require 'digest/md5'

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

  # 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
  end

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

  # Updates an existing btrieve record through the transactional BTR engine.
  def update
    btr_op(@btrieve_table.session, UPDATE, @btrieve_table.pos_buffer, @data_buffer, NULL_BUFFER, NO_CURRENCY_CHANGE)
  end
  
  # Deletes an existing btrieve record through the transactional BTR engine.
  def delete
    btr_op(@btrieve_table.session, DELETE, @btrieve_table.pos_buffer, NULL_BUFFER, NULL_BUFFER, NULL_KEY)
  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

  # 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_info = get_column_info(key_name)
    return nil if(column_info.nil?)
    @data_buffer.unpack(column_info[:unpacker])[0]
  end
  
  # Sets this record's value for a particular column.
  def []=(key_name, value)
    schema_key = get_schema_key(key_name)
    packer_string = schema_key[:unpacker]
    match = packer_string.match(/@(\d+)([a-zA-Z]+)(\d*)/)
    offset = match[1].to_i
    datatype = match[2]
    thesizeof = BtrieveSchema.sizeof(datatype)
    thesizeof *= match[3].empty? ? 1 : match[3].to_i
    packer = "#{datatype}#{thesizeof}"
    array = [value]
    packed_value = array.pack(packer)
    range = (offset..offset+packed_value.size-1)
    @data_buffer[range] = packed_value
  end
  
  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(''){|pretty_print, key| pretty_print = "#{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

  private

  def get_column_info(column_name)
    @btrieve_table.schema[:columns][column_name]
  end
end