/*
Copyright (c) Edgeless Systems GmbH

SPDX-License-Identifier: AGPL-3.0-only
*/

package client

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"path"
	"time"

	"github.com/aws/aws-sdk-go-v2/aws"
	awsconfig "github.com/aws/aws-sdk-go-v2/config"
	s3manager "github.com/aws/aws-sdk-go-v2/feature/s3/manager"
	"github.com/aws/aws-sdk-go-v2/service/cloudfront"
	cftypes "github.com/aws/aws-sdk-go-v2/service/cloudfront/types"
	"github.com/aws/aws-sdk-go-v2/service/s3"
	s3types "github.com/aws/aws-sdk-go-v2/service/s3/types"
	"github.com/edgelesssys/constellation/v2/internal/constants"
	"github.com/edgelesssys/constellation/v2/internal/logger"
	"github.com/edgelesssys/constellation/v2/internal/versionsapi"
	"go.uber.org/multierr"
	"golang.org/x/mod/semver"
)

// Client is the client for the versions API.
//
// The client needs to be authenticated with AWS. It is the interface that should
// be used in internal development and CI tools.
//
// Needed IAM permissions for read mode:
// - "s3:GetObject"
// - "s3:ListBucket"
//
// Additional needed IAM permissions for write mode:
// - "s3:PutObject"
// - "s3:DeleteObject"
// - "cloudfront:CreateInvalidation"
//
// Thread-safety of the bucket is not guaranteed. The client is not thread-safe.
type Client struct {
	config                       aws.Config
	cloudfrontClient             *cloudfront.Client
	s3Client                     *s3.Client
	uploadClient                 *s3manager.Uploader
	bucket                       string
	distributionID               string
	cacheInvalidationWaitTimeout time.Duration

	dirtyPaths []string // written paths to be invalidated
	dryRun     bool     // no write operations are performed

	log *logger.Logger
}

// NewClient creates a new client for the versions API.
func NewClient(ctx context.Context, region, bucket, distributionID string, dryRun bool,
	log *logger.Logger,
) (*Client, error) {
	cfg, err := awsconfig.LoadDefaultConfig(ctx, awsconfig.WithRegion(region))
	if err != nil {
		return nil, err
	}

	cloudfrontC := cloudfront.NewFromConfig(cfg)
	s3C := s3.NewFromConfig(cfg)
	uploadC := s3manager.NewUploader(s3C)

	return &Client{
		config:                       cfg,
		cloudfrontClient:             cloudfrontC,
		s3Client:                     s3C,
		uploadClient:                 uploadC,
		bucket:                       bucket,
		distributionID:               distributionID,
		dryRun:                       dryRun,
		log:                          log,
		cacheInvalidationWaitTimeout: 5 * time.Minute,
	}, nil
}

// FetchVersionList fetches the given version list from the versions API.
func (c *Client) FetchVersionList(ctx context.Context, list versionsapi.List) (versionsapi.List, error) {
	return fetch(ctx, c, list)
}

// UpdateVersionList updates the given version list in the versions API.
func (c *Client) UpdateVersionList(ctx context.Context, list versionsapi.List) error {
	semver.Sort(list.Versions)
	return update(ctx, c, list)
}

// FetchVersionLatest fetches the latest version from the versions API.
func (c *Client) FetchVersionLatest(ctx context.Context, latest versionsapi.Latest) (versionsapi.Latest, error) {
	return fetch(ctx, c, latest)
}

// UpdateVersionLatest updates the latest version in the versions API.
func (c *Client) UpdateVersionLatest(ctx context.Context, latest versionsapi.Latest) error {
	return update(ctx, c, latest)
}

// FetchImageInfo fetches the given image info from the versions API.
func (c *Client) FetchImageInfo(ctx context.Context, imageInfo versionsapi.ImageInfo) (versionsapi.ImageInfo, error) {
	return fetch(ctx, c, imageInfo)
}

// UpdateImageInfo updates the given image info in the versions API.
func (c *Client) UpdateImageInfo(ctx context.Context, imageInfo versionsapi.ImageInfo) error {
	return update(ctx, c, imageInfo)
}

// DeleteRef deletes the given ref from the versions API.
func (c *Client) DeleteRef(ctx context.Context, ref string) error {
	if err := versionsapi.ValidateRef(ref); err != nil {
		return fmt.Errorf("validating ref: %w", err)
	}

	refPath := path.Join(constants.CDNAPIPrefix, "ref", ref)
	if err := c.deletePath(ctx, refPath); err != nil {
		return fmt.Errorf("deleting ref path: %w", err)
	}

	return nil
}

// DeleteVersion deletes the given version from the versions API.
// The version will be removed from version lists and latest versions, and the versioned
// objects are deleted.
// Notice that the versions API can get into an inconsistent state if the version is the latest
// version but there is no older version of the same minor version available.
// Manual update of latest versions is required in this case.
func (c *Client) DeleteVersion(ctx context.Context, ver versionsapi.Version) error {
	var retErr error

	c.log.Debugf("Deleting version %s from minor version list", ver.Version)
	possibleNewLatest, err := c.deleteVersionFromMinorVersionList(ctx, ver)
	if err != nil {
		retErr = multierr.Append(retErr, fmt.Errorf("removing from minor version list: %w", err))
	}

	c.log.Debugf("Checking latest version for %s", ver.Version)
	if err := c.deleteVersionFromLatest(ctx, ver, possibleNewLatest); err != nil {
		retErr = multierr.Append(retErr, fmt.Errorf("updating latest version: %w", err))
	}

	return retErr
}

// InvalidateCache invalidates the CDN cache for the paths that have been written.
// The function should be deferred after the client has been created.
func (c *Client) InvalidateCache(ctx context.Context) error {
	if len(c.dirtyPaths) == 0 {
		c.log.Debugf("No dirty paths, skipping cache invalidation.")
		return nil
	}

	if c.dryRun {
		c.log.Debugf("DryRun: cloudfront create invalidation {DistributionID: %v, Paths: %v}", c.distributionID, c.dirtyPaths)
		return nil
	}

	c.log.Debugf("Paths to invalidate: %v", c.dirtyPaths)

	in := &cloudfront.CreateInvalidationInput{
		DistributionId: &c.distributionID,
		InvalidationBatch: &cftypes.InvalidationBatch{
			CallerReference: ptr(fmt.Sprintf("%d", time.Now().Unix())),
			Paths: &cftypes.Paths{
				Items:    c.dirtyPaths,
				Quantity: ptr(int32(len(c.dirtyPaths))),
			},
		},
	}
	invalidation, err := c.cloudfrontClient.CreateInvalidation(ctx, in)
	if err != nil {
		return fmt.Errorf("creating invalidation: %w", err)
	}

	c.log.Debugf("Waiting for invalidation %s to complete.", *invalidation.Invalidation.Id)
	waiter := cloudfront.NewInvalidationCompletedWaiter(c.cloudfrontClient)
	waitIn := &cloudfront.GetInvalidationInput{
		DistributionId: &c.distributionID,
		Id:             invalidation.Invalidation.Id,
	}
	if err := waiter.Wait(ctx, waitIn, c.cacheInvalidationWaitTimeout); err != nil {
		return fmt.Errorf("waiting for invalidation to complete: %w", err)
	}

	return nil
}

type apiObject interface {
	ValidateRequest() error
	Validate() error
	JSONPath() string
}

func fetch[T apiObject](ctx context.Context, c *Client, obj T) (T, error) {
	if err := obj.ValidateRequest(); err != nil {
		return *new(T), fmt.Errorf("validating request for %T: %w", obj, err)
	}

	in := &s3.GetObjectInput{
		Bucket: &c.bucket,
		Key:    ptr(obj.JSONPath()),
	}

	c.log.Debugf("Fetching %T from s3: %s", obj, obj.JSONPath())
	out, err := c.s3Client.GetObject(ctx, in)
	var noSuchkey *s3types.NoSuchKey
	if errors.As(err, &noSuchkey) {
		return *new(T), &NotFoundError{err: err}
	} else if err != nil {
		return *new(T), fmt.Errorf("getting s3 object at %s: %w", obj.JSONPath(), err)
	}
	defer out.Body.Close()

	var newObj T
	if err := json.NewDecoder(out.Body).Decode(&newObj); err != nil {
		return *new(T), fmt.Errorf("decoding %T: %w", obj, err)
	}

	if newObj.Validate() != nil {
		return *new(T), fmt.Errorf("received invalid %T: %w", newObj, newObj.Validate())
	}

	return newObj, nil
}

func update[T apiObject](ctx context.Context, c *Client, obj T) error {
	if err := obj.Validate(); err != nil {
		return fmt.Errorf("validating %T struct: %w", obj, err)
	}

	rawJSON, err := json.Marshal(obj)
	if err != nil {
		return fmt.Errorf("marshaling %T struct: %w", obj, err)
	}

	if c.dryRun {
		c.log.Debugf("DryRun: s3 put object {Bucket: %v, Key: %v, Body: %v", c.bucket, obj.JSONPath(), string(rawJSON))
		return nil
	}

	in := &s3.PutObjectInput{
		Bucket: &c.bucket,
		Key:    ptr(obj.JSONPath()),
		Body:   bytes.NewBuffer(rawJSON),
	}

	c.dirtyPaths = append(c.dirtyPaths, "/"+obj.JSONPath())

	c.log.Debugf("Uploading %T to s3: %v", obj, obj.JSONPath())
	if _, err := c.uploadClient.Upload(ctx, in); err != nil {
		return fmt.Errorf("uploading %T: %w", obj, err)
	}

	return nil
}

func (c *Client) deleteVersionFromMinorVersionList(ctx context.Context, ver versionsapi.Version,
) (*versionsapi.Latest, error) {
	minorList := versionsapi.List{
		Ref:         ver.Ref,
		Stream:      ver.Stream,
		Granularity: versionsapi.GranularityMinor,
		Base:        ver.WithGranularity(versionsapi.GranularityMinor),
		Kind:        versionsapi.VersionKindImage,
	}
	c.log.Debugf("Fetching minor version list for version %s", ver.Version)
	minorList, err := c.FetchVersionList(ctx, minorList)
	var notFoundErr *NotFoundError
	if errors.As(err, &notFoundErr) {
		c.log.Warnf("Minor version list for version %s not found", ver.Version)
		c.log.Warnf("Skipping update of minor version list")
		return nil, nil
	} else if err != nil {
		return nil, fmt.Errorf("fetching minor version list for version %s: %w", ver.Version, err)
	}

	if !minorList.Contains(ver.Version) {
		c.log.Warnf("Version %s is not in minor version list %s", ver.Version, minorList.JSONPath())
		c.log.Warnf("Skipping update of minor version list")
		return nil, nil
	}

	semver.Sort(minorList.Versions)
	for i, v := range minorList.Versions {
		if v == ver.Version {
			minorList.Versions = append(minorList.Versions[:i], minorList.Versions[i+1:]...)
			break
		}
	}

	var latest *versionsapi.Latest
	if len(minorList.Versions) != 0 {
		latest = &versionsapi.Latest{
			Ref:     ver.Ref,
			Stream:  ver.Stream,
			Kind:    versionsapi.VersionKindImage,
			Version: minorList.Versions[len(minorList.Versions)-1],
		}
		c.log.Debugf("Possible latest version replacement %q", latest.Version)
	}

	if c.dryRun {
		c.log.Debugf("DryRun: Updating minor version list %s to %v", minorList.JSONPath(), minorList)
		return latest, nil
	}

	c.log.Debugf("Updating minor version list %s", minorList.JSONPath())
	if err := c.UpdateVersionList(ctx, minorList); err != nil {
		return latest, fmt.Errorf("updating minor version list %s: %w", minorList.JSONPath(), err)
	}

	c.log.Debugf("Removed version %s from minor version list %s", ver.Version, minorList.JSONPath())
	return latest, nil
}

func (c *Client) deleteVersionFromLatest(ctx context.Context, ver versionsapi.Version, possibleNewLatest *versionsapi.Latest,
) error {
	latest := versionsapi.Latest{
		Ref:    ver.Ref,
		Stream: ver.Stream,
		Kind:   versionsapi.VersionKindImage,
	}
	c.log.Debugf("Fetching latest version from %s.", latest.JSONPath())
	latest, err := c.FetchVersionLatest(ctx, latest)
	var notFoundErr *NotFoundError
	if errors.As(err, &notFoundErr) {
		c.log.Warnf("Latest version for %s not found.", latest.JSONPath())
		return nil
	} else if err != nil {
		return fmt.Errorf("fetching latest version: %w", err)
	}

	if latest.Version != ver.Version {
		c.log.Debugf("Latest version is %s, not the deleted version %s.", latest.Version, ver.Version)
		return nil
	}

	if possibleNewLatest == nil {
		c.log.Errorf("Latest version is %s, but no new latest version was found.", latest.Version)
		c.log.Errorf("A manual update of latest at %s might be needed", latest.JSONPath())
		return fmt.Errorf("latest version is %s, but no new latest version was found", latest.Version)
	}

	if c.dryRun {
		c.log.Debugf("Would update latest version from %s to %s", latest.Version, possibleNewLatest.Version)
		return nil
	}

	c.log.Infof("Updating latest version from %s to %s", latest.Version, possibleNewLatest.Version)
	if err := c.UpdateVersionLatest(ctx, *possibleNewLatest); err != nil {
		return fmt.Errorf("updating latest version: %w", err)
	}

	return nil
}

func (c *Client) deletePath(ctx context.Context, path string) error {
	listIn := &s3.ListObjectsV2Input{
		Bucket: &c.bucket,
		Prefix: &path,
	}
	c.log.Debugf("Listing objects in %s", path)
	objs := []s3types.Object{}
	out := &s3.ListObjectsV2Output{IsTruncated: true}
	for out.IsTruncated {
		var err error
		out, err = c.s3Client.ListObjectsV2(ctx, listIn)
		if err != nil {
			return fmt.Errorf("listing objects in %s: %w", path, err)
		}
		objs = append(objs, out.Contents...)
	}
	c.log.Debugf("Found %d objects in %s", len(objs), path)

	if len(objs) == 0 {
		c.log.Warnf("Path %s is already empty", path)
		return nil
	}

	objIDs := make([]s3types.ObjectIdentifier, len(objs))
	for i, obj := range objs {
		objIDs[i] = s3types.ObjectIdentifier{Key: obj.Key}
	}

	if c.dryRun {
		c.log.Debugf("DryRun: Deleting %d objects with IDs %v", len(objs), objIDs)
		return nil
	}

	c.dirtyPaths = append(c.dirtyPaths, "/"+path)

	deleteIn := &s3.DeleteObjectsInput{
		Bucket: &c.bucket,
		Delete: &s3types.Delete{
			Objects: objIDs,
		},
	}
	c.log.Debugf("Deleting %d objects in %s", len(objs), path)
	if _, err := c.s3Client.DeleteObjects(ctx, deleteIn); err != nil {
		return fmt.Errorf("deleting objects in %s: %w", path, err)
	}

	return nil
}

// NotFoundError is an error that is returned when a resource is not found.
type NotFoundError struct {
	err error
}

func (e *NotFoundError) Error() string {
	return fmt.Sprintf("the requested resource was not found: %s", e.err.Error())
}

func (e *NotFoundError) Unwrap() error {
	return e.err
}

func ptr[T any](t T) *T {
	return &t
}