// Copyright (C) 2022 Storj Labs, Inc.
// See LICENSE for copying information.

package satellitedb

import (
	"context"
	"database/sql"
	"encoding/json"
	"errors"
	"time"

	"github.com/zeebo/errs"

	"storj.io/common/currency"
	"storj.io/common/uuid"
	"storj.io/private/dbutil/pgutil/pgerrcode"
	"storj.io/storj/satellite/payments/billing"
	"storj.io/storj/satellite/satellitedb/dbx"
)

// ensures that *billingDB implements billing.TransactionsDB.
var _ billing.TransactionsDB = (*billingDB)(nil)

// billingDB is billing DB.
//
// architecture: Database
type billingDB struct {
	db *satelliteDB
}

func (db billingDB) Insert(ctx context.Context, primaryTx billing.Transaction, supplementalTxs ...billing.Transaction) (_ []int64, err error) {
	defer mon.Task()(&ctx)(&err)

	// NOTE: if this is changed for bulk insertion we'll need to ensure that
	// either limits are imposed on the number of inserts, or that the work
	// is broken up into distinct batches.
	// If the latter happens, care must be taken to provide an interface where
	// even if the bulk inserts are broken up, that transactions that
	// absolutely need to be committed together can continue to do so (e.g.
	// a storjscan sourced transaction and its related bonus transaction).

	// This limit is somewhat arbitrary and can be revisited. This method is
	// NOT intended for bulk insertion but rather to provided a way for
	// related transactions to be committed together.
	const supplementalTxLimit = 5
	if len(supplementalTxs) > supplementalTxLimit {
		return nil, Error.New("Cannot insert more than %d supplemental txs (tried %d)", supplementalTxLimit, len(supplementalTxs))
	}

	for retryCount := 0; retryCount < 5; retryCount++ {
		txIDs, err := db.tryInsert(ctx, primaryTx, supplementalTxs)
		switch {
		case err == nil:
			return txIDs, nil
		case pgerrcode.IsConstraintViolation(err):
		default:
			return nil, err
		}
	}
	return nil, Error.New("Unable to insert new billing transaction after several retries: %v", err)
}

func (db billingDB) tryInsert(ctx context.Context, primaryTx billing.Transaction, supplementalTxs []billing.Transaction) (_ []int64, err error) {
	defer mon.Task()(&ctx)(&err)

	convertToUSDMicro := func(amount currency.Amount) currency.Amount {
		return currency.AmountFromDecimal(amount.AsDecimal().Truncate(currency.USDollarsMicro.DecimalPlaces()), currency.USDollarsMicro)
	}

	type balanceUpdate struct {
		OldBalance currency.Amount
		NewBalance currency.Amount
	}

	updateBalance := func(ctx context.Context, tx *dbx.Tx, userID uuid.UUID, oldBalance, newBalance currency.Amount) error {
		updatedRow, err := tx.Update_BillingBalance_By_UserId_And_Balance(ctx,
			dbx.BillingBalance_UserId(userID[:]),
			dbx.BillingBalance_Balance(oldBalance.BaseUnits()),
			dbx.BillingBalance_Update_Fields{
				Balance: dbx.BillingBalance_Balance(newBalance.BaseUnits()),
			})
		if err != nil {
			return Error.Wrap(err)
		}
		if updatedRow == nil {
			// Try an insert here, in case the user never had a record in the table.
			// If the user already had a record, and the oldBalance was not as expected,
			// the insert will fail anyways.
			err = tx.CreateNoReturn_BillingBalance(ctx,
				dbx.BillingBalance_UserId(userID[:]),
				dbx.BillingBalance_Balance(newBalance.BaseUnits()))
			if err != nil {
				return Error.Wrap(err)
			}
		}
		return nil
	}

	createTransaction := func(ctx context.Context, tx *dbx.Tx, billingTX *billing.Transaction) (int64, error) {
		amount := convertToUSDMicro(billingTX.Amount)
		dbxTX, err := tx.Create_BillingTransaction(ctx,
			dbx.BillingTransaction_UserId(billingTX.UserID[:]),
			dbx.BillingTransaction_Amount(amount.BaseUnits()),
			dbx.BillingTransaction_Currency(amount.Currency().Symbol()),
			dbx.BillingTransaction_Description(billingTX.Description),
			dbx.BillingTransaction_Source(billingTX.Source),
			dbx.BillingTransaction_Status(string(billingTX.Status)),
			dbx.BillingTransaction_Type(string(billingTX.Type)),
			dbx.BillingTransaction_Metadata(handleMetaDataZeroValue(billingTX.Metadata)),
			dbx.BillingTransaction_Timestamp(billingTX.Timestamp))
		if err != nil {
			return 0, Error.Wrap(err)
		}
		return dbxTX.Id, nil
	}

	balances := make(map[uuid.UUID]*balanceUpdate)

	adjustBalance := func(userID uuid.UUID, amount currency.Amount) error {
		balance, ok := balances[userID]
		if !ok {
			oldBalance, err := db.GetBalance(ctx, userID)
			if err != nil {
				return Error.Wrap(err)
			}
			balance = &balanceUpdate{OldBalance: oldBalance, NewBalance: oldBalance}
			balances[userID] = balance
		}
		newBalance, err := currency.Add(balance.NewBalance, convertToUSDMicro(amount))
		switch {
		case err != nil:
			return Error.Wrap(err)
		case newBalance.IsNegative():
			return billing.ErrInsufficientFunds
		}
		balance.NewBalance = newBalance
		return nil
	}

	if err := adjustBalance(primaryTx.UserID, primaryTx.Amount); err != nil {
		return nil, err
	}
	for _, supplementalTx := range supplementalTxs {
		if err := adjustBalance(supplementalTx.UserID, supplementalTx.Amount); err != nil {
			return nil, err
		}
	}

	var txIDs []int64
	err = db.db.WithTx(ctx, func(ctx context.Context, tx *dbx.Tx) error {
		for userID, update := range balances {
			if err := updateBalance(ctx, tx, userID, update.OldBalance, update.NewBalance); err != nil {
				return err
			}
		}

		txID, err := createTransaction(ctx, tx, &primaryTx)
		if err != nil {
			return err
		}
		txIDs = append(txIDs, txID)

		for _, supplementalTx := range supplementalTxs {
			txID, err := createTransaction(ctx, tx, &supplementalTx)
			if err != nil {
				return err
			}
			txIDs = append(txIDs, txID)
		}
		return nil
	})
	return txIDs, err
}

func (db billingDB) UpdateStatus(ctx context.Context, txID int64, status billing.TransactionStatus) (err error) {
	defer mon.Task()(&ctx)(&err)
	return db.db.UpdateNoReturn_BillingTransaction_By_Id(ctx, dbx.BillingTransaction_Id(txID), dbx.BillingTransaction_Update_Fields{
		Status: dbx.BillingTransaction_Status(string(status)),
	})
}

func (db billingDB) UpdateMetadata(ctx context.Context, txID int64, newMetadata []byte) (err error) {

	dbxTX, err := db.db.Get_BillingTransaction_Metadata_By_Id(ctx, dbx.BillingTransaction_Id(txID))
	if err != nil {
		return Error.Wrap(err)
	}

	updatedMetadata, err := updateMetadata(dbxTX.Metadata, newMetadata)
	if err != nil {
		return Error.Wrap(err)
	}

	return db.db.UpdateNoReturn_BillingTransaction_By_Id(ctx, dbx.BillingTransaction_Id(txID), dbx.BillingTransaction_Update_Fields{
		Metadata: dbx.BillingTransaction_Metadata(updatedMetadata),
	})
}

func (db billingDB) LastTransaction(ctx context.Context, txSource string, txType billing.TransactionType) (_ time.Time, metadata []byte, err error) {
	defer mon.Task()(&ctx)(&err)

	lastTransaction, err := db.db.First_BillingTransaction_By_Source_And_Type_OrderBy_Desc_CreatedAt(
		ctx,
		dbx.BillingTransaction_Source(txSource),
		dbx.BillingTransaction_Type(string(txType)))

	if err != nil {
		return time.Time{}, nil, Error.Wrap(err)
	}

	if lastTransaction == nil {
		return time.Time{}, nil, billing.ErrNoTransactions
	}

	return lastTransaction.Timestamp, lastTransaction.Metadata, nil
}

func (db billingDB) List(ctx context.Context, userID uuid.UUID) (txs []billing.Transaction, err error) {
	defer mon.Task()(&ctx)(&err)
	dbxTXs, err := db.db.All_BillingTransaction_By_UserId_OrderBy_Desc_Timestamp(ctx,
		dbx.BillingTransaction_UserId(userID[:]))
	if err != nil {
		return nil, Error.Wrap(err)
	}

	for _, dbxTX := range dbxTXs {
		tx, err := fromDBXBillingTransaction(dbxTX)
		if err != nil {
			return nil, Error.Wrap(err)
		}
		txs = append(txs, *tx)
	}

	return txs, nil
}

func (db billingDB) ListSource(ctx context.Context, userID uuid.UUID, txSource string) (txs []billing.Transaction, err error) {
	defer mon.Task()(&ctx)(&err)
	dbxTXs, err := db.db.All_BillingTransaction_By_UserId_And_Source_OrderBy_Desc_Timestamp(ctx,
		dbx.BillingTransaction_UserId(userID[:]), dbx.BillingTransaction_Source(txSource))
	if err != nil {
		return nil, Error.Wrap(err)
	}

	for _, dbxTX := range dbxTXs {
		tx, err := fromDBXBillingTransaction(dbxTX)
		if err != nil {
			return nil, Error.Wrap(err)
		}
		txs = append(txs, *tx)
	}

	return txs, nil
}

func (db billingDB) GetBalance(ctx context.Context, userID uuid.UUID) (_ currency.Amount, err error) {
	defer mon.Task()(&ctx)(&err)
	dbxBilling, err := db.db.Get_BillingBalance_Balance_By_UserId(ctx,
		dbx.BillingBalance_UserId(userID[:]))
	if err != nil {
		if errors.Is(err, sql.ErrNoRows) {
			return currency.USDollarsMicro.Zero(), nil
		}
		return currency.USDollarsMicro.Zero(), Error.Wrap(err)
	}

	return currency.AmountFromBaseUnits(dbxBilling.Balance, currency.USDollarsMicro), nil
}

// fromDBXBillingTransaction converts *dbx.BillingTransaction to *billing.Transaction.
func fromDBXBillingTransaction(dbxTX *dbx.BillingTransaction) (*billing.Transaction, error) {
	userID, err := uuid.FromBytes(dbxTX.UserId)
	if err != nil {
		return nil, errs.Wrap(err)
	}
	return &billing.Transaction{
		ID:          dbxTX.Id,
		UserID:      userID,
		Amount:      currency.AmountFromBaseUnits(dbxTX.Amount, currency.USDollarsMicro),
		Description: dbxTX.Description,
		Source:      dbxTX.Source,
		Status:      billing.TransactionStatus(dbxTX.Status),
		Type:        billing.TransactionType(dbxTX.Type),
		Metadata:    dbxTX.Metadata,
		Timestamp:   dbxTX.Timestamp,
		CreatedAt:   dbxTX.CreatedAt,
	}, nil
}

func updateMetadata(oldMetaData []byte, newMetaData []byte) ([]byte, error) {
	var updatedMetadata map[string]interface{}

	err := json.Unmarshal(oldMetaData, &updatedMetadata)
	if err != nil {
		return nil, err
	}

	err = json.Unmarshal(handleMetaDataZeroValue(newMetaData), &updatedMetadata)
	if err != nil {
		return nil, err
	}

	return json.Marshal(updatedMetadata)
}

func handleMetaDataZeroValue(metaData []byte) []byte {
	if metaData != nil {
		return metaData
	}
	return []byte(`{}`)
}