package vfs

import (
	"fmt"
	"github.com/golang/glog"
	"io"
	"io/ioutil"
	"k8s.io/kops/util/pkg/hashing"
	"os"
	"path"
	"sync"
)

type FSPath struct {
	location string
}

var _ Path = &FSPath{}
var _ HasHash = &FSPath{}

func NewFSPath(location string) *FSPath {
	return &FSPath{location: location}
}

func (p *FSPath) Join(relativePath ...string) Path {
	args := []string{p.location}
	args = append(args, relativePath...)
	joined := path.Join(args...)
	return &FSPath{location: joined}
}

func (p *FSPath) WriteFile(data []byte) error {
	dir := path.Dir(p.location)
	err := os.MkdirAll(dir, 0755)
	if err != nil {
		return fmt.Errorf("error creating directories %q: %v", dir, err)
	}

	f, err := ioutil.TempFile(dir, "tmp")
	if err != nil {
		return fmt.Errorf("error creating temp file in %q: %v", dir, err)
	}

	// Note from here on in we have to close f and delete or rename the temp file
	tempfile := f.Name()

	n, err := f.Write(data)
	if err == nil && n < len(data) {
		err = io.ErrShortWrite
	}

	if closeErr := f.Close(); err == nil {
		err = closeErr
	}

	if err == nil {
		err = os.Rename(tempfile, p.location)
		if err != nil {
			err = fmt.Errorf("error during file write of %q: rename failed: %v", p.location, err)
		}
	}

	if err == nil {
		return nil
	}

	// Something went wrong; try to remove the temp file
	if removeErr := os.Remove(tempfile); removeErr != nil {
		glog.Warningf("unable to remove temp file %q: %v", tempfile, removeErr)
	}

	return err
}

// To prevent concurrent creates on the same file while maintaining atomicity of writes,
// we take a process-wide lock during the operation.
// Not a great approach, but fine for a single process (with low concurrency)
// TODO: should we take a file lock or equivalent here?  Can we use RENAME_NOREPLACE ?
var createFileLock sync.Mutex

func (p *FSPath) CreateFile(data []byte) error {
	createFileLock.Lock()
	defer createFileLock.Unlock()

	// Check if exists
	_, err := os.Stat(p.location)
	if err == nil {
		return os.ErrExist
	}

	if !os.IsNotExist(err) {
		return err
	}

	return p.WriteFile(data)
}

func (p *FSPath) ReadFile() ([]byte, error) {
	return ioutil.ReadFile(p.location)
}

func (p *FSPath) ReadDir() ([]Path, error) {
	files, err := ioutil.ReadDir(p.location)
	if err != nil {
		if os.IsNotExist(err) {
			return nil, err
		}
		return nil, err
	}
	var paths []Path
	for _, f := range files {
		paths = append(paths, NewFSPath(path.Join(p.location, f.Name())))
	}
	return paths, nil
}

func (p *FSPath) ReadTree() ([]Path, error) {
	var paths []Path
	err := readTree(p.location, &paths)
	if err != nil {
		return nil, err
	}
	return paths, nil
}

func readTree(base string, dest *[]Path) error {
	files, err := ioutil.ReadDir(base)
	if err != nil {
		return err
	}
	for _, f := range files {
		p := path.Join(base, f.Name())
		*dest = append(*dest, NewFSPath(p))
		if f.IsDir() {
			err = readTree(p, dest)
			if err != nil {
				return err
			}
		}
	}
	return nil
}

func (p *FSPath) Base() string {
	return path.Base(p.location)
}

func (p *FSPath) Path() string {
	return p.location
}

func (p *FSPath) String() string {
	return p.Path()
}

func (p *FSPath) Remove() error {
	return os.Remove(p.location)
}

func (p *FSPath) PreferredHash() (*hashing.Hash, error) {
	return p.Hash(hashing.HashAlgorithmSHA256)
}

func (p *FSPath) Hash(a hashing.HashAlgorithm) (*hashing.Hash, error) {
	glog.V(2).Infof("hashing file %q", p.location)

	return a.HashFile(p.location)
}