package mount

import (
	"context"
	"fmt"
	"github.com/rs/zerolog"
	"os"
	"path/filepath"
	"strings"
	"time"

	"github.com/containerd/containerd/mount"
	"github.com/deniswernert/go-fstab"
	"github.com/hashicorp/go-multierror"
	"github.com/joho/godotenv"
	"github.com/kairos-io/immucore/pkg/profile"
	"github.com/kairos-io/kairos/pkg/utils"
	"github.com/spectrocloud-labs/herd"
)

type State struct {
	Logger      zerolog.Logger
	Rootdir     string // e.g. /sysroot inside initrd with pivot, / with nopivot
	TargetImage string // e.g. /cOS/active.img
	TargetLabel string // e.g. COS_ACTIVE

	// /run/cos-layout.env (different!)
	OverlayDir   []string          // e.g. /var
	BindMounts   []string          // e.g. /etc/kubernetes
	CustomMounts map[string]string // e.g. diskid : mountpoint

	StateDir  string // e.g. "/usr/local/.state"
	FStabFile string // e.g. /etc/fstab
	MountRoot bool   // e.g. if true, it tries to find the image to loopback mount

	fstabs []*fstab.Mount
}

const (
	opCustomMounts  = "custom-mount"
	opDiscoverState = "discover-state"
	opMountState    = "mount-state"
	opMountBind     = "mount-bind"

	opMountRoot        = "mount-root"
	opOverlayMount     = "overlay-mount"
	opWriteFstab       = "write-fstab"
	opMountBaseOverlay = "mount-base-overlay"
	opMountOEM         = "mount-oem"

	opRootfsHook = "rootfs-hook"
	opLoadConfig = "load-config"
)

func (s *State) path(p ...string) string {
	return filepath.Join(append([]string{s.Rootdir}, p...)...)
}

func (s *State) WriteFstab(fstabFile string) func(context.Context) error {
	return func(ctx context.Context) error {
		for _, fst := range s.fstabs {
			select {
			case <-ctx.Done():
			default:
				f, err := os.OpenFile(fstabFile,
					os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
				if err != nil {
					return err
				}
				defer f.Close()
				toWrite := fmt.Sprintf("%s\n", fst.String())
				s.Logger.Debug().Str("fstab", toWrite)
				if _, err := f.WriteString(toWrite); err != nil {
					return err
				}
			}
		}
		return nil
	}
}

// ln -sf -t / /sysroot/system
func (s *State) RunStageOp(stage string) func(context.Context) error {
	return func(ctx context.Context) error {
		cmd := fmt.Sprintf("elemental run-stage %s", stage)
		s.Logger.Debug().Str("cmd", cmd)
		_, err := utils.SH(cmd)
		return err
	}
}

func (s *State) MountOP(what, where, t string, options []string, timeout time.Duration) func(context.Context) error {
	s.Logger.Debug().Str("what", what).Str("where", where).Str("type", t)
	return func(c context.Context) error {
		cc := time.After(timeout)
		for {
			select {
			default:
				time.Sleep(1 * time.Second)
				mountPoint := mount.Mount{
					Type:    t,
					Source:  what,
					Options: options,
				}
				tmpFstab := mountToStab(mountPoint)
				tmpFstab.File = where
				op := mountOperation{
					MountOption: mountPoint,
					FstabEntry:  *tmpFstab,
					Target:      where,
				}

				err := op.run()
				if err != nil {
					continue
				}

				s.fstabs = append(s.fstabs, tmpFstab)

				return nil
			case <-c.Done():
				return fmt.Errorf("context canceled")
			case <-cc:
				return fmt.Errorf("timeout exhausted")
			}
		}
	}
}

func (s *State) WriteDAG(g *herd.Graph) (out string) {
	for i, layer := range g.Analyze() {
		out += fmt.Sprintf("%d.\n", (i + 1))
		for _, op := range layer {
			if op.Error != nil {
				out += fmt.Sprintf(" <%s> (error: %s) (background: %t) (weak: %t)\n", op.Name, op.Error.Error(), op.Background, op.WeakDeps)
			} else {
				out += fmt.Sprintf(" <%s> (background: %t) (weak: %t)\n", op.Name, op.Background, op.WeakDeps)
			}
		}
	}
	return
}

func readEnv(file string) (map[string]string, error) {
	var envMap map[string]string
	var err error

	f, err := os.Open(file)
	if err != nil {
		return envMap, err
	}
	defer f.Close()

	envMap, err = godotenv.Parse(f)
	if err != nil {
		return envMap, err
	}

	return envMap, err
}

func (s *State) Register(g *herd.Graph) error {
	var err error

	// TODO: add hooks, fstab (might have missed some), systemd compat
	// TODO: We should also set tmpfs here (not -related)

	// symlink
	// execute the rootfs hook

	// All of this below need to run after rootfs stage runs (so the layout file is created)
	// This is legacy - in UKI we don't need to found the img, this needs to run in a conditional
	if s.MountRoot {
		// setup loopback mount for the image target for booting
		s.Logger.Debug().Str("what", opDiscoverState).Msg("Add operation")
		err = g.Add(opDiscoverState,
			herd.WithDeps(opMountState),
			herd.WithCallback(
				func(ctx context.Context) error {
					_, err := utils.SH(fmt.Sprintf("losetup --show -f /run/initramfs/cos-state%s", s.TargetImage))
					return err
				},
			))
		if err != nil {
			s.Logger.Err(err)
		}

		// mount the state partition so to find the loopback device
		s.Logger.Debug().Str("what", opMountState).Msg("Add operation")
		err = g.Add(opMountState,
			herd.WithCallback(
				s.MountOP(
					"/dev/disk/by-label/COS_STATE",
					s.path("/run/initramfs/cos-state"),
					"auto",
					[]string{
						"ro", // or rw
					}, 60*time.Second),
			),
		)
		if err != nil {
			s.Logger.Err(err)
		}

		// mount the loopback device as root of the fs
		s.Logger.Debug().Str("what", opMountRoot).Msg("Add operation")
		err = g.Add(opMountRoot,
			herd.WithDeps(opDiscoverState),
			herd.WithCallback(
				s.MountOP(
					fmt.Sprintf("/dev/disk/by-label/%s", s.TargetLabel),
					s.Rootdir,
					"auto",
					[]string{
						"ro", // or rw
						"suid",
						"dev",
						"exec",
						"auto",
						"nouser",
						"async",
					}, 60*time.Second),
			),
		)
		if err != nil {
			s.Logger.Err(err)
		}

	}

	// depending on /run/cos-layout.env
	// This is building the mountRoot dependendency if it was enabled
	mountRootCondition := herd.ConditionalOption(func() bool { return s.MountRoot }, herd.WithDeps(opMountRoot))

	// TODO: this needs to be run after state is discovered
	// TODO: add symlink if Rootdir != ""
	// TODO: chroot?
	s.Logger.Debug().Str("what", opRootfsHook).Msg("Add operation")
	err = g.Add(opRootfsHook, mountRootCondition, herd.WithDeps(opMountOEM), herd.WithCallback(s.RunStageOp("rootfs")))
	if err != nil {
		s.Logger.Err(err)
	}

	// /run/cos-layout.env
	// populate state bindmounts, overlaymounts, custommounts
	s.Logger.Debug().Str("what", opLoadConfig).Msg("Add operation")
	err = g.Add(opLoadConfig,
		herd.WithDeps(opRootfsHook),
		herd.WithCallback(func(ctx context.Context) error {

			env, err := readEnv("/run/cos-layout.env")
			if err != nil {
				return err
			}

			// populate from env here
			s.OverlayDir = strings.Split(env["RW_PATHS"], " ")

			// TODO: PERSISTENT_STATE_TARGET /usr/local/.state
			s.BindMounts = strings.Split(env["PERSISTENT_STATE_PATHS"], " ")

			// TODO: this needs to be parsed
			//	s.CustomMounts = strings.Split(env["VOLUMES"], " ")
			return nil
		}))
	if err != nil {
		s.Logger.Err(err)
	}
	// end sysroot mount

	// overlay mount start
	if rootFSType(s.Rootdir) != "overlay" {
		s.Logger.Debug().Str("what", opMountBaseOverlay).Msg("Add operation")
		err = g.Add(opMountBaseOverlay,
			herd.WithCallback(
				func(ctx context.Context) error {
					op, err := baseOverlay(profile.Overlay{
						Base:        "/run/overlay",
						BackingBase: "tmpfs:20%",
					})
					if err != nil {
						return err
					}
					s.fstabs = append(s.fstabs, &op.FstabEntry)
					return op.run()
				},
			),
		)
		if err != nil {
			s.Logger.Err(err)
		}
	}

	overlayCondition := herd.ConditionalOption(func() bool { return rootFSType(s.Rootdir) != "overlay" }, herd.WithDeps(opMountBaseOverlay))
	// TODO: Add fsck
	// mount overlay
	s.Logger.Debug().Str("what", opOverlayMount).Msg("Add operation")
	err = g.Add(
		opOverlayMount,
		overlayCondition,
		herd.WithDeps(opLoadConfig),
		mountRootCondition,
		herd.WithCallback(
			func(ctx context.Context) error {
				var err error
				for _, p := range s.OverlayDir {
					op, err := mountWithBaseOverlay(p, s.Rootdir, "/run/overlay")
					if err != nil {
						return err
					}
					s.fstabs = append(s.fstabs, &op.FstabEntry)
					err = multierror.Append(err, op.run())
				}

				return err
			},
		),
	)
	if err != nil {
		s.Logger.Err(err)
	}
	s.Logger.Debug().Str("what", opCustomMounts).Msg("Add operation")
	err = g.Add(
		opCustomMounts,
		mountRootCondition,
		overlayCondition,
		herd.WithDeps(opLoadConfig),
		herd.WithCallback(func(ctx context.Context) error {
			var err error

			for id, mountpoint := range s.CustomMounts {

				err = multierror.Append(err, s.MountOP(
					id,
					s.path(mountpoint),
					"auto",
					[]string{
						"ro", // or rw
					},
					60*time.Second,
				)(ctx))

			}
			return err
		}),
	)
	if err != nil {
		s.Logger.Err(err)
	}

	// mount state is defined over a custom mount (/usr/local/.state for instance, needs to be mounted over a device)
	s.Logger.Debug().Str("what", opMountBind).Msg("Add operation")
	err = g.Add(
		opMountBind,
		overlayCondition,
		mountRootCondition,
		herd.WithDeps(opCustomMounts, opLoadConfig),
		herd.WithCallback(
			func(ctx context.Context) error {
				var err error

				for _, p := range s.BindMounts {

					op, err := mountBind(p, s.Rootdir, s.StateDir)
					if err != nil {
						return err
					}
					s.fstabs = append(s.fstabs, &op.FstabEntry)
					err = multierror.Append(err, op.run())
				}
				return err
			},
		),
	)
	if err != nil {
		s.Logger.Err(err)
	}

	// overlay mount end
	s.Logger.Debug().Str("what", opMountOEM).Msg("Add operation")
	err = g.Add(opMountOEM,
		overlayCondition,
		mountRootCondition,
		herd.WithCallback(
			s.MountOP(
				"/dev/disk/by-label/COS_OEM",
				s.path("/oem"),
				"auto",
				[]string{
					"rw",
					"suid",
					"dev",
					"exec",
					"noauto",
					"nouser",
					"async",
				}, 60*time.Second),
		),
	)
	if err != nil {
		s.Logger.Err(err)
	}
	s.Logger.Debug().Str("what", opWriteFstab).Msg("Add operation")
	err = g.Add(opWriteFstab,
		overlayCondition,
		mountRootCondition,
		herd.WithDeps(opMountOEM, opCustomMounts, opMountBind, opOverlayMount),
		herd.WeakDeps,
		herd.WithCallback(s.WriteFstab(s.FStabFile)))
	if err != nil {
		s.Logger.Err(err)
	}
	return err
}