package evaluators

import (
	"context"
	"time"

	"github.com/pkg/errors"
	"github.com/prysmaticlabs/prysm/v4/consensus-types/blocks"
	"github.com/prysmaticlabs/prysm/v4/consensus-types/primitives"
	ethpb "github.com/prysmaticlabs/prysm/v4/proto/prysm/v1alpha1"
	"github.com/prysmaticlabs/prysm/v4/runtime/version"
	"github.com/prysmaticlabs/prysm/v4/testing/endtoend/helpers"
	"github.com/prysmaticlabs/prysm/v4/testing/endtoend/policies"
	"github.com/prysmaticlabs/prysm/v4/testing/endtoend/types"
	"github.com/prysmaticlabs/prysm/v4/time/slots"
	"google.golang.org/grpc"
)

var streamDeadline = 1 * time.Minute
var startingFork = version.Phase0

// AltairForkTransition ensures that the Altair hard fork has occurred successfully.
var AltairForkTransition = types.Evaluator{
	Name: "altair_fork_transition_%d",
	Policy: func(e primitives.Epoch) bool {
		altair := policies.OnEpoch(helpers.AltairE2EForkEpoch)
		// TODO (11750): modify policies to take an end to end config
		if startingFork == version.Phase0 {
			return altair(e)
		}
		return false
	},
	Evaluation: altairForkOccurs,
}

// BellatrixForkTransition ensures that the Bellatrix hard fork has occurred successfully.
var BellatrixForkTransition = types.Evaluator{
	Name:       "bellatrix_fork_transition_%d",
	Policy:     policies.OnEpoch(helpers.BellatrixE2EForkEpoch),
	Evaluation: bellatrixForkOccurs,
}

// CapellaForkTransition ensures that the Capella hard fork has occurred successfully.
var CapellaForkTransition = types.Evaluator{
	Name:       "capella_fork_transition_%d",
	Policy:     policies.OnEpoch(helpers.CapellaE2EForkEpoch),
	Evaluation: capellaForkOccurs,
}

func altairForkOccurs(_ *types.EvaluationContext, conns ...*grpc.ClientConn) error {
	conn := conns[0]
	client := ethpb.NewBeaconNodeValidatorClient(conn)
	ctx, cancel := context.WithTimeout(context.Background(), streamDeadline)
	defer cancel()
	stream, err := client.StreamBlocksAltair(ctx, &ethpb.StreamBlocksRequest{VerifiedOnly: true})
	if err != nil {
		return errors.Wrap(err, "failed to get stream")
	}
	fSlot, err := slots.EpochStart(helpers.AltairE2EForkEpoch)
	if err != nil {
		return err
	}
	if ctx.Err() == context.Canceled {
		return errors.New("context canceled prematurely")
	}
	res, err := stream.Recv()
	if err != nil {
		return err
	}
	if res == nil || res.Block == nil {
		return errors.New("nil block returned by beacon node")
	}
	if res.GetPhase0Block() == nil && res.GetAltairBlock() == nil {
		return errors.New("nil block returned by beacon node")
	}
	if res.GetPhase0Block() != nil {
		return errors.New("phase 0 block returned after altair fork has occurred")
	}
	blk, err := blocks.NewSignedBeaconBlock(res.GetAltairBlock())
	if err != nil {
		return err
	}
	if err := blocks.BeaconBlockIsNil(blk); err != nil {
		return err
	}
	if blk.Block().Slot() < fSlot {
		return errors.Errorf("wanted a block >= %d but received %d", fSlot, blk.Block().Slot())
	}
	return nil
}

func bellatrixForkOccurs(_ *types.EvaluationContext, conns ...*grpc.ClientConn) error {
	conn := conns[0]
	client := ethpb.NewBeaconNodeValidatorClient(conn)
	ctx, cancel := context.WithTimeout(context.Background(), streamDeadline)
	defer cancel()
	stream, err := client.StreamBlocksAltair(ctx, &ethpb.StreamBlocksRequest{VerifiedOnly: true})
	if err != nil {
		return errors.Wrap(err, "failed to get stream")
	}
	fSlot, err := slots.EpochStart(helpers.BellatrixE2EForkEpoch)
	if err != nil {
		return err
	}
	if ctx.Err() == context.Canceled {
		return errors.New("context canceled prematurely")
	}
	res, err := stream.Recv()
	if err != nil {
		return err
	}
	if res == nil || res.Block == nil {
		return errors.New("nil block returned by beacon node")
	}
	if res.GetPhase0Block() == nil && res.GetAltairBlock() == nil && res.GetBellatrixBlock() == nil {
		return errors.New("nil block returned by beacon node")
	}
	if res.GetPhase0Block() != nil {
		return errors.New("phase 0 block returned after bellatrix fork has occurred")
	}
	if res.GetAltairBlock() != nil {
		return errors.New("altair block returned after bellatrix fork has occurred")
	}
	blk, err := blocks.NewSignedBeaconBlock(res.GetBellatrixBlock())
	if err != nil {
		return err
	}
	if err := blocks.BeaconBlockIsNil(blk); err != nil {
		return err
	}
	if blk.Block().Slot() < fSlot {
		return errors.Errorf("wanted a block >= %d but received %d", fSlot, blk.Block().Slot())
	}
	return nil
}

func capellaForkOccurs(_ *types.EvaluationContext, conns ...*grpc.ClientConn) error {
	conn := conns[0]
	client := ethpb.NewBeaconNodeValidatorClient(conn)
	ctx, cancel := context.WithTimeout(context.Background(), streamDeadline)
	defer cancel()
	stream, err := client.StreamBlocksAltair(ctx, &ethpb.StreamBlocksRequest{VerifiedOnly: true})
	if err != nil {
		return errors.Wrap(err, "failed to get stream")
	}
	fSlot, err := slots.EpochStart(helpers.CapellaE2EForkEpoch)
	if err != nil {
		return err
	}
	if ctx.Err() == context.Canceled {
		return errors.New("context canceled prematurely")
	}
	res, err := stream.Recv()
	if err != nil {
		return err
	}
	if res == nil || res.Block == nil {
		return errors.New("nil block returned by beacon node")
	}

	if res.GetBlock() == nil {
		return errors.New("nil block returned by beacon node")
	}
	if res.GetCapellaBlock() == nil {
		return errors.Errorf("non-capella block returned after the fork with type %T", res.Block)
	}
	blk, err := blocks.NewSignedBeaconBlock(res.GetCapellaBlock())
	if err != nil {
		return err
	}
	if err := blocks.BeaconBlockIsNil(blk); err != nil {
		return err
	}
	if blk.Block().Slot() < fSlot {
		return errors.Errorf("wanted a block at slot >= %d but received %d", fSlot, blk.Block().Slot())
	}
	return nil
}
