// Copyright 2017-2021 DERO Project. All rights reserved.
// Use of this source code in any form is governed by RESEARCH license.
// license can be found in the LICENSE file.
// GPG: 0F39 E425 8C65 3947 702A  8234 08B2 0360 A03A 9DE8
//
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

package p2p

import "fmt"
import "time"
import "context"
import "sync/atomic"

import "github.com/deroproject/derohe/config"
import "github.com/deroproject/derohe/globals"
import "github.com/deroproject/derohe/block"
import "github.com/deroproject/derohe/errormsg"
import "github.com/deroproject/derohe/transaction"

// we are expecting other side to have a heavier PoW chain, try to sync now
func (connection *Connection) sync_chain() {

	defer handle_connection_panic(connection)

	var request Chain_Request_Struct
	var response Chain_Response_Struct

try_again:

	// send our blocks, first 10 blocks directly, then decreasing in powers of 2
	start_point := chain.Load_TOPO_HEIGHT()
	for i := int64(0); i < start_point; {

		tr, err := chain.Store.Topo_store.Read(start_point - i) // commit everything
		if err != nil {
			continue
		}
		if tr.IsClean() {
			break
		}

		request.Block_list = append(request.Block_list, tr.BLOCK_ID)
		request.TopoHeights = append(request.TopoHeights, start_point-i)
		switch {
		case len(request.Block_list) < 20: // 20 blocks raw
			i++
		case len(request.Block_list) < 100: // 20 block with 5 steps
			i += 5
		case len(request.Block_list) < 1000: // 20 block with 50 steps
			i += 50
		case len(request.Block_list) < 10000: // 20 block with 500 steps
			i += 500
		default:
			i = i * 2
		}
	}
	// add genesis block at the end
	request.Block_list = append(request.Block_list, globals.Config.Genesis_Block_Hash)
	request.TopoHeights = append(request.TopoHeights, 0)
	fill_common(&request.Common) // fill common info

	var TimeLimit = 10 * time.Second
	ctx, _ := context.WithTimeout(context.Background(), TimeLimit)
	if err := connection.Client.CallWithContext(ctx, "Peer.Chain", request, &response); err != nil {
		connection.logger.V(2).Error(err, "Call failed Chain")
		return
	}
	// we have a response, see if its valid and try to add to get the blocks

	connection.logger.V(2).Info("Peer wants to give chain", "from topoheight", response.Start_height)

	// we do not need reorganisation if deviation is less than  or equak to 7 blocks
	// only pop blocks if the system has somehow deviated more than 7 blocks
	// if the deviation is less than 7 blocks, we internally reorganise everything
	if chain.Get_Height()-response.Start_height > config.STABLE_LIMIT && connection.SyncNode {
		// get our top block
		connection.logger.V(3).Info("rewinding status", "our topoheight", chain.Load_TOPO_HEIGHT(), "peer topoheight", response.Start_topoheight)
		pop_count := chain.Load_TOPO_HEIGHT() - response.Start_topoheight
		chain.Rewind_Chain(int(pop_count)) // pop as many blocks as necessary

		// we should NOT queue blocks, instead we sent our chain request again
		goto try_again

	} else if chain.Get_Height()-response.Common.Height != 0 && chain.Get_Height()-response.Start_height <= config.STABLE_LIMIT {
		//pop_count := chain.Load_TOPO_HEIGHT() - response.Start_topoheight
		//chain.Rewind_Chain(int(pop_count)) // pop as many blocks as necessary, assumming peer has given us good chain
	} else if chain.Get_Height()-response.Start_height > config.STABLE_LIMIT { // we must somehow notify that deviation is way too much and manual interaction is necessary, so as any bug for chain deviationmay be detected
		connection.logger.V(1).Error(nil, "we have or others have deviated too much.you may have to use --sync-node option", "our topoheight", chain.Load_TOPO_HEIGHT(), "peer topoheight start", response.Start_topoheight)
		return
	}

	// response only 128 blocks at a time
	max_blocks_to_queue := 128
	// check whether the objects are in our db or not
	// until we put in place a parallel object tracker, do it one at a time

	connection.logger.V(2).Info("response block list", "count", len(response.Block_list))
	for i := range response.Block_list {
		our_topo_order := chain.Load_Block_Topological_order(response.Block_list[i])
		if our_topo_order != (int64(i)+response.Start_topoheight) || our_topo_order == -1 { // if block is not in our chain, add it to request list
			//queue_block(request.Block_list[i])
			if max_blocks_to_queue >= 0 {
				max_blocks_to_queue--
				//connection.Send_ObjectRequest([]crypto.Hash{response.Block_list[i]}, []crypto.Hash{})
				var orequest ObjectList
				var oresponse Objects

				orequest.Block_list = append(orequest.Block_list, response.Block_list[i])
				fill_common(&orequest.Common)
				ctx, _ := context.WithTimeout(context.Background(), TimeLimit)
				if err := connection.Client.CallWithContext(ctx, "Peer.GetObject", orequest, &oresponse); err != nil {
					connection.logger.V(2).Error(err, "Call failed GetObject")
					return
				} else { // process the response
					if err = connection.process_object_response(oresponse, 0, true); err != nil {
						return
					}
				}

				//	fmt.Printf("Queuing block %x height %d  %s", response.Block_list[i], response.Start_height+int64(i), connection.logid)
			}
		} else {
			connection.logger.V(3).Info("We must have queued but we skipped it at height", "blid", fmt.Sprintf("%x", response.Block_list[i]), "height", response.Start_height+int64(i))
		}
	}

	// request alt-tips ( blocks if we are nearing the main tip )
	/*if (response.Common.TopoHeight - chain.Load_TOPO_HEIGHT()) <= 5 {
		for i := range response.TopBlocks {
			if chain.Load_Block_Topological_order(response.TopBlocks[i]) == -1 {
				//connection.Send_ObjectRequest([]crypto.Hash{response.TopBlocks[i]}, []crypto.Hash{})
				connection.logger.V(2).Info("Queuing ALT-TIP", "blid", response.TopBlocks[i])

			}

		}
	}*/

}

func (connection *Connection) process_object_response(response Objects, sent int64, syncing bool) error {
	var err error
	defer globals.Recover(2)

	for i := 0; i < len(response.CBlocks); i++ { // process incoming full blocks
		// make sure connection does not timeout and be killed while processing huge blocks

		atomic.StoreInt64(&connection.LastObjectRequestTime, time.Now().Unix())

		var cbl block.Complete_Block // parse incoming block and deserialize it
		var bl block.Block
		// lets deserialize block first and see whether it is the requested object
		cbl.Bl = &bl
		err := bl.Deserialize(response.CBlocks[i].Block)
		if err != nil { // we have a block which could not be deserialized ban peer
			connection.logger.V(2).Error(err, "Incoming block could not be deserilised")
			connection.exit()
			if syncing {
				return nil
			} else {
				return err
			}
		}

		// give the chain some more time to respond
		atomic.StoreInt64(&connection.LastObjectRequestTime, time.Now().Unix())

		// do not try to add blocks too much into future
		if syncing && int64(bl.Height) > chain.Get_Height()+4 {
			continue
		}
		// check whether the object was requested one

		// complete the txs
		for j := range response.CBlocks[i].Txs {
			var tx transaction.Transaction
			err = tx.Deserialize(response.CBlocks[i].Txs[j])
			if err != nil { // we have a tx which could not be deserialized ban peer
				connection.logger.V(2).Error(err, "Incoming TX could not be deserilised")
				connection.exit()

				if syncing {
					return nil
				} else {
					return err
				}
			}
			cbl.Txs = append(cbl.Txs, &tx)
		}

		// check if we can add ourselves to chain
		err, ok := chain.Add_Complete_Block(&cbl)
		if !ok && err == errormsg.ErrInvalidPoW {
			connection.logger.V(2).Error(err, "This peer should be banned")
			connection.exit()
			if syncing {
				return nil
			} else {
				return err
			}
		}

		if !ok && err == errormsg.ErrPastMissing {
			connection.logger.V(2).Error(err, "Incoming Block could not be added due to missing past, so skipping future block")
			if syncing {
				return nil
			} else {
				return err
			}
		}

		if !ok {
			connection.logger.V(2).Error(err, "Incoming Block could not be added due to some error")
		}

		// add the object to object pool from where it will be consume
		// queue_block_received(bl.GetHash(),&cbl)

	}

	for i := range response.Txs { // process incoming txs for mempool
		var tx transaction.Transaction
		err = tx.Deserialize(response.Txs[i])
		if err != nil { // we have a tx which could not be deserialized ban peer
			connection.logger.V(2).Error(err, "Incoming TX could not be deserilised")
			connection.exit()

			return nil
		}

		if !chain.Mempool.Mempool_TX_Exist(tx.GetHash()) { // we still donot have it, so try to process it
			if chain.Add_TX_To_Pool(&tx) == nil { // currently we are ignoring error
				broadcast_Tx(&tx, 0, sent)
			}
		}
	}

	for i := range response.Chunks { // process incoming chunks
		connection.feed_chunk(&response.Chunks[i], sent)
	}

	return nil
}