package mountlib

import (
	"context"
	"errors"
	"log"
	"sort"
	"sync"
	"time"

	"github.com/rclone/rclone/fs"
	"github.com/rclone/rclone/fs/rc"
	"github.com/rclone/rclone/vfs"
	"github.com/rclone/rclone/vfs/vfsflags"
)

var (
	// mutex to protect all the variables in this block
	mountMu sync.Mutex
	// Mount functions available
	mountFns = map[string]MountFn{}
	// Map of mounted path => MountInfo
	liveMounts = map[string]*MountPoint{}
	// Supported mount types
	supportedMountTypes = []string{"mount", "cmount", "mount2"}
)

// ResolveMountMethod returns mount function by name
func ResolveMountMethod(mountType string) (string, MountFn) {
	if mountType != "" {
		return mountType, mountFns[mountType]
	}
	for _, mountType := range supportedMountTypes {
		if mountFns[mountType] != nil {
			return mountType, mountFns[mountType]
		}
	}
	return "", nil
}

// AddRc adds mount and unmount functionality to rc
func AddRc(mountUtilName string, mountFunction MountFn) {
	mountMu.Lock()
	defer mountMu.Unlock()
	// rcMount allows the mount command to be run from rc
	mountFns[mountUtilName] = mountFunction
}

func init() {
	rc.Add(rc.Call{
		Path:         "mount/mount",
		AuthRequired: true,
		Fn:           mountRc,
		Title:        "Create a new mount point",
		Help: `rclone allows Linux, FreeBSD, macOS and Windows to mount any of
Rclone's cloud storage systems as a file system with FUSE.

If no mountType is provided, the priority is given as follows: 1. mount 2.cmount 3.mount2

This takes the following parameters:

- fs - a remote path to be mounted (required)
- mountPoint: valid path on the local machine (required)
- mountType: one of the values (mount, cmount, mount2) specifies the mount implementation to use
- mountOpt: a JSON object with Mount options in.
- vfsOpt: a JSON object with VFS options in.

Example:

    rclone rc mount/mount fs=mydrive: mountPoint=/home/<user>/mountPoint
    rclone rc mount/mount fs=mydrive: mountPoint=/home/<user>/mountPoint mountType=mount
    rclone rc mount/mount fs=TestDrive: mountPoint=/mnt/tmp vfsOpt='{"CacheMode": 2}' mountOpt='{"AllowOther": true}'

The vfsOpt are as described in options/get and can be seen in the the
"vfs" section when running and the mountOpt can be seen in the "mount" section:

    rclone rc options/get
`,
	})
}

// mountRc allows the mount command to be run from rc
func mountRc(ctx context.Context, in rc.Params) (out rc.Params, err error) {
	mountPoint, err := in.GetString("mountPoint")
	if err != nil {
		return nil, err
	}

	vfsOpt := vfsflags.Opt
	err = in.GetStructMissingOK("vfsOpt", &vfsOpt)
	if err != nil {
		return nil, err
	}

	mountOpt := Opt
	err = in.GetStructMissingOK("mountOpt", &mountOpt)
	if err != nil {
		return nil, err
	}

	mountType, err := in.GetString("mountType")

	mountMu.Lock()
	defer mountMu.Unlock()

	if err != nil {
		mountType = ""
	}
	mountType, mountFn := ResolveMountMethod(mountType)
	if mountFn == nil {
		return nil, errors.New("Mount Option specified is not registered, or is invalid")
	}

	// Get Fs.fs to be mounted from fs parameter in the params
	fdst, err := rc.GetFs(ctx, in)
	if err != nil {
		return nil, err
	}

	VFS := vfs.New(fdst, &vfsOpt)
	_, unmountFn, err := mountFn(VFS, mountPoint, &mountOpt)
	if err != nil {
		log.Printf("mount FAILED: %v", err)
		return nil, err
	}

	// Add mount to list if mount point was successfully created
	liveMounts[mountPoint] = &MountPoint{
		MountPoint: mountPoint,
		MountedOn:  time.Now(),
		MountFn:    mountFn,
		UnmountFn:  unmountFn,
		MountOpt:   mountOpt,
		VFSOpt:     vfsOpt,
		Fs:         fdst,
	}

	fs.Debugf(nil, "Mount for %s created at %s using %s", fdst.String(), mountPoint, mountType)
	return nil, nil
}

func init() {
	rc.Add(rc.Call{
		Path:         "mount/unmount",
		AuthRequired: true,
		Fn:           unMountRc,
		Title:        "Unmount selected active mount",
		Help: `
rclone allows Linux, FreeBSD, macOS and Windows to
mount any of Rclone's cloud storage systems as a file system with
FUSE.

This takes the following parameters:

- mountPoint: valid path on the local machine where the mount was created (required)

Example:

    rclone rc mount/unmount mountPoint=/home/<user>/mountPoint
`,
	})
}

// unMountRc allows the umount command to be run from rc
func unMountRc(_ context.Context, in rc.Params) (out rc.Params, err error) {
	mountPoint, err := in.GetString("mountPoint")
	if err != nil {
		return nil, err
	}
	mountMu.Lock()
	defer mountMu.Unlock()
	mountInfo, found := liveMounts[mountPoint]
	if !found {
		return nil, errors.New("mount not found")
	}
	if err = mountInfo.Unmount(); err != nil {
		return nil, err
	}
	delete(liveMounts, mountPoint)
	return nil, nil
}

func init() {
	rc.Add(rc.Call{
		Path:         "mount/types",
		AuthRequired: true,
		Fn:           mountTypesRc,
		Title:        "Show all possible mount types",
		Help: `This shows all possible mount types and returns them as a list.

This takes no parameters and returns

- mountTypes: list of mount types

The mount types are strings like "mount", "mount2", "cmount" and can
be passed to mount/mount as the mountType parameter.

Eg

    rclone rc mount/types
`,
	})
}

// mountTypesRc returns a list of available mount types.
func mountTypesRc(_ context.Context, in rc.Params) (out rc.Params, err error) {
	var mountTypes = []string{}
	mountMu.Lock()
	defer mountMu.Unlock()
	for mountType := range mountFns {
		mountTypes = append(mountTypes, mountType)
	}
	sort.Strings(mountTypes)
	return rc.Params{
		"mountTypes": mountTypes,
	}, nil
}

func init() {
	rc.Add(rc.Call{
		Path:         "mount/listmounts",
		AuthRequired: true,
		Fn:           listMountsRc,
		Title:        "Show current mount points",
		Help: `This shows currently mounted points, which can be used for performing an unmount.

This takes no parameters and returns

- mountPoints: list of current mount points

Eg

    rclone rc mount/listmounts
`,
	})
}

// MountInfo is a transitional structure for json marshaling
type MountInfo struct {
	Fs         string    `json:"Fs"`
	MountPoint string    `json:"MountPoint"`
	MountedOn  time.Time `json:"MountedOn"`
}

// listMountsRc returns a list of current mounts sorted by mount path
func listMountsRc(_ context.Context, in rc.Params) (out rc.Params, err error) {
	mountMu.Lock()
	defer mountMu.Unlock()
	var keys []string
	for key := range liveMounts {
		keys = append(keys, key)
	}
	sort.Strings(keys)
	mountPoints := []MountInfo{}
	for _, k := range keys {
		m := liveMounts[k]
		info := MountInfo{
			Fs:         m.Fs.Name(),
			MountPoint: m.MountPoint,
			MountedOn:  m.MountedOn,
		}
		mountPoints = append(mountPoints, info)
	}
	return rc.Params{
		"mountPoints": mountPoints,
	}, nil
}

func init() {
	rc.Add(rc.Call{
		Path:         "mount/unmountall",
		AuthRequired: true,
		Fn:           unmountAll,
		Title:        "Show current mount points",
		Help: `This shows currently mounted points, which can be used for performing an unmount.

This takes no parameters and returns error if unmount does not succeed.

Eg

    rclone rc mount/unmountall
`,
	})
}

// unmountAll unmounts all the created mounts
func unmountAll(_ context.Context, in rc.Params) (out rc.Params, err error) {
	mountMu.Lock()
	defer mountMu.Unlock()
	for mountPoint, mountInfo := range liveMounts {
		if err = mountInfo.Unmount(); err != nil {
			fs.Debugf(nil, "Couldn't unmount : %s", mountPoint)
			return nil, err
		}
		delete(liveMounts, mountPoint)
	}
	return nil, nil
}