package service

import (
	"context"
	"errors"
	"fmt"
	"maps"

	"github.com/samber/lo"

	"github.com/openmeterio/openmeter/openmeter/customer"
	"github.com/openmeterio/openmeter/openmeter/productcatalog"
	"github.com/openmeterio/openmeter/openmeter/subscription"
	subscriptionaddon "github.com/openmeterio/openmeter/openmeter/subscription/addon"
	"github.com/openmeterio/openmeter/openmeter/subscription/patch"
	subscriptionworkflow "github.com/openmeterio/openmeter/openmeter/subscription/workflow"
	"github.com/openmeterio/openmeter/pkg/clock"
	"github.com/openmeterio/openmeter/pkg/featuregate"
	"github.com/openmeterio/openmeter/pkg/filter"
	"github.com/openmeterio/openmeter/pkg/framework/transaction"
	"github.com/openmeterio/openmeter/pkg/models"
	"github.com/openmeterio/openmeter/pkg/pagination"
	"github.com/openmeterio/openmeter/pkg/timeutil"
)

func (s *service) CreateFromPlan(ctx context.Context, inp subscriptionworkflow.CreateSubscriptionWorkflowInput, plan subscription.Plan) (subscription.SubscriptionView, error) {
	return transaction.Run(ctx, s.TransactionManager, func(ctx context.Context) (subscription.SubscriptionView, error) {
		var def subscription.SubscriptionView

		creditEnabled := featuregate.ContextResolver().Credits(ctx)
		if !creditEnabled && plan.ToCreateSubscriptionPlanInput().SettlementMode == productcatalog.CreditOnlySettlementMode {
			return def, models.NewGenericValidationError(errors.New("credits are not enabled on this deployment of OpenMeter"))
		}

		if err := s.lockCustomer(ctx, inp.CustomerID); err != nil {
			return def, err
		}

		// Let's find the customer
		cus, err := s.CustomerService.GetCustomer(ctx, customer.GetCustomerInput{
			CustomerID: &customer.CustomerID{
				Namespace: inp.Namespace,
				ID:        inp.CustomerID,
			},
		})
		if err != nil {
			return def, fmt.Errorf("failed to fetch customer: %w", err)
		}

		if cus != nil && cus.IsDeleted() {
			return def, models.NewGenericPreConditionFailedError(
				fmt.Errorf("customer is deleted [namespace=%s customer.id=%s]", cus.Namespace, cus.ID),
			)
		}

		if cus == nil {
			return def, fmt.Errorf("unexpected nil customer")
		}

		if err := inp.Timing.ValidateForAction(subscription.SubscriptionActionCreate, nil); err != nil {
			return def, fmt.Errorf("invalid timing: %w", err)
		}

		activeFrom, err := inp.Timing.Resolve()
		if err != nil {
			return def, fmt.Errorf("failed to resolve active from: %w", err)
		}

		// Let's normalize the billing anchor to the closest iteration based on the cadence
		billingAnchor := lo.FromPtrOr(inp.BillingAnchor, activeFrom).UTC()

		// Let's create the new Spec
		spec, err := subscription.NewSpecFromPlan(plan, subscription.CreateSubscriptionCustomerInput{
			CustomerId:    cus.ID,
			Currency:      plan.Currency(),
			ActiveFrom:    activeFrom,
			MetadataModel: inp.MetadataModel,
			Name:          lo.CoalesceOrEmpty(inp.Name, plan.GetName()),
			Description:   inp.Description,
			BillingAnchor: billingAnchor,
			Annotations:   inp.Annotations,
		})

		if err := subscriptionworkflow.MapSubscriptionErrors(err); err != nil {
			return def, fmt.Errorf("failed to create spec from plan: %w", err)
		}

		if err := spec.ValidateAlignment(); err != nil {
			return def, err
		}

		// Finally, let's create the subscription
		sub, err := s.Service.Create(ctx, inp.Namespace, spec)
		if err != nil {
			return def, fmt.Errorf("failed to create subscription: %w", err)
		}

		return s.Service.GetView(ctx, sub.NamespacedID)
	})
}

func (s *service) EditRunning(ctx context.Context, subscriptionID models.NamespacedID, customizations []subscription.Patch, timing subscription.Timing) (subscription.SubscriptionView, error) {
	// Finally, let's update the subscription
	return transaction.Run(ctx, s.TransactionManager, func(ctx context.Context) (subscription.SubscriptionView, error) {
		// First, let's fetch the current state of the Subscription
		curr, err := s.Service.GetView(ctx, subscriptionID)
		if err != nil {
			return subscription.SubscriptionView{}, fmt.Errorf("failed to fetch subscription: %w", err)
		}

		adds, err := s.AddonService.List(ctx, subscriptionID.Namespace, subscriptionaddon.ListSubscriptionAddonsInput{
			SubscriptionID: subscriptionID.ID,
		})
		if err != nil {
			return subscription.SubscriptionView{}, fmt.Errorf("failed to list addons: %w", err)
		}

		if hasAddons(curr, adds.Items) {
			return subscription.SubscriptionView{}, models.NewGenericForbiddenError(fmt.Errorf("subscription with addons cannot be edited"))
		}

		// Let's set the owner subsystem
		// TODO: let's refactor, its a bit ad-hoc
		customizations = lo.Map(customizations, func(p subscription.Patch, _ int) subscription.Patch {
			if ap, ok := p.(patch.PatchAddItem); ok {
				if ap.CreateInput.CreateSubscriptionItemInput.Annotations == nil {
					ap.CreateInput.CreateSubscriptionItemInput.Annotations = models.Annotations{}
				}
				_, _ = subscription.AnnotationParser.AddOwnerSubSystem(ap.CreateInput.CreateSubscriptionItemInput.Annotations, subscription.OwnerSubscriptionSubSystem)

				subscriptionworkflow.AnnotationParser.SetUniquePatchID(ap.CreateInput.CreateSubscriptionItemInput.Annotations)

				return ap
			}

			if ap, ok := p.(*patch.PatchAddItem); ok {
				if ap.CreateInput.CreateSubscriptionItemInput.Annotations == nil {
					ap.CreateInput.CreateSubscriptionItemInput.Annotations = models.Annotations{}
				}
				_, _ = subscription.AnnotationParser.AddOwnerSubSystem(ap.CreateInput.CreateSubscriptionItemInput.Annotations, subscription.OwnerSubscriptionSubSystem)

				subscriptionworkflow.AnnotationParser.SetUniquePatchID(ap.CreateInput.CreateSubscriptionItemInput.Annotations)

				return ap
			}

			return p
		})

		// Let's validate the patches
		for i, p := range customizations {
			if err := p.Validate(); err != nil {
				return subscription.SubscriptionView{}, models.ErrorWithComponent(models.ComponentName(fmt.Sprintf("patch[%d]", i)), err)
			}
		}

		// Let's try to decode when the subscription should be patched
		if err := timing.ValidateForAction(subscription.SubscriptionActionUpdate, &curr); err != nil {
			return subscription.SubscriptionView{}, models.NewGenericValidationError(fmt.Errorf("invalid timing: %w", err))
		}

		editTime, err := timing.ResolveForSpec(curr.Spec)
		if err != nil {
			return subscription.SubscriptionView{}, fmt.Errorf("failed to resolve timing: %w", err)
		}

		// Let's apply the customizations
		spec := curr.AsSpec()

		err = spec.ApplyMany(lo.Map(customizations, subscription.ToApplies), subscription.ApplyContext{
			CurrentTime: editTime,
		})
		if err := subscriptionworkflow.MapSubscriptionErrors(err); err != nil {
			return subscription.SubscriptionView{}, fmt.Errorf("failed to apply customizations: %w", err)
		}

		if err := spec.ValidateAlignment(); err != nil {
			return subscription.SubscriptionView{}, err
		}

		sub, err := s.Service.Update(ctx, subscriptionID, spec)
		if err != nil {
			return subscription.SubscriptionView{}, fmt.Errorf("failed to update subscription: %w", err)
		}

		return s.Service.GetView(ctx, sub.NamespacedID)
	})
}

func (s *service) ChangeToPlan(ctx context.Context, subscriptionID models.NamespacedID, inp subscriptionworkflow.ChangeSubscriptionWorkflowInput, plan subscription.Plan) (subscription.Subscription, subscription.SubscriptionView, error) {
	// typing helper
	type res struct {
		curr subscription.Subscription
		new  subscription.SubscriptionView
	}

	// Changing the plan means canceling the current subscription and creating a new one with the provided timestamp
	r, err := transaction.Run(ctx, s.TransactionManager, func(ctx context.Context) (res, error) {
		creditEnabled := featuregate.ContextResolver().Credits(ctx)
		if !creditEnabled && plan.ToCreateSubscriptionPlanInput().SettlementMode == productcatalog.CreditOnlySettlementMode {
			return res{}, models.NewGenericValidationError(errors.New("credits are not enabled on this deployment of OpenMeter"))
		}

		// Second, let's try to cancel the current subscription
		curr, err := s.Service.Cancel(ctx, subscriptionID, inp.Timing)
		if err != nil {
			return res{}, fmt.Errorf("failed to end current subscription: %w", err)
		}

		// Let's create a new timing with the exact value as the create step might not be able resolve it for itself
		verbatumTiming := subscription.Timing{
			Custom: curr.ActiveTo, // We have to make sure we resolve to the exact same timestamp
		}

		inp.Timing = verbatumTiming

		// Prepare annotations for the new subscription with reference to the previous subscription
		createInputAnnotations := models.Annotations{}
		_, err = subscription.AnnotationParser.SetPreviousSubscriptionID(createInputAnnotations, curr.ID)
		if err != nil {
			return res{}, fmt.Errorf("failed to set previous subscription ID: %w", err)
		}

		// Third, let's create a new subscription with the new plan
		new, err := s.CreateFromPlan(ctx, subscriptionworkflow.CreateSubscriptionWorkflowInput{
			ChangeSubscriptionWorkflowInput: inp,
			Namespace:                       curr.Namespace,
			CustomerID:                      curr.CustomerId,
			BillingAnchor:                   lo.ToPtr(lo.FromPtrOr(inp.BillingAnchor, curr.BillingAnchor)), // We default to the current anchor
			Annotations:                     createInputAnnotations,
		}, plan)
		if err != nil {
			return res{}, fmt.Errorf("failed to create new subscription: %w", err)
		}

		// Update the current subscription to reference the new subscription as superseding
		currAnnotations := curr.Annotations
		if currAnnotations == nil {
			currAnnotations = models.Annotations{}
		} else {
			currAnnotations = maps.Clone(currAnnotations)
		}
		currAnnotations, err = subscription.AnnotationParser.SetSupersedingSubscriptionID(currAnnotations, new.Subscription.ID)
		if err != nil {
			return res{}, fmt.Errorf("failed to set superseding subscription ID: %w", err)
		}
		updatedCurr, err := s.Service.UpdateAnnotations(ctx, curr.NamespacedID, currAnnotations)
		if err != nil {
			return res{}, fmt.Errorf("failed to update current subscription annotations: %w", err)
		}
		curr = *updatedCurr

		// Let's just return after a great success
		return res{curr, new}, nil
	})

	return r.curr, r.new, err
}

func (s *service) Restore(ctx context.Context, subscriptionID models.NamespacedID) (subscription.Subscription, error) {
	multiSubscriptionEnabled, err := s.FeatureFlags.IsFeatureEnabled(ctx, subscription.MultiSubscriptionEnabledFF)
	if err != nil {
		return subscription.Subscription{}, fmt.Errorf("failed to check if multi-subscription is enabled: %w", err)
	}

	if multiSubscriptionEnabled {
		return subscription.Subscription{}, subscription.ErrRestoreSubscriptionNotAllowedForMultiSubscription
	}

	return transaction.Run(ctx, s.TransactionManager, func(ctx context.Context) (subscription.Subscription, error) {
		now := clock.Now()

		// Let's fetch the sub
		sub, err := s.Service.GetView(ctx, subscriptionID)
		if err != nil {
			return subscription.Subscription{}, fmt.Errorf("failed to fetch subscription: %w", err)
		}

		// Let's get all subs scheduled afterward
		scheduled, err := pagination.CollectAll(ctx, pagination.NewPaginator(func(ctx context.Context, page pagination.Page) (pagination.Result[subscription.Subscription], error) {
			return s.Service.List(ctx, subscription.ListSubscriptionsInput{
				CustomerID:     &filter.FilterULID{FilterString: filter.FilterString{Eq: &sub.Subscription.CustomerId}},
				Namespaces:     []string{sub.Subscription.Namespace},
				ActiveInPeriod: &timeutil.StartBoundedPeriod{From: now},
				Page:           page,
			})
		}), 1000)
		if err != nil {
			return subscription.Subscription{}, fmt.Errorf("failed to fetch scheduled subscriptions: %w", err)
		}

		// Let's filter out the current sub if present
		scheduled = lo.Filter(scheduled, func(s subscription.Subscription, _ int) bool {
			return s.NamespacedID != subscriptionID
		})
		// Let's delete all scheduled subs
		for _, sch := range scheduled {
			if err := s.Service.Delete(ctx, sch.NamespacedID); err != nil {
				return subscription.Subscription{}, fmt.Errorf("failed to delete scheduled subscription: %w", err)
			}
		}

		// Let's continue the current sub
		return s.Service.Continue(ctx, subscriptionID)
	})
}