raise "JRuby is required to use the JDOM backend for XmlMini" unless RUBY_PLATFORM =~ /java/

require 'jruby'
include Java

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

# = XmlMini JRuby JDOM implementation
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 into a simple hash using Java's jdom.
    # string::
    #   XML Document string to parse
    def parse(string)
      if string.blank?
        {}
      else
        @dbf = DocumentBuilderFactory.new_instance
        xml_string_reader = StringReader.new(string)
        xml_input_source = InputSource.new(xml_string_reader)
        doc = @dbf.new_document_builder.parse(xml_input_source)
        merge_element!({}, doc.document_element)
      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)
      merge!(hash, element.tag_name, collapse(element))
    end

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

      child_nodes = element.child_nodes
      if child_nodes.length > 0
        for i in 0...child_nodes.length
          child = child_nodes.item(i)
          merge_element!(hash, child) 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 emement to.
    # element::
    #   XML element whose texts are to me merged into the hash
    def merge_texts!(hash, element)
      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
      for i in 0...attributes.length
         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
      for i in 0...child_nodes.length
        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
      for i in 0...child_nodes.length
        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
