package one

import (
	"bufio"
	"bytes"
	"embed"
	"fmt"
	"io"
	"math"
	"regexp"

	"github.com/onyx-and-iris/aoc2024/day-01/internal/util"
)

//go:embed testdata
var files embed.FS

var reNums = regexp.MustCompile(`[0-9]+`)

func Solve(filename string) (int, error) {
	data, err := files.ReadFile(fmt.Sprintf("testdata/%s", filename))
	if err != nil {
		return 0, err
	}

	r := bytes.NewReader(data)
	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 := reNums.FindAllString(scanner.Text(), -1)

		left = util.InsertSorted(left, util.MustConv(nums[0]))
		right = util.InsertSorted(right, util.MustConv(nums[1]))
	}

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

	return left, right, nil
}