Module: Webcash::Helpers

Defined in:
lib/webcash/helpers.rb

Overview

Provides helper methods for Webcash.

Class Method Summary collapse

Class Method Details

.assert_is_array(input) ⇒ Object 



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# File 'lib/webcash/helpers.rb', line 158

def self.assert_is_array(input)
  unless input.is_a?(Array) && input.all? { |e| e.is_a?(Integer) }
    raise "This method only supports number arrays but input was: #{input}"
  end
end

.chunk_array(array, chunk_size) ⇒ Object 



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# File 'lib/webcash/helpers.rb', line 25

def self.chunk_array(array, chunk_size)
  array.each_slice(chunk_size).to_a
end

.convert_secret_hex_to_bytes(secret) ⇒ Object 



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# File 'lib/webcash/helpers.rb', line 127

def self.convert_secret_hex_to_bytes(secret)
  hex_to_padded_bytes(secret)
end

.convert_secret_value_to_public_value(secret_value) ⇒ Object 



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# File 'lib/webcash/helpers.rb', line 92

def self.convert_secret_value_to_public_value(secret_value)
  Digest::SHA256.hexdigest(secret_value)
end

.create_webcash_with_random_secret_from_amount(amount) ⇒ Object 



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# File 'lib/webcash/helpers.rb', line 117

def self.create_webcash_with_random_secret_from_amount(amount)
  "e#{amount.to_s('F')}:secret:#{generate_random_value(32)}"
end

.decimal_amount_to_string(amount) ⇒ Object

Convert a decimal amount to a string. This is used for representing different webcash when serializing webcash. When the amount is not known, the string should be “?”.



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# File 'lib/webcash/helpers.rb', line 105

def self.decimal_amount_to_string(amount)
  return "?" if amount.nil?

  if amount.frac.zero?
    amount.to_i.to_s
  else
    # Force 8 decimals and trim trailing zeros
    amount_str = format("%.8f", amount)
    amount_str.sub(/\.?0+$/, "")
  end
end

.deserialize_webcash(webcash) ⇒ Object

Raises:



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# File 'lib/webcash/helpers.rb', line 44

def self.deserialize_webcash(webcash)
  raise Error, "Unusable format for webcash." unless webcash.include?(":")

  parts = webcash.split(":")
  raise Error, "Don't know how to deserialize this webcash." if parts.length < 2

  amount_raw = parts[0]
  public_or_secret = parts[1]
  value = parts[2]

  raise Error, "Can't deserialize this webcash, value is missing." if value.nil?

  unless %w[public secret].include?(public_or_secret)
    raise Error, "Can't deserialize this webcash, needs to be either public/secret."
  end

  amount = parse_amount_from_string(amount_raw)

  if public_or_secret == "secret"
    Webcash::Secret.new(amount, value)
  else
    Webcash::Public.new(amount, value)
  end
end

.generate_random_value(length) ⇒ Object 



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# File 'lib/webcash/helpers.rb', line 174

def self.generate_random_value(length)
  (1..length).map { rand(16).to_s(16) }.join
end

.hex_to_bytes(hex) ⇒ Object 



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# File 'lib/webcash/helpers.rb', line 131

def self.hex_to_bytes(hex)
  hex = hex.sub(/^0x/i, "")
  hex.scan(/../).map { |x| x.hex }
end

.hex_to_padded_bytes(hex, padding_target_length = 32) ⇒ Object 



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# File 'lib/webcash/helpers.rb', line 121

def self.hex_to_padded_bytes(hex, padding_target_length = 32)
  bytes = [ hex.sub(/^0x/, "") ].pack("H*").bytes
  padded_bytes = Array.new(padding_target_length - bytes.length, 0) + bytes
  padded_bytes
end

.long_to_byte_array(num) ⇒ Object 



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# File 'lib/webcash/helpers.rb', line 147

def self.long_to_byte_array(num)
  byte_array = Array.new(8, 0)

  (0...byte_array.length).each do |index|
    byte_array[index] = num & 0xff
    num >>= 8
  end

  byte_array
end

.padded_bytes(bytes, padding_target_length = 32) ⇒ Object 



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# File 'lib/webcash/helpers.rb', line 136

def self.padded_bytes(bytes, padding_target_length = 32)
  if bytes.length == padding_target_length
    bytes
  elsif bytes.length > padding_target_length
    raise "Can only handle up to #{padding_target_length} bytes, int too big to convert"
  else
    padding_needed = padding_target_length - bytes.length
    Array.new(padding_needed, 0) + bytes
  end
end

.parse_amount_from_string(amount_raw) ⇒ Object 



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# File 'lib/webcash/helpers.rb', line 69

def self.parse_amount_from_string(amount_raw)
  # If there is a colon in the value, then the amount is going to be on the
  # left hand side.
  part1 = amount_raw.split(":")[0]

  # There can be at most one 'e' in the value, at the beginning.
  count = part1.count("e")
  if count.zero?
    BigDecimal(part1)
  elsif count <= 1
    # should be at the beginning
    raise Error, "Invalid amount format for webcash." unless part1[0] == "e"
    # there needs to be an actual amount
    raise Error, "Invalid amount format for webcash." unless part1 != "e"

    part2 = part1.split("e")[1]
    BigDecimal(part2)

  else
    raise Error, "Invalid amount format for webcash."
  end
end

.range(start, stop, step = 1) ⇒ Object 



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# File 'lib/webcash/helpers.rb', line 12

def self.range(start, stop, step = 1)
  return [] if (step.positive? && start >= stop) || (step.negative? && start <= stop)

  result = []
  i = start
  while step.positive? ? i < stop : i > stop
    result << i
    i += step
  end

  result
end

.sha256_from_array(array) ⇒ Object 



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# File 'lib/webcash/helpers.rb', line 164

def self.sha256_from_array(array)
  assert_is_array(array)

  # Convert the array of integers to a binary string
  binary_string = array.pack("C*")

  # Create and return the SHA256 digest
  Digest::SHA256.digest(binary_string)
end

.string_amount_to_decimal(amount) ⇒ Object

Convert from a string amount to a Decimal value.



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# File 'lib/webcash/helpers.rb', line 97

def self.string_amount_to_decimal(amount)
  BigDecimal(amount)
end

.validate_amount_decimals(amount) ⇒ Object

Check that the amount has no more than a maximum number of decimal places.

Raises:

  • (RangeError) 


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# File 'lib/webcash/helpers.rb', line 30

def self.validate_amount_decimals(amount)
  if amount.is_a?(String)
    amount = parse_amount_from_string(amount)
  elsif amount.is_a?(Float)
    amount = BigDecimal(amount.to_s)
  else
    amount = BigDecimal(amount)
  end

  raise RangeError, "Amount precision should be at most 8 decimals." unless amount.scale <= 8

  true
end