# frozen_string_literal: true

module CashAddr
  class Crypto
    CHARSET = 'qpzry9x8gf2tvdw0s3jn54khce6mua7l'

    def self.polymod(values)
      chk = 1
      generator = [
        [0x01, 0x98f2bc8e61],
        [0x02, 0x79b76d99e2],
        [0x04, 0xf33e5fb3c4],
        [0x08, 0xae2eabe2a8],
        [0x10, 0x1e4f43e470]
      ]
      values.each do |value|
        top = chk >> 35
        chk = ((chk & 0x07ffffffff) << 5) ^ value
        generator.each do |i|
          chk ^= i[1] if (top & i[0]) != 0
        end
      end
      chk ^ 1
    end

    def self.prefix_expand(prefix)
      val = if prefix
              prefix.split('').map do |i|
                i.ord & 0x1f
              end
            else
              []
            end

      val + [0]
    end

    def self.calculate_checksum(prefix, payload)
      poly = polymod(prefix_expand(prefix) + payload + [0, 0, 0, 0, 0, 0, 0, 0])
      out = []
      8.times do |i|
        out.push((poly >> 5 * (7 - i)) & 0x1f)
      end
      out
    end

    def self.verify_checksum(prefix, payload)
      polymod(prefix_expand(prefix) + payload) == 0
    rescue TypeError
      raise CashAddr::InvalidAddress
    end

    def self.b32decode(inputs)
      out = []
      return out unless inputs

      inputs.split('').each do |letter|
        out.push(CHARSET.index(letter))
      end
      out
    end

    def self.b32encode(inputs)
      out = ''
      inputs.each do |char_code|
        out += CHARSET[char_code].to_s
      end
      out
    end

    def self.convertbits(data, frombits, tobits, pad = true)
      acc = 0
      bits = 0
      ret = []
      maxv = (1 << tobits) - 1
      max_acc = (1 << (frombits + tobits - 1)) - 1
      data.each do |value|
        return nil if value < 0 || ((value >> frombits) != 0)

        acc = ((acc << frombits) | value) & max_acc
        bits += frombits
        while bits >= tobits
          bits -= tobits
          ret.push((acc >> bits) & maxv)
        end
      end
      if pad
        ret.push((acc << (tobits - bits)) & maxv) if bits != 0
      elsif bits >= frombits || (((acc << (tobits - bits)) & maxv) != 0)
        return nil
      end
      ret
    end
  end
end