//go:build !solution

package hogwarts

import (
	"log"
	"slices"
)

func singleCourseList(
	course string, prereqs map[string][]string, list []string, traversed []string,
) []string {
	if slices.Contains(traversed, course) {
		log.Panic("recursive prereqs, aborting...")
	}
	traversed = append(traversed, course)
	for _, prereqCourse := range prereqs[course] {
		if !slices.Contains(list, prereqCourse) {
			i := slices.Index(list, course)
			if i == -1 {
				list = append(list, prereqCourse)
			} else {
				list = slices.Insert(list, i, prereqCourse)
			}
		}
		list = singleCourseList(prereqCourse, prereqs, list, traversed)
	}
	return list
}

func GetCourseList(prereqs map[string][]string) []string {
	list := make([]string, 0)
	for course := range prereqs {
		if !slices.Contains(list, course) {
			list = append(list, course)
		}
		list = singleCourseList(course, prereqs, list, []string{})
	}
	return list
}