package daemon

import (
	"context"
	"errors"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"time"

	"banger/internal/daemon/imagemgr"
	"banger/internal/firecracker"
	"banger/internal/guest"
	"banger/internal/hostnat"
	"banger/internal/model"
	"banger/internal/system"
	"banger/internal/vsockagent"
	"strings"
)

type imageBuildSpec struct {
	ID            string
	Name          string
	SourceRootfs  string
	RootfsPath    string
	BuildLog      io.Writer
	KernelPath    string
	InitrdPath    string
	ModulesDir    string
	Packages      []string
	InstallDocker bool
	Size          string
}

type imageBuildVM struct {
	Name      string
	GuestIP   string
	TapDevice string
	APISock   string
	PID       int
}

func (d *Daemon) runImageBuild(ctx context.Context, spec imageBuildSpec) error {
	if d.imageBuild != nil {
		return d.imageBuild(ctx, spec)
	}
	return d.runImageBuildNative(ctx, spec)
}

func (d *Daemon) runImageBuildNative(ctx context.Context, spec imageBuildSpec) (err error) {
	if err := system.CopyFilePreferClone(spec.SourceRootfs, spec.RootfsPath); err != nil {
		return err
	}
	if spec.Size != "" {
		if err := imagemgr.ResizeRootfs(spec.SourceRootfs, spec.RootfsPath, spec.Size); err != nil {
			return err
		}
	}

	vm, cleanup, err := d.startImageBuildVM(ctx, spec)
	if err != nil {
		return err
	}
	defer func() {
		cleanupErr := cleanup(context.Background())
		if cleanupErr != nil {
			err = errors.Join(err, cleanupErr)
		}
	}()

	sshAddress := vm.GuestIP + ":22"
	if _, err := fmt.Fprintf(spec.BuildLog, "[image.build] waiting for ssh on %s\n", sshAddress); err != nil {
		return err
	}
	waitCtx, cancel := context.WithTimeout(ctx, 60*time.Second)
	defer cancel()
	if err := guest.WaitForSSH(waitCtx, sshAddress, d.config.SSHKeyPath, time.Second); err != nil {
		return err
	}

	client, err := guest.Dial(ctx, sshAddress, d.config.SSHKeyPath)
	if err != nil {
		return err
	}
	defer client.Close()
	authorizedKey, err := guest.AuthorizedPublicKey(d.config.SSHKeyPath)
	if err != nil {
		return err
	}

	vsockAgentPath, err := d.vsockAgentBinary()
	if err != nil {
		return err
	}
	helperBytes, err := os.ReadFile(vsockAgentPath)
	if err != nil {
		return err
	}
	if err := imagemgr.WriteBuildLog(spec.BuildLog, "installing vsock agent"); err != nil {
		return err
	}
	if err := client.UploadFile(ctx, vsockagent.GuestInstallPath, 0o755, helperBytes, spec.BuildLog); err != nil {
		return err
	}
	if err := imagemgr.WriteBuildLog(spec.BuildLog, "configuring guest"); err != nil {
		return err
	}
	if err := client.RunScript(ctx, imagemgr.BuildProvisionScript(vm.Name, d.config.DefaultDNS, string(authorizedKey), spec.Packages, spec.InstallDocker), spec.BuildLog); err != nil {
		return err
	}
	if strings.TrimSpace(spec.ModulesDir) != "" {
		if err := imagemgr.WriteBuildLog(spec.BuildLog, "copying kernel modules"); err != nil {
			return err
		}
		if err := client.StreamTar(ctx, spec.ModulesDir, imagemgr.BuildModulesCommand(filepath.Base(spec.ModulesDir)), spec.BuildLog); err != nil {
			return err
		}
	}
	if err := imagemgr.WriteBuildLog(spec.BuildLog, "shutting down guest"); err != nil {
		return err
	}
	if err := client.RunScript(ctx, "set -e\nsync\n", spec.BuildLog); err != nil {
		return err
	}
	return d.shutdownImageBuildVM(ctx, vm)
}

func (d *Daemon) startImageBuildVM(ctx context.Context, spec imageBuildSpec) (imageBuildVM, func(context.Context) error, error) {
	if err := d.ensureBridge(ctx); err != nil {
		return imageBuildVM{}, nil, err
	}
	if err := d.ensureSocketDir(); err != nil {
		return imageBuildVM{}, nil, err
	}
	fcPath, err := d.firecrackerBinary()
	if err != nil {
		return imageBuildVM{}, nil, err
	}

	shortID := system.ShortID(spec.ID)
	guestIP, err := d.store.NextGuestIP(ctx, bridgePrefix(d.config.BridgeIP))
	if err != nil {
		return imageBuildVM{}, nil, err
	}
	vm := imageBuildVM{
		Name:      "image-build-" + shortID,
		GuestIP:   guestIP,
		TapDevice: "tap-img-" + shortID,
		APISock:   filepath.Join(d.layout.RuntimeDir, "img-"+shortID+".sock"),
	}
	if err := os.RemoveAll(vm.APISock); err != nil && !os.IsNotExist(err) {
		return imageBuildVM{}, nil, err
	}
	if err := d.createTap(ctx, vm.TapDevice); err != nil {
		return imageBuildVM{}, nil, err
	}
	if err := hostnat.Ensure(ctx, d.runner, vm.GuestIP, vm.TapDevice, true); err != nil {
		_, _ = d.runner.RunSudo(ctx, "ip", "link", "del", vm.TapDevice)
		return imageBuildVM{}, nil, err
	}

	firecrackerCtx := context.Background()
	machine, err := firecracker.NewMachine(firecrackerCtx, firecracker.MachineConfig{
		BinaryPath:      fcPath,
		VMID:            spec.ID,
		SocketPath:      vm.APISock,
		LogPath:         spec.RootfsPath + ".firecracker.log",
		MetricsPath:     filepath.Join(filepath.Dir(spec.RootfsPath), "metrics.json"),
		KernelImagePath: spec.KernelPath,
		InitrdPath:      spec.InitrdPath,
		KernelArgs:      system.BuildBootArgsWithKernelIP(vm.Name, vm.GuestIP, d.config.BridgeIP, d.config.DefaultDNS),
		Drives: []firecracker.DriveConfig{{
			ID:       "rootfs",
			Path:     spec.RootfsPath,
			ReadOnly: false,
			IsRoot:   true,
		}},
		TapDevice: vm.TapDevice,
		VCPUCount: model.DefaultVCPUCount,
		MemoryMiB: model.DefaultMemoryMiB,
		Logger:    d.logger,
	})
	if err != nil {
		_ = hostnat.Ensure(ctx, d.runner, vm.GuestIP, vm.TapDevice, false)
		_, _ = d.runner.RunSudo(ctx, "ip", "link", "del", vm.TapDevice)
		return imageBuildVM{}, nil, err
	}
	if err := machine.Start(firecrackerCtx); err != nil {
		_ = hostnat.Ensure(ctx, d.runner, vm.GuestIP, vm.TapDevice, false)
		_, _ = d.runner.RunSudo(ctx, "ip", "link", "del", vm.TapDevice)
		return imageBuildVM{}, nil, err
	}
	vm.PID = d.resolveFirecrackerPID(firecrackerCtx, machine, vm.APISock)
	if err := d.ensureSocketAccess(ctx, vm.APISock, "firecracker api socket"); err != nil {
		_ = d.killVMProcess(context.Background(), vm.PID)
		_ = hostnat.Ensure(ctx, d.runner, vm.GuestIP, vm.TapDevice, false)
		_, _ = d.runner.RunSudo(ctx, "ip", "link", "del", vm.TapDevice)
		return imageBuildVM{}, nil, err
	}

	cleanup := func(cleanupCtx context.Context) error {
		if vm.PID > 0 && system.ProcessRunning(vm.PID, vm.APISock) {
			_ = d.killVMProcess(cleanupCtx, vm.PID)
			_ = d.waitForExit(cleanupCtx, vm.PID, vm.APISock, 10*time.Second)
		}
		_ = hostnat.Ensure(cleanupCtx, d.runner, vm.GuestIP, vm.TapDevice, false)
		if vm.TapDevice != "" {
			_, _ = d.runner.RunSudo(cleanupCtx, "ip", "link", "del", vm.TapDevice)
		}
		if vm.APISock != "" {
			_ = os.Remove(vm.APISock)
		}
		return nil
	}
	return vm, cleanup, nil
}

func (d *Daemon) shutdownImageBuildVM(ctx context.Context, vm imageBuildVM) error {
	buildVM := model.VMRecord{Runtime: model.VMRuntime{APISockPath: vm.APISock}}
	if err := d.sendCtrlAltDel(ctx, buildVM); err != nil {
		return err
	}
	return d.waitForExit(ctx, vm.PID, vm.APISock, 15*time.Second)
}