# frozen_string_literal: true

# This patch performs 2 functions
#
# 1. It caches all translations which drastically improves
#    translation performance in an LRU cache
#
# 2. It patches I18n so it only loads the translations it needs
#    on demand
#
# This patch depends on the convention that locale yml files must be named [locale_name].yml

module I18n

  # this accelerates translation a tiny bit (halves the time it takes)
  class << self
    alias_method :translate_no_cache, :translate
    alias_method :exists_no_cache?, :exists?
    alias_method :reload_no_cache!, :reload!
    alias_method :locale_no_cache=, :locale=

    LRU_CACHE_SIZE = 400

    def init_accelerator!(overrides_enabled: true)
      @overrides_enabled = overrides_enabled
      execute_reload
    end

    def reload!
      @requires_reload = true
    end

    LOAD_MUTEX = Mutex.new

    def load_locale(locale)
      LOAD_MUTEX.synchronize do
        return if @loaded_locales.include?(locale)

        if @loaded_locales.empty?
          # load all rb files
          I18n.backend.load_translations(I18n.load_path.grep(/\.rb$/))

          # load plural rules from plugins
          DiscoursePluginRegistry.locales.each do |plugin_locale, options|
            if options[:plural]
              I18n.backend.store_translations(
                plugin_locale,
                i18n: { plural: options[:plural] }
              )
            end
          end
        end

        # load it
        I18n.backend.load_translations(I18n.load_path.grep(/\.#{Regexp.escape locale}\.yml$/))

        @loaded_locales << locale
      end
    end

    def ensure_all_loaded!
      I18n.fallbacks[locale].each { |l| ensure_loaded!(l) }
    end

    def search(query, opts = {})
      execute_reload if @requires_reload

      locale = opts[:locale] || config.locale

      load_locale(locale) unless @loaded_locales.include?(locale)
      opts ||= {}

      target = opts[:backend] || backend
      results = opts[:overridden] ? {} : target.search(config.locale, query)

      regexp = I18n::Backend::DiscourseI18n.create_search_regexp(query)
      (overrides_by_locale(locale) || {}).each do |k, v|
        results.delete(k)
        results[k] = v if (k =~ regexp || v =~ regexp)
      end
      results
    end

    def ensure_loaded!(locale)
      @loaded_locales ||= []
      load_locale(locale) unless @loaded_locales.include?(locale)
    end

    # In some environments such as migrations we don't want to use overrides.
    # Use this to disable them over a block of ruby code
    def overrides_disabled
      @overrides_enabled = false
      yield
    ensure
      @overrides_enabled = true
    end

    class MissingTranslation; end

    def translate_no_override(key, options)
      # note we skip cache for :format and :count
      should_raise = false
      locale = nil

      dup_options = nil
      if options
        dup_options = options.dup
        should_raise = dup_options.delete(:raise)
        locale = dup_options.delete(:locale)
      end

      if dup_options.present?
        return translate_no_cache(key, **options)
      end

      locale ||= config.locale

      @cache ||= LruRedux::ThreadSafeCache.new(LRU_CACHE_SIZE)
      k = "#{key}#{locale}#{config.backend.object_id}"

      val = @cache.getset(k) do
        begin
          translate_no_cache(key, locale: locale, raise: true).freeze
        rescue I18n::MissingTranslationData
          MissingTranslation
        end
      end

      if val != MissingTranslation
        val
      elsif should_raise
        raise I18n::MissingTranslationData.new(locale, key)
      else
        -"translation missing: #{locale}.#{key}"
      end
    end

    def overrides_by_locale(locale)
      return unless @overrides_enabled
      return {} if GlobalSetting.skip_db?

      execute_reload if @requires_reload

      site = RailsMultisite::ConnectionManagement.current_db

      by_site = @overrides_by_site[site]
      by_site ||= {}

      if !by_site.has_key?(locale)
        # Load overrides
        translations_overrides = TranslationOverride.where(locale: locale).pluck(:translation_key, :value, :compiled_js)

        if translations_overrides.empty?
          by_site[locale] = {}
        else
          translations_overrides.each do |tuple|
            by_locale = by_site[locale] ||= {}
            by_locale[tuple[0]] = tuple[2] || tuple[1]
          end
        end

        @overrides_by_site[site] = by_site
      end

      by_site[locale].with_indifferent_access
    rescue ActiveRecord::StatementInvalid => e
      if PG::UndefinedTable === e.cause
        {}
      else
        raise
      end
    end

    def translate(*args)
      execute_reload if @requires_reload

      options  = args.last.is_a?(Hash) ? args.pop.dup : {}
      key      = args.shift
      locale   = options[:locale] || config.locale

      load_locale(locale) unless @loaded_locales.include?(locale)

      if @overrides_enabled
        overrides = {}

        # for now lets do all the expensive work for keys with count
        # no choice really
        has_override = !!options[:count]

        I18n.fallbacks[locale].each do |l|
          override = overrides[l] = overrides_by_locale(l)
          has_override ||= override.key?(key)
        end

        if has_override && overrides.present?
          if options.present?
            options[:overrides] = overrides

            # I18n likes to use throw...
            catch(:exception) do
              return backend.translate(locale, key, options)
            end
          else
            overrides.each do |_k, v|
              if result = v[key]
                return result
              end
            end
          end
        end
      end

      translate_no_override(key, options)
    end

    alias_method :t, :translate

    def exists?(key, locale = nil)
      execute_reload if @requires_reload

      locale ||= config.locale
      load_locale(locale) unless @loaded_locales.include?(locale)
      exists_no_cache?(key, locale)
    end

    def locale=(value)
      execute_reload if @requires_reload
      self.locale_no_cache = value
    end

    private

    RELOAD_MUTEX = Mutex.new

    def execute_reload
      RELOAD_MUTEX.synchronize do
        return unless @requires_reload

        @loaded_locales = []
        @cache = nil
        @overrides_by_site = {}

        reload_no_cache!
        ensure_all_loaded!

        @requires_reload = false
      end
    end
  end
end