// Copyright 2015 CoreOS, Inc.
//
// 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 system

import (
	"bufio"
	"bytes"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"os"
	"os/exec"
	"path/filepath"
	"strconv"
	"strings"
	"syscall"
	"unicode"

	"github.com/vtolstov/go-ioctl"
)

func rootMount() (string, error) {
	var err error
	var device string

	f, err := os.Open("/proc/self/mounts")
	if err != nil {
		return device, err
	}
	defer f.Close()
	br := bufio.NewReader(f)

	for {
		line, err := br.ReadString('\n')
		if err != nil {
			break
		}

		fields := strings.Fields(line)
		if fields[1] != "/" || fields[0][0] != '/' {
			continue
		}
		fi, err := os.Stat(fields[0])
		if err != nil {
			return device, err
		}

		if fi.Mode()&os.ModeSymlink == 0 {
			device, err = filepath.EvalSymlinks(fields[0])
			if err != nil {
				return device, err
			}
		} else {
			device = fields[0]
		}
	}
	return device, nil
}

func rootDevice() (string, error) {
	var device string

	mountpoint, err := rootMount()
	if err != nil {
		return device, err
	}

	numstrip := func(r rune) rune {
		if unicode.IsNumber(r) {
			return -1
		}
		return r
	}
	return strings.Map(numstrip, mountpoint), nil
}

func ResizeRootFS() error {
	var err error
	var stdout io.ReadCloser
	var stdin bytes.Buffer

	partstart := 0
	partnum := 0
	device := "/tmp/resize_dev"
	partition := "/tmp/resize_part"
	active := false
	extended := false
	parttype := "Linux"
	devFs, err := findFs()
	if err != nil {
		return err
	}
	devBlk, err := findBlock("/sys/block", devFs)
	if err != nil {
		return err
	}
	if err = syscall.Mknod(device, uint32(os.ModeDevice|syscall.S_IFBLK|0600), devBlk.Int()); err != nil {
		return err
	}
	//	defer os.Remove(device)
	//	mbr := make([]byte, 446)

	/*
		f, err := os.OpenFile(device, os.O_RDONLY, os.FileMode(0400))
		if err != nil {
			return err
		}
		_, err = io.ReadFull(f, mbr)
		f.Close()
		if err != nil {
			return err
		}
	*/
	cmd := exec.Command("fdisk", "-l", "-u", device)
	stdout, err = cmd.StdoutPipe()
	if err != nil {
		log.Printf("failed to open %s via fdisk %s 2\n", device, err.Error())
		return err
	}
	r := bufio.NewReader(stdout)

	if err = cmd.Start(); err != nil {
		log.Printf("failed to open %s via fdisk %s 3\n", device, err.Error())
		return err
	}

	for {
		line, err := r.ReadString('\n')
		if err != nil {
			break
		}

		if strings.HasPrefix(line, device) {
			partnum += 1
			///test3        *  16384 204799  188416  92M  5 Extended
			ps := strings.Fields(line)
			if ps[1] == "*" {
				active = true
				partstart, _ = strconv.Atoi(ps[2])
				if len(ps) > 7 {
					parttype = ps[6]
					if ps[7] == "Extended" {
						extended = true
					}
				} else {
					parttype = ps[5]
					if ps[6] == "Extended" {
						extended = true
					}
				}
			} else {
				active = false
				partstart, _ = strconv.Atoi(ps[1])
				if len(ps) > 6 {
					parttype = ps[5]
					if ps[6] == "Extended" {
						extended = true
					}
				} else {
					parttype = ps[4]
					if ps[5] == "Extended" {
						extended = true
					}
				}
			}
		}
	}

	if err = cmd.Wait(); err != nil || partstart == 0 {
		return fmt.Errorf("failed to open %s via fdisk 4\n", device)
	}
	if partnum > 1 {
		stdin.Write([]byte("d\n" + fmt.Sprintf("%d", partnum) + "\n"))
	} else {
		stdin.Write([]byte("d\n"))
	}
	if extended {
		stdin.Write([]byte("n\nl\n" + fmt.Sprintf("%d", partnum) + "\n" + fmt.Sprintf("%d", partstart) + "\n\n"))
	} else {
		stdin.Write([]byte("n\np\n" + fmt.Sprintf("%d", partnum) + "\n" + fmt.Sprintf("%d", partstart) + "\n\n"))
	}
	if active {
		stdin.Write([]byte("a\n" + fmt.Sprintf("%d", partnum) + "\n"))
	}
	stdin.Write([]byte("t\n" + fmt.Sprintf("%d", partnum) + "\n" + parttype + "\nw"))
	cmd = exec.Command("fdisk", "-u", device)
	cmd.Stdin = &stdin
	cmd.Run()
	stdin.Reset()

	w, err := os.OpenFile(device, os.O_WRONLY, 0600)
	if err != nil {
		return err
	}
	/*
		_, err = w.Write(mbr)
		if err != nil {
			return err
		}
		err = w.Sync()
		if err != nil {
			return err
		}
	*/
	blkerr := ioctl.BlkRRPart(w.Fd())
	err = w.Close()
	if err != nil {
		return err
	}
	if blkerr != nil {
		args := []string{}
		for _, name := range []string{"partx", "partprobe", "kpartx"} {
			if _, err = exec.LookPath(name); err == nil {
				switch name {
				case "partx":
					args = []string{"-u", device}
				default:
					args = []string{device}
				}
				log.Printf("update partition table via %s %s", name, strings.Join(args, " "))
				if err = exec.Command(name, args...).Run(); err == nil {
					break
				}
			}
		}
	}

	if err = syscall.Mknod(partition, uint32(os.ModeDevice|syscall.S_IFBLK|0600), devFs.Int()); err != nil {
		return err
	}
	//	defer os.Remove(partition)
	log.Printf("resize filesystem via %s %s", "resize2fs", partition)
	buf, err := exec.Command("resize2fs", partition).CombinedOutput()
	if err != nil {
		log.Printf("resize2fs %s", buf)
		return err
	}
	return nil
}

type Dev struct {
	Major uint64
	Minor uint64
}

func (d *Dev) String() string {
	return fmt.Sprintf("%d:%d", d.Major, d.Minor)
}

func (d *Dev) Int() int {
	return int(d.Major*256 + d.Minor)
}

func findFs() (*Dev, error) {
	var st syscall.Stat_t

	err := syscall.Stat("/", &st)
	if err != nil {
		return nil, err
	}
	return &Dev{Major: uint64(st.Dev / 256), Minor: uint64(st.Dev % 256)}, nil
}

func findBlock(start string, s *Dev) (*Dev, error) {
	var err error
	fis, err := ioutil.ReadDir(start)
	if err != nil {
		return nil, err
	}
	for _, fi := range fis {
		switch fi.Name() {
		case "bdi", "subsystem", "device", "trace":
			continue
		}
		if _, err := os.Stat(filepath.Join(start, "dev")); err == nil {
			if buf, err := ioutil.ReadFile(filepath.Join(start, "dev")); err == nil {
				dev := strings.TrimSpace(string(buf))
				if s.String() == dev {
					if buf, err = ioutil.ReadFile(filepath.Join(filepath.Dir(start), "dev")); err == nil {
						majorminor := strings.Split(strings.TrimSpace(string(buf)), ":")
						major, _ := strconv.Atoi(majorminor[0])
						minor, _ := strconv.Atoi(majorminor[1])
						return &Dev{Major: uint64(major), Minor: uint64(minor)}, nil
					}
				}
			}
		}
		devBlk, err := findBlock(filepath.Join(start, fi.Name()), s)
		if err == nil {
			return devBlk, err
		}
	}
	return nil, errors.New("failed to find dev")
}