package registry

import (
	"context"
	"encoding/base64"
	"errors"
	"fmt"
	"io"
	"log"
	"log/slog"
	"net"
	"net/http"
	"net/http/httptest"
	"net/url"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"testing"

	"github.com/google/go-containerregistry/pkg/authn"
	"github.com/google/go-containerregistry/pkg/name"
	ggcrregistry "github.com/google/go-containerregistry/pkg/registry"
	"github.com/google/go-containerregistry/pkg/v1/random"
	"github.com/google/go-containerregistry/pkg/v1/remote"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
)

var discardLog = slog.New(slog.NewTextHandler(io.Discard, nil))

func newClient() *Client { return New("test", discardLog) }

// request is one request the test registry received.
type request struct{ method, path string }

// testRegistry is an in-memory registry that records every request.
type testRegistry struct {
	srv  *httptest.Server
	host string // "127.0.0.1:port", the registry part of a ref

	mu       sync.Mutex
	requests []request
}

// newTestRegistry starts a registry. When user is set every request needs
// those basic-auth credentials.
func newTestRegistry(t *testing.T, user, pass string) *testRegistry {
	t.Helper()
	backend := ggcrregistry.New(ggcrregistry.Logger(log.New(io.Discard, "", 0)))
	tr := &testRegistry{}
	tr.srv = httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		tr.mu.Lock()
		tr.requests = append(tr.requests, request{r.Method, r.URL.Path})
		tr.mu.Unlock()
		if user != "" {
			if u, p, ok := r.BasicAuth(); !ok || u != user || p != pass {
				w.Header().Set("WWW-Authenticate", `Basic realm="test"`)
				w.WriteHeader(http.StatusUnauthorized)
				return
			}
		}
		backend.ServeHTTP(w, r)
	}))
	t.Cleanup(tr.srv.Close)
	tr.host = strings.TrimPrefix(tr.srv.URL, "http://")
	return tr
}

// pushIndex stores a random multi-arch index as repo:tag and returns its
// digest. user and pass are used when the registry requires them.
func (tr *testRegistry) pushIndex(t *testing.T, repo, tag string, opts ...remote.Option) string {
	t.Helper()
	idx, err := random.Index(64, 1, 2)
	require.NoError(t, err)
	ref, err := name.ParseReference(tr.host + "/" + repo + ":" + tag)
	require.NoError(t, err)
	require.NoError(t, remote.WriteIndex(ref, idx, opts...))
	d, err := idx.Digest()
	require.NoError(t, err)
	return d.String()
}

// manifestRequests returns the requests that touched a manifest.
func (tr *testRegistry) manifestRequests() []request {
	tr.mu.Lock()
	defer tr.mu.Unlock()
	var out []request
	for _, r := range tr.requests {
		if strings.Contains(r.path, "/manifests/") {
			out = append(out, r)
		}
	}
	return out
}

// reset forgets the requests received so far.
func (tr *testRegistry) reset() {
	tr.mu.Lock()
	defer tr.mu.Unlock()
	tr.requests = nil
}

// dockerConfig points DOCKER_CONFIG at a fresh directory holding config.json
// with the given content; "" leaves the directory empty.
func dockerConfig(t *testing.T, configJSON string) {
	t.Helper()
	dir := t.TempDir()
	if configJSON != "" {
		require.NoError(t, os.WriteFile(filepath.Join(dir, "config.json"), []byte(configJSON), 0o600))
	}
	t.Setenv("DOCKER_CONFIG", dir)
}

func TestDigestOfIndexIsIndexDigest(t *testing.T) {
	dockerConfig(t, "")
	reg := newTestRegistry(t, "", "")
	want := reg.pushIndex(t, "team/app", "1.2")

	got, err := newClient().Digest(context.Background(), reg.host+"/team/app:1.2")

	require.NoError(t, err)
	assert.Equal(t, want, got)
}

func TestDigestIgnoresDigestSuffix(t *testing.T) {
	dockerConfig(t, "")
	reg := newTestRegistry(t, "", "")
	want := reg.pushIndex(t, "team/app", "1.2")

	got, err := newClient().Digest(context.Background(), reg.host+"/team/app:1.2@sha256:"+strings.Repeat("0", 64))

	require.NoError(t, err)
	assert.Equal(t, want, got)
}

func TestDigestUsesHeadOnly(t *testing.T) {
	dockerConfig(t, "")
	reg := newTestRegistry(t, "", "")
	reg.pushIndex(t, "team/app", "1.2")
	reg.reset()

	_, err := newClient().Digest(context.Background(), reg.host+"/team/app:1.2")

	require.NoError(t, err)
	assert.Equal(t, []request{{http.MethodHead, "/v2/team/app/manifests/1.2"}}, reg.manifestRequests())
	for _, r := range reg.requests {
		if !strings.Contains(r.path, "/manifests/") {
			assert.Equal(t, request{http.MethodGet, "/v2/"}, r, "the only other request is the API ping")
		}
	}
}

func TestDigestSendsUserAgent(t *testing.T) {
	dockerConfig(t, "")
	var ua string
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		ua = r.Header.Get("User-Agent")
		w.WriteHeader(http.StatusNotFound)
	}))
	t.Cleanup(srv.Close)

	_, _ = New("package-updater-test/1", discardLog).Digest(context.Background(), strings.TrimPrefix(srv.URL, "http://")+"/a/b:1")

	assert.Contains(t, ua, "package-updater-test/1")
}

func TestCredentialsFromDockerConfig(t *testing.T) {
	reg := newTestRegistry(t, "bot", "s3cret")
	want := reg.pushIndex(t, "team/app", "1.2", remote.WithAuth(&authn.Basic{Username: "bot", Password: "s3cret"}))
	auth := base64.StdEncoding.EncodeToString([]byte("bot:s3cret"))
	dockerConfig(t, `{"auths":{"`+reg.host+`":{"auth":"`+auth+`"}}}`)

	got, err := newClient().Digest(context.Background(), reg.host+"/team/app:1.2")

	require.NoError(t, err)
	assert.Equal(t, want, got)
}

func TestWrongCredentialsFail(t *testing.T) {
	reg := newTestRegistry(t, "bot", "s3cret")
	reg.pushIndex(t, "team/app", "1.2", remote.WithAuth(&authn.Basic{Username: "bot", Password: "s3cret"}))
	auth := base64.StdEncoding.EncodeToString([]byte("bot:wrong"))
	dockerConfig(t, `{"auths":{"`+reg.host+`":{"auth":"`+auth+`"}}}`)

	_, err := newClient().Digest(context.Background(), reg.host+"/team/app:1.2")

	require.Error(t, err)
	assert.NotContains(t, err.Error(), "wrong", "credentials do not leak into errors")
	assert.NotContains(t, err.Error(), auth)
}

func TestAnonymousWithoutConfig(t *testing.T) {
	dockerConfig(t, "")
	open := newTestRegistry(t, "", "")
	want := open.pushIndex(t, "team/app", "1.2")
	protected := newTestRegistry(t, "bot", "s3cret")

	got, err := newClient().Digest(context.Background(), open.host+"/team/app:1.2")
	require.NoError(t, err)
	assert.Equal(t, want, got, "anonymous access works without a config file")

	_, err = newClient().Digest(context.Background(), protected.host+"/team/app:1.2")
	assert.Error(t, err, "a registry that needs credentials fails without them")
}

func TestUnknownTagIsAnError(t *testing.T) {
	dockerConfig(t, "")
	reg := newTestRegistry(t, "", "")
	reg.pushIndex(t, "team/app", "1.2")

	_, err := newClient().Digest(context.Background(), reg.host+"/team/app:nope")

	assert.Error(t, err)
}

func TestRefWithoutTagIsAnError(t *testing.T) {
	_, err := newClient().Digest(context.Background(), "team/app@sha256:"+strings.Repeat("a", 64))

	assert.ErrorContains(t, err, "has no tag")
}

// A config.json whose credsStore names a helper that is not installed makes
// the lookup fail for every registry, including ones that would work
// anonymously. The master container has no credential helpers, so only
// inline "auths" entries are supported there.
func TestCredsStoreWithoutHelperFailsTheLookup(t *testing.T) {
	reg := newTestRegistry(t, "", "")
	reg.pushIndex(t, "team/app", "1.2")
	dockerConfig(t, `{"credsStore":"no-such-helper-for-package-updater-tests"}`)

	_, err := newClient().Digest(context.Background(), reg.host+"/team/app:1.2")

	assert.ErrorContains(t, err, "error getting credentials")
	assert.ErrorContains(t, err, "docker-credential-no-such-helper-for-package-updater-tests")
}

// A registry that leaves out Docker-Content-Digest must not make the client
// retry with a manifest download, which Docker Hub counts as a pull.
func TestMissingDigestHeaderDoesNotFallBackToDownload(t *testing.T) {
	dockerConfig(t, "")
	var mu sync.Mutex
	var methods []string
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if !strings.Contains(r.URL.Path, "/manifests/") {
			return
		}
		mu.Lock()
		methods = append(methods, r.Method)
		mu.Unlock()
		w.Header().Set("Content-Type", "application/vnd.oci.image.index.v1+json")
		w.Header().Set("Content-Length", "10")
	}))
	t.Cleanup(srv.Close)

	_, err := newClient().Digest(context.Background(), strings.TrimPrefix(srv.URL, "http://")+"/a/b:1")

	assert.Error(t, err)
	assert.Equal(t, []string{http.MethodHead}, methods)
}

// ggcr copies up to 64 KiB of the registry's response into its errors. The
// registry host comes from an image name, so that text must not reach the
// stored poll error.
func TestRegistryErrorBodyDoesNotLeak(t *testing.T) {
	dockerConfig(t, "")
	tests := []struct {
		name string
		body string
		want string
	}{
		{"raw body", "internal-secret-body", "registry answered 400 Bad Request"},
		{"structured errors", `{"errors":[{"code":"MANIFEST_UNKNOWN","message":"internal-secret-body","detail":"internal-secret-body"},{"code":"internal-secret-body"}]}`,
			"registry answered 400 Bad Request (MANIFEST_UNKNOWN)"},
	}
	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
				// HEAD answers carry no body, so the leak is in the GET /v2/ ping.
				w.WriteHeader(http.StatusBadRequest)
				_, _ = w.Write([]byte(tt.body))
			}))
			t.Cleanup(srv.Close)
			host := strings.TrimPrefix(srv.URL, "http://")

			_, err := newClient().Digest(context.Background(), host+"/a/b:1")

			require.Error(t, err)
			assert.NotContains(t, err.Error(), "internal-secret-body")
			assert.Equal(t, "lookup "+host+"/a/b:1: "+tt.want, strings.Replace(err.Error(), "index.docker.io/", "", 1))
		})
	}
}

// ggcr puts the token server's answer into its error when the answer has no
// token, and the token server is named by the registry's challenge.
func TestNonRegistryErrorsAreFixedText(t *testing.T) {
	dockerConfig(t, "")
	tokenSrv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		_, _ = w.Write([]byte(`{"detail":"internal-secret-body"}`))
	}))
	t.Cleanup(tokenSrv.Close)
	reg := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("WWW-Authenticate", `Bearer realm="`+tokenSrv.URL+`/internal-secret-realm",service="internal-secret-service"`)
		w.WriteHeader(http.StatusUnauthorized)
	}))
	t.Cleanup(reg.Close)
	host := strings.TrimPrefix(reg.URL, "http://")

	_, err := newClient().Digest(context.Background(), host+"/a/b:1")

	require.Error(t, err)
	assert.NotContains(t, err.Error(), "internal-secret")
	assert.Equal(t, "lookup "+host+"/a/b:1: lookup failed", err.Error())
}

func TestClassify(t *testing.T) {
	refused := &url.Error{Op: "Get", URL: "http://internal-secret-host/v2/", Err: errors.New("connection refused")}
	tests := []struct {
		name string
		err  error
		want string
	}{
		{"deadline", fmt.Errorf("x: %w", context.DeadlineExceeded), "timeout"},
		{"canceled", context.Canceled, "timeout"},
		{"url error", refused, "cannot reach registry"},
		{"net error", &net.DNSError{Name: "internal-secret-host"}, "cannot reach registry"},
		{"deadline inside url error", &url.Error{Op: "Get", URL: "http://x", Err: context.DeadlineExceeded}, "timeout"},
		{"anything else", errors.New("internal-secret"), "lookup failed"},
	}
	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			assert.Equal(t, tt.want, classify(tt.err))
		})
	}
}