// Package utils provides utilities that are needed for the functioning of Kerma
package utils

import (
	"bufio"
	"errors"
	"kerma/helpers"
	"kerma/models"
	"time"

	"github.com/docker/go/canonical/json"
)

/*
A Server represents a Kerma server with the following properties:
- State - the current state of the application
- Handler - a TCPHandler that is used to handle requests to and from remote peers
- Logger
- Client - a new client that uses the same state and handler as this server
*/
type Server struct {
	State   *models.State
	Handler TCPHandler
	Logger  helpers.Logger
	Client  Client
}

/*
Construct creates a new server with the specified state and handler objects
*/
func (s *Server) Construct(state *models.State, h TCPHandler) {
	s.State = state
	s.Handler = h
	s.Client.Construct(s.State, s.Handler)
}

/*
Handle is responsible for handling requests from other Kerma nodes/clients
*/
func (s *Server) Handle() {
	// Decode message received from reader, fail on error

	scanner := bufio.NewScanner(s.Handler.Conn)

	for scanner.Scan() {
		msg, err := s.Handler.Input(scanner.Bytes())
		if err != nil {
			s.Handler.Fail(err.Error())
		}

		// Parse received message, fail on error
		msgJSON, err := json.MarshalCanonical(msg)
		if err != nil {
			s.Logger.Error("Failed parsing message " + err.Error())
			s.Handler.Fail("Failed parsing message")
		}

		s.Logger.Info("IN: " + s.Handler.GetRemotePeer() + " " + string(msgJSON))

		remotePeer := s.Handler.GetRemotePeer()

		// check message type, proceed accordingly
		if msgType, ok := msg["type"]; ok {
			switch msgType {
			case "error":
				break
			case "hello":
				// check if peer has already handshaked
				if !s.State.CheckForHandshake(remotePeer) {
					// check if hello request is valid
					var helloReq models.Hello
					err := helloReq.UnmarshalJSON(msgJSON)

					if err == nil {
						// finish handshake
						s.Logger.Info("Constructing handshake with " + remotePeer)
						var resp models.Hello
						resp.Construct()
						respJSON, _ := resp.MarshalJson()
						s.Handler.Output(respJSON)
						s.State.CompleteHandshake(remotePeer)
						s.Client.DiscoverPeers(remotePeer)
					} else {
						s.Handler.Fail("Hello request invalid")
					}
				}
				break
			case "getpeers":
				err := s.terminateIfNoHandshake(remotePeer)
				if err != nil {
					break
				}

				// create list of known peers, send to requester
				resp := s.State.FetchPeerListResponse()
				resp.Peers = append(resp.Peers, s.Handler.GetLocalPeer())
				respJSON, _ := resp.MarshalJson()
				s.Handler.Output(respJSON)
				break
			case "peers":
				err := s.terminateIfNoHandshake(remotePeer)
				if err != nil {
					break
				}

				var peers models.PeerListResponse
				json.Unmarshal(msgJSON, &peers)
				s.State.ParsePeerListResponse(&peers)
				break
			case "ihaveobject":
				err := s.terminateIfNoHandshake(remotePeer)
				if err != nil {
					break
				}

				var obj models.ObjectWrapper
				err = obj.UnmarshalJSON(msgJSON)
				if err != nil {
					s.Handler.Fail("Could not parse request")
					break
				}

				if s.State.Transactions[obj.ObjectID] == nil {
					resp := models.ObjectWrapper{
						Type:     "getobject",
						ObjectID: obj.ObjectID,
					}

					respJSON, _ := resp.MarshalJson()
					s.Handler.Output(respJSON)
				}
			case "getobject":
				err = s.terminateIfNoHandshake(remotePeer)
				if err != nil {
					break
				}

				var obj models.ObjectWrapper
				err := obj.UnmarshalJSON(msgJSON)
				if err != nil {
					s.Handler.Fail("Could not parse request")
					break
				}

				transaction := s.State.GetTransaction(obj.ObjectID)
				if transaction != nil {
					s.Logger.Debug("Found transaction: " + obj.ObjectID)
					resp := json.RawMessage(`{"type":"object","object":` + transaction.String() + `}`)

					respJSON, _ := resp.MarshalJSON()
					s.Handler.Output(respJSON)
				}

				block := s.State.GetBlock(obj.ObjectID)
				if block != nil {
					s.Logger.Debug("Found block: " + obj.ObjectID)
					resp := json.RawMessage(`{"type":"object","object":` + block.String() + `}`)

					respJSON, _ := resp.MarshalJSON()
					s.Handler.Output(respJSON)
				} else {
					s.Handler.Error("Could not find object " + obj.ObjectID)
				}
				break
			case "object":
				err = s.terminateIfNoHandshake(remotePeer)
				if err != nil {
					break
				}

				var object models.Object

				err := object.UnmarshalJSON(msgJSON)
				if err != nil {
					s.Logger.Debug("Could not unmarshal: " + err.Error())
					s.Handler.Fail("Object request invalid")
					break
				}

				val, err := object.GetObjectValue()
				if err != nil {
					s.Logger.Error("Could not parse object: " + err.Error())
					s.Handler.Fail("Could not parse object request")
					break
				}

				switch val.GetType() {
				case "transaction":
					err := s.State.AppendTransaction(val.GetEntity().(*models.Transaction))
					if err != nil {
						s.Logger.Debug("Failed appending transaction: " + err.Error())
						s.Handler.Fail("Error appending transaction")
						break
					}

					break
				case "block":
					block := val.(*models.Block)

					go s.appendBlockToChain(block)
					break
				default:
					s.Logger.Debug("Something went wrong with " + string(msgJSON))
					s.Handler.Fail("Could not parse object request")
				}
				break
			case "getchaintip":
				err := s.terminateIfNoHandshake(remotePeer)
				if err != nil {
					break
				}

				res := s.State.GetChainTip()

				var chaintip models.Chaintip
				chaintip.Construct(res.GetID())
				respJSON, _ := chaintip.MarshalJson()
				s.Handler.Output(respJSON)
				break
			case "chaintip":
				err := s.terminateIfNoHandshake(remotePeer)
				if err != nil {
					break
				}

				var chaintip models.Chaintip

				err = chaintip.UnmarshalJSON(msgJSON)
				if err != nil {
					s.Logger.Debug("Could not unmarshal: " + err.Error())
					s.Handler.Fail("Object request invalid")
					break
				}

				res := s.State.GetChainTip()
				if res.GetID() != chaintip.BlockID {
					s.Client.DiscoverObject(remotePeer, chaintip.BlockID)
				}
				break
			case "getmempool":
				err := s.terminateIfNoHandshake(remotePeer)
				if err != nil {
					break
				}

				res := s.State.GetMempoolTransactionIDs()

				var mempool models.Mempool
				mempool.Construct(res)
				respJSON, _ := mempool.MarshalJson()
				s.Handler.Output(respJSON)
				break
			case "mempool":
				err := s.terminateIfNoHandshake(remotePeer)
				if err != nil {
					break
				}

				var mempool models.Mempool

				err = mempool.UnmarshalJSON(msgJSON)
				if err != nil {
					s.Logger.Debug("Could not unmarshal: " + err.Error())
					s.Handler.Fail("Object request invalid")
					break
				}

				for _, txid := range mempool.Txids {
					res := s.State.GetTransaction(txid)
					if res == nil {
						s.Client.DiscoverObject(remotePeer, txid)
					}
				}
				break

			default:
				s.Handler.Fail("Request type not supported " + msgType.(string))
			}
		} else {
			s.Handler.Fail("Request type not specified")
		}
	}
}

func (s *Server) terminateIfNoHandshake(remotePeer string) error {
	if !s.State.CheckForHandshake(remotePeer) {
		s.Handler.Fail("Handshake not completed")
		return errors.New("handshake not completed with peer " + remotePeer)
	}
	return nil
}

func (s *Server) appendBlockToChain(block *models.Block) {
	dontAppend := false
	missingTx, err := s.State.GetMissingTransactionsInBlock(block)
	if err != nil {
		s.Logger.Debug("Failed appending block: " + err.Error())
		s.Handler.Fail("Error appending block")
		return
	}

	if len(missingTx) != 0 {
		for _, txid := range missingTx {
			s.Client.DiscoverObject(s.Handler.GetRemotePeer(), txid)
			waited := 0
			for s.State.GetTransaction(txid) == nil {
				s.Logger.Debug("Waiting for transactions " + txid)
				time.Sleep(500 * time.Millisecond)
				waited += 500
				if waited*int(time.Millisecond) >= s.State.Config.ConnTimeout*int(time.Second) {
					s.Handler.Fail("Did not receive requested transactions in time, failed appending block")
					dontAppend = true
					return
				}
			}
		}
	}

	s.getMissingBlocks(block)

	if !dontAppend {
		err = s.State.AppendToChain(block)
		if err != nil {
			s.Logger.Debug("Failed appending block: " + err.Error())
			s.Handler.Fail("Error appending block")
		}

		s.State.DumpBlockStore()
		for _, peer := range s.State.PeerList {
			if peer.Active {
				s.Client.GossipBlocks(peer.Name)
			}
		}
	}
}

func (s *Server) getMissingBlocks(block *models.Block) {
	blockId := *block.Previd
	if s.State.GetBlock(blockId) != nil {
		return
	}

	s.Logger.Debug("Block missing from chain: " + blockId)
	for _, peer := range s.State.PeerList {
		s.Client.DiscoverObject(peer.Name, blockId)
	}

	for s.State.GetBlock(blockId) == nil {
		s.Logger.Debug("Waiting for block " + blockId)
		time.Sleep(500 * time.Millisecond)
	}
}