package p2p

import (
	"fmt"
	"github.com/kaspanet/kaspad/peer"
	"github.com/kaspanet/kaspad/wire"
)

// OnGetBlockInvs is invoked when a peer receives a getblockinvs kaspa
// message.
// It finds the blue future between msg.LowHash and msg.HighHash
// and send the invs to the requesting peer.
func (sp *Peer) OnGetBlockInvs(_ *peer.Peer, msg *wire.MsgGetBlockInvs) {
	dag := sp.server.DAG
	// We want to prevent a situation where the syncing peer needs
	// to call getblocks once again, but the block we sent it
	// won't affect its selected chain, so next time it'll try
	// to find the highest shared chain block, it'll find the
	// same one as before.
	// To prevent that we use blockdag.FinalityInterval as maxHashes.
	// This way, if one getblocks is not enough to get the peer
	// synced, we can know for sure that its selected chain will
	// change, so we'll have higher shared chain block.
	hashList, err := dag.AntiPastHashesBetween(msg.LowHash, msg.HighHash,
		wire.MaxInvPerMsg)
	if err != nil {
		sp.AddBanScoreAndPushRejectMsg(wire.CmdGetBlockInvs, wire.RejectInvalid, nil,
			peer.BanScoreInvalidMsgGetBlockInvs, 0,
			fmt.Sprintf("error getting antiPast hashes between %s and %s: %s", msg.LowHash, msg.HighHash, err))
		return
	}

	// Generate inventory message.
	invMsg := wire.NewMsgInv()
	for i := range hashList {
		iv := wire.NewInvVect(wire.InvTypeSyncBlock, hashList[i])
		invMsg.AddInvVect(iv)
	}

	// Send the inventory message if there is anything to send.
	if len(invMsg.InvList) > 0 {
		sp.QueueMessage(invMsg, nil)
	}
}