/*
   Copyright 2022 Erigon-Lightclient contributors
   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 handlers

import (
	"io"

	libcommon "github.com/ledgerwatch/erigon-lib/common"
	"github.com/ledgerwatch/erigon/cl/clparams"
	"github.com/ledgerwatch/erigon/cl/cltypes"
	"github.com/ledgerwatch/erigon/cl/cltypes/solid"
	"github.com/ledgerwatch/erigon/cl/fork"
	"github.com/ledgerwatch/erigon/cl/persistence/beacon_indicies"
	"github.com/ledgerwatch/erigon/cl/sentinel/communication/ssz_snappy"
	"github.com/ledgerwatch/erigon/cl/utils"
	"github.com/libp2p/go-libp2p/core/network"
)

const MAX_REQUEST_BLOCKS = 96

func (c *ConsensusHandlers) beaconBlocksByRangeHandler(s network.Stream) error {
	peerId := s.Conn().RemotePeer().String()
	if err := c.checkRateLimit(peerId, "beaconBlocksByRange", rateLimits.beaconBlocksByRangeLimit); err != nil {
		ssz_snappy.EncodeAndWrite(s, &emptyString{}, RateLimitedPrefix)
		return err
	}

	req := &cltypes.BeaconBlocksByRangeRequest{}
	if err := ssz_snappy.DecodeAndReadNoForkDigest(s, req, clparams.Phase0Version); err != nil {
		return err
	}

	tx, err := c.indiciesDB.BeginRo(c.ctx)
	if err != nil {
		return err
	}
	defer tx.Rollback()
	// Limit the number of blocks to the count specified in the request.
	if int(req.Count) > MAX_REQUEST_BLOCKS {
		req.Count = MAX_REQUEST_BLOCKS
	}

	beaconBlockRooots, slots, err := beacon_indicies.ReadBeaconBlockRootsInSlotRange(c.ctx, tx, req.StartSlot, req.Count)
	if err != nil {
		return err
	}

	if len(beaconBlockRooots) == 0 || len(slots) == 0 {
		return ssz_snappy.EncodeAndWrite(s, &emptyString{}, ResourceUnavaiablePrefix)
	}

	for i, slot := range slots {
		r, err := c.beaconDB.BlockReader(c.ctx, slot, beaconBlockRooots[i])
		if err != nil {
			return err
		}
		defer r.Close()

		version := c.beaconConfig.GetCurrentStateVersion(slot / c.beaconConfig.SlotsPerEpoch)
		// Read the fork digest
		forkDigest, err := fork.ComputeForkDigestForVersion(
			utils.Uint32ToBytes4(c.beaconConfig.GetForkVersionByVersion(version)),
			c.genesisConfig.GenesisValidatorRoot,
		)
		if err != nil {
			return err
		}

		if _, err := s.Write([]byte{0}); err != nil {
			return err
		}

		if _, err := s.Write(forkDigest[:]); err != nil {
			return err
		}
		_, err = io.Copy(s, r)
		if err != nil {
			return err
		}
	}

	return nil
}

func (c *ConsensusHandlers) beaconBlocksByRootHandler(s network.Stream) error {
	peerId := s.Conn().RemotePeer().String()
	if err := c.checkRateLimit(peerId, "beaconBlocksByRoot", rateLimits.beaconBlocksByRootLimit); err != nil {
		ssz_snappy.EncodeAndWrite(s, &emptyString{}, RateLimitedPrefix)
		return err
	}

	var req solid.HashListSSZ = solid.NewHashList(100)
	if err := ssz_snappy.DecodeAndReadNoForkDigest(s, req, clparams.Phase0Version); err != nil {
		return err
	}

	blockRoots := []libcommon.Hash{}
	for i := 0; i < req.Length(); i++ {
		blockRoot := req.Get(i)
		blockRoots = append(blockRoots, blockRoot)
		// Limit the number of blocks to the count specified in the request.
		if len(blockRoots) >= MAX_REQUEST_BLOCKS {
			break
		}
	}
	if len(blockRoots) == 0 {
		return ssz_snappy.EncodeAndWrite(s, &emptyString{}, ResourceUnavaiablePrefix)
	}
	tx, err := c.indiciesDB.BeginRo(c.ctx)
	if err != nil {
		return err
	}
	defer tx.Rollback()

	for i, blockRoot := range blockRoots {
		slot, err := beacon_indicies.ReadBlockSlotByBlockRoot(tx, blockRoot)
		if slot == nil {
			continue
		}
		if err != nil {
			return err
		}

		r, err := c.beaconDB.BlockReader(c.ctx, *slot, blockRoots[i])
		if err != nil {
			return err
		}
		defer r.Close()

		if _, err := s.Write([]byte{0}); err != nil {
			return err
		}

		version := c.beaconConfig.GetCurrentStateVersion(*slot / c.beaconConfig.SlotsPerEpoch)
		// Read the fork digest
		forkDigest, err := fork.ComputeForkDigestForVersion(
			utils.Uint32ToBytes4(c.beaconConfig.GetForkVersionByVersion(version)),
			c.genesisConfig.GenesisValidatorRoot,
		)
		if err != nil {
			return err
		}

		if _, err := s.Write(forkDigest[:]); err != nil {
			return err
		}

		// Read block from DB
		block := cltypes.NewSignedBeaconBlock(c.beaconConfig)

		if err := ssz_snappy.DecodeAndReadNoForkDigest(r, block, clparams.Phase0Version); err != nil {
			return err
		}
		if err := ssz_snappy.EncodeAndWrite(s, block); err != nil {
			return err
		}
	}

	return nil
}

type emptyString struct{}

func (e *emptyString) EncodeSSZ(xs []byte) ([]byte, error) {
	return append(xs, 0), nil
}

func (e *emptyString) EncodingSizeSSZ() int {
	return 1
}