class AliasAndImplicationImporter
  class Error < RuntimeError; end
  attr_accessor :text, :commands, :forum_id, :skip_secondary_validations

  def initialize(text, forum_id, skip_secondary_validations = true)
    @forum_id = forum_id
    @text = text
    @skip_secondary_validations = skip_secondary_validations
  end

  def process!(approver = CurrentUser.user)
    tokens = AliasAndImplicationImporter.tokenize(text)
    parse(tokens, approver)
  end

  def validate!
    tokens = AliasAndImplicationImporter.tokenize(text)
    validate(tokens)
  end

  def self.tokenize(text)
    text.split(/\r\n|\r|\n/).reject(&:blank?).map do |line|
      line = line.gsub(/[[:space:]]+/, " ").strip

      if line =~ /^(?:create alias|aliasing|alias) (\S+) -> (\S+)$/i
        [:create_alias, $1, $2]

      elsif line =~ /^(?:create implication|implicating|implicate|imply) (\S+) -> (\S+)$/i
        [:create_implication, $1, $2]

      elsif line =~ /^(?:remove alias|unaliasing|unalias) (\S+) -> (\S+)$/i
        [:remove_alias, $1, $2]

      elsif line =~ /^(?:remove implication|unimplicating|unimplicate|unimply) (\S+) -> (\S+)$/i
        [:remove_implication, $1, $2]

      elsif line =~ /^(?:mass update|updating|update|change) (.+?) -> (.*)$/i
        [:mass_update, $1, $2]

      elsif line =~ /^category (\S+) -> (#{Tag.categories.regexp})/
        [:change_category, $1, $2]

      elsif line.strip.empty?
        # do nothing

      else
        raise Error, "Unparseable line: #{line}"
      end
    end
  end

  def validate(tokens)
    tokens.map do |token|
      case token[0]
      when :create_alias
        tag_alias = TagAlias.new(creator: User.system, forum_topic_id: forum_id, status: "pending", antecedent_name: token[1], consequent_name: token[2], skip_secondary_validations: skip_secondary_validations)
        unless tag_alias.valid?
          raise Error, "Error: #{tag_alias.errors.full_messages.join("; ")} (create alias #{tag_alias.antecedent_name} -> #{tag_alias.consequent_name})"
        end

      when :create_implication
        tag_implication = TagImplication.new(creator: User.system, forum_topic_id: forum_id, status: "pending", antecedent_name: token[1], consequent_name: token[2], skip_secondary_validations: skip_secondary_validations)
        unless tag_implication.valid?
          raise Error, "Error: #{tag_implication.errors.full_messages.join("; ")} (create implication #{tag_implication.antecedent_name} -> #{tag_implication.consequent_name})"
        end

      when :remove_alias, :remove_implication, :mass_update, :change_category
        # okay

      else
        raise NotImplementedError, "Unknown token: #{token[0]}" # should never happen
      end
    end
  end

  def affected_tags
    AliasAndImplicationImporter.tokenize(text).flat_map do |type, *args|
      case type
      when :create_alias, :remove_alias, :create_implication, :remove_implication
        [args[0], args[1]]
      when :mass_update
        tags = PostQueryBuilder.new(args[0]).tags + PostQueryBuilder.new(args[1]).tags
        tags.reject(&:negated).reject(&:optional).reject(&:wildcard).map(&:name)
      when :change_category
        args[0]
      end
    end.sort.uniq
  rescue Error
    []
  end

  private

  def parse(tokens, approver)
    ActiveRecord::Base.transaction do
      tokens.map do |token|
        case token[0]
        when :create_alias
          tag_alias = TagAlias.create(creator: approver, forum_topic_id: forum_id, status: "pending", antecedent_name: token[1], consequent_name: token[2], skip_secondary_validations: skip_secondary_validations)
          unless tag_alias.valid?
            raise Error, "Error: #{tag_alias.errors.full_messages.join("; ")} (create alias #{tag_alias.antecedent_name} -> #{tag_alias.consequent_name})"
          end
          tag_alias.approve!(approver: approver)

        when :create_implication
          tag_implication = TagImplication.create(creator: approver, forum_topic_id: forum_id, status: "pending", antecedent_name: token[1], consequent_name: token[2], skip_secondary_validations: skip_secondary_validations)
          unless tag_implication.valid?
            raise Error, "Error: #{tag_implication.errors.full_messages.join("; ")} (create implication #{tag_implication.antecedent_name} -> #{tag_implication.consequent_name})"
          end
          tag_implication.approve!(approver: approver)

        when :remove_alias
          tag_alias = TagAlias.active.find_by(antecedent_name: token[1], consequent_name: token[2])
          raise Error, "Alias for #{token[1]} not found" if tag_alias.nil?
          tag_alias.reject!

        when :remove_implication
          tag_implication = TagImplication.active.find_by(antecedent_name: token[1], consequent_name: token[2])
          raise Error, "Implication for #{token[1]} not found" if tag_implication.nil?
          tag_implication.reject!

        when :mass_update
          TagBatchChangeJob.perform_later(token[1], token[2], User.system, "127.0.0.1")

        when :change_category
          tag = Tag.find_or_create_by_name(token[1])
          tag.category = Tag.categories.value_for(token[2])
          tag.save

        else
          raise Error, "Unknown token: #{token[0]}"
        end
      end
    end
  end
end