package treasury

import (
	"context"
	"errors"
	"fmt"
	"math/big"
	"strings"
	"time"

	"github.com/tech/sendico/gateway/tgsettle/internal/service/treasury/ledger"
	"github.com/tech/sendico/gateway/tgsettle/storage"
	storagemodel "github.com/tech/sendico/gateway/tgsettle/storage/model"
	"github.com/tech/sendico/pkg/merrors"
	"github.com/tech/sendico/pkg/mlogger"
	"go.mongodb.org/mongo-driver/v2/bson"
	"go.uber.org/zap"
)

var ErrActiveTreasuryRequest = errors.New("active treasury request exists")

type CreateRequestInput struct {
	OperationType   storagemodel.TreasuryOperationType
	TelegramUserID  string
	LedgerAccountID string
	ChatID          string
	Amount          string
}

type ExecutionResult struct {
	Request        *storagemodel.TreasuryRequest
	NewBalance     *ledger.Balance
	ExecutionError error
}

type Service struct {
	logger mlogger.Logger
	repo   storage.TreasuryRequestsStore
	ledger ledger.Client

	validator      *Validator
	executionDelay time.Duration
}

func NewService(
	logger mlogger.Logger,
	repo storage.TreasuryRequestsStore,
	ledgerClient ledger.Client,
	executionDelay time.Duration,
	maxPerOperation string,
	maxDaily string,
) (*Service, error) {
	if logger == nil {
		return nil, merrors.InvalidArgument("logger is required", "logger")
	}
	if repo == nil {
		return nil, merrors.InvalidArgument("treasury repository is required", "repo")
	}
	if ledgerClient == nil {
		return nil, merrors.InvalidArgument("ledger client is required", "ledger_client")
	}
	if executionDelay <= 0 {
		executionDelay = 30 * time.Second
	}
	validator, err := NewValidator(repo, maxPerOperation, maxDaily)
	if err != nil {
		return nil, err
	}
	return &Service{
		logger:         logger.Named("treasury_service"),
		repo:           repo,
		ledger:         ledgerClient,
		validator:      validator,
		executionDelay: executionDelay,
	}, nil
}

func (s *Service) ExecutionDelay() time.Duration {
	if s == nil {
		return 0
	}
	return s.executionDelay
}

func (s *Service) MaxPerOperationLimit() string {
	if s == nil || s.validator == nil {
		return ""
	}
	return s.validator.MaxPerOperation()
}

func (s *Service) GetActiveRequestForAccount(ctx context.Context, ledgerAccountID string) (*storagemodel.TreasuryRequest, error) {
	if s == nil || s.repo == nil {
		return nil, merrors.Internal("treasury service unavailable")
	}
	return s.repo.FindActiveByLedgerAccountID(ctx, ledgerAccountID)
}

func (s *Service) GetRequest(ctx context.Context, requestID string) (*storagemodel.TreasuryRequest, error) {
	if s == nil || s.repo == nil {
		return nil, merrors.Internal("treasury service unavailable")
	}
	return s.repo.FindByRequestID(ctx, requestID)
}

func (s *Service) CreateRequest(ctx context.Context, input CreateRequestInput) (*storagemodel.TreasuryRequest, error) {
	if s == nil || s.repo == nil || s.ledger == nil || s.validator == nil {
		return nil, merrors.Internal("treasury service unavailable")
	}
	input.TelegramUserID = strings.TrimSpace(input.TelegramUserID)
	input.LedgerAccountID = strings.TrimSpace(input.LedgerAccountID)
	input.ChatID = strings.TrimSpace(input.ChatID)
	input.Amount = strings.TrimSpace(input.Amount)

	switch input.OperationType {
	case storagemodel.TreasuryOperationFund, storagemodel.TreasuryOperationWithdraw:
	default:
		return nil, merrors.InvalidArgument("treasury operation is invalid", "operation_type")
	}
	if input.TelegramUserID == "" {
		return nil, merrors.InvalidArgument("telegram_user_id is required", "telegram_user_id")
	}
	if input.LedgerAccountID == "" {
		return nil, merrors.InvalidArgument("ledger_account_id is required", "ledger_account_id")
	}
	if input.ChatID == "" {
		return nil, merrors.InvalidArgument("chat_id is required", "chat_id")
	}

	active, err := s.repo.FindActiveByLedgerAccountID(ctx, input.LedgerAccountID)
	if err != nil {
		return nil, err
	}
	if active != nil {
		return active, ErrActiveTreasuryRequest
	}

	amountRat, normalizedAmount, err := s.validator.ValidateAmount(input.Amount)
	if err != nil {
		return nil, err
	}
	if err := s.validator.ValidateDailyLimit(ctx, input.LedgerAccountID, amountRat, time.Now()); err != nil {
		return nil, err
	}

	account, err := s.ledger.GetAccount(ctx, input.LedgerAccountID)
	if err != nil {
		return nil, err
	}
	if account == nil || strings.TrimSpace(account.Currency) == "" {
		return nil, merrors.Internal("ledger account currency is unavailable")
	}
	if strings.TrimSpace(account.OrganizationRef) == "" {
		return nil, merrors.Internal("ledger account organization is unavailable")
	}

	requestID := newRequestID()
	record := &storagemodel.TreasuryRequest{
		RequestID:       requestID,
		OperationType:   input.OperationType,
		TelegramUserID:  input.TelegramUserID,
		LedgerAccountID: input.LedgerAccountID,
		OrganizationRef: account.OrganizationRef,
		ChatID:          input.ChatID,
		Amount:          normalizedAmount,
		Currency:        strings.ToUpper(strings.TrimSpace(account.Currency)),
		Status:          storagemodel.TreasuryRequestStatusCreated,
		IdempotencyKey:  fmt.Sprintf("tgsettle:%s", requestID),
		Active:          true,
	}
	if err := s.repo.Create(ctx, record); err != nil {
		if errors.Is(err, storage.ErrDuplicate) {
			active, fetchErr := s.repo.FindActiveByLedgerAccountID(ctx, input.LedgerAccountID)
			if fetchErr != nil {
				return nil, fetchErr
			}
			if active != nil {
				return active, ErrActiveTreasuryRequest
			}
			return nil, err
		}
		return nil, err
	}

	s.logRequest(record, "created", nil)
	return record, nil
}

func (s *Service) ConfirmRequest(ctx context.Context, requestID string, telegramUserID string) (*storagemodel.TreasuryRequest, error) {
	requestID = strings.TrimSpace(requestID)
	telegramUserID = strings.TrimSpace(telegramUserID)
	if requestID == "" {
		return nil, merrors.InvalidArgument("request_id is required", "request_id")
	}
	record, err := s.repo.FindByRequestID(ctx, requestID)
	if err != nil {
		return nil, err
	}
	if record == nil {
		return nil, merrors.NoData("treasury request not found")
	}
	if telegramUserID != "" && record.TelegramUserID != telegramUserID {
		return nil, merrors.Unauthorized("treasury request ownership mismatch")
	}

	switch record.Status {
	case storagemodel.TreasuryRequestStatusScheduled:
		return record, nil
	case storagemodel.TreasuryRequestStatusCreated, storagemodel.TreasuryRequestStatusConfirmed:
		now := time.Now()
		record.ConfirmedAt = now
		record.ScheduledAt = now.Add(s.executionDelay)
		record.Status = storagemodel.TreasuryRequestStatusScheduled
		record.Active = true
		record.ErrorMessage = ""
	default:
		return nil, merrors.InvalidArgument("treasury request cannot be confirmed in current status", "status")
	}
	if err := s.repo.Update(ctx, record); err != nil {
		return nil, err
	}
	s.logRequest(record, "scheduled", nil)
	return record, nil
}

func (s *Service) CancelRequest(ctx context.Context, requestID string, telegramUserID string) (*storagemodel.TreasuryRequest, error) {
	requestID = strings.TrimSpace(requestID)
	telegramUserID = strings.TrimSpace(telegramUserID)
	if requestID == "" {
		return nil, merrors.InvalidArgument("request_id is required", "request_id")
	}
	record, err := s.repo.FindByRequestID(ctx, requestID)
	if err != nil {
		return nil, err
	}
	if record == nil {
		return nil, merrors.NoData("treasury request not found")
	}
	if telegramUserID != "" && record.TelegramUserID != telegramUserID {
		return nil, merrors.Unauthorized("treasury request ownership mismatch")
	}

	switch record.Status {
	case storagemodel.TreasuryRequestStatusCancelled:
		return record, nil
	case storagemodel.TreasuryRequestStatusCreated, storagemodel.TreasuryRequestStatusConfirmed, storagemodel.TreasuryRequestStatusScheduled:
		record.Status = storagemodel.TreasuryRequestStatusCancelled
		record.CancelledAt = time.Now()
		record.Active = false
	default:
		return nil, merrors.InvalidArgument("treasury request cannot be cancelled in current status", "status")
	}

	if err := s.repo.Update(ctx, record); err != nil {
		return nil, err
	}
	s.logRequest(record, "cancelled", nil)
	return record, nil
}

func (s *Service) ExecuteRequest(ctx context.Context, requestID string) (*ExecutionResult, error) {
	requestID = strings.TrimSpace(requestID)
	if requestID == "" {
		return nil, merrors.InvalidArgument("request_id is required", "request_id")
	}
	record, err := s.repo.FindByRequestID(ctx, requestID)
	if err != nil {
		return nil, err
	}
	if record == nil {
		return nil, nil
	}

	switch record.Status {
	case storagemodel.TreasuryRequestStatusExecuted,
		storagemodel.TreasuryRequestStatusCancelled,
		storagemodel.TreasuryRequestStatusFailed:
		return nil, nil
	case storagemodel.TreasuryRequestStatusScheduled:
		claimed, err := s.repo.ClaimScheduled(ctx, requestID)
		if err != nil {
			return nil, err
		}
		if !claimed {
			return nil, nil
		}
		record, err = s.repo.FindByRequestID(ctx, requestID)
		if err != nil {
			return nil, err
		}
		if record == nil {
			return nil, nil
		}
	}

	if record.Status != storagemodel.TreasuryRequestStatusConfirmed {
		return nil, nil
	}
	return s.executeClaimed(ctx, record)
}

func (s *Service) executeClaimed(ctx context.Context, record *storagemodel.TreasuryRequest) (*ExecutionResult, error) {
	if record == nil {
		return nil, merrors.InvalidArgument("treasury request is required", "request")
	}
	postReq := ledger.PostRequest{
		AccountID:       record.LedgerAccountID,
		OrganizationRef: record.OrganizationRef,
		Amount:          record.Amount,
		Currency:        record.Currency,
		Reference:       record.RequestID,
		IdempotencyKey:  record.IdempotencyKey,
	}

	var (
		opResult *ledger.OperationResult
		err      error
	)
	switch record.OperationType {
	case storagemodel.TreasuryOperationFund:
		opResult, err = s.ledger.ExternalCredit(ctx, postReq)
	case storagemodel.TreasuryOperationWithdraw:
		opResult, err = s.ledger.ExternalDebit(ctx, postReq)
	default:
		err = merrors.InvalidArgument("treasury operation is invalid", "operation_type")
	}
	now := time.Now()
	if err != nil {
		record.Status = storagemodel.TreasuryRequestStatusFailed
		record.Active = false
		record.ExecutedAt = now
		record.ErrorMessage = strings.TrimSpace(err.Error())
		if saveErr := s.repo.Update(ctx, record); saveErr != nil {
			return nil, saveErr
		}
		s.logRequest(record, "failed", err)
		return &ExecutionResult{
			Request:        record,
			ExecutionError: err,
		}, nil
	}

	if opResult != nil {
		record.LedgerReference = strings.TrimSpace(opResult.Reference)
	}
	record.Status = storagemodel.TreasuryRequestStatusExecuted
	record.Active = false
	record.ExecutedAt = now
	record.ErrorMessage = ""

	balance, balanceErr := s.ledger.GetBalance(ctx, record.LedgerAccountID)
	if balanceErr != nil {
		record.ErrorMessage = strings.TrimSpace(balanceErr.Error())
	}

	if saveErr := s.repo.Update(ctx, record); saveErr != nil {
		return nil, saveErr
	}
	s.logRequest(record, "executed", nil)
	return &ExecutionResult{
		Request:        record,
		NewBalance:     balance,
		ExecutionError: balanceErr,
	}, nil
}

func (s *Service) DueRequests(ctx context.Context, statuses []storagemodel.TreasuryRequestStatus, now time.Time, limit int64) ([]*storagemodel.TreasuryRequest, error) {
	if s == nil || s.repo == nil {
		return nil, merrors.Internal("treasury service unavailable")
	}
	return s.repo.FindDueByStatus(ctx, statuses, now, limit)
}

func (s *Service) ScheduledRequests(ctx context.Context, limit int64) ([]*storagemodel.TreasuryRequest, error) {
	if s == nil || s.repo == nil {
		return nil, merrors.Internal("treasury service unavailable")
	}
	return s.repo.FindDueByStatus(
		ctx,
		[]storagemodel.TreasuryRequestStatus{storagemodel.TreasuryRequestStatusScheduled},
		time.Now().Add(10*365*24*time.Hour),
		limit,
	)
}

func (s *Service) ParseAmount(value string) (*big.Rat, error) {
	return parseAmountRat(value)
}

func (s *Service) logRequest(record *storagemodel.TreasuryRequest, status string, err error) {
	if s == nil || s.logger == nil || record == nil {
		return
	}
	fields := []zap.Field{
		zap.String("request_id", strings.TrimSpace(record.RequestID)),
		zap.String("telegram_user_id", strings.TrimSpace(record.TelegramUserID)),
		zap.String("ledger_account_id", strings.TrimSpace(record.LedgerAccountID)),
		zap.String("operation_type", strings.TrimSpace(string(record.OperationType))),
		zap.String("amount", strings.TrimSpace(record.Amount)),
		zap.String("currency", strings.TrimSpace(record.Currency)),
		zap.String("status", status),
	}
	if err != nil {
		fields = append(fields, zap.Error(err))
	}
	s.logger.Info("treasury_request", fields...)
}

func newRequestID() string {
	return "TGSETTLE-" + strings.ToUpper(bson.NewObjectID().Hex()[:8])
}