# --
# Copyright (C) 2008-2010 10gen Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# ++

# A hash in which the order of keys are preserved.
#
# Under Ruby 1.9 and greater, this class has no added methods because Ruby's
# Hash already keeps its keys ordered by order of insertion.
module BSON
  class OrderedHash < Hash

    def ==(other)
      begin
        !other.nil? &&
          keys == other.keys &&
          values == other.values
      rescue
        false
      end
    end

    # We only need the body of this class if the RUBY_VERSION is before 1.9
    if RUBY_VERSION < '1.9'
      attr_accessor :ordered_keys

      def self.[] *args
        oh = BSON::OrderedHash.new
        if Hash === args[0]
          oh.merge! args[0]
        elsif (args.size % 2) != 0
          raise ArgumentError, "odd number of elements for Hash"
        else
          0.step(args.size - 1, 2) do |key|
            value = key + 1
            oh[args[key]] = args[value]
          end
        end
        oh
      end

      def initialize(*a, &b)
        super
        @ordered_keys = []
      end

      def keys
        @ordered_keys || []
      end

      def []=(key, value)
        @ordered_keys ||= []
        @ordered_keys << key unless @ordered_keys.include?(key)
        super(key, value)
      end

      def each
        @ordered_keys ||= []
        @ordered_keys.each { |k| yield k, self[k] }
        self
      end
      alias :each_pair :each

      def to_a
        @ordered_keys ||= []
        @ordered_keys.map { |k| [k, self[k]] }      
      end
    
      def values
        collect { |k, v| v }
      end

      def merge(other)
        oh = self.dup
        oh.merge!(other)
        oh
      end

      def merge!(other)
        @ordered_keys ||= []
        @ordered_keys += other.keys # unordered if not an BSON::OrderedHash
        @ordered_keys.uniq!
        super(other)
      end

      alias :update :merge!

      def inspect
        str = '{'
        str << (@ordered_keys || []).collect { |k| "\"#{k}\"=>#{self.[](k).inspect}" }.join(", ")
        str << '}'
      end

      def delete(key, &block)
        @ordered_keys.delete(key) if @ordered_keys
        super
      end

      def delete_if(&block)
        self.each { |k,v|
          if yield k, v
            delete(k)
          end
        }
      end

      def clear
        super
        @ordered_keys = []
      end

      def hash
        code = 17
        each_pair do |key, value|
          code = 37 * code + key.hash
          code = 37 * code + value.hash
        end
        code & 0x7fffffff
      end

      def eql?(o)
        if o.instance_of? BSON::OrderedHash
          self.hash == o.hash
        else
          false
        end
      end

    end
  end
end