package engine

import (
	"bytes"
	"fmt"
	"io"

	"robotfs/utils"

	"github.com/aws/aws-sdk-go/aws"
	"github.com/aws/aws-sdk-go/aws/credentials"
	"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"
)

type S3Config struct {
	Region          string
	Endpoint        string
	AccessKeyID     string
	SecretAccessKey string
	BucketName      string
	UsePathStyle    bool
}

func Initialize(configuration utils.Configuration, prefix string) (*S3Config, error) {
	s3Cfg := &S3Config{
		Region:          configuration.GetString(prefix + "region"),
		Endpoint:        configuration.GetString(prefix + "endpoint"),
		AccessKeyID:     configuration.GetString(prefix + "access_key_id"),
		SecretAccessKey: configuration.GetString(prefix + "secret_access_key"),
		BucketName:      configuration.GetString(prefix + "bucket_name"),
		UsePathStyle:    configuration.GetBool(prefix + "use_path_style"),
	}

	if s3Cfg.BucketName == "" {
		return nil, fmt.Errorf("bucket_name is required")
	}

	return s3Cfg, nil
}

type StorageManager struct {
	s3Client     *s3.S3
	s3Uploader   *s3manager.Uploader
	s3Downloader *s3manager.Downloader
	bucketName   string
}

func NewStorageManager(s3Config *S3Config) (*StorageManager, error) {
	s3Config, awsSession, err := createS3Session(s3Config)
	if err != nil {
		return nil, err
	}

	s3Client := s3.New(awsSession)

	uploader := s3manager.NewUploader(awsSession)
	downloader := s3manager.NewDownloader(awsSession)

	return &StorageManager{
		s3Client:     s3Client,
		s3Uploader:   uploader,
		s3Downloader: downloader,
		bucketName:   s3Config.BucketName,
	}, nil
}

func createS3Session(config *S3Config) (*S3Config, *session.Session, error) {
	awsConfig := &aws.Config{
		Credentials:      credentials.NewStaticCredentials(config.AccessKeyID, config.SecretAccessKey, ""),
		Region:           aws.String(config.Region),
		S3ForcePathStyle: aws.Bool(config.UsePathStyle),
	}

	if config.Endpoint != "" {
		awsConfig.Endpoint = aws.String(config.Endpoint)
	}

	sess, err := session.NewSession(awsConfig)
	if err != nil {
		return config, nil, err
	}

	return config, sess, nil
}

func (sm *StorageManager) UploadData(s3Key string, data []byte, contentType string) (*s3manager.UploadOutput, error) {
	if contentType == "" {
		contentType = "application/octet-stream"
	}

	output, err := sm.s3Uploader.Upload(&s3manager.UploadInput{
		Bucket:      aws.String(sm.bucketName),
		Key:         aws.String(s3Key),
		Body:        bytes.NewReader(data),
		ContentType: aws.String(contentType),
	})
	if err != nil {
		return nil, err
	}

	return output, nil
}

func (sm *StorageManager) UploadFile(s3Key string, data io.Reader, contentType string) (*s3manager.UploadOutput, error) {
	if contentType == "" {
		contentType = "application/octet-stream"
	}

	output, err := sm.s3Uploader.Upload(&s3manager.UploadInput{
		Bucket:      aws.String(sm.bucketName),
		Key:         aws.String(s3Key),
		Body:        data,
		ContentType: aws.String(contentType),
	})
	if err != nil {
		return nil, err
	}

	return output, nil
}

func (sm *StorageManager) DownloadFile(S3Key string) (*utils.S3ReadSeeker, error) {
	head, err := sm.s3Client.HeadObject(&s3.HeadObjectInput{
		Bucket: aws.String(sm.bucketName),
		Key:    aws.String(S3Key),
	})
	if err != nil {
		return nil, err
	}

	result, err := sm.s3Client.GetObject(&s3.GetObjectInput{
		Bucket: aws.String(sm.bucketName),
		Key:    aws.String(S3Key),
	})
	if err != nil {
		return nil, err
	}

	return utils.NewS3ReadSeeker(sm.s3Client, sm.bucketName, S3Key, result.Body, *head.ContentLength), nil
}

func (sm *StorageManager) ReadObject(S3Key string) ([]byte, error) {
	buf := aws.NewWriteAtBuffer([]byte{})

	_, err := sm.s3Downloader.Download(buf, &s3.GetObjectInput{
		Bucket: aws.String(sm.bucketName),
		Key:    aws.String(S3Key),
	})
	if err != nil {
		return nil, err
	}

	return buf.Bytes(), nil
}

func (sm *StorageManager) DeleteObject(s3Key string) error {
	_, err := sm.s3Client.DeleteObject(&s3.DeleteObjectInput{
		Bucket: aws.String(sm.bucketName),
		Key:    aws.String(s3Key),
	})
	if err != nil {
		return err
	}

	return sm.s3Client.WaitUntilObjectNotExists(&s3.HeadObjectInput{
		Bucket: aws.String(sm.bucketName),
		Key:    aws.String(s3Key),
	})
}

func (sm *StorageManager) CopyObject(oldS3key, newS3Key string) error {
	_, err := sm.s3Client.CopyObject(&s3.CopyObjectInput{
		Bucket:     aws.String(sm.bucketName),
		CopySource: aws.String(fmt.Sprintf("%s/%s", sm.bucketName, oldS3key)),
		Key:        aws.String(newS3Key),
	})
	if err != nil {
		return err
	}

	return sm.s3Client.WaitUntilObjectExists(&s3.HeadObjectInput{
		Bucket: aws.String(sm.bucketName),
		Key:    aws.String(newS3Key),
	})
}

func (sm *StorageManager) ListObjects(prefix string) ([]string, error) {
	var result []string

	input := &s3.ListObjectsV2Input{
		Bucket: aws.String(sm.bucketName),
		Prefix: aws.String(prefix),
	}

	err := sm.s3Client.ListObjectsV2Pages(input, func(page *s3.ListObjectsV2Output, lastPage bool) bool {
		for _, obj := range page.Contents {
			result = append(result, *obj.Key)
		}
		return !lastPage
	})
	if err != nil {
		return nil, err
	}

	return result, nil
}