#
# setup default OCI encoding from NLS_LANG.
#

#
class OCI8

  # get the environment variable NLS_LANG.
  nls_lang = ENV['NLS_LANG']

  if nls_lang.is_a? String and nls_lang.length == 0
    nls_lang = nil
  end

  # if NLS_LANG is not set, get it from the Windows registry.
  if nls_lang.nil? and defined? OCI8::Win32Util
    dll_path = OCI8::Win32Util.dll_path.upcase
    if dll_path =~ %r{\\BIN\\OCI.DLL}
      oracle_home = $`
      OCI8::Win32Util.enum_homes do |home, lang|
        if oracle_home == home.upcase
          nls_lang = lang
          break
        end
      end
    end
  end

  # extract the charset name.
  if nls_lang
    if nls_lang =~ /\.([[:alnum:]]+)$/
      @@client_charset_name = $1.upcase
    else
      raise "Invalid NLS_LANG format: #{nls_lang}"
    end
  else
    warn "Warning: NLS_LANG is not set. fallback to US7ASCII."
    # @private
    @@client_charset_name = 'US7ASCII'
  end

  # Ruby encoding name for ruby 1.9.
  if OCI8.respond_to? :encoding
    if defined? DEFAULT_OCI8_ENCODING
      enc = DEFAULT_OCI8_ENCODING
    else
      require 'yaml'
      enc = YAML::load_file(File.dirname(__FILE__) + '/encoding.yml')[@@client_charset_name]
      if enc.nil?
        raise "Ruby encoding name is not found in encoding.yml for NLS_LANG #{nls_lang}."
      end
      if enc.is_a? Array
        # Use the first available encoding in the array.
        enc = enc.find do |e| Encoding.find(e) rescue false; end
      end
    end
    OCI8.encoding = enc
  else
    # NLS ratio, maximum number of bytes per one chracter
    case @@client_charset_name
    when 'UTF8'
      OCI8.nls_ratio = 3
    when 'AL16UTF16'
      OCI8.nls_ratio = 4
    when /^[[:alpha:]]+(\d+)/
      # convert maximum number of bits per one chracter to NLS ratio.
      #   charset name  max bits  max bytes
      #   ------------  --------  ---------
      #   US7ASCII          7         1
      #   WE8ISO8859P1      8         1
      #   JA16SJIS         16         2
      #   AL32UTF8         32         4
      #   ...
      OCI8.nls_ratio = (($1.to_i + 7) >> 3)
    else
      raise "Unknown NLS character set name format: #{@@client_charset_name}"
    end
  end
end