/*
   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 docker

import (
	"context"
	"io"
	"io/ioutil"
	"net/http"
	"path"
	"strings"
	"time"

	"github.com/containerd/containerd/content"
	"github.com/containerd/containerd/errdefs"
	"github.com/containerd/containerd/images"
	"github.com/containerd/containerd/log"
	"github.com/containerd/containerd/remotes"
	digest "github.com/opencontainers/go-digest"
	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
	"github.com/pkg/errors"
)

type dockerPusher struct {
	*dockerBase
	tag string

	// TODO: namespace tracker
	tracker StatusTracker
}

func (p dockerPusher) Push(ctx context.Context, desc ocispec.Descriptor) (content.Writer, error) {
	ctx, err := contextWithRepositoryScope(ctx, p.refspec, true)
	if err != nil {
		return nil, err
	}
	ref := remotes.MakeRefKey(ctx, desc)
	status, err := p.tracker.GetStatus(ref)
	if err == nil {
		if status.Offset == status.Total {
			return nil, errors.Wrapf(errdefs.ErrAlreadyExists, "ref %v", ref)
		}
		// TODO: Handle incomplete status
	} else if !errdefs.IsNotFound(err) {
		return nil, errors.Wrap(err, "failed to get status")
	}

	var (
		isManifest bool
		existCheck string
	)

	switch desc.MediaType {
	case images.MediaTypeDockerSchema2Manifest, images.MediaTypeDockerSchema2ManifestList,
		ocispec.MediaTypeImageManifest, ocispec.MediaTypeImageIndex:
		isManifest = true
		if p.tag == "" {
			existCheck = path.Join("manifests", desc.Digest.String())
		} else {
			existCheck = path.Join("manifests", p.tag)
		}
	default:
		existCheck = path.Join("blobs", desc.Digest.String())
	}

	req, err := http.NewRequest(http.MethodHead, p.url(existCheck), nil)
	if err != nil {
		return nil, err
	}

	req.Header.Set("Accept", strings.Join([]string{desc.MediaType, `*`}, ", "))
	resp, err := p.doRequestWithRetries(ctx, req, nil)
	if err != nil {
		if errors.Cause(err) != ErrInvalidAuthorization {
			return nil, err
		}
		log.G(ctx).WithError(err).Debugf("Unable to check existence, continuing with push")
	} else {
		if resp.StatusCode == http.StatusOK {
			var exists bool
			if isManifest && p.tag != "" {
				dgstHeader := digest.Digest(resp.Header.Get("Docker-Content-Digest"))
				if dgstHeader == desc.Digest {
					exists = true
				}
			} else {
				exists = true
			}

			if exists {
				p.tracker.SetStatus(ref, Status{
					Status: content.Status{
						Ref: ref,
						// TODO: Set updated time?
					},
				})
				return nil, errors.Wrapf(errdefs.ErrAlreadyExists, "content %v on remote", desc.Digest)
			}
		} else if resp.StatusCode != http.StatusNotFound {
			// TODO: log error
			return nil, errors.Errorf("unexpected response: %s", resp.Status)
		}
	}

	// TODO: Lookup related objects for cross repository push

	if isManifest {
		var putPath string
		if p.tag != "" {
			putPath = path.Join("manifests", p.tag)
		} else {
			putPath = path.Join("manifests", desc.Digest.String())
		}

		req, err = http.NewRequest(http.MethodPut, p.url(putPath), nil)
		if err != nil {
			return nil, err
		}
		req.Header.Add("Content-Type", desc.MediaType)
	} else {
		// TODO: Do monolithic upload if size is small

		// Start upload request
		req, err = http.NewRequest(http.MethodPost, p.url("blobs", "uploads")+"/", nil)
		if err != nil {
			return nil, err
		}

		resp, err := p.doRequestWithRetries(ctx, req, nil)
		if err != nil {
			return nil, err
		}

		switch resp.StatusCode {
		case http.StatusOK, http.StatusAccepted, http.StatusNoContent:
		default:
			// TODO: log error
			return nil, errors.Errorf("unexpected response: %s", resp.Status)
		}

		location := resp.Header.Get("Location")
		// Support paths without host in location
		if strings.HasPrefix(location, "/") {
			// Support location string containing path and query
			qmIndex := strings.Index(location, "?")
			if qmIndex > 0 {
				u := p.base
				u.Path = location[:qmIndex]
				u.RawQuery = location[qmIndex+1:]
				location = u.String()
			} else {
				u := p.base
				u.Path = location
				location = u.String()
			}
		}

		req, err = http.NewRequest(http.MethodPut, location, nil)
		if err != nil {
			return nil, err
		}
		q := req.URL.Query()
		q.Add("digest", desc.Digest.String())
		req.URL.RawQuery = q.Encode()

	}
	p.tracker.SetStatus(ref, Status{
		Status: content.Status{
			Ref:       ref,
			Total:     desc.Size,
			Expected:  desc.Digest,
			StartedAt: time.Now(),
		},
	})

	// TODO: Support chunked upload

	pr, pw := io.Pipe()
	respC := make(chan *http.Response, 1)

	req.Body = ioutil.NopCloser(pr)
	req.ContentLength = desc.Size

	go func() {
		defer close(respC)
		resp, err = p.doRequest(ctx, req)
		if err != nil {
			pr.CloseWithError(err)
			return
		}

		switch resp.StatusCode {
		case http.StatusOK, http.StatusCreated, http.StatusNoContent:
		default:
			// TODO: log error
			pr.CloseWithError(errors.Errorf("unexpected response: %s", resp.Status))
		}
		respC <- resp
	}()

	return &pushWriter{
		base:       p.dockerBase,
		ref:        ref,
		pipe:       pw,
		responseC:  respC,
		isManifest: isManifest,
		expected:   desc.Digest,
		tracker:    p.tracker,
	}, nil
}

type pushWriter struct {
	base *dockerBase
	ref  string

	pipe       *io.PipeWriter
	responseC  <-chan *http.Response
	isManifest bool

	expected digest.Digest
	tracker  StatusTracker
}

func (pw *pushWriter) Write(p []byte) (n int, err error) {
	status, err := pw.tracker.GetStatus(pw.ref)
	if err != nil {
		return n, err
	}
	n, err = pw.pipe.Write(p)
	status.Offset += int64(n)
	status.UpdatedAt = time.Now()
	pw.tracker.SetStatus(pw.ref, status)
	return
}

func (pw *pushWriter) Close() error {
	return pw.pipe.Close()
}

func (pw *pushWriter) Status() (content.Status, error) {
	status, err := pw.tracker.GetStatus(pw.ref)
	if err != nil {
		return content.Status{}, err
	}
	return status.Status, nil

}

func (pw *pushWriter) Digest() digest.Digest {
	// TODO: Get rid of this function?
	return pw.expected
}

func (pw *pushWriter) Commit(ctx context.Context, size int64, expected digest.Digest, opts ...content.Opt) error {
	// Check whether read has already thrown an error
	if _, err := pw.pipe.Write([]byte{}); err != nil && err != io.ErrClosedPipe {
		return errors.Wrap(err, "pipe error before commit")
	}

	if err := pw.pipe.Close(); err != nil {
		return err
	}
	// TODO: Update status to determine committing

	// TODO: timeout waiting for response
	resp := <-pw.responseC
	if resp == nil {
		return errors.New("no response")
	}

	// 201 is specified return status, some registries return
	// 200 or 204.
	switch resp.StatusCode {
	case http.StatusOK, http.StatusCreated, http.StatusNoContent:
	default:
		return errors.Errorf("unexpected status: %s", resp.Status)
	}

	status, err := pw.tracker.GetStatus(pw.ref)
	if err != nil {
		return errors.Wrap(err, "failed to get status")
	}

	if size > 0 && size != status.Offset {
		return errors.Errorf("unxpected size %d, expected %d", status.Offset, size)
	}

	if expected == "" {
		expected = status.Expected
	}

	actual, err := digest.Parse(resp.Header.Get("Docker-Content-Digest"))
	if err != nil {
		return errors.Wrap(err, "invalid content digest in response")
	}

	if actual != expected {
		return errors.Errorf("got digest %s, expected %s", actual, expected)
	}

	return nil
}

func (pw *pushWriter) Truncate(size int64) error {
	// TODO: if blob close request and start new request at offset
	// TODO: always error on manifest
	return errors.New("cannot truncate remote upload")
}