# --
# Copyright (C) 2008-2009 10gen Inc.
#
# This program is free software: you can redistribute it and/or modify it
# under the terms of the GNU Affero General Public License, version 3, as
# published by the Free Software Foundation.
#
# This program is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License
# for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
# ++

require 'base64'
require 'mongo/util/byte_buffer'
require 'mongo/util/ordered_hash'
require 'mongo/types/binary'
require 'mongo/types/dbref'
require 'mongo/types/objectid'
require 'mongo/types/regexp_of_holding'
require 'mongo/types/undefined'

# A BSON seralizer/deserializer.
class BSON

  MINKEY = -1
  EOO = 0
  NUMBER = 1
  STRING = 2
  OBJECT = 3
  ARRAY = 4
  BINARY = 5
  UNDEFINED = 6
  OID = 7
  BOOLEAN = 8
  DATE = 9
  NULL = 10
  REGEX = 11
  REF = 12
  CODE = 13
  SYMBOL = 14
  CODE_W_SCOPE = 15
  NUMBER_INT = 16
  MAXKEY = 127

  BYTE_TYPE = 2

  if RUBY_VERSION >= '1.9'
    def self.to_utf8(str)
      str.encode("utf-8")
    end
  else
    def self.to_utf8(str)
      str                       # TODO punt for now
    end
  end

  def self.serialize_cstr(buf, val)
    buf.put_array(to_utf8(val.to_s).unpack("C*") + [0])
  end

  def initialize(db=nil)
    # db is only needed during deserialization when the data contains a DBRef
    @db = db
    @buf = ByteBuffer.new
  end

  def to_a
    @buf.to_a
  end

  def serialize(obj)
    raise "Document is null" unless obj

    @buf.rewind
    # put in a placeholder for the total size
    @buf.put_int(0)

    obj.each {|k, v|
      type = bson_type(v, k)
      case type
      when STRING, CODE, SYMBOL
        serialize_string_element(@buf, k, v, type)
      when NUMBER, NUMBER_INT
        serialize_number_element(@buf, k, v, type)
      when OBJECT
        serialize_object_element(@buf, k, v)
      when OID
        serialize_oid_element(@buf, k, v)
      when ARRAY
        serialize_array_element(@buf, k, v)
      when REGEX
        serialize_regex_element(@buf, k, v)
      when BOOLEAN
        serialize_boolean_element(@buf, k, v)
      when DATE
        serialize_date_element(@buf, k, v)
      when NULL
        serialize_null_element(@buf, k)
      when REF
        serialize_dbref_element(@buf, k, v)
      when BINARY
        serialize_binary_element(@buf, k, v)
      when UNDEFINED
        serialize_undefined_element(@buf, k)
      when CODE_W_SCOPE
        # TODO
        raise "unimplemented type #{type}"
      else
        raise "unhandled type #{type}"
      end
    }
    serialize_eoo_element(@buf)
    @buf.put_int(@buf.size, 0)
    self
  end

  def deserialize(buf=nil, parent=nil)
    # If buf is nil, use @buf, assumed to contain already-serialized BSON.
    # This is only true during testing.
    @buf = ByteBuffer.new(buf.to_a) if buf
    @buf.rewind
    @buf.get_int                # eat message size
    doc = OrderedHash.new
    while @buf.more?
      type = @buf.get
      case type
      when STRING, CODE
        key = deserialize_cstr(@buf)
        doc[key] = deserialize_string_data(@buf)
      when SYMBOL
        key = deserialize_cstr(@buf)
        doc[key] = deserialize_string_data(@buf).intern
      when NUMBER
        key = deserialize_cstr(@buf)
        doc[key] = deserialize_number_data(@buf)
      when NUMBER_INT
        key = deserialize_cstr(@buf)
        doc[key] = deserialize_number_int_data(@buf)
      when OID
        key = deserialize_cstr(@buf)
        doc[key] = deserialize_oid_data(@buf)
      when ARRAY
        key = deserialize_cstr(@buf)
        doc[key] = deserialize_array_data(@buf, doc)
      when REGEX
        key = deserialize_cstr(@buf)
        doc[key] = deserialize_regex_data(@buf)
      when OBJECT
        key = deserialize_cstr(@buf)
        doc[key] = deserialize_object_data(@buf, doc)
      when BOOLEAN
        key = deserialize_cstr(@buf)
        doc[key] = deserialize_boolean_data(@buf)
      when DATE
        key = deserialize_cstr(@buf)
        doc[key] = deserialize_date_data(@buf)
      when NULL
        key = deserialize_cstr(@buf)
        doc[key] = nil
      when UNDEFINED
        key = deserialize_cstr(@buf)
        doc[key] = XGen::Mongo::Driver::Undefined.new
      when REF
        key = deserialize_cstr(@buf)
        doc[key] = deserialize_dbref_data(@buf, key, parent)
      when BINARY
        key = deserialize_cstr(@buf)
        doc[key] = deserialize_binary_data(@buf)
      when CODE_W_SCOPE
        # TODO
        raise "unimplemented type #{type}"
      when EOO
        break
      else
        raise "Unknown type #{type}, key = #{key}"
      end
    end
    @buf.rewind
    doc
  end

  # For debugging.
  def hex_dump
    str = ''
    @buf.to_a.each_with_index { |b,i|
      if (i % 8) == 0
        str << "\n" if i > 0
        str << '%4d:  ' % i
      else
        str << ' '
      end
      str << '%02X' % b
    }
    str
  end

  def deserialize_date_data(buf)
    millisecs = buf.get_long()
    Time.at(millisecs.to_f / 1000.0) # at() takes fractional seconds
  end

  def deserialize_boolean_data(buf)
    buf.get == 1
  end

  def deserialize_number_data(buf)
    buf.get_double
  end

  def deserialize_number_int_data(buf)
    buf.get_int
  end

  def deserialize_object_data(buf, parent)
    size = buf.get_int
    buf.position -= 4
    BSON.new(@db).deserialize(buf.get(size), parent)
  end

  def deserialize_array_data(buf, parent)
    h = deserialize_object_data(buf, parent)
    a = []
    h.each { |k, v| a[k.to_i] = v }
    a
  end

  def deserialize_regex_data(buf)
    str = deserialize_cstr(buf)
    options_str = deserialize_cstr(buf)
    options = 0
    options |= Regexp::IGNORECASE if options_str.include?('i')
    options |= Regexp::MULTILINE if options_str.include?('m')
    options |= Regexp::EXTENDED if options_str.include?('x')
    options_str.gsub!(/[imx]/, '') # Now remove the three we understand
    XGen::Mongo::Driver::RegexpOfHolding.new(str, options, options_str)
  end

  def deserialize_string_data(buf)
    len = buf.get_int
    bytes = buf.get(len)
    str = bytes[0..-2].pack("C*")
    if RUBY_VERSION >= '1.9'
      str.force_encoding("utf-8")
    end
    str
  end

  def deserialize_oid_data(buf)
    XGen::Mongo::Driver::ObjectID.new(buf.get(12))
  end

  def deserialize_dbref_data(buf, key, parent)
    ns = deserialize_string_data(buf)
    oid = deserialize_oid_data(buf)
    XGen::Mongo::Driver::DBRef.new(parent, key, @db, ns, oid)
  end

  def deserialize_binary_data(buf)
    buf.get_int                 # length + 4; ignored
    buf.get                     # byte type; ignored
    len = buf.get_int
    bytes = buf.get(len)
    str = ''
    bytes.each { |c| str << c.chr }
    str.to_mongo_binary
  end

  def serialize_eoo_element(buf)
    buf.put(EOO)
  end

  def serialize_null_element(buf, key)
    buf.put(NULL)
    self.class.serialize_cstr(buf, key)
  end

  def serialize_dbref_element(buf, key, val)
    serialize_string_element(buf, key, val.namespace, REF)
    buf.put_array(val.object_id.to_a)
  end

  def serialize_binary_element(buf, key, val)
    buf.put(BINARY)
    self.class.serialize_cstr(buf, key)

    bytes = if RUBY_VERSION >= '1.9'
              val.bytes.to_a
            else
              a = []
              val.each_byte { |byte| a << byte }
              a
            end

    num_bytes = bytes.length
    buf.put_int(num_bytes + 4)
    buf.put(BYTE_TYPE)
    buf.put_int(num_bytes)
    buf.put_array(bytes)
  end

  def serialize_undefined_element(buf, key)
    buf.put(UNDEFINED)
    self.class.serialize_cstr(buf, key)
  end

  def serialize_boolean_element(buf, key, val)
    buf.put(BOOLEAN)
    self.class.serialize_cstr(buf, key)
    buf.put(val ? 1 : 0)
  end

  def serialize_date_element(buf, key, val)
    buf.put(DATE)
    self.class.serialize_cstr(buf, key)
    millisecs = (val.to_f * 1000).to_i
    buf.put_long(millisecs)
  end

  def serialize_number_element(buf, key, val, type)
    buf.put(type)
    self.class.serialize_cstr(buf, key)
    if type == NUMBER
      buf.put_double(val)
    else
      buf.put_int(val)
    end
  end

  def serialize_object_element(buf, key, val, opcode=OBJECT)
    buf.put(opcode)
    self.class.serialize_cstr(buf, key)
    buf.put_array(BSON.new.serialize(put_id_first(val)).to_a)
  end

  # For internal use only. Looks for '_id' or :_id key of val. If there is
  # one, returns an OrderedHash where '_id' is first. If not, returns val.
  def put_id_first(val)
    oid = val.delete('_id') || val.delete(:_id)
    if oid
      h = OrderedHash.new
      h['_id'] = oid
      val.each { |k, v| h[k] = v }
      val = h
    end
    val
  end

  def serialize_array_element(buf, key, val)
    # Turn array into hash with integer indices as keys
    h = OrderedHash.new
    i = 0
    val.each { |v| h[i] = v; i += 1 }
    serialize_object_element(buf, key, h, ARRAY)
  end

  def serialize_regex_element(buf, key, val)
    buf.put(REGEX)
    self.class.serialize_cstr(buf, key)

    str = val.to_s.sub(/.*?:/, '')[0..-2] # Turn "(?xxx:yyy)" into "yyy"
    self.class.serialize_cstr(buf, str)

    options = val.options
    options_str = ''
    options_str << 'i' if ((options & Regexp::IGNORECASE) != 0)
    options_str << 'm' if ((options & Regexp::MULTILINE) != 0)
    options_str << 'x' if ((options & Regexp::EXTENDED) != 0)
    options_str << val.extra_options_str if val.respond_to?(:extra_options_str)
    # Must store option chars in alphabetical order
    self.class.serialize_cstr(buf, options_str.split(//).sort.uniq.join)
  end

  def serialize_oid_element(buf, key, val)
    buf.put(OID)
    self.class.serialize_cstr(buf, key)

    buf.put_array(val.to_a)
  end

  def serialize_string_element(buf, key, val, type)
    buf.put(type)
    self.class.serialize_cstr(buf, key)

    # Make a hole for the length
    len_pos = buf.position
    buf.put_int(0)

    # Save the string
    start_pos = buf.position
    self.class.serialize_cstr(buf, val)
    end_pos = buf.position

    # Put the string size in front
    buf.put_int(end_pos - start_pos, len_pos)

    # Go back to where we were
    buf.position = end_pos
  end

  def deserialize_cstr(buf)
    chars = ""
    while 1
      b = buf.get
      break if b == 0
      chars << b.chr
    end
    if RUBY_VERSION >= '1.9'
      chars.force_encoding("utf-8") # Mongo stores UTF-8
    end
    chars
  end

  def bson_type(o, key)
    case o
    when nil
      NULL
    when Integer
      NUMBER_INT
    when Numeric
      NUMBER
    when XGen::Mongo::Driver::Binary # must be before String
      BINARY
    when String
      # magic awful stuff - the DB requires that a where clause is sent as CODE
      key == "$where" ? CODE : STRING
    when Array
      ARRAY
    when Regexp
      REGEX
    when XGen::Mongo::Driver::ObjectID
      OID
    when XGen::Mongo::Driver::DBRef
      REF
    when true, false
      BOOLEAN
    when Time
      DATE
    when Hash
      OBJECT
    when Symbol
      SYMBOL
    when XGen::Mongo::Driver::Undefined
      UNDEFINED
    else
      raise "Unknown type of object: #{o.class.name}"
    end
  end

end