require "nokogiri"
require "pathname"

require_relative "string"

# The DSLGenerator class generates the DSL methods and files
# for use in JMeter performance testing scripts. It uses a JMeter TestPlan (idl.xml)
# to generate the methods and files.
# @see https://github.com/jlurena/jmeter_perf/wiki/3.-Generating-DSL-Methods
class DSLGenerator
  # Initializes the DSLGenerator.
  # @param dsl_dir [String] Path to the directory where DSL files will be generated.
  # @param idl_xml_path [String] Path to the XML file used for generating methods.
  def initialize(dsl_dir:, idl_xml_path:, document_dsl: true)
    @document_dsl = document_dsl
    @dsl_dir = dsl_dir
    @idl_xml_path = idl_xml_path
  end

  # Main method to generate DSL files and methods.
  # It parses the XML, generates methods, documents,
  # updates RBS files, and creates individual DSL files.
  # @return [void]
  def generate
    results = parse_xml
    methods = generate_methods(results)

    write_methods_to_dsl_md(methods) if @document_dsl
    update_rbs(methods) if @document_dsl
    create_dsl_files(results)
  end

  private

  # Parses the XML file specified by the `idl_xml_path` parameter.
  # @return [Array<Nokogiri::XML::Node>] Array of XML nodes representing valid elements.
  def parse_xml
    idl_xml = File.open(@idl_xml_path)
    doc = Nokogiri::XML(idl_xml.read.gsub(/\n\s+/, ""))
    results = []

    doc.traverse do |node|
      if valid_node?(node)
        results << node
      end
    end

    results
  end

  # Checks if a given Nokogiri XML node is valid based on specific criteria.
  #
  # A node is considered valid if:
  # - It is not an instance of Nokogiri::XML::Document.
  # - It has an attribute named "testclass".
  # - Its name is not "elementProp".
  #
  # @param node [Nokogiri::XML::Node] The XML node to be validated.
  # @return [Boolean] Returns true if the node is valid, false otherwise.
  def valid_node?(node)
    node.class != Nokogiri::XML::Document &&
      node.attributes["testclass"] &&
      node.name != "elementProp"
  end

  # Generates methods based on parsed XML results.
  # @param results [Array<Nokogiri::XML::Node>] Parsed XML nodes.
  # @return [Array<Array<String>>] Array of class and method name pairs.
  def generate_methods(results)
    results.map do |element|
      klass = JmeterPerf::Helpers::String.classify(element.attributes["testname"].to_s)
      method = JmeterPerf::Helpers::String.underscore(klass)
      [klass, method]
    end.sort_by(&:first)
  end

  # Creates individual DSL files based on parsed XML results.
  # @param results [Array<Nokogiri::XML::Node>] Parsed XML nodes.
  # @return [void]
  def create_dsl_files(results)
    FileUtils.rm_rf(@dsl_dir)
    FileUtils.mkdir_p(@dsl_dir)

    results.each do |element|
      klass = JmeterPerf::Helpers::String.classify(element.attributes["testname"].to_s)
      puts "\tfor Element #{klass}"
      File.write("#{@dsl_dir}/#{JmeterPerf::Helpers::String.underscore(klass)}.rb", <<~EOC)
        module JmeterPerf
          class DSL
            # DSL method synonymous with the JMeter Element #{klass}
            # @param [Hash] params Parameters for the #{klass} element (default: `{}`).
            # @yield block to attach to the #{klass} element
            # @return [JmeterPerf::#{klass}], a subclass of JmeterPerf::DSL that can be chained with other DSL methods.
            # @see https://github.com/jlurena/jmeter_perf/wiki/1.-DSL-Documentation##{klass.downcase}
            def #{JmeterPerf::Helpers::String.underscore(klass)}(params = {}, &)
              node = #{klass}.new(params)
              attach_node(node, &)
            end

            class #{klass}
              attr_accessor :doc
              include JmeterPerf::Helpers::XmlDocumentUpdater

              def initialize(params = {})
                testname = params.is_a?(Array) ? "#{klass}" : (params[:name] || "#{klass}")
                @doc = Nokogiri::XML(JmeterPerf::Helpers::String.strip_heredoc(
                  <<~EOS
        #{element.to_xml.gsub(/testname=".+?"/, 'testname="#{testname}"').gsub(/^/, "            ")}
                  EOS
                ))
                update params
                update_at_xpath params if params.is_a?(Hash) && params[:update_at_xpath]
              end
            end
          end
        end
      EOC
    end
  end

  # Updates the RBS file with method signatures for the DSL methods.
  # @param methods [Array<Array<String>>] Array of class and method name pairs.
  # @return [void]
  def update_rbs(methods)
    file_path = "sig/jmeter_perf.rbs"
    replace_regex = /\s*## AUTOGENERATED - DSL methods RBS(.*?)## AUTOGENERATED - DSL methods RBS/m
    new_content = <<~NEW_CONTENT
      #{methods.map { |klass, method| "    def #{method}: (Hash[Symbol, untyped], &block) -> void" }.join("\n")}
    NEW_CONTENT

    current_content = File.read(file_path)

    new_file_content = current_content.gsub(replace_regex) do
      "\n    ## AUTOGENERATED - DSL methods RBS\n\n#{new_content}\n    ## AUTOGENERATED - DSL methods RBS"
    end

    File.write(file_path, new_file_content)
  end

  # Writes the list of generated methods to a markdown file.
  # @param methods [Array<Array<String>>] Array of class and method name pairs.
  # @return [void]
  def write_methods_to_dsl_md(methods)
    output = []
    output << "# JmeterPerf::DSL methods"

    methods.each do |klass, method|
      output << "- #{klass}\n  `#{method}`"
    end

    File.write("DSL.md", output.join("\n"))
  end
end