package device

import (
	"context"
	"errors"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"time"

	"github.com/lxc/incus/v6/internal/linux"
	deviceConfig "github.com/lxc/incus/v6/internal/server/device/config"
	"github.com/lxc/incus/v6/internal/server/instance"
	"github.com/lxc/incus/v6/internal/server/instance/instancetype"
	"github.com/lxc/incus/v6/shared/revert"
	"github.com/lxc/incus/v6/shared/subprocess"
	"github.com/lxc/incus/v6/shared/util"
	"github.com/lxc/incus/v6/shared/validate"
)

type tpm struct {
	deviceCommon
}

// CanMigrate returns whether the device can be migrated to any other cluster member.
func (d *tpm) CanMigrate() bool {
	return true
}

// validateConfig checks the supplied config for correctness.
func (d *tpm) validateConfig(instConf instance.ConfigReader) error {
	if !instanceSupported(instConf.Type(), instancetype.Container, instancetype.VM) {
		return ErrUnsupportedDevType
	}

	rules := map[string]func(string) error{}

	if instConf.Type() == instancetype.Container {
		// gendoc:generate(entity=devices, group=tpm, key=path)
		//
		// ---
		//  type: string
		//  default: -
		//  required: for containers
		//  shortdesc: Only for containers: path inside the instance (for example, `/dev/tpm0`)
		rules["path"] = validate.IsNotEmpty

		// gendoc:generate(entity=devices, group=tpm, key=pathrm)
		//
		// ---
		//  type: string
		//  default: -
		//  required: for containers
		//  shortdesc: Only for containers: resource manager path inside the instance (for example, `/dev/tpmrm0`)
		rules["pathrm"] = validate.IsNotEmpty
	} else {
		rules["path"] = validate.Optional(validate.IsNotEmpty)
		rules["pathrm"] = validate.Optional(validate.IsNotEmpty)
	}

	err := d.config.Validate(rules)
	if err != nil {
		return fmt.Errorf("Failed to validate config: %w", err)
	}

	return nil
}

// validateEnvironment checks if the TPM emulator is available.
func (d *tpm) validateEnvironment() error {
	// Validate the required binary.
	_, err := exec.LookPath("swtpm")
	if err != nil {
		return fmt.Errorf("Required tool '%s' is missing", "swtpm")
	}

	if d.inst.Type() == instancetype.Container {
		// Load module tpm_vtpm_proxy which creates the /dev/vtpmx device, required
		// by the TPM emulator.
		module := "tpm_vtpm_proxy"

		err := linux.LoadModule(module)
		if err != nil {
			return fmt.Errorf("Failed to load kernel module %q: %w", module, err)
		}
	}

	return nil
}

// Start is run when the device is added to the instance.
func (d *tpm) Start() (*deviceConfig.RunConfig, error) {
	err := d.validateEnvironment()
	if err != nil {
		return nil, fmt.Errorf("Failed to validate environment: %w", err)
	}

	tpmDevPath := filepath.Join(d.inst.Path(), fmt.Sprintf("tpm.%s", d.name))

	if !util.PathExists(tpmDevPath) {
		err := os.Mkdir(tpmDevPath, 0o700)
		if err != nil {
			return nil, fmt.Errorf("Failed to create device path %q: %w", tpmDevPath, err)
		}
	}

	if d.inst.Type() == instancetype.VM {
		return d.startVM()
	}

	return d.startContainer()
}

func (d *tpm) startContainer() (*deviceConfig.RunConfig, error) {
	tpmDevPath := filepath.Join(d.inst.Path(), fmt.Sprintf("tpm.%s", d.name))
	logFileName := fmt.Sprintf("tpm.%s.log", d.name)
	logPath := filepath.Join(d.inst.LogPath(), logFileName)

	proc, err := subprocess.NewProcess("swtpm", []string{"chardev", "--tpm2", "--tpmstate", fmt.Sprintf("dir=%s", tpmDevPath), "--vtpm-proxy"}, logPath, "")
	if err != nil {
		return nil, fmt.Errorf("Failed to create new process: %w", err)
	}

	err = proc.Start(context.Background())
	if err != nil {
		return nil, fmt.Errorf("Failed to start process %q: %w", "swtpm", err)
	}

	reverter := revert.New()
	defer reverter.Fail()

	// Stop the TPM emulator if anything goes wrong.
	reverter.Add(func() { _ = proc.Stop() })

	pidPath := filepath.Join(d.inst.DevicesPath(), fmt.Sprintf("%s.pid", d.name))

	err = proc.Save(pidPath)
	if err != nil {
		return nil, fmt.Errorf("Failed to save swtpm state for device %q: %w", d.name, err)
	}

	const TPM_MINOR = 244
	const TPM_NUM_DEVICES = 65536
	var major, minor, minorRM int

	// We need to capture the output of the TPM emulator since it contains the device path. To do
	// that, we wait until something has been written to the log file (stdout redirect), and then
	// read it.
	for range 20 {
		fi, err := os.Stat(logPath)
		if err != nil {
			return nil, fmt.Errorf("Failed to stat %q: %w", logPath, err)
		}

		if fi.Size() > 0 {
			break
		}

		time.Sleep(500 * time.Millisecond)
	}

	line, err := os.ReadFile(logPath)
	if err != nil {
		return nil, fmt.Errorf("Failed to read %q: %w", logPath, err)
	}

	// The output will be something like:
	//   New TPM device: /dev/tpm1 (major/minor = 253/1)
	// We just need the major/minor numbers.
	fields := strings.Split(string(line), " ")

	if len(fields) < 7 {
		return nil, errors.New("Failed to get TPM device information")
	}

	_, err = fmt.Sscanf(fields[6], "%d/%d)", &major, &minor)
	if err != nil {
		return nil, fmt.Errorf("Failed to retrieve major/minor number: %w", err)
	}

	// Return error as we were unable to retrieve information regarding the TPM device.
	if major == 0 && minor == 0 {
		return nil, errors.New("Failed to get TPM device information")
	}

	if minor == TPM_MINOR {
		minorRM = TPM_NUM_DEVICES
	} else {
		minorRM = TPM_NUM_DEVICES + minor
	}

	runConf := deviceConfig.RunConfig{}

	err = unixDeviceSetupCharNum(d.state, d.inst.DevicesPath(), "unix", d.name, d.config, uint32(major), uint32(minor), d.config["path"], false, &runConf)
	if err != nil {
		return nil, fmt.Errorf("Failed to setup unix device: %w", err)
	}

	err = unixDeviceSetupCharNum(d.state, d.inst.DevicesPath(), "unix", d.name, d.config, uint32(major), uint32(minorRM), d.config["pathrm"], false, &runConf)
	if err != nil {
		return nil, fmt.Errorf("Failed to setup unix device: %w", err)
	}

	reverter.Success()

	return &runConf, nil
}

func (d *tpm) startVM() (*deviceConfig.RunConfig, error) {
	if d.inst.Type() == instancetype.VM && util.IsTrue(d.inst.ExpandedConfig()["migration.stateful"]) {
		return nil, errors.New("TPM devices cannot be used when migration.stateful is enabled")
	}

	tpmDevPath := filepath.Join(d.inst.Path(), fmt.Sprintf("tpm.%s", d.name))
	socketPath := filepath.Join(tpmDevPath, fmt.Sprintf("swtpm-%s.sock", d.name))
	runConf := deviceConfig.RunConfig{
		TPMDevice: []deviceConfig.RunConfigItem{
			{Key: "devName", Value: d.name},
			{Key: "path", Value: socketPath},
		},
	}

	// Delete any leftover socket.
	_ = os.Remove(socketPath)

	proc, err := subprocess.NewProcess("swtpm", []string{"socket", "--tpm2", "--tpmstate", fmt.Sprintf("dir=%s", tpmDevPath), "--ctrl", fmt.Sprintf("type=unixio,path=swtpm-%s.sock", d.name)}, "", "")
	if err != nil {
		return nil, err
	}

	proc.Cwd = tpmDevPath

	// Start the TPM emulator.
	err = proc.Start(context.Background())
	if err != nil {
		return nil, fmt.Errorf("Failed to start swtpm for device %q: %w", d.name, err)
	}

	reverter := revert.New()
	defer reverter.Fail()

	reverter.Add(func() { _ = proc.Stop() })

	pidPath := filepath.Join(d.inst.DevicesPath(), fmt.Sprintf("%s.pid", d.name))

	err = proc.Save(pidPath)
	if err != nil {
		return nil, fmt.Errorf("Failed to save swtpm state for device %q: %w", d.name, err)
	}

	// Wait for the socket to be available.
	exists := false
	for range 20 {
		if util.PathExists(socketPath) {
			exists = true
			break
		}

		time.Sleep(100 * time.Millisecond)
	}

	if !exists {
		return nil, errors.New("swtpm socket didn't appear within 2s")
	}

	reverter.Success()

	return &runConf, nil
}

// Stop terminates the TPM emulator.
func (d *tpm) Stop() (*deviceConfig.RunConfig, error) {
	pidPath := filepath.Join(d.inst.DevicesPath(), fmt.Sprintf("%s.pid", d.name))
	runConf := deviceConfig.RunConfig{}

	defer func() { _ = os.Remove(pidPath) }()

	if util.PathExists(pidPath) {
		proc, err := subprocess.ImportProcess(pidPath)
		if err != nil {
			return nil, fmt.Errorf("Failed to import process %q: %w", pidPath, err)
		}

		// The TPM emulator will usually exit automatically when the tpm device is no longer in use,
		// i.e. the instance is stopped. Therefore, we only fail if the running process couldn't
		// be stopped.
		err = proc.Stop()
		if err != nil && !errors.Is(err, subprocess.ErrNotRunning) {
			return nil, fmt.Errorf("Failed to stop imported process %q: %w", pidPath, err)
		}
	}

	if d.inst.Type() == instancetype.Container {
		err := unixDeviceRemove(d.inst.DevicesPath(), "unix", d.name, "", &runConf)
		if err != nil {
			return nil, fmt.Errorf("Failed to remove unix device: %w", err)
		}
	}

	return &runConf, nil
}

// Remove removes the TPM state file.
func (d *tpm) Remove() error {
	tpmDevPath := filepath.Join(d.inst.Path(), fmt.Sprintf("tpm.%s", d.name))

	return os.RemoveAll(tpmDevPath)
}
