// classes.groovy — classes, properties, constructors, traits and @Canonical.
import groovy.transform.Canonical
import groovy.transform.ToString

// Properties: no getters/setters to write; Groovy generates them
class Customer {
    String name
    String email
    BigDecimal creditLimit = 5000

    boolean canSpend(BigDecimal amount) { amount <= creditLimit }
}

def c = new Customer(name: 'Acme', email: 'ap@acme.test')   // named-argument constructor
println c.name                       // uses getName()
c.creditLimit = 1000                 // uses setCreditLimit()
println c.canSpend(1200)             // false

// @Canonical: equals, hashCode, toString and constructors for free
@Canonical
class Line {
    String sku
    int qty
    BigDecimal price
    BigDecimal getTotal() { qty * price }
}
def l1 = new Line('AX-200', 24, 8.50)
println l1                           // Line(AX-200, 24, 8.50, 204.00)
println l1.total                     // 204.00
println l1 == new Line('AX-200', 24, 8.50)   // true

// Traits: reusable behaviour you can mix into classes
trait Auditable {
    List<String> history = []
    void audit(String event) { history << "${java.time.LocalTime.now().withNano(0)} $event".toString() }
}
trait Validatable {
    abstract List<String> errors()
    boolean isValid() { errors().isEmpty() }
}

@ToString(includeNames = true)
class Order implements Auditable, Validatable {
    String id
    List<Line> lines = []
    List<String> errors() { lines ? [] : ['order has no lines'] }
}

def o = new Order(id: 'PO-1')
println o.valid                      // false (isValid() as a property)
o.lines << l1
o.audit('line added')
println o.valid                      // true
println o.history.size()             // 1
println o