raise "JRuby is required to use the JDOM backend for XmlMini" unless RUBY_PLATFORM.include?("java")

require "jruby"
include Java

require "active_support/core_ext/object/blank"

java_import javax.xml.parsers.DocumentBuilder unless defined? DocumentBuilder
java_import javax.xml.parsers.DocumentBuilderFactory unless defined? DocumentBuilderFactory
java_import java.io.StringReader unless defined? StringReader
java_import org.xml.sax.InputSource unless defined? InputSource
java_import org.xml.sax.Attributes unless defined? Attributes
java_import org.w3c.dom.Node unless defined? Node

module ActiveSupport
  module XmlMini_JDOM #:nodoc:
    extend self

    CONTENT_KEY = "__content__".freeze

    NODE_TYPE_NAMES = %w{ATTRIBUTE_NODE CDATA_SECTION_NODE COMMENT_NODE DOCUMENT_FRAGMENT_NODE
    DOCUMENT_NODE DOCUMENT_TYPE_NODE ELEMENT_NODE ENTITY_NODE ENTITY_REFERENCE_NODE NOTATION_NODE
    PROCESSING_INSTRUCTION_NODE TEXT_NODE}

    node_type_map = {}
    NODE_TYPE_NAMES.each { |type| node_type_map[Node.send(type)] = type }

    # Parse an XML Document string or IO into a simple hash using Java's jdom.
    # data::
    #   XML Document string or IO to parse
    def parse(data)
      if data.respond_to?(:read)
        data = data.read
      end

      if data.blank?
        {}
      else
        @dbf = DocumentBuilderFactory.new_instance
        # secure processing of java xml
        # http://www.ibm.com/developerworks/xml/library/x-tipcfsx/index.html
        @dbf.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", false)
        @dbf.setFeature("http://xml.org/sax/features/external-general-entities", false)
        @dbf.setFeature("http://xml.org/sax/features/external-parameter-entities", false)
        @dbf.setFeature(javax.xml.XMLConstants::FEATURE_SECURE_PROCESSING, true)
        xml_string_reader = StringReader.new(data)
        xml_input_source = InputSource.new(xml_string_reader)
        doc = @dbf.new_document_builder.parse(xml_input_source)
        merge_element!({ CONTENT_KEY => "" }, doc.document_element, XmlMini.depth)
      end
    end

    private

      # Convert an XML element and merge into the hash
      #
      # hash::
      #   Hash to merge the converted element into.
      # element::
      #   XML element to merge into hash
      def merge_element!(hash, element, depth)
        raise "Document too deep!" if depth == 0
        delete_empty(hash)
        merge!(hash, element.tag_name, collapse(element, depth))
      end

      def delete_empty(hash)
        hash.delete(CONTENT_KEY) if hash[CONTENT_KEY] == ""
      end

      # Actually converts an XML document element into a data structure.
      #
      # element::
      #   The document element to be collapsed.
      def collapse(element, depth)
        hash = get_attributes(element)

        child_nodes = element.child_nodes
        if child_nodes.length > 0
          (0...child_nodes.length).each do |i|
            child = child_nodes.item(i)
            merge_element!(hash, child, depth - 1) unless child.node_type == Node.TEXT_NODE
          end
          merge_texts!(hash, element) unless empty_content?(element)
          hash
        else
          merge_texts!(hash, element)
        end
      end

      # Merge all the texts of an element into the hash
      #
      # hash::
      #   Hash to add the converted element to.
      # element::
      #   XML element whose texts are to me merged into the hash
      def merge_texts!(hash, element)
        delete_empty(hash)
        text_children = texts(element)
        if text_children.join.empty?
          hash
        else
          # must use value to prevent double-escaping
          merge!(hash, CONTENT_KEY, text_children.join)
        end
      end

      # Adds a new key/value pair to an existing Hash. If the key to be added
      # already exists and the existing value associated with key is not
      # an Array, it will be wrapped in an Array. Then the new value is
      # appended to that Array.
      #
      # hash::
      #   Hash to add key/value pair to.
      # key::
      #   Key to be added.
      # value::
      #   Value to be associated with key.
      def merge!(hash, key, value)
        if hash.has_key?(key)
          if hash[key].instance_of?(Array)
            hash[key] << value
          else
            hash[key] = [hash[key], value]
          end
        elsif value.instance_of?(Array)
          hash[key] = [value]
        else
          hash[key] = value
        end
        hash
      end

      # Converts the attributes array of an XML element into a hash.
      # Returns an empty Hash if node has no attributes.
      #
      # element::
      #   XML element to extract attributes from.
      def get_attributes(element)
        attribute_hash = {}
        attributes = element.attributes
        (0...attributes.length).each do |i|
          attribute_hash[CONTENT_KEY] ||= ""
          attribute_hash[attributes.item(i).name] = attributes.item(i).value
        end
        attribute_hash
      end

      # Determines if a document element has text content
      #
      # element::
      #   XML element to be checked.
      def texts(element)
        texts = []
        child_nodes = element.child_nodes
        (0...child_nodes.length).each do |i|
          item = child_nodes.item(i)
          if item.node_type == Node.TEXT_NODE
            texts << item.get_data
          end
        end
        texts
      end

      # Determines if a document element has text content
      #
      # element::
      #   XML element to be checked.
      def empty_content?(element)
        text = ""
        child_nodes = element.child_nodes
        (0...child_nodes.length).each do |i|
          item = child_nodes.item(i)
          if item.node_type == Node.TEXT_NODE
            text << item.get_data.strip
          end
        end
        text.strip.length == 0
      end
  end
end
