package classes

import (
	"fmt"
	"math"
	"strconv"
	"time"

	"git.golem15.com/golem15/sm-quizzes-plugin/models"
	"git.golem15.com/golem15/summercms/modules/compass"
)

// IsTest reports whether the quiz runs as a test. A zero or unknown mode is
// learning, so a quiz written before test mode existed keeps its behaviour.
func IsTest(q *models.Quiz) bool { return q != nil && q.Mode == models.ModeTest }

// Withheld reports whether an attempt's solutions must stay hidden: it is
// an attempt at a test that is not finished yet. Every student serializer
// drops is_correct, points, correct answers, explanations and model answers
// while it is true.
func Withheld(a *models.Attempt) bool {
	return a != nil && IsTest(a.Quiz) && a.CompletedAt == nil
}

// OneWay reports whether a test's answers are final: navigation one_way.
// Learning quizzes ignore the navigation setting.
func OneWay(q *models.Quiz) bool { return IsTest(q) && q.Navigation == models.NavigationOneWay }

// DefaultTestGrace is the test grace without a golem15.quizzes.test.grace_seconds setting.
const DefaultTestGrace = 5 * time.Second

// maxTestGrace caps the configured grace.
const maxTestGrace = 120 * time.Second

// TestGraceFrom reads golem15.quizzes.test.grace_seconds: how long after a
// test's deadline an answer in flight is still accepted. A nil config, a
// missing key or a value that is not a number give DefaultTestGrace; the
// value is clamped to 0..120 seconds. Learning quizzes have no grace.
func TestGraceFrom(cfg *compass.Config) time.Duration {
	if cfg == nil {
		return DefaultTestGrace
	}
	v, ok := cfg.Lookup("golem15.quizzes.test.grace_seconds")
	if !ok {
		return DefaultTestGrace
	}
	secs, ok := number(v)
	if !ok {
		return DefaultTestGrace
	}
	grace := time.Duration(secs * float64(time.Second))
	return min(max(grace, 0), maxTestGrace)
}

// number is v as a float when it is a number or a numeric string.
func number(v any) (float64, bool) {
	switch n := v.(type) {
	case float64:
		return n, !math.IsNaN(n)
	case float32:
		return float64(n), true
	case int:
		return float64(n), true
	case int64:
		return float64(n), true
	case uint64:
		return float64(n), true
	case string:
		f, err := strconv.ParseFloat(n, 64)
		return f, err == nil && !math.IsNaN(f)
	}
	return 0, false
}

// AnswerDeadline is the last moment an answer to the attempt is accepted:
// the Deadline plus grace for a test, the Deadline itself for a learning
// quiz, nil without a time limit.
func AnswerDeadline(a *models.Attempt, grace time.Duration) *time.Time {
	d := Deadline(a)
	if d == nil || !IsTest(a.Quiz) {
		return d
	}
	t := d.Add(grace)
	return &t
}

// Expired reports whether an open test attempt is past its answer deadline,
// so it can be closed at its Deadline. Learning and completed attempts never
// expire this way.
func Expired(a *models.Attempt, now time.Time, grace time.Duration) bool {
	if a == nil || !IsTest(a.Quiz) || a.CompletedAt != nil {
		return false
	}
	d := AnswerDeadline(a, grace)
	return d != nil && now.After(*d)
}

// SecondsLeft is the whole seconds until the attempt's Deadline, rounded up
// and floored at 0, or nil without a time limit or once completed. The
// player runs its countdown from it, not from the client clock.
func SecondsLeft(a *models.Attempt, now time.Time) *int {
	d := Deadline(a)
	if d == nil || a.CompletedAt != nil {
		return nil
	}
	left := max(int(math.Ceil(d.Sub(now).Seconds())), 0)
	return &left
}

// AttemptsLeft is how many attempts the user may still start: nil for a
// learning quiz or a test without a limit, otherwise max(0, limit - used).
func AttemptsLeft(q *models.Quiz, used int) *int {
	if !IsTest(q) || q.MaxAttempts == nil {
		return nil
	}
	left := max(*q.MaxAttempts-used, 0)
	return &left
}

// AttemptLockKey names the advisory lock that serialises one user's test
// starts on one quiz.
func AttemptLockKey(quizID, userID uint) string {
	return fmt.Sprintf("golem15.quizzes.attempt:%d:%d", quizID, userID)
}