package main

import (
	"context"
	"encoding/json"
	"fmt"

	"git.k6n.net/mats/go-cart-actor/pkg/checkout"
	profile "git.k6n.net/mats/go-cart-actor/pkg/profile"
	messages "git.k6n.net/mats/go-cart-actor/proto/checkout"
	profileMessages "git.k6n.net/mats/go-cart-actor/proto/profile"
	"google.golang.org/protobuf/types/known/timestamppb"
)

// settledPayment carries the provider-agnostic facts about an already-settled
// payment. Each payment integration (Klarna push, Adyen CAPTURE notification,
// …) fills this in from its own callback and hands it to
// createOrderFromSettledCheckout, so the from-checkout request is identical
// regardless of which provider settled the payment.
type settledPayment struct {
	Provider  string // "klarna" | "adyen"
	Reference string // processor / PSP reference
	Amount    int64  // minor units, as charged
	Currency  string
	Country   string
	Locale    string
}

// buildOrderLinesFromGrain converts the checkout grain's cart items and delivery
// selections into from-checkout order lines. Shared by every provider so the
// order payload is built the same way no matter who settled the payment.
func buildOrderLinesFromGrain(grain *checkout.CheckoutGrain) []OrderLine {
	hasFreeShipping := false
	if grain.CartState != nil {
		for _, ap := range grain.CartState.AppliedPromotions {
			if ap.Type == "free_shipping" && !ap.Pending {
				hasFreeShipping = true
				break
			}
		}
	}

	lines := make([]OrderLine, 0, len(grain.CartState.Items)+len(grain.Deliveries))
	for _, it := range grain.CartState.Items {
		if it == nil {
			continue
		}
		// Carry the per-item store as the inventory commit location; empty when
		// no store (commit then falls back to the order country / central stock).
		location := ""
		if it.StoreId != nil {
			location = *it.StoreId
		}
		lines = append(lines, OrderLine{
			Reference: it.Sku,
			Sku:       it.Sku,
			Name:      it.Meta.Name,
			Quantity:  int32(it.Quantity),
			UnitPrice: it.Price.IncVat.Int64(),
			// CartItem.Tax and OrderLine.TaxRate share the platform basis-point scale
			// (2500 = 25%), so the rate passes through unchanged.
			TaxRate:   int32(it.Tax),
			DropShip:  it.DropShip,
			Location:  location,
		})
	}
	for _, d := range grain.Deliveries {
		if d == nil {
			continue
		}
		unitPrice := d.Price.IncVat.Int64()
		if hasFreeShipping {
			unitPrice = 0
		}
		if unitPrice <= 0 && !hasFreeShipping {
			continue
		}
		lines = append(lines, OrderLine{
			Reference: d.Provider,
			Sku:       d.Provider,
			Name:      "Delivery",
			Quantity:  1,
			UnitPrice: unitPrice,
			TaxRate:   2500, // 25% in basis points
		})
	}

	// Reflected applied promotions as negative discount lines
	if grain.CartState != nil {
		for _, ap := range grain.CartState.AppliedPromotions {
			if ap.Pending {
				continue
			}
			discountVal := int64(0)
			if ap.Discount != nil {
				discountVal = ap.Discount.IncVat.Int64()
			}
			if discountVal <= 0 {
				continue
			}
			lines = append(lines, OrderLine{
				Reference: "promo-" + ap.PromotionId,
				Sku:       "promo-" + ap.PromotionId,
				Name:      "Promotion: " + ap.Name,
				Quantity:  1,
				UnitPrice: -discountVal,
				TaxRate:   2500, // default standard tax rate (25%) in basis points
			})
		}
	}

	return lines
}

// createOrderFromSettledCheckout sends the from-checkout request for a settled
// checkout (any provider) and, on success, records the returned order id on the
// checkout grain via the OrderCreated mutation so the backoffice can link
// checkout → order.
//
// It is idempotent: the order service dedupes on "checkout-{checkoutId}", so
// repeated provider callbacks (Klarna re-push, retried Adyen CAPTURE) return the
// existing order rather than creating a duplicate.
//
// If the HTTP call fails or is not configured, it falls back to publishing the
// exact same payload to RabbitMQ via s.orderHandler.OrderCompleted(body).
func createOrderFromSettledCheckout(ctx context.Context, s *CheckoutPoolServer, grain *checkout.CheckoutGrain, pay settledPayment) (*CreateOrderResult, error) {
	if grain.CartState == nil {
		return nil, fmt.Errorf("from-checkout: checkout %s has no cart state", grain.Id)
	}

	var customerEmail, customerName string
	if grain.ContactDetails != nil {
		if grain.ContactDetails.Email != nil {
			customerEmail = *grain.ContactDetails.Email
		}
		if grain.ContactDetails.Name != nil {
			customerName = *grain.ContactDetails.Name
		}
	}

	req := CreateOrderReq{
		CheckoutId:     grain.Id.String(),
		IdempotencyKey: "checkout-" + grain.Id.String(),
		CartId:         grain.CartId.String(),
		Currency:       pay.Currency,
		Locale:         pay.Locale,
		Country:        pay.Country,
		CustomerEmail:  customerEmail,
		CustomerName:   customerName,
		Lines:          buildOrderLinesFromGrain(grain),
	}
	req.Payment.Provider = pay.Provider
	req.Payment.Reference = pay.Reference
	req.Payment.Amount = pay.Amount

	var createErr error
	if s.orderClient != nil {
		result, err := s.orderClient.CreateOrder(ctx, req, "")
		if err == nil {
			_ = s.ApplyAnywhere(ctx, grain.Id, &messages.OrderCreated{
				OrderId:   result.OrderId,
				Status:    "completed",
				CreatedAt: timestamppb.Now(),
			})
			if grain.CartState != nil && grain.CartState.UserId != "" {
				if pid, ok := profile.ParseProfileId(grain.CartState.UserId); ok {
					_ = s.ApplyAnywhere(ctx, checkout.CheckoutId(pid), &profileMessages.LinkOrder{
						OrderReference: result.OrderId,
						CartId:         uint64(grain.CartId),
						Status:         "completed",
					})
				}
			}
			return result, nil
		}
		createErr = err
		logger.WarnContext(ctx, "from-checkout HTTP call failed; falling back to AMQP", "err", err, "checkoutId", grain.Id.String())
	}

	// Fallback to AMQP
	if s.orderHandler != nil {
		body, err := json.Marshal(req)
		if err != nil {
			return nil, fmt.Errorf("failed to marshal order fallback: %w", err)
		}
		if pubErr := s.orderHandler.OrderCompleted(body); pubErr != nil {
			if createErr != nil {
				return nil, fmt.Errorf("AMQP fallback failed: %w (HTTP error: %v)", pubErr, createErr)
			}
			return nil, fmt.Errorf("AMQP fallback failed: %w", pubErr)
		}
		logger.InfoContext(ctx, "order request published to AMQP successfully as fallback", "checkoutId", grain.Id.String())
		return &CreateOrderResult{
			OrderId: "queued-" + grain.Id.String(),
		}, nil
	}

	if createErr != nil {
		return nil, createErr
	}
	return nil, fmt.Errorf("neither order client nor AMQP order handler configured")
}