Class: PlusCodes::OpenLocationCode

Inherits:
Object
  • Object
show all
Defined in:
lib/plus_codes/open_location_code.rb

Overview

OpenLocationCode

implements the Google Open Location Code(Plus+Codes) algorithm.

Author:

  • We-Ming Wu

Instance Method Summary collapse

Instance Method Details

#decode(code) ⇒ CodeArea

Decodes the given plus+codes in to a [CodeArea].

Parameters:

  • code (String) —

    a plus+codes

Returns:

  • (CodeArea) —

    a code area which contains the coordinates

Raises:

  • (ArgumentError) 


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# File 'lib/plus_codes/open_location_code.rb', line 109

def decode(code)
  raise ArgumentError,
    "Passed Open Location Code is not a valid full code: #{code}" unless full?(code)

  # Strip out separator character (we've already established the code is
  # valid so the maximum is one), padding characters and convert to upper
  # case.
  code = code.gsub(SEPARATOR, '')
  code = code.gsub(/#{PADDING}+/, '')
  code = code.upcase
  # Decode the lat/lng pair component.
  code_area = decode_pairs(code[0...[code.length, PAIR_CODE_LENGTH].min])
  # If there is a grid refinement component, decode that.
  return code_area if code.length <= PAIR_CODE_LENGTH

  grid_area = decode_grid(code[PAIR_CODE_LENGTH..-1])
  CodeArea.new(code_area.latitude_lo + grid_area.latitude_lo,
    code_area.longitude_lo + grid_area.longitude_lo,
    code_area.latitude_lo + grid_area.latitude_hi,
    code_area.longitude_lo + grid_area.longitude_hi,
    code_area.code_length + grid_area.code_length)
end

#encode(latitude, longitude, code_length = PAIR_CODE_LENGTH) ⇒ String

Encodes given latitude and longitude with the optionally provided code length.

Parameters:

  • latitude (Numeric) —

    a latitude in degrees

  • longitude (Numeric) —

    a longitude in degrees

  • code_length (Integer) (defaults to: PAIR_CODE_LENGTH) —

    the number of characters in the code, this excludes the separator

Returns:

  • (String) —

    a plus+codes



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# File 'lib/plus_codes/open_location_code.rb', line 87

def encode(latitude, longitude, code_length = PAIR_CODE_LENGTH)
  if code_length < 2 || (code_length < SEPARATOR_POSITION && code_length.odd?)
    raise ArgumentError, "Invalid Open Location Code length: #{code_length}"
  end

  latitude = clip_latitude(latitude)
  longitude = normalize_longitude(longitude)
  if latitude == 90
    latitude = latitude - compute_latitude_precision(code_length).to_f
  end
  code = encode_pairs(latitude, longitude, [code_length, PAIR_CODE_LENGTH].min)
  # If the requested length indicates we want grid refined codes.
  if code_length > PAIR_CODE_LENGTH
    code += encode_grid(latitude, longitude, code_length - PAIR_CODE_LENGTH)
  end
  code
end

#full?(code) ⇒ TrueClass, FalseClass

Checks if the given plus+codes is in full format.

Parameters:

  • code (String) —

    a plus+codes

Returns:

  • (TrueClass, FalseClass) —

    true if the code is full, false otherwise



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# File 'lib/plus_codes/open_location_code.rb', line 63

def full?(code)
  return false unless valid?(code)
  #  If it's short, it's not full.
  return false if short?(code)

  # Work out what the first latitude character indicates for latitude.
  first_lat_value = DECODE[code[0].ord] * ENCODING_BASE
  # The code would decode to a latitude of >= 90 degrees.
  return false if first_lat_value >= LATITUDE_MAX * 2
  if code.length > 1
    # Work out what the first longitude character indicates for longitude.
    first_lng_value = DECODE[code[1].ord] * ENCODING_BASE
    # The code would decode to a longitude of >= 180 degrees.
    return false if first_lng_value >= LONGITUDE_MAX * 2
  end
  true
end

#recover_nearest(short_code, reference_latitude, reference_longitude) ⇒ String

Finds the full plus+codes from given short plus+codes, reference latitude and longitude.

Parameters:

  • code (String) —

    a plus+codes

  • reference_latitude (Numeric) —

    a reference latitude in degrees

  • reference_longitude (Numeric) —

    a reference longitude in degrees

Returns:

  • (String) —

    a plus+codes



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# File 'lib/plus_codes/open_location_code.rb', line 138

def recover_nearest(short_code, reference_latitude, reference_longitude)
  unless short?(short_code)
    if full?(short_code)
      return short_code
    else
      raise ArgumentError, "ValueError: Passed short code is not valid: #{short_code}"
    end
  end

  # Ensure that latitude and longitude are valid.
  reference_latitude = clip_latitude(reference_latitude)
  reference_longitude = normalize_longitude(reference_longitude)

  # Clean up the passed code.
  short_code = short_code.upcase
  # Compute the number of digits we need to recover.
  padding_length = SEPARATOR_POSITION - short_code.index(SEPARATOR)
  # The resolution (height and width) of the padded area in degrees.
  resolution = 20 ** (2 - (padding_length / 2))
  # Distance from the center to an edge (in degrees).
  area_to_edge = resolution / 2.0

  # Now round down the reference latitude and longitude to the resolution.
  rounded_latitude = (reference_latitude / resolution).floor * resolution
  rounded_longitude = (reference_longitude / resolution).floor * resolution

  # Use the reference location to pad the supplied short code and decode it.
  code_area = decode(
    encode(rounded_latitude, rounded_longitude).slice(0, padding_length) +
      short_code)
  # How many degrees latitude is the code from the reference? If it is more
  # than half the resolution, we need to move it east or west.
  degrees_difference = code_area.latitude_center - reference_latitude
  if degrees_difference > area_to_edge
    # If the center of the short code is more than half a cell east,
    # then the best match will be one position west.
    code_area.latitude_center -= resolution
  elsif degrees_difference < -area_to_edge
    # If the center of the short code is more than half a cell west,
    # then the best match will be one position east.
    code_area.latitude_center += resolution
  end

  # How many degrees longitude is the code from the reference?
  degrees_difference = code_area.longitude_center - reference_longitude
  if degrees_difference > area_to_edge
    code_area.longitude_center -= resolution
  elsif degrees_difference < -area_to_edge
    code_area.longitude_center += resolution
  end
  encode(code_area.latitude_center, code_area.longitude_center, code_area.code_length)
end

#short?(code) ⇒ TrueClass, FalseClass

Checks if the given plus+codes is in short format.

Parameters:

  • code (String) —

    a plus+codes

Returns:

  • (TrueClass, FalseClass) —

    true if the code is short, false otherwise



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# File 'lib/plus_codes/open_location_code.rb', line 53

def short?(code)
  return false unless valid?(code)
  # If there are less characters than expected before the SEPARATOR.
  code.index(SEPARATOR) >= 0 && code.index(SEPARATOR) < SEPARATOR_POSITION
end

#shorten(code, latitude, longitude) ⇒ String

Shortens the given full plus+codes by provided reference latitude and longitude.

Parameters:

  • code (String) —

    a plus+codes

  • latitude (Numeric) —

    a latitude in degrees

  • longitude (Numeric) —

    a longitude in degrees

Returns:

  • (String) —

    a short plus+codes

Raises:

  • (ArgumentError) 


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# File 'lib/plus_codes/open_location_code.rb', line 197

def shorten(code, latitude, longitude)
  raise ArgumentError,
    "ValueError: Passed code is not valid and full: #{code}" unless full?(code)
  raise ArgumentError,
    "ValueError: Cannot shorten padded codes: #{code}" unless code.index(PADDING).nil?

  code = code.upcase
  code_area = decode(code)
  if code_area.code_length < MIN_TRIMMABLE_CODE_LEN
    raise RangeError,
      "ValueError: Code length must be at least #{MIN_TRIMMABLE_CODE_LEN}"
  end
  # Ensure that latitude and longitude are valid.
  latitude = clip_latitude(latitude)
  longitude = normalize_longitude(longitude)
  # How close are the latitude and longitude to the code center.
  range = [(code_area.latitude_center - latitude).abs,
    (code_area.longitude_center - longitude).abs].max
  i = PAIR_RESOLUTIONS.length - 2
  while i >= 1 do
    # Check if we're close enough to shorten. The range must be less than 1/2
    # the resolution to shorten at all, and we want to allow some safety, so
    # use 0.3 instead of 0.5 as a multiplier.
    return code[(i + 1) * 2..-1] if range < (PAIR_RESOLUTIONS[i] * 0.3)
    # Trim it.
    i -= 1
  end
  code
end

#valid?(code) ⇒ TrueClass, FalseClass

Validates the given plus+codes.

Parameters:

  • code (String) —

    a plus+codes

Returns:

  • (TrueClass, FalseClass) —

    true if the code is valid, false otherwise



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# File 'lib/plus_codes/open_location_code.rb', line 15

def valid?(code)
  return false if code.nil? || code.length <= 1

  separator_index = code.index(SEPARATOR)
  # There must be a single separator at an even index and position should be < SEPARATOR_POSITION.
  return false if separator_index.nil? ||
    separator_index != code.rindex(SEPARATOR) ||
    separator_index > SEPARATOR_POSITION ||
    separator_index.odd?

  # We can have an even number of padding characters before the separator,
  # but then it must be the final character.
  if code.include?(PADDING)
    return false if code.start_with?(PADDING)
    pad_match = code.scan(/#{PADDING}+/)
    return false unless pad_match.one?
    padding = pad_match[0]
    return false if padding.length.odd?
    return false if padding.length > SEPARATOR_POSITION - 2
    return false if code[-2] != PADDING
    return false if code[-1] != SEPARATOR
  end

  # If there are characters after the separator, make sure there isn't just
  # one of them (not legal).
  return false if code.length - separator_index - 1 == 1

  # Check code contains only valid characters.
  code.chars.each do |ch|
    return false if ch.ord >= DECODE.length || DECODE[ch.ord] < -1
  end
  true
end