class SylphReader

  SYLPH_LABELS = [
  		'Type',
  		'ITOW',
  		'longitude',
  		'latitude',
  		'height',
  		'v_north',
  		'v_east',
  		'v_down',
  		'Yaw',
  		'Pitch',
  		'Roll',
      'Azimuth'
  	]
  YAW_INDEX = SYLPH_LABELS.index('Yaw')
  YAW_THRESHOLD = 170 * -170
  YAW_KEEP = 30 * 4 #(30 sec (* 250ms))
  
  def SylphReader.read(file, options = {})
    sylph_data = []
    options = {:denom => 1, :skip_header => 1, :delim => /[\t,]/}.merge(options)
    denom = options[:denom]
    delim = options[:delim]
    min_size = SYLPH_LABELS.size
    min_size -= 1 if options[:notype]
    min_size -= 1 if options[:noazimuth]
    read_file = proc{|io|
      options[:skip_header].times{io.readline}
      line_no = 0
      io.each{|line|
        line_no += 1
        if (line_no % denom) != 0 then next end
        temp = line.chop.split(delim)
        next if temp.size < min_size
        sylph_data << temp
      }
    }
    if file == '-' then
      read_file.call($stdin)
    else
      open(file){|io| read_file.call(io)}
    end
    sylph_data.each{|v| v.insert(0, "N/A")} if options[:notype]
    sylph_data.each{|v| v  << 0} if options[:noazimuth]
    sylph_data.collect!{|v|
      [v[0], (v[1].to_f * 1000).to_i] + v[2..-1].collect{|v2| v2.to_f}
    }
    if options[:range_t_ms] then
      range_t_ms = options[:range_t_ms]
      sylph_data = sylph_data.select{|v| range_t_ms.include?(v[1])}
    end
    return sylph_data
  end
  
  def SylphReader.yawsimple(sylph_data)
    i = 1
    while i < sylph_data.size do
      if sylph_data[i - 1][YAW_INDEX] * sylph_data[i][YAW_INDEX] < YAW_THRESHOLD then
        j = i + 1
        while (j < sylph_data.size) && (j < i + YAW_KEEP)
          if sylph_data[i][YAW_INDEX] * sylph_data[j][YAW_INDEX] < YAW_THRESHOLD then
            offset = sylph_data[i][YAW_INDEX] < 0 ? 360 : -360
            (i...j).each{|k|
              sylph_data[k][YAW_INDEX] += offset
            }
            j += 1
            break
          end
          j += 1
        end
        i = j
      else
        i += 1
      end
    end
  end
end