/*
 * MinIO Cloud Storage, (C) 2020 MinIO, Inc.
 *
 * 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 cmd

import (
	"context"
	"fmt"
	"net/http"
	"sync"

	miniogo "github.com/minio/minio-go/v7"
	"github.com/minio/minio-go/v7/pkg/credentials"
	"github.com/minio/minio/pkg/bucket/versioning"
	"github.com/minio/minio/pkg/madmin"
)

// BucketTargetSys represents bucket targets subsystem
type BucketTargetSys struct {
	sync.RWMutex
	arnRemotesMap map[string]*miniogo.Core
	targetsMap    map[string][]madmin.BucketTarget
	clientsCache  map[string]*miniogo.Core
}

// ListTargets - gets list of bucket targets for this bucket.
func (sys *BucketTargetSys) ListTargets(ctx context.Context, bucket string) (*madmin.BucketTargets, error) {
	if globalIsGateway {
		return nil, nil
	}
	tgts, ok := sys.targetsMap[bucket]
	if ok {
		return &madmin.BucketTargets{Targets: tgts}, nil
	}
	return nil, fmt.Errorf("No remote targets exist for bucket %s", bucket)
}

// SetTarget - sets a new minio-go client target for this bucket.
func (sys *BucketTargetSys) SetTarget(ctx context.Context, bucket string, tgt *madmin.BucketTarget) error {
	if globalIsGateway {
		return nil
	}
	if !tgt.Type.IsValid() {
		return BucketRemoteArnTypeInvalid{Bucket: bucket}
	}
	clnt, err := sys.getRemoteTargetClient(tgt)
	if err != nil {
		return BucketRemoteTargetNotFound{Bucket: tgt.TargetBucket}
	}

	if tgt.Type == madmin.ReplicationArn {
		vcfg, err := clnt.GetBucketVersioning(ctx, tgt.TargetBucket)
		if err != nil || vcfg.Status != string(versioning.Enabled) {
			if isErrBucketNotFound(err) {
				return BucketRemoteTargetNotFound{Bucket: tgt.TargetBucket}
			}
			return BucketReplicationTargetNotVersioned{Bucket: tgt.TargetBucket}
		}
	}

	sys.Lock()
	defer sys.Unlock()

	tgts := sys.targetsMap[bucket]
	newtgts := make([]madmin.BucketTarget, len(tgts))
	found := false
	for idx, t := range tgts {
		if t.Type == tgt.Type {
			if t.Arn == tgt.Arn {
				return BucketRemoteAlreadyExists{Bucket: t.TargetBucket}
			}
			newtgts[idx] = *tgt
			found = true
			continue
		}
		newtgts[idx] = t
	}
	if !found {
		newtgts = append(newtgts, *tgt)
	}

	sys.targetsMap[bucket] = newtgts
	sys.arnRemotesMap[tgt.Arn] = clnt
	if _, ok := sys.clientsCache[clnt.EndpointURL().String()]; !ok {
		sys.clientsCache[clnt.EndpointURL().String()] = clnt
	}
	return nil
}

// RemoveTarget - removes a remote bucket target for this source bucket.
func (sys *BucketTargetSys) RemoveTarget(ctx context.Context, bucket, arnStr string) error {
	if globalIsGateway {
		return nil
	}
	if arnStr == "" {
		return BucketRemoteArnInvalid{Bucket: bucket}
	}
	arn, err := madmin.ParseARN(arnStr)
	if err != nil {
		return BucketRemoteArnInvalid{Bucket: bucket}
	}
	if arn.Type == madmin.ReplicationArn {
		// reject removal of remote target if replication configuration is present
		rcfg, err := getReplicationConfig(ctx, bucket)
		if err == nil && rcfg.ReplicationArn == arnStr {
			if _, ok := sys.arnRemotesMap[arnStr]; ok {
				return BucketRemoteRemoveDisallowed{Bucket: bucket}
			}
		}
	}
	// delete ARN type from list of matching targets
	sys.Lock()
	defer sys.Unlock()
	targets := make([]madmin.BucketTarget, 0)
	tgts := sys.targetsMap[bucket]
	for _, tgt := range tgts {
		if tgt.Arn != arnStr {
			targets = append(targets, tgt)
		}
	}
	sys.targetsMap[bucket] = targets
	delete(sys.arnRemotesMap, arnStr)
	return nil
}

// GetReplicationTargetClient returns minio-go client for replication target instance
func (sys *BucketTargetSys) GetReplicationTargetClient(ctx context.Context, arn string) *miniogo.Core {
	sys.RLock()
	defer sys.RUnlock()
	return sys.arnRemotesMap[arn]
}

// NewBucketTargetSys - creates new replication system.
func NewBucketTargetSys() *BucketTargetSys {
	return &BucketTargetSys{
		arnRemotesMap: make(map[string]*miniogo.Core),
		targetsMap:    make(map[string][]madmin.BucketTarget),
		clientsCache:  make(map[string]*miniogo.Core),
	}
}

// Init initializes the bucket targets subsystem for buckets which have targets configured.
func (sys *BucketTargetSys) Init(ctx context.Context, buckets []BucketInfo, objAPI ObjectLayer) error {
	if objAPI == nil {
		return errServerNotInitialized
	}

	// In gateway mode, bucket targets is not supported.
	if globalIsGateway {
		return nil
	}

	// Load bucket targets once during boot.
	sys.load(ctx, buckets, objAPI)
	return nil
}

// create minio-go clients for buckets having remote targets
func (sys *BucketTargetSys) load(ctx context.Context, buckets []BucketInfo, objAPI ObjectLayer) {
	for _, bucket := range buckets {
		cfg, err := globalBucketMetadataSys.GetBucketTargetsConfig(bucket.Name)
		if err != nil {
			continue
		}
		if cfg == nil || cfg.Empty() {
			continue
		}
		if len(cfg.Targets) > 0 {
			sys.targetsMap[bucket.Name] = cfg.Targets
		}
		for _, tgt := range cfg.Targets {
			tgtClient, err := sys.getRemoteTargetClient(&tgt)
			if err != nil {
				continue
			}
			sys.arnRemotesMap[tgt.Arn] = tgtClient
			if _, ok := sys.clientsCache[tgtClient.EndpointURL().String()]; !ok {
				sys.clientsCache[tgtClient.EndpointURL().String()] = tgtClient
			}
		}
		sys.targetsMap[bucket.Name] = cfg.Targets
	}
}

// getRemoteTargetInstanceTransport contains a singleton roundtripper.
var getRemoteTargetInstanceTransport http.RoundTripper
var getRemoteTargetInstanceTransportOnce sync.Once

// Returns a minio-go Client configured to access remote host described in replication target config.
func (sys *BucketTargetSys) getRemoteTargetClient(tcfg *madmin.BucketTarget) (*miniogo.Core, error) {
	if clnt, ok := sys.clientsCache[tcfg.Endpoint]; ok {
		return clnt, nil
	}
	config := tcfg.Credentials
	creds := credentials.NewStaticV4(config.AccessKey, config.SecretKey, "")

	getRemoteTargetInstanceTransportOnce.Do(func() {
		getRemoteTargetInstanceTransport = NewGatewayHTTPTransport()
	})
	core, err := miniogo.NewCore(tcfg.Endpoint, &miniogo.Options{
		Creds:     creds,
		Secure:    tcfg.Secure,
		Transport: getRemoteTargetInstanceTransport,
	})
	return core, err
}

// getRemoteARN gets existing ARN for an endpoint or generates a new one.
func (sys *BucketTargetSys) getRemoteARN(bucket string, target *madmin.BucketTarget) string {
	if target == nil {
		return ""
	}
	tgts := sys.targetsMap[bucket]
	for _, tgt := range tgts {
		if tgt.Type == target.Type && tgt.TargetBucket == target.TargetBucket && target.URL() == tgt.URL() {
			return tgt.Arn
		}
	}
	if !madmin.ArnType(target.Type).IsValid() {
		return ""
	}
	arn := madmin.ARN{
		Type:   target.Type,
		ID:     mustGetUUID(),
		Region: target.Region,
		Bucket: target.TargetBucket,
	}
	return arn.String()
}