package service

import (
	"context"
	"database/sql"
	"encoding/hex"
	"strings"
	"time"

	"github.com/getAlby/lndhub.go/db/models"
	"github.com/lightningnetwork/lnd/lnrpc"
	"github.com/uptrace/bun"
)

func (svc *LndhubService) ProcessInvoiceUpdate(ctx context.Context, rawInvoice *lnrpc.Invoice) error {
	var invoice models.Invoice
	rHashStr := hex.EncodeToString(rawInvoice.RHash)

	svc.Logger.Infof("Invoice update: r_hash:%s state:%v", rHashStr, rawInvoice.State.String())

	// Search for an incoming invoice with the r_hash that is NOT settled in our DB
	err := svc.DB.NewSelect().Model(&invoice).Where("type = ? AND r_hash = ? AND state <> ? ", "incoming", rHashStr, "settled").Limit(1).Scan(context.TODO())
	if err != nil {
		return err
	}

	// Update the DB entry of the invoice
	// If the invoice is settled we save the settle date and the status otherwise we just store the lnd status
	// Additionally to the invoice update we create a transaction entry from the user's incoming account to the user's current account
	// This transaction entry makes the balance available for the user
	svc.Logger.Infof("Invoice update: invoice_id:%v settled:%v value:%v state:%v", invoice.ID, rawInvoice.Settled, rawInvoice.AmtPaidSat, rawInvoice.State)

	// Get the user's current account for the transaction entry
	creditAccount, err := svc.AccountFor(ctx, "current", invoice.UserID)
	if err != nil {
		svc.Logger.Errorf("Could not find current account user_id:%v invoice_id:%v", invoice.UserID, invoice.ID)
		return err
	}
	// Get the user's incoming account for the transaction entry
	debitAccount, err := svc.AccountFor(ctx, "incoming", invoice.UserID)
	if err != nil {
		svc.Logger.Errorf("Could not find incoming account user_id:%v invoice_id:%v", invoice.UserID, invoice.ID)
		return err
	}

	// Process any update in a DB transaction
	tx, err := svc.DB.BeginTx(ctx, &sql.TxOptions{})
	if err != nil {
		svc.Logger.Errorf("Failed to update the invoice invoice_id:%v r_hash:%s %v", invoice.ID, rHashStr, err)
		return err
	}

	// if the invoice is NOT settled we just update the invoice state
	if !rawInvoice.Settled {
		svc.Logger.Infof("Invoice not settled invoice_id:%v state:", invoice.ID, rawInvoice.State.String())
		invoice.State = strings.ToLower(rawInvoice.State.String())

	} else {
		// if the invoice is settled we update the state and create an transaction entry to the current account
		invoice.SettledAt = bun.NullTime{Time: time.Unix(rawInvoice.SettleDate, 0)}
		invoice.State = "settled"
		_, err = tx.NewUpdate().Model(&invoice).WherePK().Exec(context.TODO())
		if err != nil {
			tx.Rollback()
			svc.Logger.Errorf("Could not update invoice invoice_id:%v", invoice.ID)
			return err
		}

		// Transfer the amount from the user's incoming account to the user's current account
		entry := models.TransactionEntry{
			UserID:          invoice.UserID,
			InvoiceID:       invoice.ID,
			CreditAccountID: creditAccount.ID,
			DebitAccountID:  debitAccount.ID,
			Amount:          invoice.Amount,
		}

		// Save the transaction entry
		_, err = tx.NewInsert().Model(&entry).Exec(context.TODO())
		if err != nil {
			tx.Rollback()
			svc.Logger.Errorf("Could not create incoming->current transaction user_id:%v invoice_id:%v  %v", invoice.UserID, invoice.ID, err)
			return err
		}
	}
	// Commit the DB transaction. Done, everything worked
	err = tx.Commit()
	if err != nil {
		svc.Logger.Errorf("Failed to commit DB transaction user_id:%v invoice_id:%v  %v", invoice.UserID, invoice.ID, err)
		return err
	}

	return nil
}

func (svc *LndhubService) ConnectInvoiceSubscription(ctx context.Context) (lnrpc.Lightning_SubscribeInvoicesClient, error) {
	invoiceSubscriptionOptions := lnrpc.InvoiceSubscription{}
	return svc.LndClient.SubscribeInvoices(ctx, &invoiceSubscriptionOptions)
}

func (svc *LndhubService) InvoiceUpdateSubscription(ctx context.Context) error {
	invoiceSubscriptionStream, err := svc.ConnectInvoiceSubscription(ctx)
	if err != nil {
		return err
	}
	svc.Logger.Info("Subscribed to invoice updates starting from index: ")
	for {
		// receive the next invoice update
		rawInvoice, err := invoiceSubscriptionStream.Recv()
		if err != nil {
			// TODO: sentry notification
			svc.Logger.Errorf("Error processing invoice update subscription: %v", err)
			// TODO: close the stream somehoe before retrying?
			// Wait 30 seconds and try to reconnect
			// TODO: implement some backoff
			time.Sleep(30 * time.Second)
			invoiceSubscriptionStream, _ = svc.ConnectInvoiceSubscription(ctx)
			continue
		}

		// Ignore updates for open invoices
		// We store the invoice details in the AddInvoice call
		// Processing open invoices here could cause a race condition:
		// We could get this notification faster than we finish the AddInvoice call
		if rawInvoice.State == lnrpc.Invoice_OPEN {
			svc.Logger.Infof("Invoice state is open. Ignoring update. r_hash:%v", hex.EncodeToString(rawInvoice.RHash))
			continue
		}

		processingError := svc.ProcessInvoiceUpdate(ctx, rawInvoice)
		if processingError != nil {
			svc.Logger.Error(err)
			// TODO sentry notification
		}
	}
}