package repocli

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"io"
	"os"
	"path/filepath"

	ocidigest "github.com/opencontainers/go-digest"
	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
)

type Imager struct {
	index ocispec.Index
	place string
}

func NewEmptyImager(place string) *Imager {
	imager := &Imager{
		index: ocispec.Index{
			MediaType: MediaTypeOIIv1,
			Manifests: make([]ocispec.Descriptor, 0),
		},
		place: place,
	}
	imager.index.SchemaVersion = 2
	return imager
}

func (ima *Imager) WriteManifest(ctx context.Context, digest, mime string, payload []byte) error {
	var err error
	digestobj, err := ocidigest.Parse(digest)
	if err != nil {
		return err
	}
	subdir := string(digestobj.Algorithm())
	dir := filepath.Join(ima.place, subdir)
	err = os.MkdirAll(dir, 0750)
	if err != nil {
		return err
	}
	mpath := filepath.Join(dir, digestobj.Encoded())
	mfile, err := os.OpenFile(mpath, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0640)
	if err != nil {
		return err
	}
	defer mfile.Close()
	reader := bytes.NewReader(payload)

	verifier := digestobj.Verifier()
	mwriter := io.MultiWriter(verifier, mfile)
	recsize, err := io.Copy(mwriter, reader)
	size := int64(len(payload))
	if size != recsize {
		err = errors.New("Mismatch manigest sizes")
		return err
	}
	if !verifier.Verified() {
		err = errors.New("Mismatch manifest digests")
		return err
	}
	descr := ocispec.Descriptor{
		MediaType: mime,
		Digest:    digestobj,
		Size:      size,
	}
	ima.index.Manifests = append(ima.index.Manifests, descr)
	indexdat, err := json.Marshal(ima.index)
	if err != nil {
		return err
	}
	// Flush index
	ipath := filepath.Join(dir, "index.json")
	ifile, err := os.OpenFile(ipath, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0640)
	if err != nil {
		return err
	}
	defer ifile.Close()
	reader = bytes.NewReader(indexdat)
	recsize, err = io.Copy(ifile, reader)
	if err != nil {
		return err
	}
	if recsize != int64(len(indexdat)) {
		err = errors.New("Mismatch index sizes")
		return err
	}
	return err
}

func (ima *Imager) WriteLayer(ctx context.Context, digest string, size int64, reader io.Reader) error {
	var err error
	digestobj, err := ocidigest.Parse(digest)
	if err != nil {
		return err
	}
	subdir := string(digestobj.Algorithm())
	dir := filepath.Join(ima.place, subdir)
	err = os.MkdirAll(dir, 0750)
	if err != nil {
		return err
	}
	fpath := filepath.Join(dir, digestobj.Encoded())
	file, err := os.OpenFile(fpath, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0640)
	if err != nil {
		return err
	}
	verifier := digestobj.Verifier()
	mwriter := io.MultiWriter(verifier, file)
	recsize, err := io.Copy(mwriter, reader)
	if size != recsize {
		err = errors.New("Mismatch sizes")
		return err
	}
	if !verifier.Verified() {
		err = errors.New("Mismatch digests")
		return err
	}
	return err
}