package vm

import (
	"encoding/hex"
	"fmt"
	"log/slog"
	"net"
	"os"
	"path/filepath"
	"runtime"
	"strings"
	"time"

	"github.com/AlexSSD7/linsk/nettap"
	"github.com/AlexSSD7/linsk/osspecifics"
	"github.com/AlexSSD7/linsk/qemucli"
	"github.com/AlexSSD7/linsk/utils"
	"github.com/pkg/errors"
)

func getUniqueQEMUNetID() string {
	return "net" + utils.IntToStr(time.Now().UnixNano())
}

func getUniqueQEMUDriveID() string {
	return "drive" + utils.IntToStr(time.Now().UnixNano())
}

func cleanQEMUPath(s string) string {
	path := filepath.Clean(s)
	if osspecifics.IsWindows() {
		// QEMU doesn't work well with Windows backslashes, so we're replacing them to forward slashes
		// that work perfectly fine.
		path = strings.ReplaceAll(s, "\\", "/")
	}

	return path
}

func configureBaseVMCmd(logger *slog.Logger, cfg Config) (string, []qemucli.Arg, error) {
	baseCmd := "qemu-system"

	if osspecifics.IsWindows() {
		baseCmd += ".exe"
	}

	args := []qemucli.Arg{
		qemucli.MustNewStringArg("serial", "stdio"),
		qemucli.MustNewUintArg("m", cfg.MemoryAlloc),
		qemucli.MustNewUintArg("smp", runtime.NumCPU()),
	}

	var accel string
	switch {
	case osspecifics.IsWindows():
		// TODO: To document: For Windows, we need to install QEMU using an installer and add it to PATH.
		// Then, we should enable Windows Hypervisor Platform in "Turn Windows features on or off".
		// IMPORTANT: We should also install libusbK drivers for USB devices we want to pass through.
		// This can be easily done with a program called Zadiag by Akeo.
		accel = "whpx,kernel-irqchip=off"
	case osspecifics.IsMacOS():
		accel = "hvf"
	default:
		accel = "kvm"
	}

	switch runtime.GOARCH {
	case "amd64":
		baseCmd += "-x86_64"
	case "arm64":
		if cfg.BIOSPath == "" {
			logger.Warn("BIOS image path is not specified while attempting to run an aarch64 (arm64) VM. The VM will not boot.")
		}

		// "highmem=off" is required for M1.
		args = append(args,
			qemucli.MustNewKeyValueArg("machine", []qemucli.KeyValueArgItem{
				{Key: "type", Value: "virt"},
				{Key: "highmem", Value: "off"},
			}),
			qemucli.MustNewStringArg("cpu", "host"),
		)

		baseCmd += "-aarch64"
	default:
		return "", nil, fmt.Errorf("arch '%v' is not supported", runtime.GOARCH)
	}

	args = append(args, qemucli.MustNewStringArg("accel", accel))

	if cfg.BIOSPath != "" {
		biosPath := cleanQEMUPath(cfg.BIOSPath)
		biosArg, err := qemucli.NewStringArg("bios", biosPath)
		if err != nil {
			return "", nil, errors.Wrapf(err, "create bios arg (path '%v')", biosPath)
		}

		args = append(args, biosArg)
	}

	if !cfg.ShowDisplay {
		args = append(args, qemucli.MustNewStringArg("display", "none"))
	}

	// TODO: There is no video configured by default on arm64, rendering --vm-debug useless.

	if cfg.CdromImagePath != "" {
		cdromPath := cleanQEMUPath(cfg.CdromImagePath)
		cdromArg, err := qemucli.NewStringArg("cdrom", cdromPath)
		if err != nil {
			return "", nil, errors.Wrapf(err, "create cdrom arg (path '%v')", cdromPath)
		}

		args = append(args, cdromArg, qemucli.MustNewStringArg("boot", "d"))
	}

	return baseCmd, args, nil
}

func configureVMCmdUserNetwork(ports []PortForwardingRule, unrestricted bool) ([]qemucli.Arg, error) {
	netID := getUniqueQEMUNetID()

	userNetdevValues := []qemucli.KeyValueArgItem{
		{Key: "type", Value: "user"},
		{Key: "id", Value: netID},
	}

	if !unrestricted {
		userNetdevValues = append(userNetdevValues, qemucli.KeyValueArgItem{Key: "restrict", Value: "on"})
	}

	for _, pf := range ports {
		hostIPStr := ""
		if pf.HostIP != nil {
			hostIPStr = pf.HostIP.String()
		}

		userNetdevValues = append(userNetdevValues, qemucli.KeyValueArgItem{
			Key:   "hostfwd",
			Value: "tcp:" + hostIPStr + ":" + utils.UintToStr(pf.HostPort) + "-:" + utils.UintToStr(pf.VMPort),
		})
	}

	netdevArg, err := qemucli.NewKeyValueArg("netdev", userNetdevValues)
	if err != nil {
		return nil, errors.Wrap(err, "create netdev key-value arg")
	}

	deviceArg, err := qemucli.NewKeyValueArg("device", []qemucli.KeyValueArgItem{{Key: "driver", Value: "virtio-net"}, {Key: "netdev", Value: netID}})
	if err != nil {
		return nil, errors.Wrap(err, "create device key-value arg")
	}

	args := []qemucli.Arg{
		netdevArg,
		deviceArg,
	}

	return args, nil
}

func configureVMCmdTapNetwork(tapName string) ([]qemucli.Arg, error) {
	err := nettap.ValidateTapName(tapName)
	if err != nil {
		return nil, errors.Wrapf(err, "validate network tap name '%v'", tapName)
	}

	netID := getUniqueQEMUNetID()

	netdevArg, err := qemucli.NewKeyValueArg("netdev", []qemucli.KeyValueArgItem{{Key: "type", Value: "tap"}, {Key: "id", Value: netID}, {Key: "ifname", Value: tapName}, {Key: "script", Value: "no"}, {Key: "downscript", Value: "no"}})
	if err != nil {
		return nil, errors.Wrap(err, "create netdev key-value arg")
	}

	deviceArg, err := qemucli.NewKeyValueArg("device", []qemucli.KeyValueArgItem{{Key: "driver", Value: "virtio-net"}, {Key: "netdev", Value: netID}})
	if err != nil {
		return nil, errors.Wrap(err, "create device key-value arg")
	}

	return []qemucli.Arg{netdevArg, deviceArg}, nil
}

func configureVMCmdNetworking(logger *slog.Logger, cfg Config, sshPort uint16) ([]qemucli.Arg, error) {
	// SSH port config.
	ports := []PortForwardingRule{{
		HostIP:   net.ParseIP("127.0.0.1"),
		HostPort: sshPort,
		VMPort:   22,
	}}

	ports = append(ports, cfg.ExtraPortForwardingRules...)

	if cfg.UnrestrictedNetworking {
		logger.Warn("Using unrestricted VM networking")
	}

	args, err := configureVMCmdUserNetwork(ports, cfg.UnrestrictedNetworking)
	if err != nil {
		return nil, errors.Wrap(err, "configure vm cmd user network")
	}

	for i, tap := range cfg.Taps {
		tapNetArgs, err := configureVMCmdTapNetwork(tap.Name)
		if err != nil {
			return nil, errors.Wrapf(err, "configure tap network #%v", i)
		}

		args = append(args, tapNetArgs...)
	}

	return args, nil
}

func configureVMCmdDrives(cfg Config) ([]qemucli.Arg, error) {
	var args []qemucli.Arg

	for i, drive := range cfg.Drives {
		_, err := os.Stat(filepath.Clean(drive.Path))
		if err != nil {
			return nil, errors.Wrapf(err, "stat drive #%v path", i)
		}

		driveID := getUniqueQEMUDriveID()
		drivePath := cleanQEMUPath(drive.Path)

		driveKVItems := []qemucli.KeyValueArgItem{
			{Key: "file", Value: drivePath},
			{Key: "format", Value: "qcow2"},
			{Key: "if", Value: "none"},
			{Key: "id", Value: driveID},
		}

		if drive.SnapshotMode {
			driveKVItems = append(driveKVItems, qemucli.KeyValueArgItem{
				Key:   "snapshot",
				Value: "on",
			})
		}

		deviceKVItems := []qemucli.KeyValueArgItem{
			{Key: "driver", Value: "virtio-blk-pci"},
			{Key: "drive", Value: driveID},
		}

		if cfg.CdromImagePath == "" {
			deviceKVItems = append(deviceKVItems, qemucli.KeyValueArgItem{
				Key:   "bootindex",
				Value: utils.IntToStr(i),
			})
		}

		driveArg, err := qemucli.NewKeyValueArg("drive", driveKVItems)
		if err != nil {
			return nil, errors.Wrapf(err, "create drive key-value arg (path '%v')", drivePath)
		}

		deviceArg, err := qemucli.NewKeyValueArg("device", deviceKVItems)
		if err != nil {
			return nil, errors.Wrapf(err, "create device key-value arg (path '%v')", drivePath)
		}

		args = append(args, driveArg, deviceArg)
	}

	return args, nil
}

func configureVMCmdUSBPassthrough(cfg Config) []qemucli.Arg {
	var args []qemucli.Arg

	if len(cfg.PassthroughConfig.USB) != 0 {
		args = append(args, qemucli.MustNewKeyValueArg("device", []qemucli.KeyValueArgItem{{Key: "driver", Value: "nec-usb-xhci"}}))

		for _, dev := range cfg.PassthroughConfig.USB {
			args = append(args, qemucli.MustNewKeyValueArg("device", []qemucli.KeyValueArgItem{
				{Key: "driver", Value: "usb-host"},
				{Key: "vendorid", Value: "0x" + hex.EncodeToString(utils.Uint16ToBytesBE(dev.VendorID))},
				{Key: "productid", Value: "0x" + hex.EncodeToString(utils.Uint16ToBytesBE(dev.ProductID))},
			}))
		}
	}

	return args
}

func configureVMCmdBlockDevicePassthrough(logger *slog.Logger, cfg Config) ([]qemucli.Arg, error) {
	var args []qemucli.Arg

	if len(cfg.PassthroughConfig.Block) != 0 {
		logger.Warn("Using raw block device passthrough. Please note that it's YOUR responsibility to ensure that no device is mounted in your OS and the VM at the same time. Otherwise, you run serious risks. No further warnings will be issued.")
	}

	for _, dev := range cfg.PassthroughConfig.Block {
		// It's always a user's responsibility to ensure that no drives are mounted
		// in both host and guest system. This should serve as the last resort.
		{
			seemsMounted, err := osspecifics.CheckDeviceSeemsMounted(dev.Path)
			if err != nil {
				return nil, errors.Wrapf(err, "check whether device seems to be mounted (path '%v')", dev.Path)
			}

			if seemsMounted {
				return nil, fmt.Errorf("device '%v' seems to be already mounted in the host system", dev.Path)
			}
		}

		devPath := cleanQEMUPath(dev.Path)

		driveArg, err := qemucli.NewKeyValueArg("drive", []qemucli.KeyValueArgItem{
			{Key: "file", Value: devPath},
			{Key: "format", Value: "raw"},
			{Key: "if", Value: "virtio"},
			{Key: "cache", Value: "none"},
		})
		if err != nil {
			return nil, errors.Wrapf(err, "create drive key-value arg (path '%v')", devPath)
		}

		args = append(args, driveArg)
	}

	return args, nil
}