// Freeze toggles the container's freezer cgroup depending on the state
// provided
func (m *Manager) Freeze(state configs.FreezerState) error {
	d, err := getCgroupData(m.Cgroups, 0)
	if err != nil {
		return err
	}

	dir, err := d.path("freezer")
	if err != nil {
		return err
	}
	if !cgroups.PathExists(dir) {
		return cgroups.NewNotFoundError("freezer")
	}

	prevState := m.Cgroups.Freezer
	m.Cgroups.Freezer = state

	freezer := subsystems["freezer"]
	err = freezer.Set(dir, m.Cgroups)
	if err != nil {
		m.Cgroups.Freezer = prevState
		return err
	}

	return nil
}

func (m *Manager) Set(container *configs.Config) error {
	for name, path := range m.Paths {
		sys, ok := subsystems[name]
		if !ok || !cgroups.PathExists(path) {
			continue
		}
		if err := sys.Set(path, container.Cgroups); err != nil {
			return err
		}
	}

	return nil
}

func (m *Manager) GetStats() (*cgroups.Stats, error) {
	stats := cgroups.NewStats()
	for name, path := range m.Paths {
		sys, ok := subsystems[name]
		if !ok || !cgroups.PathExists(path) {
			continue
		}
		if err := sys.GetStats(path, stats); err != nil {
			return nil, err
		}
	}

	return stats, nil
}

func GetStats(systemPaths map[string]string) (*cgroups.Stats, error) {
	stats := cgroups.NewStats()
	for name, path := range systemPaths {
		sys, ok := subsystems[name]
		if !ok || !cgroups.PathExists(path) {
			continue
		}
		if err := sys.GetStats(path, stats); err != nil {
			return nil, err
		}
	}

	return stats, nil
}

func (m *Manager) GetPids() ([]int, error) {
	d, err := getCgroupData(m.Cgroups, 0)
	if err != nil {
		return nil, err
	}

	dir, err := d.path("devices")
	if err != nil {
		return nil, err
	}
	if !cgroups.PathExists(dir) {
		return nil, cgroups.NewNotFoundError("devices")
	}

	return cgroups.ReadProcsFile(dir)
}

func (m *Manager) Apply(pid int) error {
	if m.Cgroups == nil {
		return nil
	}

	d, err := getCgroupData(m.Cgroups, pid)
	if err != nil {
		return err
	}

	paths := make(map[string]string)
	defer func() {
		if err != nil {
			cgroups.RemovePaths(paths)
		}
	}()
	for name, sys := range subsystems {
		if err := sys.Apply(d); err != nil {
			return err
		}
		// TODO: Apply should, ideally, be reentrant or be broken up into a separate
		// create and join phase so that the cgroup hierarchy for a container can be
		// created then join consists of writing the process pids to cgroup.procs
		p, err := d.path(name)
		if err != nil {
			return err
		}
		if !cgroups.PathExists(p) {
			continue
		}

		paths[name] = p
	}
	m.Paths = paths

	return nil
}