package syncing

import (
	"bufio"
	"net"
	"sync"
	"time"

	"github.com/Workiva/go-datastructures/queue"
	"github.com/harmony-one/harmony/blockchain"
	"github.com/harmony-one/harmony/p2p"
	proto_node "github.com/harmony-one/harmony/proto/node"
)

// SyncPeerConfig is peer config to sync.
type SyncPeerConfig struct {
	peer        p2p.Peer
	conn        net.Conn
	w           *bufio.Writer
	err         error
	trusted     bool
	blockHashes [][32]byte
}

// SyncBlockTask is the task struct to sync a specific block.
type SyncBlockTask struct {
	index     int
	blockHash [32]byte
}

// SyncConfig contains an array of SyncPeerConfig.
type SyncConfig struct {
	peers []SyncPeerConfig
}

// StateSync is the main object used to do state sync.
type StateSync struct {
}

// ProcessStateSync used to do state sync.
func (ss *StateSync) ProcessStateSync(peers []p2p.Peer, bc *blockchain.Blockchain) (chan struct{}, error) {
	done := make(chan struct{})
	go func() {
		ss.StartStateSync(peers, bc)
		done <- struct{}{}
	}()
	return done, nil
}

// StartStateSync starts state sync.
func (ss *StateSync) StartStateSync(peers []p2p.Peer, bc *blockchain.Blockchain) {
	peerNumber := len(peers)
	syncConfig := SyncConfig{
		peers: make([]SyncPeerConfig, peerNumber),
	}
	for id := range syncConfig.peers {
		syncConfig.peers[id].peer = peers[id]
		syncConfig.peers[id].trusted = false
	}

	var wg sync.WaitGroup
	wg.Add(peerNumber)

	for id := range syncConfig.peers {
		go func(peerConfig *SyncPeerConfig) {
			defer wg.Done()
			peerConfig.conn, peerConfig.err = p2p.DialWithSocketClient(peerConfig.peer.Ip, peerConfig.peer.Port)
		}(&syncConfig.peers[id])
	}
	wg.Wait()

	activePeerNumber := 0
	for _, configPeer := range syncConfig.peers {
		if configPeer.err == nil {
			activePeerNumber++
			configPeer.w = bufio.NewWriter(configPeer.conn)
			configPeer.trusted = true
		}
	}

	// Looping to get an array of block hashes from honest nodes.
LOOP_HONEST_NODE:
	for {
		var wg sync.WaitGroup
		wg.Add(activePeerNumber)

		for _, configPeer := range syncConfig.peers {
			if configPeer.err != nil {
				continue
			}
			go func(peerConfig *SyncPeerConfig) {
				defer wg.Done()
				msg := proto_node.ConstructBlockchainSyncMessage(proto_node.GetLastBlockHashes, [32]byte{})
				peerConfig.w.Write(msg)
				peerConfig.w.Flush()
				var content []byte
				content, peerConfig.err = p2p.ReadMessageContent(peerConfig.conn)
				if peerConfig.err != nil {
					peerConfig.trusted = false
					return
				}
				var blockchainSyncMessage *proto_node.BlockchainSyncMessage
				blockchainSyncMessage, peerConfig.err = proto_node.DeserializeBlockchainSyncMessage(content)
				if peerConfig.err != nil {
					peerConfig.trusted = false
					return
				}
				peerConfig.blockHashes = blockchainSyncMessage.BlockHashes
			}(&configPeer)
		}
		wg.Wait()

		if getConsensus(&syncConfig) {
			break LOOP_HONEST_NODE
		}
	}

	taskSyncQueue := queue.New(0)
	blockSize := 0
TASK_LOOP:
	for _, configPeer := range syncConfig.peers {
		if configPeer.trusted {
			for id, blockHash := range configPeer.blockHashes {
				taskSyncQueue.Put(SyncBlockTask{index: id, blockHash: blockHash})
			}
			blockSize = len(configPeer.blockHashes)
			break TASK_LOOP
		}
	}
	// Initialize blockchain
	bc.Blocks = make([]*blockchain.Block, blockSize)
	wg.Add(activePeerNumber)
	for _, configPeer := range syncConfig.peers {
		if configPeer.err != nil {
			continue
		}
		go func(peerConfig *SyncPeerConfig, taskSyncQueue *queue.Queue, bc *blockchain.Blockchain) {
			defer wg.Done()
			for !taskSyncQueue.Empty() {
				task, err := taskSyncQueue.Poll(1, time.Millisecond)
				if err == queue.ErrTimeout {
					break
				}
				syncTask := task[0].(SyncBlockTask)
				msg := proto_node.ConstructBlockchainSyncMessage(proto_node.GetBlock, syncTask.blockHash)
				peerConfig.w.Write(msg)
				peerConfig.w.Flush()
				var content []byte
				content, peerConfig.err = p2p.ReadMessageContent(peerConfig.conn)
				if peerConfig.err != nil {
					peerConfig.trusted = false
					return
				}
				block, err := blockchain.DeserializeBlock(content)
				if err == nil {
					bc.Blocks[syncTask.index] = block
				}
			}
		}(&configPeer, taskSyncQueue, bc)
	}
	wg.Wait()
}

func getConsensus(syncConfig *SyncConfig) bool {
	return true
}