package one

import (
	"bufio"
	"bytes"
	"io"
	"math"
	"strings"
)

func Solve(buf []byte) (int, error) {
	r := bytes.NewReader(buf)
	left, right, err := parseLines(r)
	if err != nil {
		return 0, err
	}

	var sum int
	for i, n := range left {
		sum += int(math.Abs(float64(n - right[i])))
	}
	return sum, nil
}

func parseLines(r io.Reader) ([]int, []int, error) {
	var left, right []int

	scanner := bufio.NewScanner(r)
	for scanner.Scan() {
		nums := strings.Fields(scanner.Text())

		left = insertSorted(left, mustConv(nums[0]))
		right = insertSorted(right, mustConv(nums[1]))
	}

	if err := scanner.Err(); err != nil {
		return nil, nil, err
	}

	return left, right, nil
}