package s3

import (
	"context"
	"errors"
	"fmt"
	"io"
	"io/fs"
	"log"
	"mime"
	"path"

	"github.com/minio/minio-go/v7"
)

type S3File struct {
	fs    *S3FS
	obj   *minio.Object
	objw  *io.PipeWriter
	donew chan error
	pos   int64
	entries []fs.FileInfo
	Path  S3Path
}

func NewS3File(s *S3FS, path string) (*S3File, error) {
	f := new(S3File)
	f.fs = s
	f.pos = 0
	f.entries = nil
	f.Path = NewS3Path(path)
	return f, nil
}

func (f *S3File) Close() error {
	err := make([]error, 0)

	if f.obj != nil {
		err = append(err, f.obj.Close())
		f.obj = nil
	}

	if f.objw != nil {
		// wait that minio completes its transfers in background
		err = append(err, f.objw.Close())
		err = append(err, <-f.donew)
		f.donew = nil
		f.objw = nil
	}

	count := 0
	for _, e := range err {
		if e != nil {
			count++
			log.Println(e)
		}
	}
	if count > 0 {
		return errors.New(fmt.Sprintf("%d errors when closing this WebDAV File. Read previous logs to know more.", count))
	}
	return nil
}

func (f *S3File) loadObject() error {
	if f.obj == nil {
		obj, err := f.fs.mc.GetObject(f.fs.ctx, f.Path.Bucket, f.Path.Key, minio.GetObjectOptions{})
		if err != nil {
			return err
		}
		f.obj = obj
	}
	return nil
}

func (f *S3File) Read(p []byte) (n int, err error) {
	log.Printf("s3 Read\n")
	//if f.Stat() & OBJECT == 0 { /* @FIXME Ideally we would check against OBJECT but we need a non OPAQUE_KEY */
	//	return 0, os.ErrInvalid
	//}
	if err := f.loadObject(); err != nil {
		return 0, err
	}

	return f.obj.Read(p)
}

func (f *S3File) ReadAt(p []byte, off int64) (n int, err error) {
	log.Printf("s3 ReadAt %v\n", off)
	if err := f.loadObject(); err != nil {
		return 0, err
	}

	return f.obj.ReadAt(p, off)
}

func (f *S3File) WriteAt(p []byte, off int64) (n int, err error) {
	return 0, errors.New("not implemented")

}

func (f *S3File) Write(p []byte) (n int, err error) {
	/*if f.path.class != OBJECT {
		return 0, os.ErrInvalid
	}*/

	if f.objw == nil {
		if f.pos != 0 {
			return 0, errors.New("writing with an offset is not implemented")
		}

		r, w := io.Pipe()
		f.donew = make(chan error, 1)
		f.objw = w

		contentType := mime.TypeByExtension(path.Ext(f.Path.Key))
		go func() {
			/* @FIXME
			PutObject has a strange behaviour when used with unknown size, it supposes the final size will be 5TiB.
			Then it computes that, following the final size of the file, each part of the multipart upload should be 512MiB, which leads to big allocations.
			The culprit is OptimalPartInfo: https://github.com/minio/minio-go/blob/62beca8cd87e9960d88793320220ad2c159bb5e5/api-put-object-common.go#L70
			We set this value to the minimum allowed one, 5MiB.
			The minimum value is set here: https://github.com/minio/minio-go/blob/62beca8cd87e9960d88793320220ad2c159bb5e5/constants.go#L24
			Because Multipart uploads seems to be limited to 10 000 parts, it might be possible that we are limited to 50 GiB files, which is still good enough.
			Ref: https://github.com/minio/minio-go/blob/62beca8cd87e9960d88793320220ad2c159bb5e5/api-put-object-common.go#L110-L112
			*/
			_, err := f.fs.mc.PutObject(context.Background(), f.Path.Bucket, f.Path.Key, r, -1, minio.PutObjectOptions{ContentType: contentType, PartSize: 5*1024*1024})
			f.donew <- err
		}()
	}

	return f.objw.Write(p)
}

func (f *S3File) Seek(offset int64, whence int) (int64, error) {
	if err := f.loadObject(); err != nil {
		return 0, err
	}

	pos, err := f.obj.Seek(offset, whence)
	f.pos += pos
	return pos, err
}

/*
ReadDir reads the contents of the directory associated with the file f and returns a slice of DirEntry values in directory order. Subsequent calls on the same file will yield later DirEntry records in the directory.

If n > 0, ReadDir returns at most n DirEntry records. In this case, if ReadDir returns an empty slice, it will return an error explaining why. At the end of a directory, the error is io.EOF.

If n <= 0, ReadDir returns all the DirEntry records remaining in the directory. When it succeeds, it returns a nil error (not io.EOF).
*/
func (f *S3File) Readdir(count int) ([]fs.FileInfo, error) {
	if f.Path.Class == ROOT {
		return f.readDirRoot(count)
	} else {
		return f.readDirChild(count)
	}
}

func min(a, b int64) int64 {
    if a < b {
        return a
    }
    return b
}

func (f *S3File) readDirRoot(count int) ([]fs.FileInfo, error) {
	var err error
	if f.entries == nil {
		buckets, err := f.fs.mc.ListBuckets(f.fs.ctx)
		if err != nil {
			return nil, err
		}

		f.entries = make([]fs.FileInfo, 0, len(buckets))
		for _, bucket := range buckets {
			//log.Println("Stat from GarageFile.readDirRoot()", "/"+bucket.Name)
			nf, err := NewS3Stat(f.fs, "/"+bucket.Name)
			if err != nil {
				return nil, err
			}
			f.entries = append(f.entries, nf)
		}
	}
	beg := f.pos
	end := int64(len(f.entries))
	if count > 0 {
		end = min(beg + int64(count), end)
	}
	f.pos = end

	if end - beg == 0 {
		err = io.EOF
	}

	return f.entries[beg:end], err
}

func (f *S3File) readDirChild(count int) ([]fs.FileInfo, error) {
	var err error
	if f.entries == nil {
		prefix := f.Path.Key
		if len(prefix) > 0 && prefix[len(prefix)-1:] != "/" {
			prefix = prefix + "/"
		}

		objs_info := f.fs.mc.ListObjects(f.fs.ctx, f.Path.Bucket, minio.ListObjectsOptions{
			Prefix:    prefix,
			Recursive: false,
		})

		f.entries = make([]fs.FileInfo, 0)
		for object := range objs_info {
			if object.Err != nil {
				return nil, object.Err
			}
			//log.Println("Stat from GarageFile.readDirChild()", path.Join("/", f.path.bucket, object.Key))
			nf, err := NewS3StatFromObjectInfo(f.fs, f.Path.Bucket, object)
			if err != nil {
				return nil, err
			}
			f.entries = append(f.entries, nf)
		}
	}
	beg := f.pos
	end := int64(len(f.entries))
	if count > 0 {
		end = min(beg + int64(count), end)
	}
	f.pos = end

	if end - beg == 0 {
		err = io.EOF
	}

	return f.entries[beg:end], err
}

func (f *S3File) Stat() (fs.FileInfo, error) {
	return NewS3Stat(f.fs, f.Path.Path)
}