package putsvc

import (
	"fmt"
	"sync"
	"sync/atomic"

	"github.com/nspcc-dev/neofs-node/pkg/core/object"
	svcutil "github.com/nspcc-dev/neofs-node/pkg/services/object/util"
	"github.com/nspcc-dev/neofs-node/pkg/services/object_manager/placement"
	"github.com/nspcc-dev/neofs-node/pkg/services/object_manager/transformer"
	"github.com/nspcc-dev/neofs-node/pkg/util"
	"github.com/nspcc-dev/neofs-node/pkg/util/logger"
)

type distributedTarget struct {
	traverseOpts []placement.Option

	workerPool util.WorkerPool

	obj *object.RawObject

	chunks [][]byte

	nodeTargetInitializer func(nodeDesc) transformer.ObjectTarget

	isLocalKey func([]byte) bool

	relay func(nodeDesc) error

	fmt *object.FormatValidator

	log *logger.Logger
}

type nodeDesc struct {
	local bool

	info placement.Node
}

// errIncompletePut is returned if processing on a container fails.
type errIncompletePut struct {
	singleErr error // error from the last responding node
}

func (x errIncompletePut) Error() string {
	const commonMsg = "incomplete object PUT by placement"

	if x.singleErr != nil {
		return fmt.Sprintf("%s: %v", commonMsg, x.singleErr)
	}

	return commonMsg
}

func (t *distributedTarget) WriteHeader(obj *object.RawObject) error {
	t.obj = obj

	return nil
}

func (t *distributedTarget) Write(p []byte) (n int, err error) {
	t.chunks = append(t.chunks, p)

	return len(p), nil
}

func (t *distributedTarget) Close() (*transformer.AccessIdentifiers, error) {
	sz := 0

	for i := range t.chunks {
		sz += len(t.chunks[i])
	}

	payload := make([]byte, 0, sz)

	for i := range t.chunks {
		payload = append(payload, t.chunks[i]...)
	}

	t.obj.SetPayload(payload)

	if err := t.fmt.ValidateContent(t.obj.Object()); err != nil {
		return nil, fmt.Errorf("(%T) could not validate payload content: %w", t, err)
	}

	return t.iteratePlacement(t.sendObject)
}

func (t *distributedTarget) sendObject(node nodeDesc) error {
	if !node.local && t.relay != nil {
		return t.relay(node)
	}

	target := t.nodeTargetInitializer(node)

	if err := target.WriteHeader(t.obj); err != nil {
		return fmt.Errorf("could not write header: %w", err)
	} else if _, err := target.Close(); err != nil {
		return fmt.Errorf("could not close object stream: %w", err)
	}
	return nil
}

func (t *distributedTarget) iteratePlacement(f func(nodeDesc) error) (*transformer.AccessIdentifiers, error) {
	traverser, err := placement.NewTraverser(
		append(t.traverseOpts, placement.ForObject(t.obj.ID()))...,
	)
	if err != nil {
		return nil, fmt.Errorf("(%T) could not create object placement traverser: %w", t, err)
	}

	var resErr atomic.Value

loop:
	for {
		addrs := traverser.Next()
		if len(addrs) == 0 {
			break
		}

		wg := new(sync.WaitGroup)

		for i := range addrs {
			wg.Add(1)

			addr := addrs[i]

			isLocal := t.isLocalKey(addr.Key())

			if err := t.workerPool.Submit(func() {
				defer wg.Done()

				if err := f(nodeDesc{local: isLocal, info: addr}); err != nil {
					resErr.Store(err)
					svcutil.LogServiceError(t.log, "PUT", addr.Addresses(), err)
					return
				}

				traverser.SubmitSuccess()
			}); err != nil {
				wg.Done()

				svcutil.LogWorkerPoolError(t.log, "PUT", err)

				break loop
			}
		}

		wg.Wait()
	}

	if !traverser.Success() {
		var err errIncompletePut

		err.singleErr, _ = resErr.Load().(error)

		return nil, err
	}

	return new(transformer.AccessIdentifiers).
		WithSelfID(t.obj.ID()), nil
}