package middleware

import (
	"context"
	"encoding/json"
	"errors"
	"strings"
	"time"

	"github.com/google/uuid"
	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/metadata"
	"google.golang.org/grpc/status"
	"gorm.io/gorm"
	"gorm.io/gorm/clause"
	"stream.api/internal/database/model"
	"stream.api/internal/database/query"
	"stream.api/pkg/logger"
)

const (
	ActorMarkerMetadataKey = "x-stream-internal-auth"
	ActorIDMetadataKey     = "x-stream-actor-id"
	ActorEmailMetadataKey  = "x-stream-actor-email"
	ActorRoleMetadataKey   = "x-stream-actor-role"
)

type AuthResult struct {
	UserID string
	User   *model.User
}

type Actor struct {
	UserID string
	Email  string
	Role   string
}

type Authenticator struct {
	db            *gorm.DB
	logger        logger.Logger
	trustedMarker string
}

func NewAuthenticator(db *gorm.DB, l logger.Logger, trustedMarker string) *Authenticator {
	return &Authenticator{
		db:            db,
		logger:        l,
		trustedMarker: strings.TrimSpace(trustedMarker),
	}
}

func (a *Authenticator) Authenticate(ctx context.Context) (*AuthResult, error) {
	actor, err := a.RequireActor(ctx)
	if err != nil {
		return nil, err
	}

	u := query.User
	user, err := u.WithContext(ctx).Where(u.ID.Eq(actor.UserID)).First()
	if err != nil {
		return nil, status.Error(codes.Unauthenticated, "Unauthorized")
	}

	user, err = a.syncSubscriptionState(ctx, user)
	if err != nil {
		a.logger.Error("Failed to sync subscription state", "error", err, "user_id", actor.UserID)
		return nil, status.Error(codes.Internal, "Failed to load user subscription state")
	}

	if user.Role != nil && strings.EqualFold(strings.TrimSpace(*user.Role), "block") {
		return nil, status.Error(codes.PermissionDenied, "Forbidden: User is blocked")
	}

	return &AuthResult{
		UserID: user.ID,
		User:   user,
	}, nil
}

func (a *Authenticator) RequireActor(ctx context.Context) (*Actor, error) {
	md, err := a.requireTrustedMetadata(ctx)
	if err != nil {
		return nil, err
	}

	userID := strings.TrimSpace(firstMetadataValue(md, ActorIDMetadataKey))
	role := strings.TrimSpace(firstMetadataValue(md, ActorRoleMetadataKey))
	if userID == "" || role == "" {
		return nil, status.Error(codes.Unauthenticated, "Missing actor identity")
	}

	return &Actor{
		UserID: userID,
		Email:  strings.TrimSpace(firstMetadataValue(md, ActorEmailMetadataKey)),
		Role:   role,
	}, nil
}

func (a *Authenticator) RequireInternalCall(ctx context.Context) error {
	_, err := a.requireTrustedMetadata(ctx)
	return err
}

func (a *Authenticator) requireTrustedMetadata(ctx context.Context) (metadata.MD, error) {
	md, ok := metadata.FromIncomingContext(ctx)
	if !ok {
		return nil, status.Error(codes.Unauthenticated, "Missing actor metadata")
	}

	marker := firstMetadataValue(md, ActorMarkerMetadataKey)
	if marker == "" || marker != a.trustedMarker {
		return nil, status.Error(codes.Unauthenticated, "Invalid internal auth marker")
	}

	return md, nil
}

func firstMetadataValue(md metadata.MD, key string) string {
	values := md.Get(key)
	if len(values) == 0 {
		return ""
	}
	return values[0]
}

func (a *Authenticator) syncSubscriptionState(ctx context.Context, user *model.User) (*model.User, error) {
	subscription, err := model.GetLatestPlanSubscription(ctx, a.db, user.ID)
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return user, nil
		}
		return nil, err
	}

	now := time.Now().UTC()
	if err := a.db.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
		var lockedSubscription model.PlanSubscription
		if err := tx.WithContext(ctx).
			Clauses(clause.Locking{Strength: "UPDATE"}).
			Where("id = ?", subscription.ID).
			First(&lockedSubscription).Error; err != nil {
			return err
		}

		if lockedSubscription.ExpiresAt.After(now) {
			if user.PlanID == nil || strings.TrimSpace(*user.PlanID) != lockedSubscription.PlanID {
				if err := tx.WithContext(ctx).
					Model(&model.User{}).
					Where("id = ?", user.ID).
					Update("plan_id", lockedSubscription.PlanID).Error; err != nil {
					return err
				}
				user.PlanID = &lockedSubscription.PlanID
			}

			reminderDays, reminderField := reminderFieldForSubscription(&lockedSubscription, now)
			if reminderField != "" {
				sentAt := now
				notification := &model.Notification{
					ID:          uuidString(),
					UserID:      user.ID,
					Type:        "billing.subscription_expiring",
					Title:       "Plan expiring soon",
					Message:     reminderMessage(reminderDays),
					ActionURL:   model.StringPtr("/settings/billing"),
					ActionLabel: model.StringPtr("Renew plan"),
					Metadata:    model.StringPtr(mustMarshalAuthJSON(map[string]interface{}{"plan_id": lockedSubscription.PlanID, "expires_at": lockedSubscription.ExpiresAt.UTC().Format(time.RFC3339), "reminder_days": reminderDays})),
				}
				if err := tx.WithContext(ctx).Create(notification).Error; err != nil {
					return err
				}
				if err := tx.WithContext(ctx).
					Model(&model.PlanSubscription{}).
					Where("id = ?", lockedSubscription.ID).
					Update(reminderField, sentAt).Error; err != nil {
					return err
				}
			}

			return nil
		}

		if user.PlanID != nil && strings.TrimSpace(*user.PlanID) != "" {
			if err := tx.WithContext(ctx).
				Model(&model.User{}).
				Where("id = ?", user.ID).
				Update("plan_id", nil).Error; err != nil {
				return err
			}
			user.PlanID = nil
		}

		return nil
	}); err != nil {
		return nil, err
	}

	return user, nil
}

func reminderFieldForSubscription(subscription *model.PlanSubscription, now time.Time) (int, string) {
	if subscription == nil || !subscription.ExpiresAt.After(now) {
		return 0, ""
	}

	remaining := subscription.ExpiresAt.Sub(now)
	switch {
	case remaining <= 24*time.Hour:
		if subscription.Reminder1DSentAt == nil {
			return 1, "reminder_1d_sent_at"
		}
	case remaining <= 72*time.Hour:
		if subscription.Reminder3DSentAt == nil {
			return 3, "reminder_3d_sent_at"
		}
	case remaining <= 7*24*time.Hour:
		if subscription.Reminder7DSentAt == nil {
			return 7, "reminder_7d_sent_at"
		}
	}

	return 0, ""
}

func reminderMessage(days int) string {
	switch days {
	case 1:
		return "Your current plan expires in 1 day. Renew now to avoid interruption."
	case 3:
		return "Your current plan expires in 3 days. Renew now to keep access active."
	default:
		return "Your current plan expires in 7 days. Renew now to keep your plan active."
	}
}

func mustMarshalAuthJSON(value interface{}) string {
	encoded, err := json.Marshal(value)
	if err != nil {
		return "{}"
	}
	return string(encoded)
}

func uuidString() string {
	return uuid.New().String()
}