dec.cr

require "./src/pg"
# require "../hexdump/hex.cr"

require "big_int"

struct Numeric
  property ndigits
  property weight
  property sign
  property dscale
  property digits

  TenK = BigInt.new(10000)

  enum Sign
    Pos = 0x0000
    Neg = 0x4000
    Nan = 0xC000
  end

  def initialize(bytes)
    int_d = PG::Decoder::Int2Decoder.new
    @ndigits = int_d.decode(bytes[0, 2])
    @weight = int_d.decode(bytes[2, 2])
    @sign = int_d.decode(bytes[4, 2])
    @dscale = int_d.decode(bytes[6, 2])
    @digits = (0...(bytes.size - 8)/2).map { |i| int_d.decode(bytes[i*2 + 8, 2]) }
  end

  def integer_part
    digits_to_bigint @digits[0..weight]
  end

  def fractional_part
    digits_to_bigint @digits[weight + 1..-1]
  end

  def to_s
    p sign
    if sign == Sign::Nan.value
      "NaN"
    else
      "#{"-" if sign == Sign::Neg.value}#{integer_part}#{".#{fractional_part.to_s[0..dscale - 1]}" if dscale > 0}"
    end
  end

  private def digits_to_bigint(digit_arr)
    digit_arr.reduce(BigInt.new(0)) { |a, i| a*TenK + BigInt.new(i) }
  end
end

class NumericDecoder < PG::Decoder::Decoder
  def decode(bytes)
    #  puts bytes.hexdump
    Numeric.new(bytes)
  end
end

PG::Decoder.register_decoder NumericDecoder.new, 1700

DB = PG.connect(ENV["DATABASE_URL"]? || "postgres:///")

def try(n)
  p n
  r = DB.exec({Numeric}, "select #{n}::numeric")
  n = r.rows[0].first
  p ({ndigits: n.ndigits, weight: n.weight, sign: n.sign, dscale: n.dscale, digits: n.digits})
  p n.to_s
  puts
end

try "1"
try "1.1"
try "1.10"
try "11.11"
try "12.3456789"
try "123.456789"
try "12345.6789"
try "123451234523498293847982374987342987.987654321"
try "1.23451234523498293847982374987342987987654321"
try "99999999999999999999999.99999999999999999999"
try "0.000000000000000000000000000000000000009999999999999999999"
try "-1"
try "'nan'"