require 'digest/md5'

# Represents a single btrieve record for a particular BTR table.
class BtrieveRecord
  include Btrieve
  attr_reader :data_buffer, :btrieve_table
  attr_accessor :position

  # Initializes a btrieve record.
  def initialize(btrieve_table, data_buffer=nil)
    @btrieve_table = btrieve_table
    @data_buffer = data_buffer.nil? ? Btrieve.create_string_buffer(@btrieve_table.schema[:record_size]) : data_buffer
    reset_physical_position
  end

  # Inserts a new btrieve record through the transactional BTR engine.
  def insert
    btr_op(INSERT, @btrieve_table.pos_buffer, @data_buffer, NULL_BUFFER, SYSTEM_LOG_KEY)
    set_physical_position
  end

  # Updates an existing btrieve record through the transactional BTR engine.
  def update
    new_state="#{@data_buffer}"
    @data_buffer[0..3]=@position
    btr_op(GET_DIRECT, @btrieve_table.pos_buffer, @data_buffer, NULL_BUFFER, SYSTEM_LOG_KEY)
    btr_op(UPDATE, @btrieve_table.pos_buffer, new_state, NULL_BUFFER, SYSTEM_LOG_KEY)
    set_physical_position
  end

  # Deletes an existing btrieve record through the transactional BTR engine.
  def delete
    @data_buffer[0..3]=@position
    btr_op(GET_DIRECT, @btrieve_table.pos_buffer, @data_buffer, NULL_BUFFER, SYSTEM_LOG_KEY)
    btr_op(DELETE, @btrieve_table.pos_buffer, NULL_BUFFER, NULL_BUFFER, NULL_KEY)
    reset_physical_position
  end

  # Returns hash of column-value pairs for this btrieve record, given an array of named columns.
  # If the array is nil, the hash will contain ALL the column-value pairs defined by the schema.
  def values(column_names=nil)
    if(column_names.nil?)
      column_names=@btrieve_table.schema[:columns].keys.sort.inject([]){|array,column|array<< column;array}
    end
    column_names.inject({}){|vals, key| vals[key]=self[key]; vals}
  end

  # Sets the column valuesof this record based on the values passed through the 'column_values' map.
  def values=(column_values)
    column_values.each{ |key, value| self[key]=value }
  end

  # Returns this record's primary key value. Supports composite keys.
  def primary_key()
    values(@btrieve_table.primary_key)
  end

  # Returns this record's value of the column passed in.
  def [](key_name)
    column = @btrieve_table.schema[:columns][key_name]
    return nil if(column.nil?)
    val = @data_buffer.unpack(column[:unpacker])[0]
    val = val.strip if val.respond_to?('strip')
    val
  end

  # Sets this record's value for a particular column.
  def []=(key_name, value)
    column = @btrieve_table.schema[:columns][key_name]
    packed_value = @btrieve_table.pack_value(column, value)
    offset = column[:offset]
    range = (offset..offset+packed_value.size-1)
    @data_buffer[range] = packed_value
  end

  # Determines if a record is nil.
  def nil?()
    @data_buffer.gsub("\x00", "").size==0
  end

  # Returns a string representation of this record.
  def to_s()
    @btrieve_table.schema[:columns].keys.inject("[position=>'#{position.unpack('i')[0]}'"){|pretty_print, key| pretty_print << ", #{key}=>'#{self[key]}'"; pretty_print } << "]"
  end

  # Returns this record's version as a MD5 Digest value.
  def version()
    Digest::MD5.hexdigest(@data_buffer)
  end

  # TODO - documentation
  def set_physical_position
    reset_physical_position
    btr_op(GET_POSITION, @btrieve_table.pos_buffer, @position, NULL_BUFFER, NULL_KEY)
    self
  end

  # TODO - documentation
  def reset_physical_position
    @position = Btrieve.create_string_buffer(RECORD_POSITION_SIZE)
  end

end