package resource

import (
	"bytes"
	"context"
	"errors"
	"github.com/aws/aws-sdk-go/aws"
	"github.com/aws/aws-sdk-go/aws/session"
	"github.com/aws/aws-sdk-go/service/s3"
	"github.com/aws/aws-sdk-go/service/s3/s3manager"
	"log"
	"net/url"
	"os"
	"resource-manager/domain/cache"
	"strconv"
	"strings"
	"sync"
	"time"
)

func newS3Bucket(cacheManager cache.Manager, expiration time.Duration) Manager {
	sess, err := session.NewSession(&aws.Config{
		Region: aws.String(os.Getenv("AWS_REGION_NAME"))},
	)
	if err != nil {
		panic(err)
	}
	uploader := s3manager.NewUploader(sess)
	downloader := s3manager.NewDownloader(sess)
	upload := make(chan UploadRequest, 20)
	manager := awsManager{
		cacheManager,
		upload,
		make(map[string][]onUpload),
		sync.Mutex{},
		expiration,
		uploader,
		downloader,
	}
	go manager.uploadRunner()
	return &manager
}

type onUpload chan bool

type awsManager struct {
	cache              cache.Manager
	requests           chan UploadRequest
	currentlyUploading map[string][]onUpload
	uploadSync         sync.Mutex
	expiration         time.Duration
	uploader           *s3manager.Uploader
	downloader         *s3manager.Downloader
}

func (a *awsManager) uploadRunner() {
	for req := range a.requests {
		status := true
		if !a.doesFileExist(req.Path) {
			status = a.upload(req.Path, req.Buffer.Bytes(), req.MimeType)
		}
		a.notifyOnUploadComplete(req.Path, status)
	}
}
func (a *awsManager) Upload(request UploadRequest) {
	a.addToCurrentlyUploading(request.Path)
	a.requests <- request
}
func (a *awsManager) Presign(_ context.Context, path string) (string, error) {
	if !a.waitForUploadComplete(path) {
		return "", errors.New("failed upload")
	}
	// ask cache for latest url
	if uri, err := a.cache.Get(path); err == nil {
		return uri, nil
	}
	// if there is no value in cache, presign url and add it to cache
	uri, err := a.presign(path, a.expiration)
	if err != nil {
		_ = a.cache.Set(path, uri, a.expiration)
	}
	return uri, err
}
func (a *awsManager) Download(_ context.Context, path string) (file []byte, err error) {
	return a.download(path)
}
func (a *awsManager) Copy(from string, to string, overwrite bool) error {
	fromPath := strings.SplitN(from, "/", 2)
	toPath := strings.SplitN(to, "/", 2)
	output, err := a.downloader.S3.ListObjectsV2(&s3.ListObjectsV2Input{
		Bucket: aws.String(fromPath[0]),
		Prefix: aws.String(fromPath[1]),
	})
	if err != nil {
		return err
	}
	for _, obj := range output.Contents {
		if overwrite || !a.doesFileExist(strings.Replace(*obj.Key, fromPath[1], toPath[1], 1)) {
			_, err = a.downloader.S3.CopyObject(&s3.CopyObjectInput{
				Bucket:     aws.String(toPath[0]),
				CopySource: aws.String(url.PathEscape(from)),
				Key:        aws.String(toPath[1]),
			})
			if err != nil {
				return err
			}
		}
	}
	return nil
}
func (a *awsManager) Delete(path string) error {
	paths := strings.SplitN(path, "/", 2)
	_, err := a.uploader.S3.DeleteObject(&s3.DeleteObjectInput{
		Bucket: aws.String(paths[0]),
		Key:    aws.String(paths[1]),
	})
	if err != nil {
		return err
	}
	a.cache.Remove(path)
	return nil
}

func (a *awsManager) addToCurrentlyUploading(path string) {
	a.uploadSync.Lock()
	log.Println("Manager | (" + path + ") added to upload list")
	a.currentlyUploading[path] = make([]onUpload, 0)
	a.uploadSync.Unlock()
}
func (a *awsManager) waitForUploadComplete(path string) bool {
	a.uploadSync.Lock()
	defer a.uploadSync.Unlock()
	if _, contains := a.currentlyUploading[path]; contains {
		upload := make(onUpload)
		a.currentlyUploading[path] = append(a.currentlyUploading[path], upload)
		return <-upload
	}
	return true
}
func (a *awsManager) notifyOnUploadComplete(path string, status bool) {
	a.uploadSync.Lock()
	defer a.uploadSync.Unlock()

	log.Println("Manager | (" + path + ") finished uploading, success: " + strconv.FormatBool(status))

	for _, upload := range a.currentlyUploading[path] {
		upload <- status
		close(upload)
	}
	delete(a.currentlyUploading, path)
}

func (a *awsManager) upload(path string, data []byte, mimeType string) bool {
	log.Println("Manager | (" + path + ") uploading")
	paths := strings.SplitN(path, "/", 2)
	_, err := a.uploader.Upload(&s3manager.UploadInput{
		Bucket:      aws.String(paths[0]),
		ContentType: aws.String(mimeType),
		Key:         aws.String(paths[1]),
		Body:        bytes.NewReader(data),
	})
	return err == nil
}
func (a *awsManager) presign(path string, expiration time.Duration) (string, error) {
	paths := strings.SplitN(path, "/", 2)
	requestInput := s3.GetObjectInput{
		Bucket: aws.String(paths[0]),
		Key:    aws.String(paths[1]),
	}
	request, _ := a.downloader.S3.GetObjectRequest(&requestInput)
	if request.Error != nil {
		log.Println("Manager | (" + path + ") failed presiging, cause: " + request.Error.Error())
	}
	return request.Presign(expiration)
}
func (a *awsManager) download(path string) ([]byte, error) {
	paths := strings.SplitN(path, "/", 2)
	requestInput := s3.GetObjectInput{
		Bucket: aws.String(paths[0]),
		Key:    aws.String(paths[1]),
	}
	buf := aws.NewWriteAtBuffer([]byte{})
	_, err := a.downloader.Download(buf, &requestInput)
	if err != nil {
		log.Println("Manager | (" + path + ") failed downloading, cause: " + err.Error())
	}
	return buf.Bytes(), err
}
func (a *awsManager) doesFileExist(path string) bool {
	paths := strings.SplitN(path, "/", 2)
	requestInput := s3.HeadObjectInput{
		Bucket: aws.String(paths[0]),
		Key:    aws.String(paths[1]),
	}
	_, err := a.downloader.S3.HeadObject(&requestInput)
	if err != nil && err.Error() == s3.ErrCodeNoSuchKey {
		return true
	}
	return false
}