package cart

import (
	"fmt"
	"strings"
	"time"

	messages "git.k6n.net/go-cart-actor/pkg/messages"
)

// PaymentStarted registers the beginning of a payment attempt for a cart.
// It either upserts the payment entry (based on paymentId) or creates a new one,
// marks the cart as having an in-progress payment, and recalculates the PaidInFull flag.
func PaymentStarted(grain *CartGrain, msg *messages.PaymentStarted) error {
	if msg == nil {
		return fmt.Errorf("PaymentStarted: nil payload")
	}
	paymentID := strings.TrimSpace(msg.PaymentId)
	if paymentID == "" {
		return fmt.Errorf("PaymentStarted: missing paymentId")
	}
	if msg.Amount < 0 {
		return fmt.Errorf("PaymentStarted: amount cannot be negative")
	}

	currency := strings.TrimSpace(msg.Currency)
	provider := strings.TrimSpace(msg.Provider)
	method := copyOptionalString(msg.Method)

	startedAt := time.Now().UTC()
	if msg.StartedAt != nil {
		startedAt = msg.StartedAt.AsTime()
	}

	payment, found := grain.FindPayment(paymentID)

	if found {
		if payment.Status != PaymentStatusPending {
			return fmt.Errorf("PaymentStarted: payment already started")
		}
		if payment.PaymentId != paymentID {
			payment.PaymentId = paymentID
		}
		payment.Status = PaymentStatusPending
		payment.Amount = msg.Amount
		if currency != "" {
			payment.Currency = currency
		}
		if provider != "" {
			payment.Provider = provider
		}
		if method != nil {
			payment.Method = method
		}
		payment.StartedAt = &startedAt
		payment.CompletedAt = nil
		payment.ProcessorReference = nil
	} else {
		grain.Payments = append(grain.Payments, &CartPayment{
			PaymentId: paymentID,
			Status:    PaymentStatusPending,
			Amount:    msg.Amount,
			Currency:  currency,
			Provider:  provider,
			Method:    method,
			StartedAt: &startedAt,
		})
	}

	grain.PaymentInProgress++
	grain.PaymentStatus = PaymentStatusPending

	return nil
}

func copyOptionalString(src *string) *string {
	if src == nil {
		return nil
	}
	trimmed := strings.TrimSpace(*src)
	if trimmed == "" {
		return nil
	}
	dst := trimmed
	return &dst
}