Add per-account historical bank imports without resetting sync cursors

internal/app/import.go

@@ -92,6 +92,76 @@ func (a *App) ImportCSV(ctx context.Context, rev, accountID string, r io.Reader)
 	}
 	return ImportResult{}, errors.New("unknown account")
 }
+
+func (a *App) Backfill(ctx context.Context, rev, accountID string, historyMonths int) (ImportResult, error) {
+	a.mu.Lock()
+	defer a.mu.Unlock()
+	if historyMonths < 1 || historyMonths > 120 {
+		return ImportResult{}, errors.New("history_months must be an integer between 1 and 120")
+	}
+	s, err := a.snapshot(ctx)
+	if err != nil {
+		return ImportResult{}, err
+	}
+	if rev != s.Revision {
+		return ImportResult{}, errors.New("revision conflict: reload before importing")
+	}
+	if a.bank == nil {
+		return ImportResult{}, errors.New("Enable Banking is not configured")
+	}
+	index := slices.IndexFunc(s.Data.Accounts, func(account domain.Account) bool { return account.ID == accountID })
+	if index < 0 {
+		return ImportResult{}, errors.New("unknown account")
+	}
+	account := s.Data.Accounts[index]
+	if account.ExternalAccountID == "" {
+		return ImportResult{}, errors.New("account is not connected")
+	}
+	var session *banking.Session
+	for i := len(a.ops.Sessions) - 1; i >= 0; i-- {
+		saved := &a.ops.Sessions[i]
+		if slices.ContainsFunc(saved.Accounts, func(linked domain.Account) bool {
+			return linked.ID == account.ID && linked.ExternalAccountID == account.ExternalAccountID
+		}) {
+			session = saved
+			break
+		}
+	}
+	if session == nil || session.ID == "" {
+		return ImportResult{}, errors.New("account is not connected")
+	}
+	expiry, err := time.Parse(time.RFC3339, session.ValidUntil)
+	if a.ops.Consents[session.ID].NeedsReconnect || err != nil || !expiry.After(time.Now()) {
+		return ImportResult{}, banking.ErrReconnect
+	}
+	current, err := a.bank.Status(ctx, session.ID)
+	if err != nil {
+		if errors.Is(err, banking.ErrReconnect) {
+			return ImportResult{}, banking.ErrReconnect
+		}
+		return ImportResult{}, errors.New("bank connection unavailable; retry importing history")
+	}
+	expiry, err = time.Parse(time.RFC3339, current.ValidUntil)
+	if err != nil || !expiry.After(time.Now()) {
+		return ImportResult{}, banking.ErrReconnect
+	}
+	if !slices.ContainsFunc(current.Accounts, func(linked domain.Account) bool {
+		return linked.ExternalAccountID == account.ExternalAccountID
+	}) {
+		return ImportResult{}, banking.ErrReconnect
+	}
+	now := time.Now().UTC()
+	facts, err := a.bank.Transactions(ctx, account, now.AddDate(0, -historyMonths, 0).Format("2006-01-02"), now.Format("2006-01-02"))
+	if err != nil {
+		if errors.Is(err, banking.ErrReconnect) {
+			return ImportResult{}, banking.ErrReconnect
+		}
+		return ImportResult{}, errors.New("transaction retrieval failed; retry importing history")
+	}
+	// Use normal import processing without changing sync cursors or saved consent
+	// settings, including when the requested range adds no transactions.
+	return a.importFacts(ctx, s, facts)
+}
 func (a *App) Authorize(ctx context.Context, institution, country string, historyMonths int) (string, error) {
 	a.mu.Lock()
 	defer a.mu.Unlock()