Method AddDependency

agent/unit/manager.go:158–182

AddDependency adds a dependency relationship between units. The unit depends on the dependsOn unit reaching the requiredStatus.

(unit ID, dependsOn ID, requiredStatus Status)

// AddDependency adds a dependency relationship between units.
// The unit depends on the dependsOn unit reaching the requiredStatus.
func (m *Manager) AddDependency(unit ID, dependsOn ID, requiredStatus Status) error {
	m.mu.Lock()
	defer m.mu.Unlock()

	switch {
	case unit == "":
		return xerrors.Errorf("dependent name cannot be empty: %w", ErrUnitIDRequired)
	case dependsOn == "":
		return xerrors.Errorf("dependency name cannot be empty: %w", ErrUnitIDRequired)
	case !m.registered(unit):
		return xerrors.Errorf("dependent unit %q must be registered first: %w", unit, ErrUnitNotFound)
	}

	// Add the dependency edge to the graph
	// The edge goes from unit to dependsOn, representing the dependency
	err := m.graph.AddEdge(unit, dependsOn, requiredStatus)
	if err != nil {
		return xerrors.Errorf("adding edge for unit %q: %w", unit, errors.Join(ErrFailedToAddDependency, err))
	}

	// Recalculate readiness for the unit since it now has a new dependency
	m.recalculateReadinessUnsafe(unit)

	return nil
}

// UpdateStatus updates a unit's status and recalculates readiness for affected dependents.
func (m *Manager) UpdateStatus(unit ID, newStatus Status) error {