// Copyright (C) 2019-2020 Zilliz. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance
// with the License. You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software distributed under the License
// is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
// or implied. See the License for the specific language governing permissions and limitations under the License.

package miniokv

import (
	"context"
	"fmt"
	"sync"

	"io"
	"strings"

	"github.com/milvus-io/milvus/internal/log"
	"github.com/milvus-io/milvus/internal/util/retry"
	"github.com/minio/minio-go/v7"
	"github.com/minio/minio-go/v7/pkg/credentials"
	"go.uber.org/zap"
)

type MinIOKV struct {
	ctx         context.Context
	minioClient *minio.Client
	bucketName  string
}

type Option struct {
	Address           string
	AccessKeyID       string
	BucketName        string
	SecretAccessKeyID string
	UseSSL            bool
	CreateBucket      bool // when bucket not existed, create it
}

// NewMinIOKV creates MinIOKV to save and load object to MinIOKV.
func NewMinIOKV(ctx context.Context, option *Option) (*MinIOKV, error) {
	var minIOClient *minio.Client
	var err error
	log.Debug("MinioKV NewMinioKV", zap.Any("option", option))
	minIOClient, err = minio.New(option.Address, &minio.Options{
		Creds:  credentials.NewStaticV4(option.AccessKeyID, option.SecretAccessKeyID, ""),
		Secure: option.UseSSL,
	})
	// options nil or invalid formatted endpoint, don't need retry
	if err != nil {
		return nil, err
	}
	var bucketExists bool
	// check valid in first query
	checkBucketFn := func() error {
		bucketExists, err = minIOClient.BucketExists(ctx, option.BucketName)
		if err != nil {
			return err
		}
		if !bucketExists {
			log.Debug("MinioKV NewMinioKV", zap.Any("Check bucket", "bucket not exist"))
			if option.CreateBucket {
				log.Debug("MinioKV NewMinioKV create bucket.")
				return minIOClient.MakeBucket(ctx, option.BucketName, minio.MakeBucketOptions{})
			}
			return fmt.Errorf("bucket %s not Existed", option.BucketName)
		}
		return nil
	}
	err = retry.Do(ctx, checkBucketFn, retry.Attempts(300))
	if err != nil {
		return nil, err
	}

	kv := &MinIOKV{
		ctx:         ctx,
		minioClient: minIOClient,
		bucketName:  option.BucketName,
	}
	log.Debug("MinioKV new MinioKV success.")

	return kv, nil
}

// Exist check whether a key exists in MinIO.
func (kv *MinIOKV) Exist(key string) bool {
	_, err := kv.minioClient.StatObject(kv.ctx, kv.bucketName, key, minio.StatObjectOptions{})
	return err == nil
}

// LoadWithPrefix load objects with the same prefix @key from minio .
func (kv *MinIOKV) LoadWithPrefix(key string) ([]string, []string, error) {
	objects := kv.minioClient.ListObjects(kv.ctx, kv.bucketName, minio.ListObjectsOptions{Prefix: key})

	var objectsKeys []string
	var objectsValues []string

	for object := range objects {
		objectsKeys = append(objectsKeys, object.Key)
	}
	objectsValues, err := kv.MultiLoad(objectsKeys)
	if err != nil {
		log.Debug("MinIO", zap.String("cannot load value with prefix:%s", key))
	}

	return objectsKeys, objectsValues, nil
}

// LoadWithPrefix load an object with @key.
func (kv *MinIOKV) Load(key string) (string, error) {
	object, err := kv.minioClient.GetObject(kv.ctx, kv.bucketName, key, minio.GetObjectOptions{})
	if object != nil {
		defer object.Close()
	}
	if err != nil {
		return "", err
	}

	buf := new(strings.Builder)
	_, err = io.Copy(buf, object)
	if err != nil && err != io.EOF {
		return "", err
	}
	return buf.String(), nil
}

// FGetObject download file from minio to local storage system.
func (kv *MinIOKV) FGetObject(key, localPath string) error {
	err := kv.minioClient.FGetObject(kv.ctx, kv.bucketName, key, localPath+key, minio.GetObjectOptions{})
	if err != nil {
		return err
	}
	return nil
}

// FGetObjects download file from minio to local storage system.
// For parallell downloads file, n goroutines will be started to download n keys.
func (kv *MinIOKV) FGetObjects(keys []string, localPath string) error {
	var wg sync.WaitGroup
	el := make(errorList, len(keys))
	for i, key := range keys {
		wg.Add(1)
		go func(i int, key string) {
			err := kv.minioClient.FGetObject(kv.ctx, kv.bucketName, key, localPath+key, minio.GetObjectOptions{})
			if err != nil {
				el[i] = err
			}
			wg.Done()
		}(i, key)
	}
	wg.Wait()
	for _, err := range el {
		if err != nil {
			return el
		}
	}
	return nil
}

// MultiLoad loads objects with multi @keys.
func (kv *MinIOKV) MultiLoad(keys []string) ([]string, error) {
	var resultErr error
	var objectsValues []string
	for _, key := range keys {
		objectValue, err := kv.Load(key)
		if err != nil {
			if resultErr == nil {
				resultErr = err
			}
		}
		objectsValues = append(objectsValues, objectValue)
	}

	return objectsValues, resultErr
}

// Save object with @key to Minio. Object value is @value.
func (kv *MinIOKV) Save(key, value string) error {
	reader := strings.NewReader(value)
	_, err := kv.minioClient.PutObject(kv.ctx, kv.bucketName, key, reader, int64(len(value)), minio.PutObjectOptions{})

	if err != nil {
		return err
	}

	return err
}

// Save MultiObject, the path is the key of @kvs. The object value is the value
// of @kvs.
func (kv *MinIOKV) MultiSave(kvs map[string]string) error {
	var resultErr error
	for key, value := range kvs {
		err := kv.Save(key, value)
		if err != nil {
			if resultErr == nil {
				resultErr = err
			}
		}
	}
	return resultErr
}

// LoadWithPrefix remove all objects with the same prefix @prefix from minio .
func (kv *MinIOKV) RemoveWithPrefix(prefix string) error {
	objectsCh := make(chan minio.ObjectInfo)

	go func() {
		defer close(objectsCh)

		for object := range kv.minioClient.ListObjects(kv.ctx, kv.bucketName, minio.ListObjectsOptions{Prefix: prefix}) {
			objectsCh <- object
		}
	}()

	for rErr := range kv.minioClient.RemoveObjects(kv.ctx, kv.bucketName, objectsCh, minio.RemoveObjectsOptions{GovernanceBypass: true}) {
		if rErr.Err != nil {
			return rErr.Err
		}
	}
	return nil
}

// Remove delete an object with @key.
func (kv *MinIOKV) Remove(key string) error {
	err := kv.minioClient.RemoveObject(kv.ctx, kv.bucketName, string(key), minio.RemoveObjectOptions{})
	return err
}

// MultiRemove delete a objects with @keys.
func (kv *MinIOKV) MultiRemove(keys []string) error {
	var resultErr error
	for _, key := range keys {
		err := kv.Remove(key)
		if err != nil {
			if resultErr == nil {
				resultErr = err
			}
		}
	}
	return resultErr
}

func (kv *MinIOKV) Close() {

}

type errorList []error

func (el errorList) Error() string {
	var builder strings.Builder
	builder.WriteString("All downloads results:\n")
	for index, err := range el {
		builder.WriteString(fmt.Sprintf("downloads #%d:%s\n", index+1, err.Error()))
	}
	return builder.String()
}