package store

import (
	"context"
	"errors"
	"strings"
	"time"

	"github.com/tech/sendico/gateway/chain/storage"
	"github.com/tech/sendico/gateway/chain/storage/model"
	"github.com/tech/sendico/pkg/db/repository"
	"github.com/tech/sendico/pkg/db/repository/builder"
	ri "github.com/tech/sendico/pkg/db/repository/index"
	"github.com/tech/sendico/pkg/merrors"
	"github.com/tech/sendico/pkg/mlogger"
	"github.com/tech/sendico/pkg/mservice"
	"go.mongodb.org/mongo-driver/bson/primitive"
	"go.mongodb.org/mongo-driver/mongo"
	"go.uber.org/zap"
)

const (
	defaultTransferPageSize int64 = 50
	maxTransferPageSize     int64 = 200
)

type Transfers struct {
	logger mlogger.Logger
	repo   repository.Repository
}

// NewTransfers constructs a Mongo-backed transfers store.
func NewTransfers(logger mlogger.Logger, db *mongo.Database) (*Transfers, error) {
	if db == nil {
		return nil, merrors.InvalidArgument("mongo database is nil")
	}
	repo := repository.CreateMongoRepository(db, mservice.ChainTransfers)
	indexes := []*ri.Definition{
		{
			Keys:   []ri.Key{{Field: "transferRef", Sort: ri.Asc}},
			Unique: true,
		},
		{
			Keys:   []ri.Key{{Field: "idempotencyKey", Sort: ri.Asc}},
			Unique: true,
		},
		{
			Keys: []ri.Key{{Field: "sourceWalletRef", Sort: ri.Asc}, {Field: "status", Sort: ri.Asc}},
		},
		{
			Keys: []ri.Key{{Field: "destination.managedWalletRef", Sort: ri.Asc}},
		},
	}
	for _, def := range indexes {
		if err := repo.CreateIndex(def); err != nil {
			logger.Error("Failed to ensure transfer index", zap.Error(err), zap.String("collection", repo.Collection()))
			return nil, err
		}
	}

	childLogger := logger.Named("transfers")
	childLogger.Debug("Transfers store initialised")

	return &Transfers{
		logger: childLogger,
		repo:   repo,
	}, nil
}

func (t *Transfers) Create(ctx context.Context, transfer *model.Transfer) (*model.Transfer, error) {
	if transfer == nil {
		return nil, merrors.InvalidArgument("transfersStore: nil transfer")
	}
	transfer.Normalize()
	if strings.TrimSpace(transfer.TransferRef) == "" {
		return nil, merrors.InvalidArgument("transfersStore: empty transferRef")
	}
	if strings.TrimSpace(transfer.IdempotencyKey) == "" {
		return nil, merrors.InvalidArgument("transfersStore: empty idempotencyKey")
	}
	if transfer.Status == "" {
		transfer.Status = model.TransferStatusPending
	}
	if transfer.LastStatusAt.IsZero() {
		transfer.LastStatusAt = time.Now().UTC()
	}
	if strings.TrimSpace(transfer.IdempotencyKey) == "" {
		return nil, merrors.InvalidArgument("transfersStore: empty idempotencyKey")
	}
	if err := t.repo.Insert(ctx, transfer, repository.Filter("idempotencyKey", transfer.IdempotencyKey)); err != nil {
		if errors.Is(err, merrors.ErrDataConflict) {
			t.logger.Debug("Transfer already exists", zap.String("transfer_ref", transfer.TransferRef), zap.String("idempotency_key", transfer.IdempotencyKey))
			return transfer, nil
		}
		return nil, err
	}
	t.logger.Debug("Transfer created", zap.String("transfer_ref", transfer.TransferRef))
	return transfer, nil
}

func (t *Transfers) Get(ctx context.Context, transferRef string) (*model.Transfer, error) {
	transferRef = strings.TrimSpace(transferRef)
	if transferRef == "" {
		return nil, merrors.InvalidArgument("transfersStore: empty transferRef")
	}
	transfer := &model.Transfer{}
	if err := t.repo.FindOneByFilter(ctx, repository.Filter("transferRef", transferRef), transfer); err != nil {
		return nil, err
	}
	return transfer, nil
}

func (t *Transfers) List(ctx context.Context, filter model.TransferFilter) (*model.TransferList, error) {
	query := repository.Query()
	if src := strings.TrimSpace(filter.SourceWalletRef); src != "" {
		query = query.Filter(repository.Field("sourceWalletRef"), src)
	}
	if dst := strings.TrimSpace(filter.DestinationWalletRef); dst != "" {
		query = query.Filter(repository.Field("destination.managedWalletRef"), dst)
	}
	if status := strings.TrimSpace(string(filter.Status)); status != "" {
		query = query.Filter(repository.Field("status"), status)
	}

	if cursor := strings.TrimSpace(filter.Cursor); cursor != "" {
		if oid, err := primitive.ObjectIDFromHex(cursor); err == nil {
			query = query.Comparison(repository.IDField(), builder.Gt, oid)
		} else {
			t.logger.Warn("Ignoring invalid transfer cursor", zap.String("cursor", cursor), zap.Error(err))
		}
	}

	limit := sanitizeTransferLimit(filter.Limit)
	fetchLimit := limit + 1
	query = query.Sort(repository.IDField(), true).Limit(&fetchLimit)

	transfers := make([]*model.Transfer, 0, fetchLimit)
	decoder := func(cur *mongo.Cursor) error {
		item := &model.Transfer{}
		if err := cur.Decode(item); err != nil {
			return err
		}
		transfers = append(transfers, item)
		return nil
	}

	if err := t.repo.FindManyByFilter(ctx, query, decoder); err != nil && !errors.Is(err, merrors.ErrNoData) {
		return nil, err
	}

	nextCursor := ""
	if int64(len(transfers)) == fetchLimit {
		last := transfers[len(transfers)-1]
		nextCursor = last.ID.Hex()
		transfers = transfers[:len(transfers)-1]
	}

	return &model.TransferList{
		Items:      transfers,
		NextCursor: nextCursor,
	}, nil
}

func (t *Transfers) UpdateStatus(ctx context.Context, transferRef string, status model.TransferStatus, failureReason string, txHash string) (*model.Transfer, error) {
	transferRef = strings.TrimSpace(transferRef)
	if transferRef == "" {
		return nil, merrors.InvalidArgument("transfersStore: empty transferRef")
	}
	transfer := &model.Transfer{}
	if err := t.repo.FindOneByFilter(ctx, repository.Filter("transferRef", transferRef), transfer); err != nil {
		return nil, err
	}

	transfer.Status = status
	if status == model.TransferStatusFailed {
		transfer.FailureReason = strings.TrimSpace(failureReason)
	} else {
		transfer.FailureReason = ""
	}
	if hash := strings.TrimSpace(txHash); hash != "" {
		transfer.TxHash = strings.ToLower(hash)
	}
	transfer.LastStatusAt = time.Now().UTC()
	if err := t.repo.Update(ctx, transfer); err != nil {
		return nil, err
	}
	return transfer, nil
}

func sanitizeTransferLimit(requested int32) int64 {
	if requested <= 0 {
		return defaultTransferPageSize
	}
	if requested > int32(maxTransferPageSize) {
		return maxTransferPageSize
	}
	return int64(requested)
}

var _ storage.TransfersStore = (*Transfers)(nil)