package graph

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"io/ioutil"

	log "github.com/Sirupsen/logrus"
	"github.com/docker/docker/engine"
	"github.com/docker/docker/pkg/tarsum"
	"github.com/docker/docker/registry"
	"github.com/docker/docker/runconfig"
	"github.com/docker/libtrust"
)

func (s *TagStore) newManifest(localName, remoteName, tag string) ([]byte, error) {
	manifest := &registry.ManifestData{
		Name:          remoteName,
		Tag:           tag,
		SchemaVersion: 1,
	}
	localRepo, err := s.Get(localName)
	if err != nil {
		return nil, err
	}
	if localRepo == nil {
		return nil, fmt.Errorf("Repo does not exist: %s", localName)
	}

	// Get the top-most layer id which the tag points to
	layerId, exists := localRepo[tag]
	if !exists {
		return nil, fmt.Errorf("Tag does not exist for %s: %s", localName, tag)
	}
	layersSeen := make(map[string]bool)

	layer, err := s.graph.Get(layerId)
	if err != nil {
		return nil, err
	}
	manifest.Architecture = layer.Architecture
	manifest.FSLayers = make([]*registry.FSLayer, 0, 4)
	manifest.History = make([]*registry.ManifestHistory, 0, 4)
	var metadata runconfig.Config
	if layer.Config != nil {
		metadata = *layer.Config
	}

	for ; layer != nil; layer, err = layer.GetParent() {
		if err != nil {
			return nil, err
		}

		if layersSeen[layer.ID] {
			break
		}
		if layer.Config != nil && metadata.Image != layer.ID {
			err = runconfig.Merge(&metadata, layer.Config)
			if err != nil {
				return nil, err
			}
		}

		checksum, err := layer.GetCheckSum(s.graph.ImageRoot(layer.ID))
		if err != nil {
			return nil, fmt.Errorf("Error getting image checksum: %s", err)
		}
		if tarsum.VersionLabelForChecksum(checksum) != tarsum.Version1.String() {
			archive, err := layer.TarLayer()
			if err != nil {
				return nil, err
			}

			defer archive.Close()

			tarSum, err := tarsum.NewTarSum(archive, true, tarsum.Version1)
			if err != nil {
				return nil, err
			}
			if _, err := io.Copy(ioutil.Discard, tarSum); err != nil {
				return nil, err
			}

			checksum = tarSum.Sum(nil)

			// Save checksum value
			if err := layer.SaveCheckSum(s.graph.ImageRoot(layer.ID), checksum); err != nil {
				return nil, err
			}
		}

		jsonData, err := layer.RawJson()
		if err != nil {
			return nil, fmt.Errorf("Cannot retrieve the path for {%s}: %s", layer.ID, err)
		}

		manifest.FSLayers = append(manifest.FSLayers, &registry.FSLayer{BlobSum: checksum})

		layersSeen[layer.ID] = true

		manifest.History = append(manifest.History, &registry.ManifestHistory{V1Compatibility: string(jsonData)})
	}

	manifestBytes, err := json.MarshalIndent(manifest, "", "   ")
	if err != nil {
		return nil, err
	}

	return manifestBytes, nil
}

// loadManifest loads a manifest from a byte array and verifies its content.
// The signature must be verified or an error is returned. If the manifest
// contains no signatures by a trusted key for the name in the manifest, the
// image is not considered verified. The parsed manifest object and a boolean
// for whether the manifest is verified is returned.
func (s *TagStore) loadManifest(eng *engine.Engine, manifestBytes []byte) (*registry.ManifestData, bool, error) {
	sig, err := libtrust.ParsePrettySignature(manifestBytes, "signatures")
	if err != nil {
		return nil, false, fmt.Errorf("error parsing payload: %s", err)
	}

	keys, err := sig.Verify()
	if err != nil {
		return nil, false, fmt.Errorf("error verifying payload: %s", err)
	}

	payload, err := sig.Payload()
	if err != nil {
		return nil, false, fmt.Errorf("error retrieving payload: %s", err)
	}

	var manifest registry.ManifestData
	if err := json.Unmarshal(payload, &manifest); err != nil {
		return nil, false, fmt.Errorf("error unmarshalling manifest: %s", err)
	}
	if manifest.SchemaVersion != 1 {
		return nil, false, fmt.Errorf("unsupported schema version: %d", manifest.SchemaVersion)
	}

	var verified bool
	for _, key := range keys {
		job := eng.Job("trust_key_check")
		b, err := key.MarshalJSON()
		if err != nil {
			return nil, false, fmt.Errorf("error marshalling public key: %s", err)
		}
		namespace := manifest.Name
		if namespace[0] != '/' {
			namespace = "/" + namespace
		}
		stdoutBuffer := bytes.NewBuffer(nil)

		job.Args = append(job.Args, namespace)
		job.Setenv("PublicKey", string(b))
		// Check key has read/write permission (0x03)
		job.SetenvInt("Permission", 0x03)
		job.Stdout.Add(stdoutBuffer)
		if err = job.Run(); err != nil {
			return nil, false, fmt.Errorf("error running key check: %s", err)
		}
		result := engine.Tail(stdoutBuffer, 1)
		log.Debugf("Key check result: %q", result)
		if result == "verified" {
			verified = true
		}
	}

	return &manifest, verified, nil
}

func checkValidManifest(manifest *registry.ManifestData) error {
	if len(manifest.FSLayers) != len(manifest.History) {
		return fmt.Errorf("length of history not equal to number of layers")
	}

	if len(manifest.FSLayers) == 0 {
		return fmt.Errorf("no FSLayers in manifest")
	}

	return nil
}