package main

import (
	"bufio"
	"fmt"
	"io"
	"strconv"
	"unicode"
)

type day01 struct {
}

type buffer struct {
	first bool
	d1    rune

	last bool
	d2   rune
}

func (b *buffer) value() (value uint64) {
	var d2 rune

	if b.last {
		d2 = b.d2
	} else {
		d2 = b.d1
	}

	str := fmt.Sprintf("%c%c", b.d1, d2)
	value, _ = strconv.ParseUint(str, 10, 64)

	b.first, b.last = false, false
	return
}

func (b *buffer) record(digit rune) {
	if !b.first {
		b.d1 = digit
		b.first = true
	} else {
		b.d2 = digit
		b.last = true
	}
}

func (d day01) solve(r io.Reader) string {
	var (
		buffer buffer
		total  uint64
		buf    = bufio.NewReader(r)
	)

	for {
		b, _, err := buf.ReadRune()
		if err != nil {
			return fmt.Sprintf("%d", total+buffer.value())
		}

		if unicode.IsDigit(b) {
			buffer.record(b)
		} else if b == '\n' {
			total += buffer.value()
		}

	}
}