package processor

import (
	"context"
	"errors"
	"fmt"
	"time"

	"github.com/google/uuid"

	"apskel-pos-be/internal/constants"
	"apskel-pos-be/internal/entities"
	"apskel-pos-be/internal/logger"
)

const (
	// voucherProviderTimeout bounds one call to a provider. A call that runs out is an
	// unknown outcome, settled later by the recovery job.
	voucherProviderTimeout = 10 * time.Second
	// voucherRecoveryAfter is how long a PENDING redemption waits before the recovery
	// job asks its provider again.
	voucherRecoveryAfter = 2 * time.Minute
	// voucherMaxAttempts is how many calls a redemption gets before the job gives up,
	// refunds it and marks it FAILED.
	voucherMaxAttempts = 10
	// voucherRecoveryBatch is how many PENDING redemptions one run of the job claims.
	voucherRecoveryBatch = 50
)

// issueExternal asks an EXTERNAL voucher's provider for the voucher of a PENDING
// redemption, outside any transaction, and settles the redemption with the answer
// (docs/rfc-enakgame.md §7.5). With lookup, it first asks whether the provider already
// issued it, and only asks to issue when the provider never got the request.
//
// The call does not stop when the customer's request does: an answer the provider
// gave must not be thrown away.
func (p *VoucherRedemptionProcessor) issueExternal(ctx context.Context, r *entities.VoucherRedemption, v *entities.Voucher, lookup bool) (*entities.VoucherRedemption, error) {
	provider, ok := p.providerOf(v)
	var issue *VoucherIssue
	var err error
	if ok {
		req := VoucherIssueRequest{RedemptionID: r.ID, ProviderRef: v.ProviderRef, VoucherID: v.ID, FaceValue: r.FaceValue, CustomerID: r.CustomerID}
		callCtx, cancel := context.WithTimeout(context.WithoutCancel(ctx), voucherProviderTimeout)
		if lookup {
			issue, err = provider.Lookup(callCtx, req)
		}
		if !lookup || classifyVoucherIssue(issue, err) == voucherNotFound {
			issue, err = provider.Issue(callCtx, req)
		}
		cancel()
	} else {
		err = fmt.Errorf("no adapter for provider %q", providerName(v))
	}
	outcome := classifyVoucherIssue(issue, err)
	if outcome == voucherUnknown || outcome == voucherNotFound {
		logger.FromContext(ctx).WithError(err).Warn("Voucher provider gave no answer; the redemption stays PENDING")
	}
	return p.settleExternal(ctx, r.ID, outcome, issue, err)
}

// settleExternal applies a provider's answer to a redemption that is still PENDING,
// under its customer's wallet lock: COMPLETED with the voucher and its cost split, or
// FAILED with its EnakPoint refunded. An unknown answer leaves it PENDING, until it
// has had voucherMaxAttempts calls; then it is refunded too. A redemption no longer
// PENDING is left as it is, so settling twice refunds nothing twice.
func (p *VoucherRedemptionProcessor) settleExternal(ctx context.Context, id uuid.UUID, outcome voucherIssueOutcome, issue *VoucherIssue, callErr error) (*entities.VoucherRedemption, error) {
	var settled *entities.VoucherRedemption
	err := p.tx.WithTransaction(ctx, func(ctx context.Context) error {
		r, err := p.redemptions.GetRedemption(ctx, id)
		if err != nil {
			return err
		}
		if err := p.wallet.LockWallet(ctx, r.CustomerID); err != nil {
			return err
		}
		if r, err = p.redemptions.GetRedemption(ctx, id); err != nil {
			return err
		}
		settled = r
		if r.Status != constants.VoucherRedemptionPending {
			return nil
		}
		now := p.now()
		switch outcome {
		case voucherIssued:
			code, ref := issue.Code, issue.Ref
			var refPtr *string
			if ref != "" {
				refPtr = &ref
			}
			moved, err := p.redemptions.MarkCompleted(ctx, r.ID, &code, refPtr, now)
			if err != nil || !moved {
				return err
			}
			r.Status, r.ExternalCode, r.ExternalRef, r.CompletedAt = constants.VoucherRedemptionCompleted, &code, refPtr, &now
			return p.recordCost(ctx, r)
		case voucherRejected:
			return p.refundExternal(ctx, r, "the provider refused: "+callErr.Error())
		}
		attempts, err := p.redemptions.TouchPending(ctx, r.ID)
		if err != nil {
			return err
		}
		r.Attempts = attempts
		if attempts >= voucherMaxAttempts {
			return p.refundExternal(ctx, r, fmt.Sprintf("the provider did not confirm the voucher after %d attempts", attempts))
		}
		return nil
	})
	if err != nil {
		return nil, err
	}
	return settled, nil
}

// refundExternal gives back the EnakPoint of a redemption that will not complete and
// marks it FAILED (§7.5). The refund keeps the expiry of the lots the debit drew from,
// with at least seven days left (§6.3).
func (p *VoucherRedemptionProcessor) refundExternal(ctx context.Context, r *entities.VoucherRedemption, reason string) error {
	lots, err := p.wallet.RefundLots(ctx, r.DebitTransactionID)
	if err != nil {
		return err
	}
	debitID := r.DebitTransactionID
	refund, err := p.wallet.Credit(ctx, WalletCreditInput{
		WalletEntry: WalletEntry{
			CustomerID:            r.CustomerID,
			Currency:              constants.WalletCurrencyPoint,
			Type:                  constants.WalletTxTypeRewardRedeemRefund,
			Amount:                r.PointCost,
			ReferenceType:         constants.WalletRefTypeRewardRedemption,
			ReferenceID:           r.ID,
			ReversesTransactionID: &debitID,
			Description:           "Pengembalian EnakPoint voucher",
			Metadata:              entities.Metadata{"voucher_id": r.VoucherID.String(), "reason": reason},
			IdempotencyKey:        "redeem-refund:" + r.ID.String(),
		},
		Lots: lots,
	})
	if err != nil {
		return err
	}
	moved, err := p.redemptions.MarkFailed(ctx, r.ID, refund.Transaction.ID, reason)
	if err != nil {
		return err
	}
	if !moved {
		return errors.New("voucher redemption left PENDING during its refund")
	}
	r.Status, r.RefundTransactionID, r.FailureReason = constants.VoucherRedemptionFailed, &refund.Transaction.ID, &reason
	return nil
}

// RecoverPending is the recovery job (§7.5 step 4): it asks the provider again about
// every redemption PENDING for longer than voucherRecoveryAfter, and settles it. It
// returns how many it completed and how many it failed.
func (p *VoucherRedemptionProcessor) RecoverPending(ctx context.Context) (completed, failed int, err error) {
	claimed, err := p.redemptions.ClaimStalePending(ctx, p.now().Add(-voucherRecoveryAfter), voucherRecoveryBatch)
	if err != nil {
		return 0, 0, err
	}
	var failures []error
	for i := range claimed {
		r := &claimed[i]
		v, err := p.vouchers.GetVoucher(ctx, r.OrganizationID, r.VoucherID)
		if err == nil {
			r, err = p.issueExternal(ctx, r, v, true)
		}
		if err != nil {
			failures = append(failures, fmt.Errorf("redemption %s: %w", claimed[i].ID, err))
			continue
		}
		switch r.Status {
		case constants.VoucherRedemptionCompleted:
			completed++
		case constants.VoucherRedemptionFailed:
			failed++
		}
	}
	return completed, failed, errors.Join(failures...)
}

func (p *VoucherRedemptionProcessor) providerOf(v *entities.Voucher) (VoucherProvider, bool) {
	if v.Provider == nil {
		return nil, false
	}
	provider, ok := p.providers[*v.Provider]
	return provider, ok
}

func providerName(v *entities.Voucher) string {
	if v.Provider == nil {
		return ""
	}
	return *v.Provider
}