package initialsync

import (
	"context"
	"errors"
	"fmt"
	"strings"

	"github.com/prysmaticlabs/prysm/beacon-chain/blockchain"
	pb "github.com/prysmaticlabs/prysm/proto/beacon/p2p/v1"
	"github.com/prysmaticlabs/prysm/shared/hashutil"
	"github.com/prysmaticlabs/prysm/shared/p2p"
	"github.com/prysmaticlabs/prysm/shared/params"
	"go.opencensus.io/trace"
)

func (s *InitialSync) processBlockAnnounce(msg p2p.Message) {
	_, span := trace.StartSpan(msg.Ctx, "beacon-chain.sync.initial-sync.processBlockAnnounce")
	defer span.End()
	data := msg.Data.(*pb.BeaconBlockAnnounce)
	recBlockAnnounce.Inc()

	if s.stateReceived && data.SlotNumber > s.highestObservedSlot {
		s.requestBatchedBlocks(s.lastRequestedSlot, data.SlotNumber)
		s.lastRequestedSlot = data.SlotNumber
	}
}

// processBlock is the main method that validates each block which is received
// for initial sync. It checks if the blocks are valid and then will continue to
// process and save it into the db.
func (s *InitialSync) processBlock(ctx context.Context, block *pb.BeaconBlock) {
	ctx, span := trace.StartSpan(ctx, "beacon-chain.sync.initial-sync.processBlock")
	defer span.End()
	recBlock.Inc()

	if block.Slot == s.highestObservedSlot {
		s.currentSlot = s.highestObservedSlot
		if err := s.exitInitialSync(s.ctx, block); err != nil {
			log.Errorf("Could not exit initial sync: %v", err)
			return
		}
		return
	}

	if block.Slot < s.currentSlot {
		return
	}

	// if it isn't the block in the next slot we check if it is a skipped slot.
	// if it isn't skipped we save it in memory.
	if block.Slot != (s.currentSlot + 1) {
		// if parent exists we validate the block.
		if s.doesParentExist(block) {
			if err := s.validateAndSaveNextBlock(ctx, block); err != nil {
				// Debug error so as not to have noisy error logs
				if strings.HasPrefix(err.Error(), debugError) {
					log.Debug(strings.TrimPrefix(err.Error(), debugError))
					return
				}
				log.Errorf("Unable to save block: %v", err)
			}
			return
		}
		s.mutex.Lock()
		defer s.mutex.Unlock()
		if _, ok := s.inMemoryBlocks[block.Slot]; !ok {
			s.inMemoryBlocks[block.Slot] = block
		}
		return
	}

	if err := s.validateAndSaveNextBlock(ctx, block); err != nil {
		// Debug error so as not to have noisy error logs
		if strings.HasPrefix(err.Error(), debugError) {
			log.Debug(strings.TrimPrefix(err.Error(), debugError))
			return
		}
		log.Errorf("Unable to save block: %v", err)
	}
}

// processBatchedBlocks processes all the received blocks from
// the p2p message.
func (s *InitialSync) processBatchedBlocks(msg p2p.Message) {
	ctx, span := trace.StartSpan(msg.Ctx, "beacon-chain.sync.initial-sync.processBatchedBlocks")
	defer span.End()
	batchedBlockReq.Inc()

	response := msg.Data.(*pb.BatchedBeaconBlockResponse)
	batchedBlocks := response.BatchedBlocks
	if len(batchedBlocks) == 0 {
		// Do not process empty responses.
		return
	}

	log.Debug("Processing batched block response")
	for _, block := range batchedBlocks {
		s.processBlock(ctx, block)
	}
	log.Debug("Finished processing batched blocks")
}

// requestBatchedBlocks sends out a request for multiple blocks till a
// specified bound slot number.
func (s *InitialSync) requestBatchedBlocks(startSlot uint64, endSlot uint64) {
	ctx, span := trace.StartSpan(context.Background(), "beacon-chain.sync.initial-sync.requestBatchedBlocks")
	defer span.End()
	sentBatchedBlockReq.Inc()
	if startSlot > endSlot {
		log.Debugf(
			"Invalid batched request from slot %d to %d",
			startSlot-params.BeaconConfig().GenesisSlot, endSlot-params.BeaconConfig().GenesisSlot,
		)
		return
	}
	blockLimit := params.BeaconConfig().BatchBlockLimit
	if startSlot+blockLimit < endSlot {
		endSlot = startSlot + blockLimit
	}
	log.Debugf(
		"Requesting batched blocks from slot %d to %d",
		startSlot-params.BeaconConfig().GenesisSlot, endSlot-params.BeaconConfig().GenesisSlot,
	)
	s.p2p.Broadcast(ctx, &pb.BatchedBeaconBlockRequest{
		StartSlot: startSlot,
		EndSlot:   endSlot,
	})
}

// validateAndSaveNextBlock will validate whether blocks received from the blockfetcher
// routine can be added to the chain.
func (s *InitialSync) validateAndSaveNextBlock(ctx context.Context, block *pb.BeaconBlock) error {
	ctx, span := trace.StartSpan(ctx, "beacon-chain.sync.initial-sync.validateAndSaveNextBlock")
	defer span.End()
	if block == nil {
		return errors.New("received nil block")
	}
	root, err := hashutil.HashBeaconBlock(block)
	if err != nil {
		return err
	}
	if err := s.checkBlockValidity(ctx, block); err != nil {
		return err
	}
	log.Infof("Saving block with root %#x and slot %d for initial sync", root, block.Slot-params.BeaconConfig().GenesisSlot)
	s.currentSlot = block.Slot

	s.mutex.Lock()
	defer s.mutex.Unlock()
	// delete block from memory.
	if _, ok := s.inMemoryBlocks[block.Slot]; ok {
		delete(s.inMemoryBlocks, block.Slot)
	}
	state, err := s.db.HeadState(ctx)
	if err != nil {
		return err
	}
	if err := s.chainService.VerifyBlockValidity(ctx, block, state); err != nil {
		return err
	}
	if err := s.db.SaveBlock(block); err != nil {
		return err
	}
	state, err = s.chainService.ApplyBlockStateTransition(ctx, block, state)
	if err != nil {
		switch err.(type) {
		case *blockchain.BlockFailedProcessingErr:
			// If the block fails processing, we delete it from our DB.
			if err := s.db.DeleteBlock(block); err != nil {
				return fmt.Errorf("could not delete bad block from db: %v", err)
			}
		default:
			return fmt.Errorf("could not apply block state transition: %v", err)
		}
	}
	if err := s.chainService.CleanupBlockOperations(ctx, block); err != nil {
		return err
	}
	return s.db.UpdateChainHead(ctx, block, state)
}