package deploy_test

import (
	"context"
	"database/sql"
	"encoding/json"
	"fmt"
	"io"
	"log/slog"
	"maps"
	"net/http"
	"net/http/httptest"
	"os"
	"slices"
	"strings"
	"sync"
	"testing"

	"github.com/docker/docker/pkg/stdcopy"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
	"go.uber.org/fx/fxtest"

	"sneak.berlin/go/upaas/internal/config"
	"sneak.berlin/go/upaas/internal/database"
	"sneak.berlin/go/upaas/internal/docker"
	"sneak.berlin/go/upaas/internal/logger"
	"sneak.berlin/go/upaas/internal/models"
	"sneak.berlin/go/upaas/internal/service/deploy"
)

// fakeImageAPI is a fake Docker API that keeps images and their tags as
// Docker does: a build gives its tag to the image it builds, and removing
// an image's last tag, or an untagged image by its ID, deletes the image.
// It also answers the steps of a git clone that reports shortSHA.
type fakeImageAPI struct {
	mu       sync.Mutex
	images   map[string][]string // image ID -> tags
	shortSHA string              // the commit's short hash the clone reports
	nextID   string              // ID of the image the next build creates
	removed  []string            // each tag or ID removed
	forced   bool                // whether a removal was forced
}

func (api *fakeImageAPI) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	api.mu.Lock()
	defer api.mu.Unlock()

	w.Header().Set("Content-Type", "application/json")

	_, name, isImage := strings.Cut(r.URL.Path, "/images/")

	switch {
	case strings.HasSuffix(r.URL.Path, "/images/json"):
		dangling := strings.Contains(r.URL.Query().Get("filters"), "dangling")
		api.listImages(w, dangling)
	case isImage && r.Method == http.MethodDelete:
		api.forced = api.forced || r.URL.Query().Get("force") != ""
		api.removeImage(w, name)
	case isImage && strings.HasSuffix(name, "/json"):
		api.inspectImage(w, strings.TrimSuffix(name, "/json"))
	case strings.HasSuffix(r.URL.Path, "/build"):
		tag := r.URL.Query().Get("t")
		api.untag(tag)
		api.images[api.nextID] = append(api.images[api.nextID], tag)
	case strings.HasSuffix(r.URL.Path, "/version"):
		_, _ = w.Write([]byte(`{"Version":"27.3.1","ApiVersion":"1.47"}`))
	case strings.HasSuffix(r.URL.Path, "/containers/create"):
		_, _ = w.Write([]byte(`{"Id":"gitcontainer"}`))
	case strings.HasSuffix(r.URL.Path, "/logs"):
		writeCloneOutput(w, api.shortSHA)
	default:
		// The other steps of the git clone, which succeeds.
		_, _ = w.Write([]byte(`{}`))
	}
}

// fakeImage is an image as the fake Docker API lists and inspects it.
type fakeImage struct {
	ID       string `json:"Id"`
	RepoTags []string
}

// listImages lists the untagged images, or else the tagged ones.
func (api *fakeImageAPI) listImages(w http.ResponseWriter, dangling bool) {
	list := []fakeImage{}

	for _, id := range slices.Sorted(maps.Keys(api.images)) {
		if (len(api.images[id]) == 0) == dangling {
			list = append(list, fakeImage{ID: id, RepoTags: api.images[id]})
		}
	}

	_ = json.NewEncoder(w).Encode(list)
}

func (api *fakeImageAPI) inspectImage(w http.ResponseWriter, name string) {
	for id, tags := range api.images {
		if id == name || slices.Contains(tags, name) {
			_ = json.NewEncoder(w).Encode(fakeImage{ID: id, RepoTags: tags})

			return
		}
	}

	w.WriteHeader(http.StatusNotFound)
	_, _ = w.Write([]byte(`{"message":"No such image"}`))
}

func (api *fakeImageAPI) removeImage(w http.ResponseWriter, name string) {
	api.removed = append(api.removed, name)

	id := name
	if _, isID := api.images[name]; !isID {
		id = api.untag(name)
	}

	if len(api.images[id]) == 0 {
		delete(api.images, id)
	}

	_, _ = w.Write([]byte(`[]`))
}

// untag removes tag from the image that has it, leaving the image, and
// returns the image's ID.
func (api *fakeImageAPI) untag(tag string) string {
	for id, tags := range api.images {
		if slices.Contains(tags, tag) {
			api.images[id] = slices.DeleteFunc(tags, func(t string) bool { return t == tag })

			return id
		}
	}

	return ""
}

// state returns each image's tags and each tag or ID removed.
func (api *fakeImageAPI) state() (map[string][]string, []string) {
	api.mu.Lock()
	defer api.mu.Unlock()

	return maps.Clone(api.images), slices.Clone(api.removed)
}

// writeCloneOutput writes the line of a git clone's output that gives the
// commit's short hash, as Docker sends a container's log: after a header.
func writeCloneOutput(w io.Writer, shortSHA string) {
	out := stdcopy.NewStdWriter(w, stdcopy.Stdout)

	_, _ = fmt.Fprintf(out, "SHORT_SHA:%s\n", shortSHA)
}

// newImageTestService returns a deploy service that uses api as its
// Docker API, and its database.
func newImageTestService(
	t *testing.T,
	api *fakeImageAPI,
) (*deploy.Service, *database.Database) {
	t.Helper()

	srv := httptest.NewServer(api)
	t.Cleanup(srv.Close)

	log := slog.New(slog.NewTextHandler(os.Stderr, nil))
	lifecycle := fxtest.NewLifecycle(t)

	dockerClient, err := docker.New(lifecycle, docker.Params{
		Logger: logger.NewForTest(log),
		Config: &config.Config{DockerHost: "tcp://" + srv.Listener.Addr().String()},
	})
	require.NoError(t, err)

	lifecycle.RequireStart()
	t.Cleanup(lifecycle.RequireStop)

	db := database.NewTestDatabase(t)
	dataDir := t.TempDir()
	cfg := &config.Config{DataDir: dataDir, HostDataDir: dataDir}

	return deploy.NewTestServiceWithConfig(log, cfg, db, dockerClient), db
}

// saveApp saves an app with the given current and previous image.
func saveApp(
	t *testing.T,
	db *database.Database,
	name, imageID, previousImageID string,
) *models.App {
	t.Helper()

	app := models.NewApp(db)
	app.ID = name + "-id"
	app.Name = name
	app.ImageID = sql.NullString{String: imageID, Valid: true}
	app.PreviousImageID = sql.NullString{String: previousImageID, Valid: true}
	require.NoError(t, app.Save(context.Background()))

	return app
}

// TestRecordDeployedImageRemovesOldImages runs the step after a deploy
// against a fake Docker API. Image one has a tag from before images were
// tagged with their commit, and is also tagged for another app. Image two
// was the previous image, three the current one, four is new. Image five is
// the other app's previous image, which a redeploy of its commit left
// without the other app's tag.
func TestRecordDeployedImageRemovesOldImages(t *testing.T) {
	t.Parallel()

	api := &fakeImageAPI{images: map[string][]string{
		"sha256:one":   {"upaas-myapp:140", "upaas-otherapp:1a2b3c4"},
		"sha256:two":   {"upaas-myapp:2b3c4d5"},
		"sha256:three": {"upaas-myapp:3c4d5e6"},
		"sha256:four":  {"upaas-myapp:4d5e6f7"},
		"sha256:five":  {"upaas-myapp:5e6f7a8"},
	}}
	svc, db := newImageTestService(t, api)
	ctx := context.Background()

	app := saveApp(t, db, "myapp", "sha256:three", "sha256:two")
	saveApp(t, db, "otherapp", "sha256:other", "sha256:five")

	deployment := models.NewDeployment(db)
	deployment.AppID = app.ID
	require.NoError(t, deployment.Save(ctx))

	err := svc.RecordDeployedImage(ctx, app, deployment, "sha256:four")
	require.NoError(t, err)

	assert.Equal(t, "sha256:four", app.ImageID.String)
	assert.Equal(t, "sha256:three", app.PreviousImageID.String)

	images, removed := api.state()

	assert.Equal(t, []string{"upaas-myapp:140", "upaas-myapp:2b3c4d5"}, removed)
	assert.Equal(t, map[string][]string{
		"sha256:one":   {"upaas-otherapp:1a2b3c4"},
		"sha256:three": {"upaas-myapp:3c4d5e6"},
		"sha256:four":  {"upaas-myapp:4d5e6f7"},
		"sha256:five":  {"upaas-myapp:5e6f7a8"},
	}, images)
	assert.False(t, api.forced, "old images must be removed without force")
}

// TestRedeployRemovesImagesLeftWithoutTag deploys commits against a fake
// Docker API, some of them again. A build takes the commit's tag from the
// image an earlier build of it made. That image is kept, without a tag,
// while the app runs it or Rollback would start it, and is removed by its
// ID once neither does.
func TestRedeployRemovesImagesLeftWithoutTag(t *testing.T) {
	t.Parallel()

	const (
		tagABC1234   = "upaas-myapp:abc1234"
		tag0123ABC   = "upaas-myapp:0123abc"
		retriedImage = "sha256:retried-0123abc"
	)

	// The app runs commit abc1234 and would roll back to def5678. The last
	// deploy, of commit 0123abc, failed after its build.
	api := &fakeImageAPI{images: map[string][]string{
		"sha256:built-abc1234":  {tagABC1234},
		"sha256:built-def5678":  {"upaas-myapp:def5678"},
		"sha256:failed-0123abc": {tag0123ABC},
	}}
	svc, db := newImageTestService(t, api)
	ctx := context.Background()

	app := saveApp(t, db, "myapp", "sha256:built-abc1234", "sha256:built-def5678")

	for imageID := range api.images {
		deployment := models.NewDeployment(db)
		deployment.AppID = app.ID
		deployment.ImageID = sql.NullString{String: imageID, Valid: true}
		require.NoError(t, deployment.Save(ctx))
	}

	deployCommit := func(shortSHA, imageID string) {
		t.Helper()

		api.mu.Lock()
		api.shortSHA = shortSHA
		api.nextID = imageID
		api.mu.Unlock()

		deployment := models.NewDeployment(db)
		deployment.AppID = app.ID
		require.NoError(t, deployment.Save(ctx))

		built, err := svc.BuildImage(ctx, app, deployment)
		require.NoError(t, err)
		require.NoError(t, svc.RecordDeployedImage(ctx, app, deployment, built))
	}

	// The failed deploy's image loses its tag, and nothing uses it.
	deployCommit("0123abc", retriedImage)

	images, _ := api.state()
	assert.Equal(t, map[string][]string{
		"sha256:built-abc1234": {tagABC1234},
		retriedImage:           {tag0123ABC},
	}, images)

	// The running image loses its tag and becomes the one Rollback starts.
	deployCommit("0123abc", "sha256:rebuilt-0123abc")

	images, _ = api.state()
	assert.Equal(t, map[string][]string{
		"sha256:rebuilt-0123abc": {tag0123ABC},
		retriedImage:             {},
	}, images)
	assert.Equal(t, retriedImage, app.PreviousImageID.String)

	// Once Rollback no longer needs it, the untagged image is removed.
	deployCommit("4567def", "sha256:built-4567def")

	images, removed := api.state()
	assert.Equal(t, map[string][]string{
		"sha256:built-4567def":   {"upaas-myapp:4567def"},
		"sha256:rebuilt-0123abc": {tag0123ABC},
	}, images)
	assert.Equal(t, []string{
		"sha256:failed-0123abc", "upaas-myapp:def5678", // first deploy
		tagABC1234,   // second deploy
		retriedImage, // third deploy
	}, removed)
	assert.False(t, api.forced, "old images must be removed without force")
}