package oss

import (
	"context"
	"errors"
	"io"
	"net/url"
	"strings"

	"github.com/minio/minio-go/v7"
	"github.com/minio/minio-go/v7/pkg/credentials"

	"github.com/tinode/chat/server/media"
	"github.com/tinode/chat/server/store"
	"github.com/tinode/chat/server/store/types"
)

const minioLocationPrefix = "minio://"

type minioConfig struct {
	Endpoint        string `json:"endpoint"`
	Bucket          string `json:"bucket"`
	Region          string `json:"region"`
	AccessKeyID     string `json:"access_key_id"`
	SecretAccessKey string `json:"secret_access_key"`
}

type minioStorage struct {
	client *minio.Client
	bucket string
}

func newMinIOStorage(conf minioConfig) (*minioStorage, error) {
	if conf.Endpoint == "" || conf.Bucket == "" || conf.AccessKeyID == "" || conf.SecretAccessKey == "" {
		return nil, nil
	}
	endpoint := strings.TrimSpace(conf.Endpoint)
	secure := true
	if strings.Contains(endpoint, "://") {
		parsed, err := url.Parse(endpoint)
		if err != nil || parsed.Host == "" || parsed.Path != "" || parsed.RawQuery != "" || parsed.Fragment != "" || (parsed.Scheme != "http" && parsed.Scheme != "https") {
			return nil, errors.New("invalid MinIO endpoint")
		}
		endpoint = parsed.Host
		secure = parsed.Scheme == "https"
	}
	client, err := minio.New(endpoint, &minio.Options{
		Creds:  credentials.NewStaticV4(conf.AccessKeyID, conf.SecretAccessKey, ""),
		Secure: secure,
		Region: conf.Region,
	})
	if err != nil {
		return nil, err
	}
	return &minioStorage{client: client, bucket: conf.Bucket}, nil
}

func (oh *ossHandler) uploadMinIO(fd *types.FileDef, file io.Reader) (string, int64, error) {
	key, err := tenantObjectKey(fd.TenantID, fd.Uid().String32(), fd.CreatedAt)
	if err != nil {
		return "", 0, err
	}
	if err := store.Files.StartUpload(fd.TenantID, fd); err != nil {
		return "", 0, err
	}
	result, err := oh.minio.client.PutObject(context.Background(), oh.minio.bucket, key, file, remainingSize(file), minio.PutObjectOptions{
		ContentType:  fd.MimeType,
		CacheControl: oh.conf.CacheControl,
	})
	if err != nil {
		return "", 0, err
	}
	fd.Location = minioLocation(oh.minio.bucket, key)
	fd.ETag = strings.Trim(result.ETag, "\"")
	return oh.conf.ServeURL + media.FileURLName(fd), result.Size, nil
}

func (oh *ossHandler) uploadPublicMinIO(fd *media.PublicFileDef, file io.Reader) (string, int64, error) {
	key, err := publicObjectKey(fd.Purpose, fd.ID, fd.CreatedAt)
	if err != nil {
		return "", 0, err
	}
	result, err := oh.minio.client.PutObject(context.Background(), oh.minio.bucket, key, file, remainingSize(file), minio.PutObjectOptions{
		ContentType:  fd.MimeType,
		CacheControl: oh.conf.CacheControl,
	})
	if err != nil {
		return "", 0, err
	}
	fd.Location = minioLocation(oh.minio.bucket, key)
	fd.ETag = strings.Trim(result.ETag, "\"")
	return fd.Location, result.Size, nil
}

func (oh *ossHandler) downloadMinIO(fd *types.FileDef) (*types.FileDef, media.ReadSeekCloser, error) {
	bucket, key, err := oh.minioObject(fd.Location)
	if err != nil {
		return nil, nil, err
	}
	if fd.Size <= 0 {
		meta, err := oh.minio.client.StatObject(context.Background(), bucket, key, minio.StatObjectOptions{})
		if err != nil {
			return nil, nil, err
		}
		fd.Size = meta.Size
	}
	reader := &ossReadSeekCloser{size: fd.Size}
	reader.open = func(offset int64) (io.ReadCloser, error) {
		options := minio.GetObjectOptions{}
		if offset > 0 {
			if err := options.SetRange(offset, fd.Size-1); err != nil {
				return nil, err
			}
		}
		return oh.minio.client.GetObject(context.Background(), bucket, key, options)
	}
	return fd, reader, nil
}

func (oh *ossHandler) deleteMinIO(location string) error {
	bucket, key, err := oh.minioObject(location)
	if err != nil {
		return err
	}
	return oh.minio.client.RemoveObject(context.Background(), bucket, key, minio.RemoveObjectOptions{})
}

func (oh *ossHandler) minioObject(location string) (string, string, error) {
	if oh.minio == nil {
		return "", "", errors.New("MinIO is not configured for stored file")
	}
	bucket, key, ok := strings.Cut(strings.TrimPrefix(location, minioLocationPrefix), "/")
	if !strings.HasPrefix(location, minioLocationPrefix) || !ok || bucket != oh.minio.bucket || key == "" {
		return "", "", types.ErrMalformed
	}
	return bucket, key, nil
}

func minioLocation(bucket, key string) string {
	return minioLocationPrefix + bucket + "/" + key
}

func remainingSize(reader io.Reader) int64 {
	seeker, ok := reader.(io.Seeker)
	if !ok {
		return -1
	}
	current, err := seeker.Seek(0, io.SeekCurrent)
	if err != nil {
		return -1
	}
	end, err := seeker.Seek(0, io.SeekEnd)
	if err != nil {
		_, _ = seeker.Seek(current, io.SeekStart)
		return -1
	}
	if _, err := seeker.Seek(current, io.SeekStart); err != nil {
		return -1
	}
	return end - current
}