bagage/s3_fs.go

package main

import (
	"context"
	"errors"
	"io"
	"log"
	"os"
	"path"
	"strings"
	"time"

	"github.com/minio/minio-go/v7"
	"golang.org/x/net/webdav"
)

/*
 * S3FS lifetime is limited to a single request
 * Conversely, Golang's abstraction has been thought to be shared between users
 * Sharing an instance between users would be very dangerous (as we would need many checks between shared values)
 */
type S3FS struct {
	cache map[string]*S3Stat
	mc    *minio.Client
	ctx   context.Context
}

func NewS3FS(mc *minio.Client) S3FS {
	return S3FS{
		cache: make(map[string]*S3Stat),
		mc:    mc,
	}
}

func (s S3FS) Mkdir(ctx context.Context, name string, perm os.FileMode) error {
	s.ctx = ctx

	p := NewS3Path(name)

	if p.class == ROOT {
		return errors.New("Unable to create another root folder")
	} else if p.class == BUCKET {
		log.Println("Creating bucket is not implemented yet")
		return nil
	}

	f, err := NewS3File(&s, path.Join(name, ".bagage"))
	if err != nil {
		return err
	}
	defer f.Close()

	_, err = io.Copy(f, strings.NewReader("This is a placeholder"))
	return nil
}

func (s S3FS) OpenFile(ctx context.Context, name string, flag int, perm os.FileMode) (webdav.File, error) {
	s.ctx = ctx

	// If the file does not exist when opening it, we create a stub
	if _, ok := s.cache[name]; !ok {
		st := new(S3Stat)
		st.fs = &s
		st.path = NewS3Path(name)
		st.path.class = OBJECT
		st.obj.Key = st.path.key
		st.obj.LastModified = time.Now()
		s.cache[name] = st
	}

	return NewS3File(&s, name)
}

func (s S3FS) RemoveAll(ctx context.Context, name string) error {
	//@FIXME nautilus deletes files one by one, at the end, it does not find its folder as it is "already deleted"
	s.ctx = ctx

	p := NewS3Path(name)
	if p.class == ROOT {
		return errors.New("Unable to create another root folder")
	} else if p.class == BUCKET {
		log.Println("Deleting bucket is not implemented yet")
		return nil
	}

	objCh := s.mc.ListObjects(s.ctx, p.bucket, minio.ListObjectsOptions{Prefix: p.key, Recursive: true})
	rmCh := s.mc.RemoveObjects(s.ctx, p.bucket, objCh, minio.RemoveObjectsOptions{})

	for rErr := range rmCh {
		return rErr.Err
	}

	return nil
}

func (s S3FS) Rename(ctx context.Context, oldName, newName string) error {
	s.ctx = ctx

	po := NewS3Path(oldName)
	pn := NewS3Path(newName)
	if po.class == ROOT || pn.class == ROOT {
		return errors.New("Unable to rename root folder")
	} else if po.class == BUCKET || pn.class == BUCKET {
		log.Println("Moving a bucket is not implemented yet")
		return nil
	}

	//Check that newName is not inside oldName
	if len(newName) > len(oldName) && newName[:len(oldName)] == oldName {
		return errors.New("Cannot move an entity inside itself (eg. moving /data in /data/test is impossible)")
	}

	//Gather all keys, copy the object, delete the original
	objCh := s.mc.ListObjects(s.ctx, po.bucket, minio.ListObjectsOptions{Prefix: po.key, Recursive: true})
	for obj := range objCh {
		src := minio.CopySrcOptions{
			Bucket: po.bucket,
			Object: obj.Key,
		}

		dst := minio.CopyDestOptions{
			Bucket: pn.bucket,
			Object: path.Join(pn.key, obj.Key[len(po.key):]),
		}

		_, err := s.mc.CopyObject(s.ctx, dst, src)
		if err != nil {
			return err
		}

		err = s.mc.RemoveObject(s.ctx, po.bucket, obj.Key, minio.RemoveObjectOptions{})
		var e minio.ErrorResponse
		log.Println(errors.As(err, &e))
		log.Println(e)
		if errors.As(err, &e) && e.StatusCode == 200 {
			/* @FIXME workaround for garage's bug #98 */
		} else if err != nil {
			return err
		}
	}

	return nil
}

func (s S3FS) Stat(ctx context.Context, name string) (os.FileInfo, error) {
	s.ctx = ctx
	return NewS3Stat(&s, name)
}