Module: GeoDelta::Encoder

Defined in:
lib/geodelta/encoder.rb

Constant Summary collapse

WORLD_DELTA_TABLE = 
[
  [0, "Z"],
  [1, "Y"],
  [2, "X"],
  [3, "W"],
  [4, "V"],
  [5, "T"],
  [6, "S"],
  [7, "R"],
].each(&:freeze).freeze
WORLD_ID_TO_CHAR = 
WORLD_DELTA_TABLE.inject({}) { |memo, (num, char)| memo[num] = char; memo }.freeze
WORLD_CHAR_TO_ID = 
WORLD_DELTA_TABLE.inject({}) { |memo, (num, char)| memo[char] = num; memo }.freeze
SUB_DELTA_TABLE = 
[
  [[0, 0], "2"],
  [[0, 1], "3"],
  [[0, 2], "4"],
  [[0, 3], "5"],
  [[1, 0], "6"],
  [[1, 1], "7"],
  [[1, 2], "8"],
  [[1, 3], "A"],
  [[2, 0], "B"],
  [[2, 1], "C"],
  [[2, 2], "D"],
  [[2, 3], "E"],
  [[3, 0], "F"],
  [[3, 1], "G"],
  [[3, 2], "H"],
  [[3, 3], "J"],
  [[0]   , "K"],
  [[1]   , "M"],
  [[2]   , "N"],
  [[3]   , "P"],
].each(&:freeze).freeze
SUB_IDS_TO_CHAR = 
SUB_DELTA_TABLE.inject({}) { |memo, (nums, char)| memo[nums] = char; memo }.freeze
SUB_CHAR_TO_IDS = 
SUB_DELTA_TABLE.inject({}) { |memo, (nums, char)| memo[char] = nums; memo }.freeze

Class Method Summary collapse

Class Method Details

.decode(codes) ⇒ Object 



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# File 'lib/geodelta/encoder.rb', line 72

def self.decode(codes)
  raise("delta codes is empty") if codes.empty?
  result  = [self.decode_world_delta(codes[0])]
  result += self.decode_sub_delta(codes[1..-1]) if codes.size >= 2
  return result
end

.decode_sub_delta(codes) ⇒ Object 



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# File 'lib/geodelta/encoder.rb', line 58

def self.decode_sub_delta(codes)
  raise("sub delta codes is empty") if codes.empty?
  return codes.chars.inject([]) { |memo, char|
    memo + (SUB_CHAR_TO_IDS[char] || raise("invalid sub delta code -- #{char}"))
  }
end

.decode_world_delta(code) ⇒ Object 



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# File 'lib/geodelta/encoder.rb', line 47

def self.decode_world_delta(code)
  return WORLD_CHAR_TO_ID[code] || raise("invalid world delta code -- #{code}")
end

.encode(ids) ⇒ Object 



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# File 'lib/geodelta/encoder.rb', line 65

def self.encode(ids)
  raise("delta ids is empty") if ids.empty?
  result  = self.encode_world_delta(ids[0])
  result += self.encode_sub_delta(ids[1..-1]) if ids.size >= 2
  return result
end

.encode_sub_delta(ids) ⇒ Object 



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# File 'lib/geodelta/encoder.rb', line 51

def self.encode_sub_delta(ids)
  raise("sub delta ids is empty") if ids.empty?
  return ids.each_slice(2).map { |part|
    SUB_IDS_TO_CHAR[part] || raise("invalid sub delta ids -- #{part}")
  }.join("")
end

.encode_world_delta(id) ⇒ Object 



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# File 'lib/geodelta/encoder.rb', line 43

def self.encode_world_delta(id)
  return WORLD_ID_TO_CHAR[id] || raise("invalid world delta id -- #{id}")
end