require "time"
require "base64"
require "bigdecimal"
require "active_support/core_ext/module/delegation"
require "active_support/core_ext/string/inflections"
require "active_support/core_ext/date_time/calculations"

module ActiveSupport
  # = XmlMini
  #
  # To use the much faster libxml parser:
  #   gem 'libxml-ruby', '=0.9.7'
  #   XmlMini.backend = 'LibXML'
  module XmlMini
    extend self

    # This module decorates files deserialized using Hash.from_xml with
    # the <tt>original_filename</tt> and <tt>content_type</tt> methods.
    module FileLike #:nodoc:
      attr_writer :original_filename, :content_type

      def original_filename
        @original_filename || "untitled"
      end

      def content_type
        @content_type || "application/octet-stream"
      end
    end

    DEFAULT_ENCODINGS = {
      "binary" => "base64"
    } unless defined?(DEFAULT_ENCODINGS)

    unless defined?(TYPE_NAMES)
      TYPE_NAMES = {
        "Symbol"     => "symbol",
        "Integer"    => "integer",
        "BigDecimal" => "decimal",
        "Float"      => "float",
        "TrueClass"  => "boolean",
        "FalseClass" => "boolean",
        "Date"       => "date",
        "DateTime"   => "dateTime",
        "Time"       => "dateTime",
        "Array"      => "array",
        "Hash"       => "hash"
      }

      # No need to map these on Ruby 2.4+
      TYPE_NAMES["Fixnum"] = "integer" unless Fixnum == Integer
      TYPE_NAMES["Bignum"] = "integer" unless Bignum == Integer
    end

    FORMATTING = {
      "symbol"   => Proc.new { |symbol| symbol.to_s },
      "date"     => Proc.new { |date| date.to_s(:db) },
      "dateTime" => Proc.new { |time| time.xmlschema },
      "binary"   => Proc.new { |binary| ::Base64.encode64(binary) },
      "yaml"     => Proc.new { |yaml| yaml.to_yaml }
    } unless defined?(FORMATTING)

    # TODO use regexp instead of Date.parse
    unless defined?(PARSING)
      PARSING = {
        "symbol"       => Proc.new { |symbol|  symbol.to_s.to_sym },
        "date"         => Proc.new { |date|    ::Date.parse(date) },
        "datetime"     => Proc.new { |time|    Time.xmlschema(time).utc rescue ::DateTime.parse(time).utc },
        "integer"      => Proc.new { |integer| integer.to_i },
        "float"        => Proc.new { |float|   float.to_f },
        "decimal"      => Proc.new { |number|  BigDecimal(number) },
        "boolean"      => Proc.new { |boolean| %w(1 true).include?(boolean.to_s.strip) },
        "string"       => Proc.new { |string|  string.to_s },
        "yaml"         => Proc.new { |yaml|    YAML::load(yaml) rescue yaml },
        "base64Binary" => Proc.new { |bin|     ::Base64.decode64(bin) },
        "binary"       => Proc.new { |bin, entity| _parse_binary(bin, entity) },
        "file"         => Proc.new { |file, entity| _parse_file(file, entity) }
      }

      PARSING.update(
        "double"   => PARSING["float"],
        "dateTime" => PARSING["datetime"]
      )
    end

    attr_accessor :depth
    self.depth = 100

    delegate :parse, to: :backend

    def backend
      current_thread_backend || @backend
    end

    def backend=(name)
      backend = name && cast_backend_name_to_module(name)
      self.current_thread_backend = backend if current_thread_backend
      @backend = backend
    end

    def with_backend(name)
      old_backend = current_thread_backend
      self.current_thread_backend = name && cast_backend_name_to_module(name)
      yield
    ensure
      self.current_thread_backend = old_backend
    end

    def to_tag(key, value, options)
      type_name = options.delete(:type)
      merged_options = options.merge(root: key, skip_instruct: true)

      if value.is_a?(::Method) || value.is_a?(::Proc)
        if value.arity == 1
          value.call(merged_options)
        else
          value.call(merged_options, key.to_s.singularize)
        end
      elsif value.respond_to?(:to_xml)
        value.to_xml(merged_options)
      else
        type_name ||= TYPE_NAMES[value.class.name]
        type_name ||= value.class.name if value && !value.respond_to?(:to_str)
        type_name   = type_name.to_s   if type_name
        type_name   = "dateTime" if type_name == "datetime"

        key = rename_key(key.to_s, options)

        attributes = options[:skip_types] || type_name.nil? ? { } : { type: type_name }
        attributes[:nil] = true if value.nil?

        encoding = options[:encoding] || DEFAULT_ENCODINGS[type_name]
        attributes[:encoding] = encoding if encoding

        formatted_value = FORMATTING[type_name] && !value.nil? ?
          FORMATTING[type_name].call(value) : value

        options[:builder].tag!(key, formatted_value, attributes)
      end
    end

    def rename_key(key, options = {})
      camelize  = options[:camelize]
      dasherize = !options.has_key?(:dasherize) || options[:dasherize]
      if camelize
        key = true == camelize ? key.camelize : key.camelize(camelize)
      end
      key = _dasherize(key) if dasherize
      key
    end

    protected

      def _dasherize(key)
        # $2 must be a non-greedy regex for this to work
        left, middle, right = /\A(_*)(.*?)(_*)\Z/.match(key.strip)[1,3]
        "#{left}#{middle.tr('_ ', '--')}#{right}"
      end

    # TODO: Add support for other encodings
      def _parse_binary(bin, entity) #:nodoc:
        case entity["encoding"]
        when "base64"
          ::Base64.decode64(bin)
        else
          bin
        end
      end

      def _parse_file(file, entity)
        f = StringIO.new(::Base64.decode64(file))
        f.extend(FileLike)
        f.original_filename = entity["name"]
        f.content_type = entity["content_type"]
        f
      end

    private

      def current_thread_backend
        Thread.current[:xml_mini_backend]
      end

      def current_thread_backend=(name)
        Thread.current[:xml_mini_backend] = name && cast_backend_name_to_module(name)
      end

      def cast_backend_name_to_module(name)
        if name.is_a?(Module)
          name
        else
          require "active_support/xml_mini/#{name.downcase}"
          ActiveSupport.const_get("XmlMini_#{name}")
        end
      end
  end

  XmlMini.backend = "REXML"
end