Class: Forecaster::Forecast

Inherits:
Object
  • Object
show all
Defined in:
lib/forecaster/forecast.rb

Instance Method Summary collapse

Constructor Details

#initialize(year, month, day, hour_of_run, hour_of_forecast) ⇒ Forecast

Returns a new instance of Forecast.



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# File 'lib/forecaster/forecast.rb', line 5

def initialize(year, month, day, hour_of_run, hour_of_forecast)
  @year = year
  @month = month
  @day = day
  @hour_of_run = hour_of_run
  @hour_of_forecast = hour_of_forecast
end

Instance Method Details

#dirname ⇒ Object 



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# File 'lib/forecaster/forecast.rb', line 13

def dirname
  subdir = "%04d%02d%02d%02d" % [
    @year, @month, @day, @hour_of_run
  ]
  File.join(Forecaster.configuration.cache_dir, subdir)
end

#fetch ⇒ Object

This method will save the forecast file in the cache directory. But only the parts of the file containing the fields defined in the configuration will be downloaded.



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# File 'lib/forecaster/forecast.rb', line 40

def fetch
  return self if fetched?

  curl = Forecaster.configuration.curl_path

  FileUtils.mkpath(File.join(dirname))

  path = File.join(dirname, filename)

  # puts "Downloading '#{url}.idx' ..."
  cmd = "#{curl} -fsS -o #{path}.idx #{url}.idx"
  raise "Download of '#{url}.idx' failed" unless system(cmd)

  lines = IO.readlines("#{path}.idx")
  n = lines.count
  ranges = lines.each_index.reduce([]) do |r, i|
    records = Forecaster.configuration.records
    if records.values.any? { |record| lines[i].include?(record) }
      first = lines[i].split(":")[1].to_i
      last = ""

      j = i
      while (j += 1) < n
        last = lines[j].split(":")[1].to_i - 1
        break if last != first - 1
      end

      r << "#{first}-#{last}" # cURL syntax for a range
    else
      r
    end
  end
  system("rm #{path}.idx")

  # puts "Downloading '#{url}' ..."
  cmd = "#{curl} -fsS -r #{ranges.join(",")} -o #{path} #{url}"
  raise "Download of '#{url}' failed" unless system(cmd)

  self
end

#fetched? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/forecaster/forecast.rb', line 33

def fetched?
  File.exist?(File.join(dirname, filename))
end

#filename ⇒ Object 



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# File 'lib/forecaster/forecast.rb', line 20

def filename
  "gfs.t%02dz.pgrb2.0p25.f%03d" % [
    @hour_of_run, @hour_of_forecast
  ]
end

#read(field, latitude: 0.0, longitude: 0.0) ⇒ Object 



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# File 'lib/forecaster/forecast.rb', line 81

def read(field, latitude: 0.0, longitude: 0.0)
  wgrib2 = Forecaster.configuration.wgrib2_path
  record = Forecaster.configuration.records[field]
  path = File.join(dirname, filename)

  raise "'#{path}' not found" unless File.exists?(path)

  coords = "#{longitude} #{latitude}"
  output = `#{wgrib2} #{path} -lon #{coords} -match "#{record}"`

  raise "Could not read '#{record}' in '#{path}'" if output.empty?

  fields = output.split("\n").first.split(":")
  params = Hash[*fields.last.split(",").map { |s| s.split("=") }.flatten]

  params["val"]
end

#url ⇒ Object 



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# File 'lib/forecaster/forecast.rb', line 26

def url
  server = Forecaster.configuration.server
  "%s/gfs.%04d%02d%02d%02d/%s" % [
    server, @year, @month, @day, @hour_of_run, filename
  ]
end