package checkout

import (
	"encoding/json"
	"fmt"
	"strings"
	"time"

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

// PaymentStarted registers the beginning of a payment attempt for a checkout.
// It either upserts the payment entry (based on paymentId) or creates a new one,
// marks the checkout as having a payment in progress.
func HandlePaymentStarted(g *CheckoutGrain, m *messages.PaymentStarted) error {
	if m == nil {
		return fmt.Errorf("PaymentStarted: nil payload")
	}
	paymentID := strings.TrimSpace(m.PaymentId)
	if paymentID == "" {
		return fmt.Errorf("PaymentStarted: missing paymentId")
	}
	if m.Amount < 0 {
		return fmt.Errorf("PaymentStarted: amount cannot be negative")
	}

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

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

	payment, found := g.FindPayment(paymentID)

	if found {
		if payment.Status != "pending" {
			return fmt.Errorf("PaymentStarted: payment already started")
		}
		if payment.PaymentId != paymentID {
			payment.PaymentId = paymentID
		}
		payment.Status = "pending"
		payment.Amount = m.Amount
		if currency != "" {
			payment.Currency = currency
		}
		if provider != "" {
			payment.Provider = provider
		}
		if method != nil {
			payment.Method = method
		}
		if m.SessionData != nil {
			payment.SessionData = (*json.RawMessage)(&m.SessionData.Value)
		}
		payment.StartedAt = &startedAt
		payment.CompletedAt = nil
		payment.ProcessorReference = nil
	} else {
		g.PaymentInProgress++
		g.Payments = append(g.Payments, &Payment{
			PaymentId:   paymentID,
			Status:      "pending",
			Amount:      m.Amount,
			SessionData: (*json.RawMessage)(&m.SessionData.Value),
			Currency:    currency,
			Provider:    provider,
			Method:      method,
			StartedAt:   &startedAt,
		})
	}

	return nil
}

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