Add full monorepo: virtual-banker, backend, frontend, docs, scripts, deployment

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/banking/ledger/ledger.go

@@ -0,0 +1,89 @@
+package ledger
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+// Ledger handles double-entry accounting
+type Ledger struct {
+	db *pgxpool.Pool
+}
+
+// NewLedger creates a new ledger
+func NewLedger(db *pgxpool.Pool) *Ledger {
+	return &Ledger{db: db}
+}
+
+// Entry represents a ledger entry
+type Entry struct {
+	ID          string
+	CustomerID  string
+	AccountType string // "asset", "liability", "equity"
+	Amount      string
+	Currency    string
+	Description string
+	Reference   string
+	CreatedAt   time.Time
+}
+
+// CreateEntry creates a double-entry ledger entry
+func (l *Ledger) CreateEntry(ctx context.Context, debit, credit *Entry) error {
+	tx, err := l.db.Begin(ctx)
+	if err != nil {
+		return fmt.Errorf("failed to begin transaction: %w", err)
+	}
+	defer tx.Rollback(ctx)
+
+	// Insert debit entry
+	debitQuery := `
+		INSERT INTO ledger_entries (
+			customer_id, account_type, amount, currency, description, reference, side, created_at
+		) VALUES ($1, $2, $3, $4, $5, $6, 'debit', NOW())
+	`
+	_, err = tx.Exec(ctx, debitQuery,
+		debit.CustomerID, debit.AccountType, debit.Amount, debit.Currency,
+		debit.Description, debit.Reference,
+	)
+	if err != nil {
+		return fmt.Errorf("failed to create debit entry: %w", err)
+	}
+
+	// Insert credit entry
+	creditQuery := `
+		INSERT INTO ledger_entries (
+			customer_id, account_type, amount, currency, description, reference, side, created_at
+		) VALUES ($1, $2, $3, $4, $5, $6, 'credit', NOW())
+	`
+	_, err = tx.Exec(ctx, creditQuery,
+		credit.CustomerID, credit.AccountType, credit.Amount, credit.Currency,
+		credit.Description, credit.Reference,
+	)
+	if err != nil {
+		return fmt.Errorf("failed to create credit entry: %w", err)
+	}
+
+	return tx.Commit(ctx)
+}
+
+// GetBalance gets account balance for a customer
+func (l *Ledger) GetBalance(ctx context.Context, customerID, accountType string) (string, error) {
+	query := `
+		SELECT 
+			SUM(CASE WHEN side = 'debit' THEN amount::numeric ELSE -amount::numeric END) as balance
+		FROM ledger_entries
+		WHERE customer_id = $1 AND account_type = $2
+	`
+
+	var balance string
+	err := l.db.QueryRow(ctx, query, customerID, accountType).Scan(&balance)
+	if err != nil {
+		return "0", nil
+	}
+
+	return balance, nil
+}
+