package ledger

import (
	"context"
	"fmt"
	"time"

	"github.com/tech/sendico/ledger/storage"
	"github.com/tech/sendico/ledger/storage/model"
	storageMongo "github.com/tech/sendico/ledger/storage/mongo"
	"github.com/tech/sendico/pkg/api/routers/gsresponse"
	"github.com/tech/sendico/pkg/merrors"
	ledgerv1 "github.com/tech/sendico/pkg/proto/ledger/v1"
	"go.mongodb.org/mongo-driver/bson/primitive"
	"go.uber.org/zap"
)

// postDebitResponder implements debit posting with charges
func (s *Service) postDebitResponder(_ context.Context, req *ledgerv1.PostDebitRequest) gsresponse.Responder[ledgerv1.PostResponse] {
	return func(ctx context.Context) (*ledgerv1.PostResponse, error) {
		if req.IdempotencyKey == "" {
			return nil, merrors.InvalidArgument("idempotency_key is required")
		}
		if req.OrganizationRef == "" {
			return nil, merrors.InvalidArgument("organization_ref is required")
		}
		if req.LedgerAccountRef == "" {
			return nil, merrors.InvalidArgument("ledger_account_ref is required")
		}
		if err := validateMoney(req.Money, "money"); err != nil {
			return nil, err
		}

		orgRef, err := parseObjectID(req.OrganizationRef)
		if err != nil {
			return nil, err
		}
		accountRef, err := parseObjectID(req.LedgerAccountRef)
		if err != nil {
			return nil, err
		}

		existingEntry, err := s.storage.JournalEntries().GetByIdempotencyKey(ctx, orgRef, req.IdempotencyKey)
		if err == nil && existingEntry != nil {
			recordDuplicateRequest("debit")
			s.logger.Info("duplicate debit request (idempotency)",
				zap.String("idempotencyKey", req.IdempotencyKey),
				zap.String("existingEntryID", existingEntry.GetID().Hex()))
			return &ledgerv1.PostResponse{
				JournalEntryRef: existingEntry.GetID().Hex(),
				Version:         existingEntry.Version,
				EntryType:       ledgerv1.EntryType_ENTRY_DEBIT,
			}, nil
		}
		if err != nil && err != storage.ErrJournalEntryNotFound {
			s.logger.Warn("failed to check idempotency", zap.Error(err))
			return nil, merrors.Internal("failed to check idempotency")
		}

		account, err := s.storage.Accounts().Get(ctx, accountRef)
		if err != nil {
			if err == storage.ErrAccountNotFound {
				return nil, merrors.NoData("account not found")
			}
			s.logger.Warn("failed to get account", zap.Error(err))
			return nil, merrors.Internal("failed to get account")
		}
		if err := validateAccountForOrg(account, orgRef, req.Money.Currency); err != nil {
			return nil, err
		}

		accountsByRef := map[primitive.ObjectID]*model.Account{accountRef: account}

		eventTime := getEventTime(req.EventTime)
		debitAmount, _ := parseDecimal(req.Money.Amount)
		entryTotal := debitAmount.Neg()

		charges := req.Charges
		if len(charges) == 0 {
			if computed, err := s.quoteFeesForDebit(ctx, req); err != nil {
				s.logger.Warn("failed to quote fees", zap.Error(err))
			} else if len(computed) > 0 {
				charges = computed
			}
		}
		if err := validatePostingLines(charges); err != nil {
			return nil, err
		}

		postingLines := make([]*model.PostingLine, 0, 2+len(charges))
		mainLine := &model.PostingLine{
			JournalEntryRef: primitive.NilObjectID,
			AccountRef:      accountRef,
			Amount:          debitAmount.Neg().String(),
			Currency:        req.Money.Currency,
			LineType:        model.LineTypeMain,
		}
		mainLine.OrganizationRef = orgRef
		postingLines = append(postingLines, mainLine)

		for i, charge := range charges {
			chargeAccountRef, err := parseObjectID(charge.LedgerAccountRef)
			if err != nil {
				return nil, err
			}
			if charge.Money.Currency != req.Money.Currency {
				return nil, merrors.InvalidArgument(fmt.Sprintf("charges[%d]: currency mismatch", i))
			}

			chargeAccount, err := s.getAccount(ctx, accountsByRef, chargeAccountRef)
			if err != nil {
				if err == storage.ErrAccountNotFound {
					return nil, merrors.NoData(fmt.Sprintf("charges[%d]: account not found", i))
				}
				s.logger.Warn("failed to get charge account", zap.Error(err), zap.String("chargeAccountRef", chargeAccountRef.Hex()))
				return nil, merrors.Internal("failed to get charge account")
			}
			if err := validateAccountForOrg(chargeAccount, orgRef, charge.Money.Currency); err != nil {
				return nil, merrors.InvalidArgument(fmt.Sprintf("charges[%d]: %s", i, err.Error()))
			}

			chargeAmount, err := parseDecimal(charge.Money.Amount)
			if err != nil {
				return nil, err
			}
			entryTotal = entryTotal.Add(chargeAmount)

			chargeLine := &model.PostingLine{
				JournalEntryRef: primitive.NilObjectID,
				AccountRef:      chargeAccountRef,
				Amount:          chargeAmount.String(),
				Currency:        charge.Money.Currency,
				LineType:        protoLineTypeToModel(charge.LineType),
			}
			chargeLine.OrganizationRef = orgRef
			postingLines = append(postingLines, chargeLine)
		}

		contraAccount, err := s.resolveSettlementAccount(ctx, orgRef, req.Money.Currency, req.ContraLedgerAccountRef, accountsByRef)
		if err != nil {
			recordJournalEntryError("debit", "contra_resolve_failed")
			return nil, err
		}
		contraAccountID := contraAccount.GetID()
		if contraAccountID == nil {
			recordJournalEntryError("debit", "contra_missing_id")
			return nil, merrors.Internal("contra account missing identifier")
		}

		contraAmount := entryTotal.Neg()
		if !contraAmount.IsZero() || len(postingLines) == 1 {
			contraLine := &model.PostingLine{
				JournalEntryRef: primitive.NilObjectID,
				AccountRef:      *contraAccountID,
				Amount:          contraAmount.String(),
				Currency:        req.Money.Currency,
				LineType:        model.LineTypeMain,
			}
			contraLine.OrganizationRef = orgRef
			postingLines = append(postingLines, contraLine)
			entryTotal = entryTotal.Add(contraAmount)
		}

		if !entryTotal.IsZero() {
			recordJournalEntryError("debit", "unbalanced_after_contra")
			return nil, merrors.Internal("failed to balance journal entry")
		}

		mongoStore, ok := s.storage.(*storageMongo.Store)
		if !ok {
			return nil, merrors.Internal("storage does not support transactions")
		}

		result, err := mongoStore.TransactionFactory().CreateTransaction().Execute(ctx, func(txCtx context.Context) (any, error) {
			entry := &model.JournalEntry{
				IdempotencyKey: req.IdempotencyKey,
				EventTime:      eventTime,
				EntryType:      model.EntryTypeDebit,
				Description:    req.Description,
				Metadata:       req.Metadata,
				Version:        time.Now().UnixNano(),
			}
			entry.OrganizationRef = orgRef

			if err := s.storage.JournalEntries().Create(txCtx, entry); err != nil {
				s.logger.Warn("failed to create journal entry", zap.Error(err))
				return nil, merrors.Internal("failed to create journal entry")
			}

			entryRef := entry.GetID()
			if entryRef == nil {
				return nil, merrors.Internal("journal entry missing identifier")
			}

			for _, line := range postingLines {
				line.JournalEntryRef = *entryRef
			}

			if err := validateBalanced(postingLines); err != nil {
				return nil, err
			}

			if err := s.storage.PostingLines().CreateMany(txCtx, postingLines); err != nil {
				s.logger.Warn("failed to create posting lines", zap.Error(err))
				return nil, merrors.Internal("failed to create posting lines")
			}

			if err := s.upsertBalances(txCtx, postingLines, accountsByRef); err != nil {
				return nil, err
			}

			if err := s.enqueueOutbox(txCtx, entry, postingLines); err != nil {
				return nil, err
			}

			return &ledgerv1.PostResponse{
				JournalEntryRef: entryRef.Hex(),
				Version:         entry.Version,
				EntryType:       ledgerv1.EntryType_ENTRY_DEBIT,
			}, nil
		})

		if err != nil {
			recordJournalEntryError("debit", "transaction_failed")
			return nil, err
		}

		amountFloat, _ := debitAmount.Float64()
		recordTransactionAmount(req.Money.Currency, "debit", amountFloat)
		recordJournalEntry("debit", "success", 0)
		return result.(*ledgerv1.PostResponse), nil
	}
}