import static java.util.Collections.unmodifiableList;

import java.util.ArrayList;

import java.util.List;

/** POJO representing a User in the database. */

public class User {

private final String name;

private final List<Iou> owes;

private final List<Iou> owedBy;

private User(String name, List<Iou> owes, List<Iou> owedBy) {

this.name = name;

this.owes = new ArrayList<>(owes);

this.owedBy = new ArrayList<>(owedBy);

}

public String name() {

return name;

}

/** IOUs this user owes to other users. */

public List<Iou> owes() {

return unmodifiableList(owes);

}

/** IOUs other users owe to this user. */

public List<Iou> owedBy() {

return unmodifiableList(owedBy);

}

public static Builder builder() {

return new Builder();

}

public static class Builder {

private String name;

private final List<Iou> owes = new ArrayList<>();

private final List<Iou> owedBy = new ArrayList<>();

public Builder setName(String name) {

this.name = name;

return this;

}

public Builder owes(String name, double amount) {

owes.add(new Iou(name, amount));

return this;

}

public Builder owedBy(String name, double amount) {

owedBy.add(new Iou(name, amount));

return this;

}

public User build() {

return new User(name, owes, owedBy);

}

}

}