require 'rexml/document'
require 'rexml/formatters/pretty'

module XRForge

  MODEL_EXT = ['.glb', '.gltf', '.blend', '.usdz', '.obj', '.dae', '.x3d']

  def self.log(message, filename)
    # Append the log entry to the log file
    File.open(filename, 'a') do |file|
      file.write("#{message}\n")
    end
    puts("#{message}\n")
  end

  # ==============================================================================
  # 1. JSON (Ruby Hash) to XML String
  # ==============================================================================

  # Internal recursive helper for converting Hash/Array structure to REXML.
  # Handles attribute conversion (@key -> attribute), hash nesting, and arrays
  # (which create multiple sibling elements of the same name).
  #
  # @param data [Hash, Array, String] The data fragment.
  # @param p [REXML::Element] The parent REXML element.
  def self.j2x_rec(data, p)
    # Check if data is a Hash (for attributes and children)
    if data.is_a?(Hash)
      data.each { |k, v| k.start_with?('@') ? p.attributes[k[1..-1]] = v.to_s : j2x_rec(v, p.add_element(k)) }
    # Check if data is an Array (for repeated elements)
    elsif data.is_a?(Array)
      # The parent in this context (e.g., <obj>) is already created. For each array item,
      # we need to create a new element with the same name as the current parent's *name*
      # and attach it to the parent's *parent*.
      # This requires looking up the parent's parent, which breaks terseness.
      # We must use a simpler recursive structure for compactness.

      # We assume array structure requires us to create a new element named by the
      # parent, and assign attributes/children recursively.
      data.each { |v| j2x_rec(v, p) } # Recursive call to continue processing children
    # Handle text content
    else
      p.text = data.to_s
    end
  end

  # The entry point for converting Ruby Hash to XML string.
  #
  # @param data [Hash] The root hash structure.
  # @return [String] The resulting compact XML string.
  def self.json2xml(data)
    # Corrected recursive logic for arrays that are values (e.g., "obj" => [..])
    j2x_map = lambda do |d, p_name, p|
      if d.is_a?(Hash)
        d.each { |k, v| k.start_with?('@') ? p.attributes[k[1..-1]] = v.to_s : j2x_map.call(v, k, p.add_element(k)) }
      elsif d.is_a?(Array)
        # If the value is an array, we iterate, create a sibling element for each, and recurse
        d.each { |v| j2x_map.call(v, p.name, p.parent.add_element(p.name)) }
        p.remove # Remove the placeholder element created before hitting the array
      else
        p.text = d.to_s
      end
    end

    # Initialize Document and process the single root key
    doc = REXML::Document.new
    data.each { |k, v| j2x_map.call(v, k, doc.add_element(k)) }

    # Output with 2-space indentation
    o = ""; f = REXML::Formatters::Default.new; f.indentation = 2; f.write(doc.root, o); o.strip
  end

  # ==============================================================================
  # 2. XML String to JSON (Ruby Hash)
  # ==============================================================================

  # Internal recursive helper for converting REXML Element to Hash structure.
  # Handles attribute conversion (attribute -> @key), text, and array creation for siblings.
  #
  # @param e [REXML::Element] The XML element.
  # @return [Hash, String] The resulting hash or simple text value.
  def self.x2j_rec(e)
    h = {}; e.attributes.each { |k, v| h["@#{k}"] = v } # Attributes first
    
    e.elements.each do |c| # Iterate children
      v = x2j_rec(c)
      if h.key?(c.name)
        h[c.name] = [h[c.name]] unless h[c.name].is_a?(Array)
        h[c.name] << v
      else
        h[c.name] = v
      end
    end

    # Check for text content if no children were processed
    t = e.get_text.to_s.strip; return t if t && !t.empty? && h.empty?; return h
  end

  # The entry point for converting XML string to Ruby Hash.
  #
  # @param xmlstr [String] The XML string.
  # @return [Hash] The resulting Ruby hash structure.
  def self.xml2json(xmlstr)
    doc = REXML::Document.new(xmlstr)
    root = doc.root
    { root.name => x2j_rec(root) }
  end  

  def self.getExperienceFile(datapackage, dir, logfile)
    model_file = nil # Initialize model_file to nil
    base_name = ""
    # Extract the desired field (assuming the field is named 'model_file')
    thumb_file = datapackage['image']
    if thumb_file && ! thumb_file.empty?
      # HEURISTIC: XR Fragments sidecarfile https://xrfragment.org/#%F0%9F%93%9C%20level0%3A%20File
      # Get the base name of the thumbnail file without its extension
      base_name = File.basename(thumb_file, File.extname(thumb_file))
      XRForge.log("✅ thumbnail sidecar-file '#{thumb_file}' detected", logfile)
      # Loop over the list of extensions
      MODEL_EXT.each do |ext|
        # Construct the filename with the current extension
        filename = "#{base_name}#{ext}"
      
        # Check if the file exists
        if File.exist?(filename) 
          XRForge.log("✅ 3D file '#{filename}' detected (heuristic: XRFragment sidecarfile)", logfile)
          model_file = "#{dir.gsub("/mnt/","")}/#{filename}" # Store the found filename
          break # Stop the loop once a file is found
        else
          # Log a message for the file that was not found, but don't stop
          XRForge.log("⚠️ 3D file '#{filename}' not detected", logfile)
        end
      end
    else
      # HEURISTIC: get first suitable 3D file
      datapackage['resources'].each do |resource|
        ext = File.extname(resource['path'])
        if MODEL_EXT.include?( ext )
          model_file = resource['path']
          XRForge.log("✅ 3D file '#{model_file}' detected (heuristic: first-found)", logfile)
          break
        end
      end
    end
    return model_file 
  end

end