package handlers

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"io/ioutil"
	"net/http"
	"net/http/httptest"
	"net/http/httputil"
	"net/url"
	"os"
	"path"
	"reflect"
	"strings"
	"testing"

	"code.google.com/p/go-uuid/uuid"
	"github.com/docker/distribution/configuration"
	"github.com/docker/distribution/digest"
	"github.com/docker/distribution/manifest"
	"github.com/docker/distribution/registry/api/v2"
	_ "github.com/docker/distribution/registry/storage/driver/inmemory"
	"github.com/docker/distribution/testutil"
	"github.com/docker/libtrust"
	"github.com/gorilla/handlers"
	"golang.org/x/net/context"
)

// TestCheckAPI hits the base endpoint (/v2/) ensures we return the specified
// 200 OK response.
func TestCheckAPI(t *testing.T) {
	env := newTestEnv(t)

	baseURL, err := env.builder.BuildBaseURL()
	if err != nil {
		t.Fatalf("unexpected error building base url: %v", err)
	}

	resp, err := http.Get(baseURL)
	if err != nil {
		t.Fatalf("unexpected error issuing request: %v", err)
	}
	defer resp.Body.Close()

	checkResponse(t, "issuing api base check", resp, http.StatusOK)
	checkHeaders(t, resp, http.Header{
		"Content-Type":   []string{"application/json; charset=utf-8"},
		"Content-Length": []string{"2"},
	})

	p, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		t.Fatalf("unexpected error reading response body: %v", err)
	}

	if string(p) != "{}" {
		t.Fatalf("unexpected response body: %v", string(p))
	}
}

func TestURLPrefix(t *testing.T) {
	config := configuration.Configuration{
		Storage: configuration.Storage{
			"inmemory": configuration.Parameters{},
		},
	}
	config.HTTP.Prefix = "/test/"

	env := newTestEnvWithConfig(t, &config)

	baseURL, err := env.builder.BuildBaseURL()
	if err != nil {
		t.Fatalf("unexpected error building base url: %v", err)
	}

	parsed, _ := url.Parse(baseURL)
	if !strings.HasPrefix(parsed.Path, config.HTTP.Prefix) {
		t.Fatalf("Prefix %v not included in test url %v", config.HTTP.Prefix, baseURL)
	}

	resp, err := http.Get(baseURL)
	if err != nil {
		t.Fatalf("unexpected error issuing request: %v", err)
	}
	defer resp.Body.Close()

	checkResponse(t, "issuing api base check", resp, http.StatusOK)
	checkHeaders(t, resp, http.Header{
		"Content-Type":   []string{"application/json; charset=utf-8"},
		"Content-Length": []string{"2"},
	})

}

// TestLayerAPI conducts a full test of the of the layer api.
func TestLayerAPI(t *testing.T) {
	// TODO(stevvooe): This test code is complete junk but it should cover the
	// complete flow. This must be broken down and checked against the
	// specification *before* we submit the final to docker core.
	env := newTestEnv(t)

	imageName := "foo/bar"
	// "build" our layer file
	layerFile, tarSumStr, err := testutil.CreateRandomTarFile()
	if err != nil {
		t.Fatalf("error creating random layer file: %v", err)
	}

	layerDigest := digest.Digest(tarSumStr)

	// -----------------------------------
	// Test fetch for non-existent content
	layerURL, err := env.builder.BuildBlobURL(imageName, layerDigest)
	if err != nil {
		t.Fatalf("error building url: %v", err)
	}

	resp, err := http.Get(layerURL)
	if err != nil {
		t.Fatalf("unexpected error fetching non-existent layer: %v", err)
	}

	checkResponse(t, "fetching non-existent content", resp, http.StatusNotFound)

	// ------------------------------------------
	// Test head request for non-existent content
	resp, err = http.Head(layerURL)
	if err != nil {
		t.Fatalf("unexpected error checking head on non-existent layer: %v", err)
	}

	checkResponse(t, "checking head on non-existent layer", resp, http.StatusNotFound)

	// ------------------------------------------
	// Start an upload, check the status then cancel
	uploadURLBase, uploadUUID := startPushLayer(t, env.builder, imageName)

	// A status check should work
	resp, err = http.Get(uploadURLBase)
	if err != nil {
		t.Fatalf("unexpected error getting upload status: %v", err)
	}
	checkResponse(t, "status of deleted upload", resp, http.StatusNoContent)
	checkHeaders(t, resp, http.Header{
		"Location":           []string{"*"},
		"Range":              []string{"0-0"},
		"Docker-Upload-UUID": []string{uploadUUID},
	})

	req, err := http.NewRequest("DELETE", uploadURLBase, nil)
	if err != nil {
		t.Fatalf("unexpected error creating delete request: %v", err)
	}

	resp, err = http.DefaultClient.Do(req)
	if err != nil {
		t.Fatalf("unexpected error sending delete request: %v", err)
	}

	checkResponse(t, "deleting upload", resp, http.StatusNoContent)

	// A status check should result in 404
	resp, err = http.Get(uploadURLBase)
	if err != nil {
		t.Fatalf("unexpected error getting upload status: %v", err)
	}
	checkResponse(t, "status of deleted upload", resp, http.StatusNotFound)

	// -----------------------------------------
	// Do layer push with an empty body and different digest
	uploadURLBase, uploadUUID = startPushLayer(t, env.builder, imageName)
	resp, err = doPushLayer(t, env.builder, imageName, layerDigest, uploadURLBase, bytes.NewReader([]byte{}))
	if err != nil {
		t.Fatalf("unexpected error doing bad layer push: %v", err)
	}

	checkResponse(t, "bad layer push", resp, http.StatusBadRequest)
	checkBodyHasErrorCodes(t, "bad layer push", resp, v2.ErrorCodeDigestInvalid)

	// -----------------------------------------
	// Do layer push with an empty body and correct digest
	zeroDigest, err := digest.FromTarArchive(bytes.NewReader([]byte{}))
	if err != nil {
		t.Fatalf("unexpected error digesting empty buffer: %v", err)
	}

	uploadURLBase, uploadUUID = startPushLayer(t, env.builder, imageName)
	pushLayer(t, env.builder, imageName, zeroDigest, uploadURLBase, bytes.NewReader([]byte{}))

	// -----------------------------------------
	// Do layer push with an empty body and correct digest

	// This is a valid but empty tarfile!
	emptyTar := bytes.Repeat([]byte("\x00"), 1024)
	emptyDigest, err := digest.FromTarArchive(bytes.NewReader(emptyTar))
	if err != nil {
		t.Fatalf("unexpected error digesting empty tar: %v", err)
	}

	uploadURLBase, uploadUUID = startPushLayer(t, env.builder, imageName)
	pushLayer(t, env.builder, imageName, emptyDigest, uploadURLBase, bytes.NewReader(emptyTar))

	// ------------------------------------------
	// Now, actually do successful upload.
	layerLength, _ := layerFile.Seek(0, os.SEEK_END)
	layerFile.Seek(0, os.SEEK_SET)

	uploadURLBase, uploadUUID = startPushLayer(t, env.builder, imageName)
	pushLayer(t, env.builder, imageName, layerDigest, uploadURLBase, layerFile)

	// ------------------------------------------
	// Now, push just a chunk
	layerFile.Seek(0, 0)

	uploadURLBase, uploadUUID = startPushLayer(t, env.builder, imageName)
	uploadURLBase, dgst := pushChunk(t, env.builder, imageName, uploadURLBase, layerFile, layerLength)
	finishUpload(t, env.builder, imageName, uploadURLBase, dgst)
	// ------------------------
	// Use a head request to see if the layer exists.
	resp, err = http.Head(layerURL)
	if err != nil {
		t.Fatalf("unexpected error checking head on existing layer: %v", err)
	}

	checkResponse(t, "checking head on existing layer", resp, http.StatusOK)
	checkHeaders(t, resp, http.Header{
		"Content-Length":        []string{fmt.Sprint(layerLength)},
		"Docker-Content-Digest": []string{layerDigest.String()},
	})

	// ----------------
	// Fetch the layer!
	resp, err = http.Get(layerURL)
	if err != nil {
		t.Fatalf("unexpected error fetching layer: %v", err)
	}

	checkResponse(t, "fetching layer", resp, http.StatusOK)
	checkHeaders(t, resp, http.Header{
		"Content-Length":        []string{fmt.Sprint(layerLength)},
		"Docker-Content-Digest": []string{layerDigest.String()},
	})

	// Verify the body
	verifier, err := digest.NewDigestVerifier(layerDigest)
	if err != nil {
		t.Fatalf("unexpected error getting digest verifier: %s", err)
	}
	io.Copy(verifier, resp.Body)

	if !verifier.Verified() {
		t.Fatalf("response body did not pass verification")
	}

	// ----------------
	// Fetch the layer with an invalid digest
	badURL := strings.Replace(layerURL, "tarsum", "trsum", 1)
	resp, err = http.Get(badURL)
	if err != nil {
		t.Fatalf("unexpected error fetching layer: %v", err)
	}

	checkResponse(t, "fetching layer bad digest", resp, http.StatusBadRequest)

	// Missing tests:
	// 	- Upload the same tarsum file under and different repository and
	//       ensure the content remains uncorrupted.
}

func TestManifestAPI(t *testing.T) {
	env := newTestEnv(t)

	imageName := "foo/bar"
	tag := "thetag"

	manifestURL, err := env.builder.BuildManifestURL(imageName, tag)
	if err != nil {
		t.Fatalf("unexpected error getting manifest url: %v", err)
	}

	// -----------------------------
	// Attempt to fetch the manifest
	resp, err := http.Get(manifestURL)
	if err != nil {
		t.Fatalf("unexpected error getting manifest: %v", err)
	}
	defer resp.Body.Close()

	checkResponse(t, "getting non-existent manifest", resp, http.StatusNotFound)
	checkBodyHasErrorCodes(t, "getting non-existent manifest", resp, v2.ErrorCodeManifestUnknown)

	tagsURL, err := env.builder.BuildTagsURL(imageName)
	if err != nil {
		t.Fatalf("unexpected error building tags url: %v", err)
	}

	resp, err = http.Get(tagsURL)
	if err != nil {
		t.Fatalf("unexpected error getting unknown tags: %v", err)
	}
	defer resp.Body.Close()

	// Check that we get an unknown repository error when asking for tags
	checkResponse(t, "getting unknown manifest tags", resp, http.StatusNotFound)
	checkBodyHasErrorCodes(t, "getting unknown manifest tags", resp, v2.ErrorCodeNameUnknown)

	// --------------------------------
	// Attempt to push unsigned manifest with missing layers
	unsignedManifest := &manifest.Manifest{
		Versioned: manifest.Versioned{
			SchemaVersion: 1,
		},
		Name: imageName,
		Tag:  tag,
		FSLayers: []manifest.FSLayer{
			{
				BlobSum: "asdf",
			},
			{
				BlobSum: "qwer",
			},
		},
	}

	unsignedManifest.History = generateHistory(t, len(unsignedManifest.FSLayers), false)

	resp = putManifest(t, "putting unsigned manifest", manifestURL, unsignedManifest)
	defer resp.Body.Close()
	checkResponse(t, "posting unsigned manifest", resp, http.StatusBadRequest)
	_, p, counts := checkBodyHasErrorCodes(t, "putting unsigned manifest", resp,
		v2.ErrorCodeManifestUnverified, v2.ErrorCodeBlobUnknown, v2.ErrorCodeDigestInvalid)

	expectedCounts := map[v2.ErrorCode]int{
		v2.ErrorCodeManifestUnverified: 1,
		v2.ErrorCodeBlobUnknown:        2,
		v2.ErrorCodeDigestInvalid:      2,
	}

	if !reflect.DeepEqual(counts, expectedCounts) {
		t.Fatalf("unexpected number of error codes encountered: %v\n!=\n%v\n---\n%s", counts, expectedCounts, string(p))
	}

	// TODO(stevvooe): Add a test case where we take a mostly valid registry,
	// tamper with the content and ensure that we get a unverified manifest
	// error.

	// Push 2 random layers
	expectedLayers := make(map[digest.Digest]io.ReadSeeker)

	for i := range unsignedManifest.FSLayers {
		rs, dgstStr, err := testutil.CreateRandomTarFile()

		if err != nil {
			t.Fatalf("error creating random layer %d: %v", i, err)
		}
		dgst := digest.Digest(dgstStr)

		expectedLayers[dgst] = rs
		unsignedManifest.FSLayers[i].BlobSum = dgst

		uploadURLBase, _ := startPushLayer(t, env.builder, imageName)
		pushLayer(t, env.builder, imageName, dgst, uploadURLBase, rs)
	}

	// -----------------------
	// mostly valid, but we have an extra parent point in history.
	unsignedManifest.History = generateHistory(t, len(unsignedManifest.FSLayers), true)

	signedManifest, err := manifest.Sign(unsignedManifest, env.pk)
	if err != nil {
		t.Fatalf("unexpected error signing manifest: %v", err)
	}

	payload, err := signedManifest.Payload()
	checkErr(t, err, "getting manifest payload")

	dgst, err := digest.FromBytes(payload)
	checkErr(t, err, "digesting manifest")

	manifestDigestURL, err := env.builder.BuildManifestURL(imageName, dgst.String())
	checkErr(t, err, "building manifest url")

	resp = putManifest(t, "putting signed manifest with bad parent", manifestURL, signedManifest)
	checkResponse(t, "putting signed manifest with bad parent", resp, http.StatusBadRequest)
	_, p, counts = checkBodyHasErrorCodes(t, "putting unsigned manifest with bad parent", resp, v2.ErrorCodeManifestInvalid)

	expectedCounts = map[v2.ErrorCode]int{
		v2.ErrorCodeManifestInvalid: 1,
	}

	if !reflect.DeepEqual(counts, expectedCounts) {
		t.Fatalf("unexpected number of error codes encountered: %v\n!=\n%v\n---\n%s", counts, expectedCounts, string(p))
	}

	// -------------------
	// Push the signed manifest with all layers pushed.
	unsignedManifest.History = generateHistory(t, len(unsignedManifest.FSLayers), false)

	signedManifest, err = manifest.Sign(unsignedManifest, env.pk)
	if err != nil {
		t.Fatalf("unexpected error signing manifest: %v", err)
	}

	payload, err = signedManifest.Payload()
	checkErr(t, err, "getting manifest payload")

	dgst, err = digest.FromBytes(payload)
	checkErr(t, err, "digesting manifest")

	manifestDigestURL, err = env.builder.BuildManifestURL(imageName, dgst.String())
	checkErr(t, err, "building manifest url")

	resp = putManifest(t, "putting signed manifest", manifestURL, signedManifest)
	checkResponse(t, "putting signed manifest", resp, http.StatusAccepted)
	checkHeaders(t, resp, http.Header{
		"Location":              []string{manifestDigestURL},
		"Docker-Content-Digest": []string{dgst.String()},
	})

	// --------------------
	// Push by digest -- should get same result
	resp = putManifest(t, "putting signed manifest", manifestDigestURL, signedManifest)
	checkResponse(t, "putting signed manifest", resp, http.StatusAccepted)
	checkHeaders(t, resp, http.Header{
		"Location":              []string{manifestDigestURL},
		"Docker-Content-Digest": []string{dgst.String()},
	})

	// ------------------
	// Fetch by tag name
	resp, err = http.Get(manifestURL)
	if err != nil {
		t.Fatalf("unexpected error fetching manifest: %v", err)
	}
	defer resp.Body.Close()

	checkResponse(t, "fetching uploaded manifest", resp, http.StatusOK)
	checkHeaders(t, resp, http.Header{
		"Docker-Content-Digest": []string{dgst.String()},
	})

	var fetchedManifest manifest.SignedManifest
	dec := json.NewDecoder(resp.Body)
	if err := dec.Decode(&fetchedManifest); err != nil {
		t.Fatalf("error decoding fetched manifest: %v", err)
	}

	if !bytes.Equal(fetchedManifest.Raw, signedManifest.Raw) {
		t.Fatalf("manifests do not match")
	}

	// ---------------
	// Fetch by digest
	resp, err = http.Get(manifestDigestURL)
	checkErr(t, err, "fetching manifest by digest")
	defer resp.Body.Close()

	checkResponse(t, "fetching uploaded manifest", resp, http.StatusOK)
	checkHeaders(t, resp, http.Header{
		"Docker-Content-Digest": []string{dgst.String()},
	})

	var fetchedManifestByDigest manifest.SignedManifest
	dec = json.NewDecoder(resp.Body)
	if err := dec.Decode(&fetchedManifestByDigest); err != nil {
		t.Fatalf("error decoding fetched manifest: %v", err)
	}

	if !bytes.Equal(fetchedManifestByDigest.Raw, signedManifest.Raw) {
		t.Fatalf("manifests do not match")
	}

	// Ensure that the tag is listed.
	resp, err = http.Get(tagsURL)
	if err != nil {
		t.Fatalf("unexpected error getting unknown tags: %v", err)
	}
	defer resp.Body.Close()

	// Check that we get an unknown repository error when asking for tags
	checkResponse(t, "getting unknown manifest tags", resp, http.StatusOK)
	dec = json.NewDecoder(resp.Body)

	var tagsResponse tagsAPIResponse

	if err := dec.Decode(&tagsResponse); err != nil {
		t.Fatalf("unexpected error decoding error response: %v", err)
	}

	if tagsResponse.Name != imageName {
		t.Fatalf("tags name should match image name: %v != %v", tagsResponse.Name, imageName)
	}

	if len(tagsResponse.Tags) != 1 {
		t.Fatalf("expected some tags in response: %v", tagsResponse.Tags)
	}

	if tagsResponse.Tags[0] != tag {
		t.Fatalf("tag not as expected: %q != %q", tagsResponse.Tags[0], tag)
	}
}

type testEnv struct {
	pk      libtrust.PrivateKey
	ctx     context.Context
	config  configuration.Configuration
	app     *App
	server  *httptest.Server
	builder *v2.URLBuilder
}

func newTestEnv(t *testing.T) *testEnv {
	config := configuration.Configuration{
		Storage: configuration.Storage{
			"inmemory": configuration.Parameters{},
		},
	}

	return newTestEnvWithConfig(t, &config)
}

func newTestEnvWithConfig(t *testing.T, config *configuration.Configuration) *testEnv {
	ctx := context.Background()

	app := NewApp(ctx, *config)
	server := httptest.NewServer(handlers.CombinedLoggingHandler(os.Stderr, app))
	builder, err := v2.NewURLBuilderFromString(server.URL + config.HTTP.Prefix)

	if err != nil {
		t.Fatalf("error creating url builder: %v", err)
	}

	pk, err := libtrust.GenerateECP256PrivateKey()
	if err != nil {
		t.Fatalf("unexpected error generating private key: %v", err)
	}

	return &testEnv{
		pk:      pk,
		ctx:     ctx,
		config:  *config,
		app:     app,
		server:  server,
		builder: builder,
	}
}

func putManifest(t *testing.T, msg, url string, v interface{}) *http.Response {
	var body []byte
	if sm, ok := v.(*manifest.SignedManifest); ok {
		body = sm.Raw
	} else {
		var err error
		body, err = json.MarshalIndent(v, "", "   ")
		if err != nil {
			t.Fatalf("unexpected error marshaling %v: %v", v, err)
		}
	}

	req, err := http.NewRequest("PUT", url, bytes.NewReader(body))
	if err != nil {
		t.Fatalf("error creating request for %s: %v", msg, err)
	}

	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		t.Fatalf("error doing put request while %s: %v", msg, err)
	}

	return resp
}

func startPushLayer(t *testing.T, ub *v2.URLBuilder, name string) (location string, uuid string) {
	layerUploadURL, err := ub.BuildBlobUploadURL(name)
	if err != nil {
		t.Fatalf("unexpected error building layer upload url: %v", err)
	}

	resp, err := http.Post(layerUploadURL, "", nil)
	if err != nil {
		t.Fatalf("unexpected error starting layer push: %v", err)
	}
	defer resp.Body.Close()

	checkResponse(t, fmt.Sprintf("pushing starting layer push %v", name), resp, http.StatusAccepted)

	u, err := url.Parse(resp.Header.Get("Location"))
	if err != nil {
		t.Fatalf("error parsing location header: %v", err)
	}

	uuid = path.Base(u.Path)
	checkHeaders(t, resp, http.Header{
		"Location":           []string{"*"},
		"Content-Length":     []string{"0"},
		"Docker-Upload-UUID": []string{uuid},
	})

	return resp.Header.Get("Location"), uuid
}

// doPushLayer pushes the layer content returning the url on success returning
// the response. If you're only expecting a successful response, use pushLayer.
func doPushLayer(t *testing.T, ub *v2.URLBuilder, name string, dgst digest.Digest, uploadURLBase string, body io.Reader) (*http.Response, error) {
	u, err := url.Parse(uploadURLBase)
	if err != nil {
		t.Fatalf("unexpected error parsing pushLayer url: %v", err)
	}

	u.RawQuery = url.Values{
		"_state": u.Query()["_state"],

		"digest": []string{dgst.String()},
	}.Encode()

	uploadURL := u.String()

	// Just do a monolithic upload
	req, err := http.NewRequest("PUT", uploadURL, body)
	if err != nil {
		t.Fatalf("unexpected error creating new request: %v", err)
	}

	return http.DefaultClient.Do(req)
}

// pushLayer pushes the layer content returning the url on success.
func pushLayer(t *testing.T, ub *v2.URLBuilder, name string, dgst digest.Digest, uploadURLBase string, body io.Reader) string {
	digester := digest.NewCanonicalDigester()

	resp, err := doPushLayer(t, ub, name, dgst, uploadURLBase, io.TeeReader(body, &digester))
	if err != nil {
		t.Fatalf("unexpected error doing push layer request: %v", err)
	}
	defer resp.Body.Close()

	checkResponse(t, "putting monolithic chunk", resp, http.StatusCreated)

	if err != nil {
		t.Fatalf("error generating sha256 digest of body")
	}

	sha256Dgst := digester.Digest()

	expectedLayerURL, err := ub.BuildBlobURL(name, sha256Dgst)
	if err != nil {
		t.Fatalf("error building expected layer url: %v", err)
	}

	checkHeaders(t, resp, http.Header{
		"Location":              []string{expectedLayerURL},
		"Content-Length":        []string{"0"},
		"Docker-Content-Digest": []string{sha256Dgst.String()},
	})

	return resp.Header.Get("Location")
}

func finishUpload(t *testing.T, ub *v2.URLBuilder, name string, uploadURLBase string, dgst digest.Digest) string {
	resp, err := doPushLayer(t, ub, name, dgst, uploadURLBase, nil)
	if err != nil {
		t.Fatalf("unexpected error doing push layer request: %v", err)
	}
	defer resp.Body.Close()

	checkResponse(t, "putting monolithic chunk", resp, http.StatusCreated)

	expectedLayerURL, err := ub.BuildBlobURL(name, dgst)
	if err != nil {
		t.Fatalf("error building expected layer url: %v", err)
	}

	checkHeaders(t, resp, http.Header{
		"Location":              []string{expectedLayerURL},
		"Content-Length":        []string{"0"},
		"Docker-Content-Digest": []string{dgst.String()},
	})

	return resp.Header.Get("Location")
}

func doPushChunk(t *testing.T, uploadURLBase string, body io.Reader) (*http.Response, digest.Digest, error) {
	u, err := url.Parse(uploadURLBase)
	if err != nil {
		t.Fatalf("unexpected error parsing pushLayer url: %v", err)
	}

	u.RawQuery = url.Values{
		"_state": u.Query()["_state"],
	}.Encode()

	uploadURL := u.String()

	digester := digest.NewCanonicalDigester()

	req, err := http.NewRequest("PATCH", uploadURL, io.TeeReader(body, digester))
	if err != nil {
		t.Fatalf("unexpected error creating new request: %v", err)
	}
	req.Header.Set("Content-Type", "application/octet-stream")

	resp, err := http.DefaultClient.Do(req)

	return resp, digester.Digest(), err
}

func pushChunk(t *testing.T, ub *v2.URLBuilder, name string, uploadURLBase string, body io.Reader, length int64) (string, digest.Digest) {
	resp, dgst, err := doPushChunk(t, uploadURLBase, body)
	if err != nil {
		t.Fatalf("unexpected error doing push layer request: %v", err)
	}
	defer resp.Body.Close()

	checkResponse(t, "putting chunk", resp, http.StatusAccepted)

	if err != nil {
		t.Fatalf("error generating sha256 digest of body")
	}

	checkHeaders(t, resp, http.Header{
		"Range":          []string{fmt.Sprintf("0-%d", length-1)},
		"Content-Length": []string{"0"},
	})

	return resp.Header.Get("Location"), dgst
}

func checkResponse(t *testing.T, msg string, resp *http.Response, expectedStatus int) {
	if resp.StatusCode != expectedStatus {
		t.Logf("unexpected status %s: %v != %v", msg, resp.StatusCode, expectedStatus)
		maybeDumpResponse(t, resp)

		t.FailNow()
	}
}

// checkBodyHasErrorCodes ensures the body is an error body and has the
// expected error codes, returning the error structure, the json slice and a
// count of the errors by code.
func checkBodyHasErrorCodes(t *testing.T, msg string, resp *http.Response, errorCodes ...v2.ErrorCode) (v2.Errors, []byte, map[v2.ErrorCode]int) {
	p, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		t.Fatalf("unexpected error reading body %s: %v", msg, err)
	}

	var errs v2.Errors
	if err := json.Unmarshal(p, &errs); err != nil {
		t.Fatalf("unexpected error decoding error response: %v", err)
	}

	if len(errs.Errors) == 0 {
		t.Fatalf("expected errors in response")
	}

	// TODO(stevvooe): Shoot. The error setup is not working out. The content-
	// type headers are being set after writing the status code.
	// if resp.Header.Get("Content-Type") != "application/json; charset=utf-8" {
	// 	t.Fatalf("unexpected content type: %v != 'application/json'",
	// 		resp.Header.Get("Content-Type"))
	// }

	expected := map[v2.ErrorCode]struct{}{}
	counts := map[v2.ErrorCode]int{}

	// Initialize map with zeros for expected
	for _, code := range errorCodes {
		expected[code] = struct{}{}
		counts[code] = 0
	}

	for _, err := range errs.Errors {
		if _, ok := expected[err.Code]; !ok {
			t.Fatalf("unexpected error code %v encountered during %s: %s ", err.Code, msg, string(p))
		}
		counts[err.Code]++
	}

	// Ensure that counts of expected errors were all non-zero
	for code := range expected {
		if counts[code] == 0 {
			t.Fatalf("expected error code %v not encounterd during %s: %s", code, msg, string(p))
		}
	}

	return errs, p, counts
}

func maybeDumpResponse(t *testing.T, resp *http.Response) {
	if d, err := httputil.DumpResponse(resp, true); err != nil {
		t.Logf("error dumping response: %v", err)
	} else {
		t.Logf("response:\n%s", string(d))
	}
}

// matchHeaders checks that the response has at least the headers. If not, the
// test will fail. If a passed in header value is "*", any non-zero value will
// suffice as a match.
func checkHeaders(t *testing.T, resp *http.Response, headers http.Header) {
	for k, vs := range headers {
		if resp.Header.Get(k) == "" {
			t.Fatalf("response missing header %q", k)
		}

		for _, v := range vs {
			if v == "*" {
				// Just ensure there is some value.
				if len(resp.Header[k]) > 0 {
					continue
				}
			}

			for _, hv := range resp.Header[k] {
				if hv != v {
					t.Fatalf("%v header value not matched in response: %q != %q", k, hv, v)
				}
			}
		}
	}
}

func checkErr(t *testing.T, err error, msg string) {
	if err != nil {
		t.Fatalf("unexpected error %s: %v", msg, err)
	}
}

// generateHistory creates a valid history entry of length n.
func generateHistory(t *testing.T, n int, extraParent bool) []manifest.History {
	var images []map[string]interface{}

	// first pass: create images entries.
	for i := 0; i < n; i++ {
		// simulate correct id -> parent links in v1Compatibility, using uuids.
		image := map[string]interface{}{
			"id": uuid.New(),
		}

		images = append(images, image)
	}

	var history []manifest.History

	for i, image := range images {
		if i+1 < len(images) {
			image["parent"] = images[i+1]["id"]
		}

		if extraParent && i == len(images)-1 {
			image["parent"] = uuid.New()
		}

		p, err := json.Marshal(image)
		if err != nil {
			t.Fatalf("error generating image json: %v", err)
		}

		history = append(history, manifest.History{
			V1Compatibility: string(p),
		})
	}

	return history
}