package q01

import (
	_ "embed"
	"fmt"
	"strconv"
	"strings"
	"text/template"

	"github.com/hhhapz/codequest/models"
	"github.com/hhhapz/codequest/question"
)

func init() {
	t := template.New("directions")
	var err error
	t, err = t.Parse(q01Text)
	if err != nil {
		panic(err)
	}
	question.Register(
		&question.Question{
			ID:    "directions",
			Name:  "No Time for Directions!",
			Text:  t,
			Level: question.Level1,
			Generate: func(u *models.User) string {
				return strings.Join(generate(u), "\n")
			},
			Validate: func(u *models.User, part question.Part, solution string) bool {
				return Validate(u, part, solution)
			},
		})
}

func total(a, b int) int {
	if a < 0 {
		a = -a
	}
	if b < 0 {
		b = -b
	}
	return a + b
}

const (
	// totalSteps in the input
	totalSteps = 100

	// stepRange is the range of steps within each step
	stepRange = 30

	// randRage is the range of steps between where the duplicate will be
	// present
	randRange = 20

	// earliestCandidate the earliest step where the duplicate candidate is
	earliestCandidate = 10

	// earliestDupe is the earliest step where the candidate is visited
	earliestDupe = 35

	// directions for a step
	directions = "NSWE"
)

func generate(u *models.User) []string {
	res := make([]string, 0, totalSteps)

	r := question.UserRandom(u)

	// known is used to disallow duplicate steps before the chosen dupe
	known := make(map[int]map[int]bool)
	var x, y int

	for len(res) != cap(res) {
		dir := directions[r.Intn(4)]
		steps := r.Intn(stepRange) + 1

		newX, newY := move(x, y, dir, steps)
		if known[newX] == nil {
			known[newX] = make(map[int]bool)
		}
		if known[newX][newY] {
			continue
		}

		known[newX][newY] = true
		x, y = newX, newY

		res = append(res, fmt.Sprintf("%c%d", dir, steps))
	}

	// the location of the candidate for the duplicate
	n := r.Intn(randRange) + earliestCandidate
	locX, locY := solveP1(res[:n])

	// the location where the candidate is revisited
	n = r.Intn(randRange) + earliestDupe
	lastX, lastY := solveP2(res[:n])

	// jump to the candidate
	if locX > lastX {
		res[n] = fmt.Sprintf("E%d", locX-lastX)
		n++
	} else if locX < lastX {
		res[n] = fmt.Sprintf("W%d", lastX-locX)
		n++
	}

	if locY > lastY {
		res[n] = fmt.Sprintf("N%d", locY-lastY)
	} else if locY < lastY {
		res[n] = fmt.Sprintf("S%d", lastY-locY)
	}

	return res
}

func Validate(u *models.User, p question.Part, sol string) bool {
	inp := generate(u)

	var t int
	switch p {
	case question.Part1:
		t = total(solveP1(inp))
	case question.Part2:
		t = total(solveP2(inp))

	default:
		return false
	}

	return strconv.Itoa(t) == sol
}

//go:embed q01.md
var q01Text string