package tools

import (
	"crypto/sha256"
	"encoding/hex"
	"hash"
	"io"

	"github.com/git-lfs/git-lfs/errors"
	"github.com/git-lfs/git-lfs/progress"
)

type readSeekCloserWrapper struct {
	readSeeker io.ReadSeeker
}

func (r *readSeekCloserWrapper) Read(p []byte) (n int, err error) {
	return r.readSeeker.Read(p)
}

func (r *readSeekCloserWrapper) Seek(offset int64, whence int) (int64, error) {
	return r.readSeeker.Seek(offset, whence)
}

func (r *readSeekCloserWrapper) Close() error {
	return nil
}

// NewReadSeekCloserWrapper wraps an io.ReadSeeker and implements a no-op Close() function
// to make it an io.ReadCloser
func NewReadSeekCloserWrapper(r io.ReadSeeker) io.ReadCloser {
	return &readSeekCloserWrapper{r}
}

// CopyWithCallback copies reader to writer while performing a progress callback
func CopyWithCallback(writer io.Writer, reader io.Reader, totalSize int64, cb progress.CopyCallback) (int64, error) {
	if success, _ := CloneFile(writer, reader); success {
		if cb != nil {
			cb(totalSize, totalSize, 0)
		}
		return totalSize, nil
	}
	if cb == nil {
		return io.Copy(writer, reader)
	}

	cbReader := &progress.CallbackReader{
		C:         cb,
		TotalSize: totalSize,
		Reader:    reader,
	}
	return io.Copy(writer, cbReader)
}

// Get a new Hash instance of the type used to hash LFS content
func NewLfsContentHash() hash.Hash {
	return sha256.New()
}

// HashingReader wraps a reader and calculates the hash of the data as it is read
type HashingReader struct {
	reader io.Reader
	hasher hash.Hash
}

func NewHashingReader(r io.Reader) *HashingReader {
	return &HashingReader{r, NewLfsContentHash()}
}

func NewHashingReaderPreloadHash(r io.Reader, hash hash.Hash) *HashingReader {
	return &HashingReader{r, hash}
}

func (r *HashingReader) Hash() string {
	return hex.EncodeToString(r.hasher.Sum(nil))
}

func (r *HashingReader) Read(b []byte) (int, error) {
	w, err := r.reader.Read(b)
	if err == nil || err == io.EOF {
		_, e := r.hasher.Write(b[0:w])
		if e != nil && err == nil {
			return w, e
		}
	}

	return w, err
}

// RetriableReader wraps a error response of reader as RetriableError()
type RetriableReader struct {
	reader io.Reader
}

func NewRetriableReader(r io.Reader) io.Reader {
	return &RetriableReader{r}
}

func (r *RetriableReader) Read(b []byte) (int, error) {
	n, err := r.reader.Read(b)

	// EOF is a successful response as it is used to signal a graceful end
	// of input c.f. https://git.io/v6riQ
	//
	// Otherwise, if the error is non-nil and already retriable (in the
	// case that the underlying reader `r.reader` is itself a
	// `*RetriableReader`, return the error wholesale:
	if err == nil || err == io.EOF || errors.IsRetriableError(err) {
		return n, err
	}

	return n, errors.NewRetriableError(err)
}