package server

import (
	"context"
	"errors"
	"fmt"
	"strings"

	"github.com/gin-gonic/gin"
	"github.com/google/uuid"
	"go.uber.org/zap"

	"scrabble/backend/internal/payments"
)

// consoleRefund refunds a paid order in full at the operator's request: it records the reversal — a
// refund ledger row and a floor-0 chip revoke (never negative, D27) — and, on the direct rail, moves
// the money back through the provider's refund API first, so one click does the whole job and the
// ledger cannot claim a refund the provider never made. The rails with no refund API of ours (VK
// support, Telegram refundStarPayment, the Robokassa cabinet) still need the operator to move the
// money by hand; this records that. Idempotent either way.
func (s *Server) consoleRefund(c *gin.Context) {
	id, ok := s.consoleUUID(c, "/_gm/users")
	if !ok {
		return
	}
	back := consoleReturnTo(c.PostForm("back"), "/_gm/users/"+id.String())
	if s.payments == nil {
		s.renderConsoleMessage(c, "Unavailable", "payments are not enabled", back)
		return
	}
	orderID, err := uuid.Parse(strings.TrimSpace(c.PostForm("order_id")))
	if err != nil {
		s.renderConsoleMessage(c, "Refund failed", "no order to refund", back)
		return
	}
	ctx := c.Request.Context()
	ref, err := s.payments.OrderProviderRef(ctx, orderID)
	if err != nil {
		s.renderConsoleMessage(c, "Refund failed", err.Error(), back)
		return
	}
	out, err := s.refundOrder(ctx, ref)
	if err != nil {
		s.renderConsoleMessage(c, "Refund failed", err.Error(), back)
		return
	}
	if out.AlreadyRefunded {
		if ref.Provider == providerYooKassa {
			// The provider refunded the money on this very click, so this is a success, not a repeat.
			// The reversal was already in the ledger because the provider's own refund notification
			// reached us first — it names the same refund id, which is exactly why the idempotency
			// index caught it and nothing was revoked twice. Saying "already refunded" here would read
			// as "you clicked twice".
			s.renderConsoleMessage(c, "Refunded", "the money is back with the customer; the reversal was already recorded, so nothing changed just now", back)
			return
		}
		s.renderConsoleMessage(c, "Already refunded", "this order was already refunded", back)
		return
	}
	s.publishBannerChange(id)
	msg := fmt.Sprintf("revoked %d chips", out.Revoked)
	if out.Loss > 0 {
		msg += fmt.Sprintf("; %d chips were already spent (recorded as a loss + abuse flag)", out.Loss)
	}
	s.renderConsoleMessage(c, "Refunded", msg, back)
}

// consoleReturnTo picks where the result page links back to: the caller's requested destination when
// it is a console page, else the fallback. A refund can be started from the account card or from the
// ledger (where the operator wants to land back on the same filtered slice), so the destination
// travels with the form — but only ever as a console-relative path, never as an arbitrary URL a
// crafted form could point elsewhere.
func consoleReturnTo(requested, fallback string) string {
	if strings.HasPrefix(requested, "/_gm/") && !strings.HasPrefix(requested, "/_gm//") {
		return requested
	}
	return fallback
}

// refundOrder reverses a paid order, moving the money back through the rail's own refund API when
// there is one. The provider call comes first and a failure aborts with nothing recorded: the ledger
// must never claim a refund that did not happen. The reversal is then recorded under the provider's
// own refund id, which keeps the ledger reconcilable against the provider's records.
//
// A rail with no refund API of ours records under the operator's key instead, and the operator moves
// the money by hand (VK support, Telegram refundStarPayment, the Robokassa cabinet).
func (s *Server) refundOrder(ctx context.Context, ref payments.OrderRef) (payments.RefundOutcome, error) {
	if ref.Provider != providerYooKassa {
		return s.payments.RefundOrderFull(ctx, ref.OrderID)
	}
	refundID, err := s.refundYooKassa(ctx, ref)
	if errors.Is(err, errRefundNotFinal) {
		// The money is on its way but not settled. Nothing is recorded yet; pressing again is safe —
		// the idempotency key returns the same refund rather than paying a second time.
		s.log.Warn("yookassa refund not final", zap.String("order", ref.OrderID.String()), zap.Error(err))
		return payments.RefundOutcome{}, fmt.Errorf("%w — nothing was recorded; try again in a minute", err)
	}
	if err != nil {
		s.log.Error("yookassa refund failed", zap.String("order", ref.OrderID.String()), zap.Error(err))
		return payments.RefundOutcome{}, fmt.Errorf("the provider did not refund the payment, nothing was recorded: %w", err)
	}
	return s.payments.RefundOrderFullAs(ctx, ref.OrderID, providerYooKassa, refundID)
}