# frozen_string_literal: true
require 'easy_translate'
require 'i18n/tasks/html_keys'

module I18n::Tasks
  module GoogleTranslation
    # @param [I18n::Tasks::Tree::Siblings] forest to translate to the locales of its root nodes
    # @param [String] from locale
    # @return [I18n::Tasks::Tree::Siblings] translated forest
    def google_translate_forest(forest, from)
      forest.inject empty_forest do |result, root|
        translated = google_translate_list(root.key_values(root: true), to: root.key, from: from)
        result.merge! Data::Tree::Siblings.from_flat_pairs(translated)
      end
    end

    # @param [Array<[String, Object]>] list of key-value pairs
    # @return [Array<[String, Object]>] translated list
    def google_translate_list(list, opts) # rubocop:disable Metrics/AbcSize
      return [] if list.empty?
      opts = opts.dup
      opts[:key] ||= translation_config[:api_key]
      validate_google_translate_api_key! opts[:key]
      key_pos = list.each_with_index.inject({}) { |idx, ((k, _v), i)| idx.update(k => i) }
      # copy reference keys as is, instead of translating
      reference_key_vals = list.select { |_k, v| v.is_a? Symbol } || []
      list -= reference_key_vals
      result = list.group_by { |k_v| html_key? k_v[0], opts[:from] }.map do |is_html, list_slice|
        fetch_google_translations list_slice, opts.merge(is_html ? { html: true } : { format: 'text' })
      end.reduce(:+) || []
      result.concat(reference_key_vals)
      result.sort! { |a, b| key_pos[a[0]] <=> key_pos[b[0]] }
      result
    end

    # @param [Array<[String, Object]>] list of key-value pairs
    # @return [Array<[String, Object]>] translated list
    def fetch_google_translations(list, opts)
      from_values(list, EasyTranslate.translate(to_values(list), opts)).tap do |result|
        if result.blank?
          fail CommandError, I18n.t('i18n_tasks.google_translate.errors.no_results')
        end
      end
    end

    private

    def validate_google_translate_api_key!(key)
      if key.blank?
        fail CommandError, I18n.t('i18n_tasks.google_translate.errors.no_api_key')
      end
    end

    # @param [Array<[String, Object]>] list of key-value pairs
    # @return [Array<String>] values for translation extracted from list
    def to_values(list)
      list.map { |l| dump_value l[1] }.flatten.compact
    end

    # @param [Array<[String, Object]>] list
    # @param [Array<String>] translated_values
    # @return [Array<[String, Object]>] translated key-value pairs
    def from_values(list, translated_values)
      keys                = list.map(&:first)
      untranslated_values = list.map(&:last)
      keys.zip parse_value(untranslated_values, translated_values.to_enum)
    end

    # Prepare value for translation.
    # @return [String, Array<String, nil>, nil] value for Google Translate or nil for non-string values
    def dump_value(value)
      case value
      when Array
        # dump recursively
        value.map { |v| dump_value v }
      when String
        replace_interpolations value
      end
    end

    # Parse translated value from the each_translated enumerator
    # @param [Object] untranslated
    # @param [Enumerator] each_translated
    # @return [Object] final translated value
    def parse_value(untranslated, each_translated)
      case untranslated
      when Array
        # implode array
        untranslated.map { |from| parse_value(from, each_translated) }
      when String
        restore_interpolations untranslated, each_translated.next
      else
        untranslated
      end
    end

    INTERPOLATION_KEY_RE  = /%\{[^}]+\}/
    UNTRANSLATABLE_STRING = 'zxzxzx'

    # @param [String] value
    # @return [String] 'hello, %{name}' => 'hello, <round-trippable string>'
    def replace_interpolations(value)
      value.gsub INTERPOLATION_KEY_RE, UNTRANSLATABLE_STRING
    end

    # @param [String] untranslated
    # @param [String] translated
    # @return [String] 'hello, <round-trippable string>' => 'hello, %{name}'
    def restore_interpolations(untranslated, translated)
      return translated if untranslated !~ INTERPOLATION_KEY_RE
      each_value = untranslated.scan(INTERPOLATION_KEY_RE).to_enum
      translated.gsub(Regexp.new(UNTRANSLATABLE_STRING, Regexp::IGNORECASE)) { each_value.next }
    end
  end
end