Module: Bakong::Khqr::Controllers::DecodeNonKHQR

Defined in:
lib/bakong/khqr/controllers/decode_non_khqr.rb

Overview

Generic EMVCo TLV decoder for QR strings that may or may not be KHQR. Walks up to three levels of nested TLV for the same composite-tag ranges the upstream JS package handles (26–51, 80–99, 62, 64).

Class Method Summary collapse

Class Method Details

.call(qr) ⇒ Object 



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# File 'lib/bakong/khqr/controllers/decode_non_khqr.rb', line 12

def call(qr)
  first_level = {}
  final_data = {}
  remainder = qr

  loop do
    parsed = extract_tlv(remainder)
    break unless valid?(parsed[:tag], parsed[:length], parsed[:value])

    first_level[parsed[:tag]] = parsed[:value]
    remainder = parsed[:remain]
    break if remainder.nil? || remainder.empty?
  end

  first_level.each do |tag, value|
    final_data[tag] = value
    next unless composite_tag?(tag)
    next if value.length < 6

    second_level = {}
    remaining_value = value

    loop do
      third_level = {}
      parsed = extract_tlv(remaining_value)
      break unless valid?(parsed[:tag], parsed[:length], parsed[:value])

      sub_tag = parsed[:tag]
      sub_value = parsed[:value]
      remaining_value = parsed[:remain]

      if tag == "62" && (50..99).cover?(sub_tag.to_i)
        inner = sub_value
        loop do
          inner_parsed = extract_tlv(inner)
          break unless valid?(inner_parsed[:tag], inner_parsed[:length], inner_parsed[:value])

          third_level[inner_parsed[:tag]] = inner_parsed[:value]
          inner = inner_parsed[:remain]
          break if inner.nil? || inner.empty?
        end
      end

      second_level[sub_tag] = third_level.empty? ? sub_value : third_level
      break if remaining_value.nil? || remaining_value.empty?
    end

    final_data[tag] = second_level unless second_level.empty?
  end

  final_data
end

.composite_tag?(tag) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/bakong/khqr/controllers/decode_non_khqr.rb', line 73

def composite_tag?(tag)
  int = tag.to_i
  (26..51).cover?(int) || (80..99).cover?(int) || tag == "64" || tag == "62"
end

.extract_tlv(string) ⇒ Object 



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# File 'lib/bakong/khqr/controllers/decode_non_khqr.rb', line 65

def extract_tlv(string)
  tag = string[0, 2].to_s
  length = string[2, 2].to_i
  value = string[4, length].to_s
  remain = string[(4 + length)..] || ""
  { tag: tag, length: length, value: value, remain: remain }
end

.valid?(tag, length, value) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/bakong/khqr/controllers/decode_non_khqr.rb', line 78

def valid?(tag, length, value)
  tag.match?(/\A\d+\z/) && length == value.length
end