//go:build linux
// +build linux

package spec

import (
	"context"
	"fmt"
	"path/filepath"
	"strings"
	"time"

	"github.com/opencontainers/cgroups/devices/config"
	"github.com/opencontainers/runc/libcontainer/devices"
	oci "github.com/opencontainers/runtime-spec/specs-go"
	"github.com/pkg/errors"
	"github.com/sirupsen/logrus"

	"github.com/Microsoft/hcsshim/internal/guest/storage/pci"
	"github.com/Microsoft/hcsshim/internal/log"
	"github.com/Microsoft/hcsshim/internal/oc"
)

const (
	sysfsDevPathFormat = "/sys/dev/%s/%d:%d"

	charType  = "char"
	blockType = "block"

	// TODO: consolidate with `internal\uvm\virtual_device.go` and use in both locations
	gpuDeviceIDType        = "gpu"
	vpciDeviceIDTypeLegacy = "vpci"
	vpciDeviceIDType       = "vpci-instance-id"
)

// AddAssignedDevice goes through the assigned devices that have been enumerated
// on the spec and updates the spec so that the correct device nodes can be mounted
// into the resulting container by the runtime.
//
// GPU devices are skipped, since they are handled in [addNvidiaDeviceHook].
func AddAssignedDevice(ctx context.Context, spec *oci.Spec) (err error) {
	ctx, span := oc.StartSpan(ctx, "AddAssignedDevice")
	defer span.End()
	defer func() { oc.SetSpanStatus(span, err) }()

	// Add an explicit timeout before we try to find the dev nodes so we
	// aren't waiting forever.
	ctx, cancel := context.WithTimeout(ctx, 60*time.Second)
	defer cancel()

	for _, d := range spec.Windows.Devices {
		entry := log.G(ctx).WithField("windows-device", log.Format(ctx, d))

		switch d.IDType {
		case vpciDeviceIDTypeLegacy, vpciDeviceIDType:
			entry.Trace("adding vPCI device")
			// validate that the device is available
			fullPCIPath, err := pci.FindDeviceFullPath(ctx, d.ID)
			if err != nil {
				return errors.Wrapf(err, "failed to find device pci path for device %v", d)
			}

			entry.WithField("path", fullPCIPath).Trace("found PCI path for Windows device")
			// find the device nodes that link to the pci path we just got
			devs, err := devicePathsFromPCIPath(ctx, fullPCIPath)
			if err != nil {
				return errors.Wrapf(err, "failed to find dev node for device %v with path %q", d, fullPCIPath)
			}

			if logrus.IsLevelEnabled(logrus.DebugLevel) {
				entry.WithFields(logrus.Fields{
					"pci-path":     fullPCIPath,
					"host-devices": log.Format(ctx, devs),
				}).Debug("adding host devices associated with Windows device")
			}
			for _, dev := range devs {
				AddLinuxDeviceToSpec(ctx, dev, spec, true)
			}
		case gpuDeviceIDType:
			entry.Trace("skipping GPU device")
		default:
			entry.Warn("unknown device type")
		}
	}

	return nil
}

// devicePathsFromPCIPath takes a sysfs bus path to the pci device assigned into the guest
// and attempts to find the dev nodes in the guest that map to it.
func devicePathsFromPCIPath(ctx context.Context, pciPath string) ([]*config.Device, error) {
	// get the full pci path to make sure that it's the final path
	pciFullPath, err := filepath.EvalSymlinks(pciPath)
	if err != nil {
		return nil, err
	}

	for {
		select {
		case <-ctx.Done():
			return nil, fmt.Errorf("find the device nodes for sysfs pci path cancelled: %w", ctx.Err())
		default:
		}

		// some drivers create multiple dev nodes associated with the PCI device
		out := []*config.Device{}

		// get all host dev devices
		hostDevices, err := devices.HostDevices()
		if err != nil {
			return nil, err
		}

		// find corresponding entries in sysfs
		for _, d := range hostDevices {
			entry := log.G(ctx).WithField("host-device", log.Format(ctx, d))
			entry.Trace("looking at host device")

			major := d.Major
			minor := d.Minor

			deviceTypeString := ""
			switch d.Type {
			case config.BlockDevice:
				deviceTypeString = blockType
			case config.CharDevice:
				deviceTypeString = charType
			default:
				return nil, errors.New("unsupported device type")
			}

			sysfsDevPath := fmt.Sprintf(sysfsDevPathFormat, deviceTypeString, major, minor)
			sysfsFullPath, err := filepath.EvalSymlinks(sysfsDevPath)
			if err != nil {
				// Some drivers will make dev nodes that do not have a matching block or
				// char device -- skip those.
				entry.WithError(err).Debugf("failed to find sysfs path for device %s", d.Path)
				continue
			}
			if strings.HasPrefix(sysfsFullPath, pciFullPath) {
				out = append(out, d)
			}
		}

		if len(out) != 0 {
			return out, nil
		}

		// There is not a generic way to determine when a device is ready for use after
		// being hot-added. As a result, there may be a race between when the device
		// was hot-added and when the related /dev nodes are read from the filesystem.
		// Best we can do is retry until we get results. However, it's still possible we
		// will miss some /dev nodes since we don't know ahead of time how many to expect.
		// TODO(katiewasnothere): find a better way to make sure we find all the nodes.
		time.Sleep(time.Millisecond * 500)
	}
}

func AddLinuxDeviceToSpec(ctx context.Context, hostDevice *config.Device, spec *oci.Spec, addCgroupDevice bool) {
	rd := oci.LinuxDevice{
		Path:  hostDevice.Path,
		Type:  string(hostDevice.Type),
		Major: hostDevice.Major,
		Minor: hostDevice.Minor,
		UID:   &hostDevice.Uid,
		GID:   &hostDevice.Gid,
	}
	if hostDevice.Major == 0 && hostDevice.Minor == 0 {
		// Invalid device, most likely a symbolic link, skip it.
		return
	}
	found := false
	for i, dev := range spec.Linux.Devices {
		if dev.Path == rd.Path {
			found = true
			spec.Linux.Devices[i] = rd
			break
		}
		if dev.Type == rd.Type && dev.Major == rd.Major && dev.Minor == rd.Minor {
			log.G(ctx).Warnf("The same type '%s', major '%d' and minor '%d', should not be used for multiple devices.", dev.Type, dev.Major, dev.Minor)
		}
	}
	if !found {
		spec.Linux.Devices = append(spec.Linux.Devices, rd)
		if addCgroupDevice {
			deviceCgroup := oci.LinuxDeviceCgroup{
				Allow:  true,
				Type:   string(hostDevice.Type),
				Major:  &hostDevice.Major,
				Minor:  &hostDevice.Minor,
				Access: string(hostDevice.Permissions),
			}
			spec.Linux.Resources.Devices = append(spec.Linux.Resources.Devices, deviceCgroup)
		}
	}
}
