package util

import (
	"fmt"

	"github.com/nspcc-dev/neofs-node/pkg/core/container"
	"github.com/nspcc-dev/neofs-node/pkg/core/netmap"
	"github.com/nspcc-dev/neofs-node/pkg/network"
	"github.com/nspcc-dev/neofs-node/pkg/services/object_manager/placement"
	netmapSDK "github.com/nspcc-dev/neofs-sdk-go/netmap"
	addressSDK "github.com/nspcc-dev/neofs-sdk-go/object/address"
)

type localPlacement struct {
	builder placement.Builder

	netmapKeys netmap.AnnouncedKeys
}

type remotePlacement struct {
	builder placement.Builder

	netmapKeys netmap.AnnouncedKeys
}

// TraverserGenerator represents tool that generates
// container traverser for the particular need.
type TraverserGenerator struct {
	netMapSrc netmap.Source

	cnrSrc container.Source

	netmapKeys netmap.AnnouncedKeys

	customOpts []placement.Option
}

func NewLocalPlacement(b placement.Builder, s netmap.AnnouncedKeys) placement.Builder {
	return &localPlacement{
		builder:    b,
		netmapKeys: s,
	}
}

func (p *localPlacement) BuildPlacement(addr *addressSDK.Address, policy *netmapSDK.PlacementPolicy) ([]netmapSDK.Nodes, error) {
	vs, err := p.builder.BuildPlacement(addr, policy)
	if err != nil {
		return nil, fmt.Errorf("(%T) could not build object placement: %w", p, err)
	}

	for i := range vs {
		for j := range vs[i] {
			var addr network.AddressGroup

			err := addr.FromIterator(vs[i][j])
			if err != nil {
				continue
			}

			if p.netmapKeys.IsLocalKey(vs[i][j].PublicKey()) {
				return []netmapSDK.Nodes{{vs[i][j]}}, nil
			}
		}
	}

	return nil, fmt.Errorf("(%T) local node is outside of object placement", p)
}

// NewRemotePlacementBuilder creates, initializes and returns placement builder that
// excludes local node from any placement vector.
func NewRemotePlacementBuilder(b placement.Builder, s netmap.AnnouncedKeys) placement.Builder {
	return &remotePlacement{
		builder:    b,
		netmapKeys: s,
	}
}

func (p *remotePlacement) BuildPlacement(addr *addressSDK.Address, policy *netmapSDK.PlacementPolicy) ([]netmapSDK.Nodes, error) {
	vs, err := p.builder.BuildPlacement(addr, policy)
	if err != nil {
		return nil, fmt.Errorf("(%T) could not build object placement: %w", p, err)
	}

	for i := range vs {
		for j := 0; j < len(vs[i]); j++ {
			var addr network.AddressGroup

			err := addr.FromIterator(vs[i][j])
			if err != nil {
				continue
			}

			if p.netmapKeys.IsLocalKey(vs[i][j].PublicKey()) {
				vs[i] = append(vs[i][:j], vs[i][j+1:]...)
				j--
			}
		}
	}

	return vs, nil
}

// NewTraverserGenerator creates, initializes and returns new TraverserGenerator instance.
func NewTraverserGenerator(nmSrc netmap.Source, cnrSrc container.Source, netmapKeys netmap.AnnouncedKeys) *TraverserGenerator {
	return &TraverserGenerator{
		netMapSrc:  nmSrc,
		cnrSrc:     cnrSrc,
		netmapKeys: netmapKeys,
	}
}

// WithTraverseOptions returns TraverseGenerator that additionally applies provided options.
func (g *TraverserGenerator) WithTraverseOptions(opts ...placement.Option) *TraverserGenerator {
	return &TraverserGenerator{
		netMapSrc:  g.netMapSrc,
		cnrSrc:     g.cnrSrc,
		netmapKeys: g.netmapKeys,
		customOpts: opts,
	}
}

// GenerateTraverser generates placement Traverser for provided object address
// using epoch-th network map.
func (g *TraverserGenerator) GenerateTraverser(addr *addressSDK.Address, epoch uint64) (*placement.Traverser, error) {
	// get network map by epoch
	nm, err := g.netMapSrc.GetNetMapByEpoch(epoch)
	if err != nil {
		return nil, fmt.Errorf("could not get network map #%d: %w", epoch, err)
	}

	// get container related container
	cnr, err := g.cnrSrc.Get(addr.ContainerID())
	if err != nil {
		return nil, fmt.Errorf("could not get container: %w", err)
	}

	// allocate placement traverser options
	traverseOpts := make([]placement.Option, 0, 3+len(g.customOpts))
	traverseOpts = append(traverseOpts, g.customOpts...)

	// create builder of the remote nodes from network map
	builder := NewRemotePlacementBuilder(
		placement.NewNetworkMapBuilder(nm),
		g.netmapKeys,
	)

	traverseOpts = append(traverseOpts,
		// set processing container
		placement.ForContainer(cnr),

		// set identifier of the processing object
		placement.ForObject(addr.ObjectID()),

		// set placement builder
		placement.UseBuilder(builder),
	)

	return placement.NewTraverser(traverseOpts...)
}