class ActiveSupport::OrderedHash

def self.[](*args)
  ordered_hash = new
  if (args.length == 1 && args.first.is_a?(Array))
    args.first.each do |key_value_pair|
      next unless (key_value_pair.is_a?(Array))
      ordered_hash[key_value_pair[0]] = key_value_pair[1]
    end
    return ordered_hash
  end
  unless (args.size % 2 == 0)
    raise ArgumentError.new("odd number of arguments for Hash")
  end
  args.each_with_index do |val, ind|
    next if (ind % 2 != 0)
    ordered_hash[val] = args[ind + 1]
  end
  ordered_hash
end

def []=(key, value)
  @keys << key if !has_key?(key)
  super
end

def clear
  super
  @keys.clear
  self
end

def delete(key)
  if has_key? key
    index = @keys.index(key)
    @keys.delete_at index
  end
  super
end

def delete_if
  super
  sync_keys!
  self
end

def each
  @keys.each {|key| yield [key, self[key]]}
end

def each_key
  @keys.each { |key| yield key }
end

def each_value
  @keys.each { |key| yield self[key]}
end

def initialize(*args, &block)
  super
  @keys = []
end

def initialize_copy(other)
  super
  # make a deep copy of keys
  @keys = other.keys
end

def inspect
  "#<OrderedHash #{super}>"
end

def invert
  OrderedHash[self.to_a.map!{|key_value_pair| key_value_pair.reverse}]
end

def keys
  @keys.dup
end

def merge(other_hash, &block)
  dup.merge!(other_hash, &block)
end

def merge!(other_hash)
  if block_given?
    other_hash.each { |k, v| self[k] = key?(k) ? yield(k, self[k], v) : v }
  else
    other_hash.each { |k, v| self[k] = v }
  end
  self
end

def reject(&block)
  dup.reject!(&block)
end

def reject!
  super
  sync_keys!
  self
end

def replace(other)
  super
  @keys = other.keys
  self
end

def shift
  k = @keys.first
  v = delete(k)
  [k, v]
end

def sync_keys!
  @keys.delete_if {|k| !has_key?(k)}
end

def to_a
  @keys.map { |key| [ key, self[key] ] }
end

def to_hash
  self
end

def to_yaml(opts = {})
  YAML.quick_emit(self, opts) do |out|
    out.seq(taguri, to_yaml_style) do |seq|
      each do |k, v|
        seq.add(k => v)
      end
    end
  end
end

def to_yaml_type
  "!tag:yaml.org,2002:omap"
end

def values
  @keys.collect { |key| self[key] }
end