package putsvc

import (
	"context"
	"crypto/ecdsa"
	"errors"
	"fmt"

	"git.frostfs.info/TrueCloudLab/frostfs-node/internal/logs"
	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/core/client"
	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/core/object"
	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/core/policy"
	svcutil "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/services/object/util"
	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/services/object_manager/placement"
	containerSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/container"
	objectSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
	"git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/erasurecode"
	"git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/transformer"
	"go.uber.org/zap"
	"golang.org/x/sync/errgroup"
)

var _ transformer.ObjectWriter = (*ecWriter)(nil)

var errUnsupportedECObject = errors.New("object is not supported for erasure coding")

type ecWriter struct {
	cfg           *cfg
	placementOpts []placement.Option
	container     containerSDK.Container
	key           *ecdsa.PrivateKey
	commonPrm     *svcutil.CommonPrm
	relay         func(context.Context, client.NodeInfo, client.MultiAddressClient) error

	objMeta      object.ContentMeta
	objMetaValid bool
}

func (e *ecWriter) WriteObject(ctx context.Context, obj *objectSDK.Object) error {
	relayed, err := e.relayIfNotContainerNode(ctx)
	if err != nil {
		return err
	}
	if relayed {
		return nil
	}

	if !object.IsECSupported(obj) {
		// must be resolved by caller
		return errUnsupportedECObject
	}

	if !e.objMetaValid {
		if e.objMeta, err = e.cfg.fmtValidator.ValidateContent(obj); err != nil {
			return fmt.Errorf("(%T) could not validate payload content: %w", e, err)
		}
		e.objMetaValid = true
	}

	if obj.ECHeader() != nil {
		return e.writeECPart(ctx, obj)
	}
	return e.writeRawObject(ctx, obj)
}

func (e *ecWriter) relayIfNotContainerNode(ctx context.Context) (bool, error) {
	if e.relay == nil {
		return false, nil
	}
	currentNodeIsContainerNode, err := e.currentNodeIsContainerNode()
	if err != nil {
		return false, err
	}
	if currentNodeIsContainerNode {
		// object can be splitted or saved local
		return false, nil
	}
	if err := e.relayToContainerNode(ctx); err != nil {
		return false, err
	}
	return true, nil
}

func (e *ecWriter) currentNodeIsContainerNode() (bool, error) {
	t, err := placement.NewTraverser(e.placementOpts...)
	if err != nil {
		return false, err
	}
	for {
		nodes := t.Next()
		if len(nodes) == 0 {
			break
		}
		for _, node := range nodes {
			if e.cfg.netmapKeys.IsLocalKey(node.PublicKey()) {
				return true, nil
			}
		}
	}
	return false, nil
}

func (e *ecWriter) relayToContainerNode(ctx context.Context) error {
	t, err := placement.NewTraverser(e.placementOpts...)
	if err != nil {
		return err
	}
	var lastErr error
	for {
		nodes := t.Next()
		if len(nodes) == 0 {
			break
		}
		for _, node := range nodes {
			var info client.NodeInfo
			client.NodeInfoFromNetmapElement(&info, node)

			c, err := e.cfg.clientConstructor.Get(info)
			if err != nil {
				return fmt.Errorf("could not create SDK client %s: %w", info.AddressGroup(), err)
			}

			completed := make(chan interface{})
			if poolErr := e.cfg.remotePool.Submit(func() {
				defer close(completed)
				err = e.relay(ctx, info, c)
			}); poolErr != nil {
				close(completed)
				svcutil.LogWorkerPoolError(e.cfg.log, "PUT", poolErr)
				return poolErr
			}
			<-completed

			if err == nil {
				return nil
			}
			e.cfg.log.Logger.Warn(logs.ECFailedToSendToContainerNode, zap.Stringers("address_group", info.AddressGroup()))
			lastErr = err
		}
	}
	if lastErr == nil {
		return nil
	}
	return errIncompletePut{
		singleErr: lastErr,
	}
}

func (e *ecWriter) writeECPart(ctx context.Context, obj *objectSDK.Object) error {
	t, err := placement.NewTraverser(e.placementOpts...)
	if err != nil {
		return err
	}

	eg, egCtx := errgroup.WithContext(ctx)
	for {
		nodes := t.Next()
		if len(nodes) == 0 {
			break
		}

		eg.Go(func() error {
			return e.writePart(egCtx, obj, int(obj.ECHeader().Index()), nodes)
		})
	}
	if err := eg.Wait(); err != nil {
		return errIncompletePut{
			singleErr: err,
		}
	}
	return nil
}

func (e *ecWriter) writeRawObject(ctx context.Context, obj *objectSDK.Object) error {
	// now only single EC policy is supported
	c, err := erasurecode.NewConstructor(policy.ECDataCount(e.container.PlacementPolicy()), policy.ECParityCount(e.container.PlacementPolicy()))
	if err != nil {
		return err
	}
	parts, err := c.Split(obj, e.key)
	if err != nil {
		return err
	}
	t, err := placement.NewTraverser(e.placementOpts...)
	if err != nil {
		return err
	}

	eg, egCtx := errgroup.WithContext(ctx)
	for {
		nodes := t.Next()
		if len(nodes) == 0 {
			break
		}

		for idx := range parts {
			idx := idx
			eg.Go(func() error {
				return e.writePart(egCtx, parts[idx], idx, nodes)
			})
		}
	}
	if err := eg.Wait(); err != nil {
		return errIncompletePut{
			singleErr: err,
		}
	}
	return nil
}

func (e *ecWriter) writePart(ctx context.Context, obj *objectSDK.Object, partIdx int, nodes []placement.Node) error {
	var err error
	node := nodes[partIdx%len(nodes)]
	if e.cfg.netmapKeys.IsLocalKey(node.PublicKey()) {
		err = e.writePartLocal(ctx, obj)
	} else {
		err = e.writePartRemote(ctx, obj, node)
	}
	if err == nil {
		return nil
	}
	e.cfg.log.Warn(logs.ECFailedToSaveECPart, zap.Stringer("parent_object", object.AddressOf(obj)), zap.Error(err))
	return err
}

func (e *ecWriter) writePartLocal(ctx context.Context, obj *objectSDK.Object) error {
	var err error
	localTarget := localTarget{
		storage: e.cfg.localStore,
	}
	completed := make(chan interface{})
	if poolErr := e.cfg.localPool.Submit(func() {
		defer close(completed)
		err = localTarget.WriteObject(ctx, obj, e.objMeta)
	}); poolErr != nil {
		close(completed)
		return poolErr
	}
	<-completed
	return err
}

func (e *ecWriter) writePartRemote(ctx context.Context, obj *objectSDK.Object, node placement.Node) error {
	var clientNodeInfo client.NodeInfo
	client.NodeInfoFromNetmapElement(&clientNodeInfo, node)

	remoteTaget := remoteTarget{
		privateKey:        e.key,
		clientConstructor: e.cfg.clientConstructor,
		commonPrm:         e.commonPrm,
		nodeInfo:          clientNodeInfo,
	}

	var err error
	completed := make(chan interface{})
	if poolErr := e.cfg.remotePool.Submit(func() {
		defer close(completed)
		err = remoteTaget.WriteObject(ctx, obj, e.objMeta)
	}); poolErr != nil {
		close(completed)
		return poolErr
	}
	<-completed
	return err
}