s currently selected language.
func L(_ key: String) -> String {
    appLocalized(key, language: currentAppLanguage())
}

/// Localized CV template title. Built-in templates use English keys in `Localizable.strings`;
/// AI-generated titles fall back to per-word translation when no exact key exists.
func localizedTemplateName(_ nameKey: String) -> String {
    let language = currentAppLanguage()
    let trimmed = nameKey.trimmingCharacters(in: .whitespacesAndNewlines)
    guard !trimmed.isEmpty else { return nameKey }

    let exact = appLocalized(trimmed, language: language)
    if !exact.isEmpty, exact != trimmed { return exact }

    guard language != .english else { return trimmed }

    let expandedPhrase = tokenizeTemplateName(trimmed).joined(separator: " ")
    if expandedPhrase != trimmed {
        let phrase = appLocalized(expandedPhrase, language: language)
        if !phrase.isEmpty, phrase != expandedPhrase { return phrase }
    }

    let tokenized = translateTemplateNameByTokens(trimmed, language: language)
    return tokenized.isEmpty ? trimmed : tokenized
}

/// Splits space-separated, camelCase, and punctuation-joined AI template titles into words.
private func tokenizeTemplateName(_ name: String) -> [String] {
    var s = name.trimmingCharacters(in: .whitespacesAndNewlines)
    guard !s.isEmpty else { return [] }

    for separator in ["&", "·", "-", "_", "/"] {
        s = s.replacingOccurrences(of: separator, with: " ")
    }

    var expanded = ""
    let chars = Array(s)
    for index in chars.indices {
        let char = chars[index]
        if index > 0 {
            let prev = chars[index - 1]
            if char.isUppercase, prev.isLowercase {
                expanded.append(" ")
            } else if char.isUppercase, prev.isUppercase, index + 1 < chars.count, chars[index + 1].isLowercase {
                expanded.append(" ")
            }
        }
        expanded.append(char)
    }

    return expanded
        .split(whereSeparator: \.isWhitespace)
        .map(String.init)
        .filter { !$0.isEmpty }
}

private func translateTemplateNameByTokens(_ name: String, language: AppLanguage) -> String {
    let tokens = tokenizeTemplateName(name)
    guard !tokens.isEmpty else { return name }

    let translated = tokens.map { translateTemplateNameToken($0, language: language) }

    switch language {
    case .chineseSimplified, .chineseTraditional:
        return translated.joined()
    case .arabic, .english, .french, .frenchCanada, .german, .swedish:
        return translated.joined(separator: " ")
    }
}

private func translateTemplateNameToken(_ token: String, language: AppLanguage) -> String {
    let trimmed = token.trimmingCharacters(in: .whitespacesAndNewlines)
    guard !trimmed.isEmpty else { return token }

    let candidates = [
        trimmed,
        trimmed.capitalized,
        trimmed.prefix(1).uppercased() + trimmed.dropFirst().lowercased()
    ]

    for candidate in candidates where !candidate.isEmpty {
        let localized = appLocalized(candidate, language: language)
        if !localized.isEmpty, localized != candidate { return localized }
        if let lex = TemplateNameTokenLexicon.lookup(candidate, language: language) {
            return lex
        }
    }

    return trimmed.prefix(1).uppercased() + trimmed.dropFirst().lowercased()
}


@MainActor
final class AppLanguageManager {
    static let shared = AppLanguageManager()

    static let didChangeNotification = Notification.Name("AppLanguageManager.didChange")

    private static let legacyPreferredLanguageKey = "com.appforindeed.preferredLanguage"

    /// Settings override for this run only; cleared on launch so UI follows macOS each time.
    nonisolated(unsafe) private static var sessionOverride: AppLanguage?

    nonisolated static var resolvedLanguage: AppLanguage {
        sessionOverride ?? AppLanguage.systemLanguage
    }

    var current: AppLanguage {
        Self.resolvedLanguage
    }

    func applyStoredPreferenceOnLaunch() {
        // UI copy uses `appLocalized`; do not drive layout from `AppleLanguages` (Arabic forces RTL and breaks CV templates).
        Self.sessionOverride = nil
        UserDefaults.standard.removeObject(forKey: "AppleLanguages")
        UserDefaults.standard.removeObject(forKey: Self.legacyPreferredLanguageKey)
    }

    func setLanguage(_ language: AppLanguage, notify: Bool = true) {
        Self.sessionOverride = language
        UserDefaults.standard.removeObject(forKey: "AppleLanguages")
        if notify {
            NotificationCenter.default.post(name: Self.didChangeNotification, object: self)
        }
    }

    func setLanguage(code: String, notify: Bool = true) {
        guard let language = AppLanguage.allCases.first(where: { $0.localeIdentifier == code }) else { return }
        setLanguage(language, notify: notify)
    }
}