package domain

import (
	"strings"
	"time"
)

type SubscriptionCategory string

const (
	SubscriptionCategoryLearnEnglish SubscriptionCategory = "LEARN_ENGLISH"
	SubscriptionCategoryIELTS        SubscriptionCategory = "IELTS"
	SubscriptionCategoryDuolingo     SubscriptionCategory = "DUOLINGO"
)

// SubscriptionExpiryReminder is a Learn English subscription expiring in seven days.
type SubscriptionExpiryReminder struct {
	UserID    int64
	PlanName  string
	ExpiresAt time.Time
}

// CategorySubscriptionGateDisabled skips subscription enforcement on learner-facing routes (temporary).
var CategorySubscriptionGateDisabled = false

// ExamPrepSubscriptionGateDisabled skips IELTS/DUOLINGO subscription checks on exam-prep routes (temporary).
var ExamPrepSubscriptionGateDisabled = true

// IsLMSSubscriptionCategory reports plan categories that unlock Learn English (LMS) content.
func IsLMSSubscriptionCategory(category string) bool {
	return normalizeSubscriptionCategory(category) == string(SubscriptionCategoryLearnEnglish)
}

// IsExamPrepSubscriptionCategory reports plan categories that unlock exam-prep content.
func IsExamPrepSubscriptionCategory(category string) bool {
	switch normalizeSubscriptionCategory(category) {
	case string(SubscriptionCategoryIELTS), string(SubscriptionCategoryDuolingo):
		return true
	default:
		return false
	}
}

// IsLMSContentCategory reports content categories stored on LMS programs.
func IsLMSContentCategory(category string) bool {
	return IsLMSSubscriptionCategory(category)
}

// IsExamPrepContentCategory reports content categories stored on exam-prep catalog courses.
func IsExamPrepContentCategory(category string) bool {
	return IsExamPrepSubscriptionCategory(category)
}

// SubscriptionGrantsContentAccess reports whether an active plan category unlocks the given content category.
func SubscriptionGrantsContentAccess(subscriptionCategory, contentCategory string) bool {
	sub := normalizeSubscriptionCategory(subscriptionCategory)
	content := normalizeSubscriptionCategory(contentCategory)
	if IsLMSContentCategory(content) {
		return sub == string(SubscriptionCategoryLearnEnglish)
	}
	if IsExamPrepContentCategory(content) {
		return sub == content
	}
	return false
}

func normalizeSubscriptionCategory(category string) string {
	return strings.ToUpper(strings.TrimSpace(category))
}

type DurationUnit string

const (
	DurationUnitDay   DurationUnit = "DAY"
	DurationUnitWeek  DurationUnit = "WEEK"
	DurationUnitMonth DurationUnit = "MONTH"
	DurationUnitYear  DurationUnit = "YEAR"
)

type SubscriptionStatus string

const (
	SubscriptionStatusPending   SubscriptionStatus = "PENDING"
	SubscriptionStatusActive    SubscriptionStatus = "ACTIVE"
	SubscriptionStatusExpired   SubscriptionStatus = "EXPIRED"
	SubscriptionStatusCancelled SubscriptionStatus = "CANCELLED"
)

type SubscriptionPlan struct {
	ID            int64
	Name          string
	Description   *string
	Category      string
	DurationValue int32
	DurationUnit  string
	Price         float64
	Currency      string
	IsActive      bool
	CreatedAt     time.Time
	UpdatedAt     *time.Time
}

type UserSubscription struct {
	ID               int64
	UserID           int64
	PlanID           int64
	StartsAt         time.Time
	ExpiresAt        time.Time
	Status           string
	PaymentReference *string
	PaymentMethod    *string
	AutoRenew        bool
	CancelledAt      *time.Time
	CreatedAt        time.Time
	UpdatedAt        *time.Time
	// Joined fields from plan
	PlanName      *string
	DurationValue *int32
	DurationUnit  *string
	Price         *float64
	Currency      *string
}

type CreateSubscriptionPlanInput struct {
	Name          string
	Description   *string
	Category      string
	DurationValue int32
	DurationUnit  string
	Price         float64
	Currency      string
	IsActive      *bool
}

type UpdateSubscriptionPlanInput struct {
	Name          *string
	Description   *string
	Category      *string
	DurationValue *int32
	DurationUnit  *string
	Price         *float64
	Currency      *string
	IsActive      *bool
}

type CreateUserSubscriptionInput struct {
	UserID           int64
	PlanID           int64
	StartsAt         *time.Time
	ExpiresAt        time.Time
	Status           *string
	PaymentReference *string
	PaymentMethod    *string
	AutoRenew        *bool
}

// LifetimeSubscriptionExpiresAt is stored for one-time (non-expiring) DUOLINGO subscriptions.
var LifetimeSubscriptionExpiresAt = time.Date(9999, 12, 31, 23, 59, 59, 0, time.UTC)

// IsLifetimeSubscriptionCategory reports categories that grant permanent access after purchase.
func IsLifetimeSubscriptionCategory(category string) bool {
	return strings.ToUpper(strings.TrimSpace(category)) == string(SubscriptionCategoryDuolingo)
}

// CalculateSubscriptionExpiresAt returns when a subscription ends. DUOLINGO plans never expire.
func CalculateSubscriptionExpiresAt(startTime time.Time, category string, durationValue int32, durationUnit string) time.Time {
	if IsLifetimeSubscriptionCategory(category) {
		return LifetimeSubscriptionExpiresAt
	}
	return CalculateExpiryDate(startTime, durationValue, durationUnit)
}

// CalculateExpiryDate calculates the expiry date based on plan duration
func CalculateExpiryDate(startTime time.Time, durationValue int32, durationUnit string) time.Time {
	switch durationUnit {
	case string(DurationUnitDay):
		return startTime.AddDate(0, 0, int(durationValue))
	case string(DurationUnitWeek):
		return startTime.AddDate(0, 0, int(durationValue)*7)
	case string(DurationUnitMonth):
		return startTime.AddDate(0, int(durationValue), 0)
	case string(DurationUnitYear):
		return startTime.AddDate(int(durationValue), 0, 0)
	default:
		return startTime.AddDate(0, int(durationValue), 0) // Default to months
	}
}