/*
Copyright 2018 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package cephfs

import (
	"bytes"
	"errors"
	"fmt"
	"os"
	"os/exec"
)

const (
	volumeMounterFuse   = "fuse"
	volumeMounterKernel = "kernel"
)

var (
	availableMounters []string
)

// Load available ceph mounters installed on system into availableMounters
// Called from driver.go's Run()
func loadAvailableMounters() error {
	// #nosec
	fuseMounterProbe := exec.Command("ceph-fuse", "--version")
	// #nosec
	kernelMounterProbe := exec.Command("mount.ceph")

	if fuseMounterProbe.Run() == nil {
		availableMounters = append(availableMounters, volumeMounterFuse)
	}

	if kernelMounterProbe.Run() == nil {
		availableMounters = append(availableMounters, volumeMounterKernel)
	}

	if len(availableMounters) == 0 {
		return errors.New("no ceph mounters found on system")
	}

	return nil
}

type volumeMounter interface {
	mount(mountPoint string, cr *credentials, volOptions *volumeOptions, volID volumeID) error
	name() string
}

func newMounter(volOptions *volumeOptions) (volumeMounter, error) {
	// Get the mounter from the configuration

	wantMounter := volOptions.Mounter

	if wantMounter == "" {
		wantMounter = DefaultVolumeMounter
	}

	// Verify that it's available

	var chosenMounter string

	for _, availMounter := range availableMounters {
		if chosenMounter == "" {
			if availMounter == wantMounter {
				chosenMounter = wantMounter
			}
		}
	}

	if chosenMounter == "" {
		// Otherwise pick whatever is left
		chosenMounter = availableMounters[0]
	}

	// Create the mounter

	switch chosenMounter {
	case volumeMounterFuse:
		return &fuseMounter{}, nil
	case volumeMounterKernel:
		return &kernelMounter{}, nil
	}

	return nil, fmt.Errorf("unknown mounter '%s'", chosenMounter)
}

type fuseMounter struct{}

func mountFuse(mountPoint string, cr *credentials, volOptions *volumeOptions, volID volumeID) error {
	args := [...]string{
		mountPoint,
		"-m", volOptions.Monitors,
		"-c", cephConfigPath,
		"-n", cephEntityClientPrefix + cr.id, "--key=" + cr.key,
		"-r", volOptions.RootPath,
		"-o", "nonempty",
	}

	_, stderr, err := execCommand("ceph-fuse", args[:]...)
	if err != nil {
		return err
	}

	if !bytes.Contains(stderr, []byte("starting fuse")) {
		return fmt.Errorf("ceph-fuse failed: %s", stderr)
	}

	return nil
}

func (m *fuseMounter) mount(mountPoint string, cr *credentials, volOptions *volumeOptions, volID volumeID) error {
	if err := createMountPoint(mountPoint); err != nil {
		return err
	}

	return mountFuse(mountPoint, cr, volOptions, volID)
}

func (m *fuseMounter) name() string { return "Ceph FUSE driver" }

type kernelMounter struct{}

func mountKernel(mountPoint string, cr *credentials, volOptions *volumeOptions, volID volumeID) error {
	if err := execCommandErr("modprobe", "ceph"); err != nil {
		return err
	}

	return execCommandErr("mount",
		"-t", "ceph",
		fmt.Sprintf("%s:%s", volOptions.Monitors, volOptions.RootPath),
		mountPoint,
		"-o", fmt.Sprintf("name=%s,secret=%s", cr.id, cr.key),
	)
}

func (m *kernelMounter) mount(mountPoint string, cr *credentials, volOptions *volumeOptions, volID volumeID) error {
	if err := createMountPoint(mountPoint); err != nil {
		return err
	}

	return mountKernel(mountPoint, cr, volOptions, volID)
}

func (m *kernelMounter) name() string { return "Ceph kernel client" }

func bindMount(from, to string, readOnly bool) error {
	if err := execCommandErr("mount", "--bind", from, to); err != nil {
		return fmt.Errorf("failed to bind-mount %s to %s: %v", from, to, err)
	}

	if readOnly {
		if err := execCommandErr("mount", "-o", "remount,ro,bind", to); err != nil {
			return fmt.Errorf("failed read-only remount of %s: %v", to, err)
		}
	}

	return nil
}

func unmountVolume(mountPoint string) error {
	return execCommandErr("umount", mountPoint)
}

func createMountPoint(root string) error {
	return os.MkdirAll(root, 0750)
}