package payments

import (
	"context"
	"fmt"

	"github.com/google/uuid"
)

// OrderResult is what CreateOrder returns to the transport: the created order id and the details a
// provider launch payload needs — the amount to charge and a human title for the payment.
type OrderResult struct {
	OrderID uuid.UUID
	Amount  Money
	Title   string
}

// CreateOrder opens a pending order to fund a chip pack in the execution context's payment method,
// tagged with the provider that will settle it. It gate-checks the context (trusted, not the
// VK-iOS spend freeze) and that the method's funding segment is attached, prices the pack in the
// method's currency, then writes the order. The caller enforces any account-level precondition
// (e.g. the direct email anchor, D36) before calling — payments holds no cross-schema identity
// knowledge.
func (s *Service) CreateOrder(ctx context.Context, accountID uuid.UUID, cxt Context, present []Source, productID uuid.UUID, provider string) (OrderResult, error) {
	if !cxt.Trusted() || cxt.vkFrozen() {
		return OrderResult{}, ErrUntrusted
	}
	method := cxt.Kind
	if !has(present, method) {
		return OrderResult{}, ErrUntrusted // the funding segment is not attached to the account
	}
	pack, err := s.store.loadPackForOrder(ctx, productID, method)
	if err != nil {
		return OrderResult{}, err
	}
	orderID, err := uuid.NewV7()
	if err != nil {
		return OrderResult{}, fmt.Errorf("payments: order id: %w", err)
	}
	o := newOrder{
		orderID:   orderID,
		accountID: accountID,
		platform:  string(method),
		productID: productID,
		amount:    pack.price,
		origin:    method,
		provider:  provider,
	}
	if err := s.store.createOrder(ctx, o, s.clock()); err != nil {
		return OrderResult{}, err
	}
	return OrderResult{OrderID: orderID, Amount: pack.price, Title: pack.title}, nil
}

// Fund credits a paid order into its funded segment exactly once, from a verified provider callback
// — the single writer for every rail. It matches the order, verifies the paid amount, appends the
// fund ledger row (idempotent on (provider, provider_payment_id)), credits the balance and marks
// the order paid. A duplicate callback returns AlreadyCredited without a second credit; a valid
// callback is honoured even on an expired order (§9/D23).
func (s *Service) Fund(ctx context.Context, orderID uuid.UUID, provider, providerPaymentID string, paid Money) (FundOutcome, error) {
	return s.store.fund(ctx, orderID, provider, providerPaymentID, paid, s.clock())
}

// ExpireOrders marks pending orders older than the configured lifetime as expired, returning how
// many were swept. It backs the periodic pending reaper; expiry is cosmetic (a late valid callback
// still credits — see Fund).
func (s *Service) ExpireOrders(ctx context.Context) (int, error) {
	ttl, err := s.store.orderTTL(ctx)
	if err != nil {
		return 0, err
	}
	return s.store.expirePending(ctx, ttl, s.clock())
}