module I18n
  module JS
    module Utils
      PLURAL_KEYS = %i[zero one two few many other].freeze

      # Based on deep_merge by Stefan Rusterholz, see <http://www.ruby-forum.com/topic/142809>.
      # This method is used to handle I18n fallbacks. Given two equivalent path nodes in two locale trees:
      # 1. If the node in the current locale appears to be an I18n pluralization (:one, :other, etc.),
      #    use the node, but merge in any missing/non-nil keys from the fallback (default) locale.
      # 2. Else if both nodes are Hashes, combine (merge) the key-value pairs of the two nodes into one,
      #    prioritizing the current locale.
      # 3. Else if either node is nil, use the other node.
      PLURAL_MERGER = proc do |_key, v1, v2|
        v1 || v2
      end
      MERGER = proc do |_key, v1, v2|
        if Hash === v1 && Hash === v2
          if (v2.keys - PLURAL_KEYS).empty?
            slice(v2.merge(v1, &PLURAL_MERGER), v2.keys)
          else
            v1.merge(v2, &MERGER)
          end
        else
          v2 || v1
        end
      end

      HASH_NIL_VALUE_CLEANER_PROC = proc do |k, v|
        v.kind_of?(Hash) ? (v.delete_if(&HASH_NIL_VALUE_CLEANER_PROC); false) : v.nil?
      end

      def self.slice(hash, keys)
        if hash.respond_to?(:slice) # ruby 2.5 onwards
          hash.slice(*keys)
        else
          hash.select {|key, _| keys.include?(key)}
        end
      end

      def self.strip_keys_with_nil_values(hash)
        hash.dup.delete_if(&HASH_NIL_VALUE_CLEANER_PROC)
      end

      def self.deep_merge(target_hash, hash) # :nodoc:
        target_hash.merge(hash, &MERGER)
      end

      def self.deep_merge!(target_hash, hash) # :nodoc:
        target_hash.merge!(hash, &MERGER)
      end

      def self.deep_reject(hash, scopes = [], &block)
        hash.each_with_object({}) do |(k, v), memo|
          unless block.call(k, v, scopes + [k.to_s])
            memo[k] = v.kind_of?(Hash) ? deep_reject(v, scopes + [k.to_s], &block) : v
          end
        end
      end

      def self.scopes_match?(scopes1, scopes2)
        if scopes1.length == scopes2.length
          [scopes1, scopes2].transpose.all? do |scope1, scope2|
            scope1.to_s == '*' || scope2.to_s == '*' || scope1.to_s == scope2.to_s
          end
        end
      end

      def self.deep_key_sort(hash)
        # Avoid things like `true` or `1` from YAML which causes error
        hash.keys.sort {|a, b| a.to_s <=> b.to_s}.
          each_with_object({}) do |key, seed|
          value = hash[key]
          seed[key] = value.is_a?(Hash) ? deep_key_sort(value) : value
        end
      end

      def self.deep_remove_procs(hash)
        # procs exist in `i18n.plural.rule` as pluralizer
        # But having it in translation causes the exported JS/JSON changes every time
        # https://github.com/ruby-i18n/i18n/blob/v1.8.7/lib/i18n/backend/pluralization.rb#L51
        hash.keys.
          each_with_object({}) do |key, seed|
          value = hash[key]
          next if value.is_a?(Proc)

          seed[key] = value.is_a?(Hash) ? deep_remove_procs(value) : value
        end
      end
    end
  end
end