/*
   Copyright The containerd Authors.

   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 proxy

import (
	"context"
	"fmt"
	"io"

	contentapi "github.com/containerd/containerd/api/services/content/v1"
	"github.com/containerd/containerd/content"
	"github.com/containerd/containerd/protobuf"
	"github.com/containerd/errdefs"
	digest "github.com/opencontainers/go-digest"
)

type remoteWriter struct {
	ref    string
	client contentapi.Content_WriteClient
	offset int64
	digest digest.Digest
}

// send performs a synchronous req-resp cycle on the client.
func (rw *remoteWriter) send(req *contentapi.WriteContentRequest) (*contentapi.WriteContentResponse, error) {
	if err := rw.client.Send(req); err != nil {
		return nil, err
	}

	resp, err := rw.client.Recv()

	if err == nil {
		// try to keep these in sync
		if resp.Digest != "" {
			rw.digest = digest.Digest(resp.Digest)
		}
	}

	return resp, err
}

func (rw *remoteWriter) Status() (content.Status, error) {
	resp, err := rw.send(&contentapi.WriteContentRequest{
		Action: contentapi.WriteAction_STAT,
	})
	if err != nil {
		return content.Status{}, fmt.Errorf("error getting writer status: %w", errdefs.FromGRPC(err))
	}

	return content.Status{
		Ref:       rw.ref,
		Offset:    resp.Offset,
		Total:     resp.Total,
		StartedAt: protobuf.FromTimestamp(resp.StartedAt),
		UpdatedAt: protobuf.FromTimestamp(resp.UpdatedAt),
	}, nil
}

func (rw *remoteWriter) Digest() digest.Digest {
	return rw.digest
}

func (rw *remoteWriter) Write(p []byte) (n int, err error) {
	offset := rw.offset

	resp, err := rw.send(&contentapi.WriteContentRequest{
		Action: contentapi.WriteAction_WRITE,
		Offset: offset,
		Data:   p,
	})
	if err != nil {
		return 0, fmt.Errorf("failed to send write: %w", errdefs.FromGRPC(err))
	}

	n = int(resp.Offset - offset)
	if n < len(p) {
		err = io.ErrShortWrite
	}

	rw.offset += int64(n)
	if resp.Digest != "" {
		rw.digest = digest.Digest(resp.Digest)
	}
	return
}

func (rw *remoteWriter) Commit(ctx context.Context, size int64, expected digest.Digest, opts ...content.Opt) (err error) {
	defer func() {
		err1 := rw.Close()
		if err == nil {
			err = err1
		}
	}()

	var base content.Info
	for _, opt := range opts {
		if err := opt(&base); err != nil {
			return err
		}
	}
	resp, err := rw.send(&contentapi.WriteContentRequest{
		Action:   contentapi.WriteAction_COMMIT,
		Total:    size,
		Offset:   rw.offset,
		Expected: expected.String(),
		Labels:   base.Labels,
	})
	if err != nil {
		return fmt.Errorf("commit failed: %w", errdefs.FromGRPC(err))
	}

	if size != 0 && resp.Offset != size {
		return fmt.Errorf("unexpected size: %v != %v", resp.Offset, size)
	}

	actual := digest.Digest(resp.Digest)
	if expected != "" && actual != expected {
		return fmt.Errorf("unexpected digest: %v != %v", resp.Digest, expected)
	}

	rw.digest = actual
	rw.offset = resp.Offset
	return nil
}

func (rw *remoteWriter) Truncate(size int64) error {
	// This truncation won't actually be validated until a write is issued.
	rw.offset = size
	return nil
}

func (rw *remoteWriter) Close() error {
	return rw.client.CloseSend()
}
