/*
Copyright IBM Corp. 2016 All Rights Reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

		 http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package producer

import (
	"fmt"
	"strconv"

	"github.com/golang/protobuf/proto"

	"github.com/hyperledger/fabric/msp/mgmt"
	pb "github.com/hyperledger/fabric/protos/peer"
)

type handler struct {
	ChatStream       pb.Events_ChatServer
	interestedEvents map[string]*pb.Interest
}

func newEventHandler(stream pb.Events_ChatServer) (*handler, error) {
	d := &handler{
		ChatStream: stream,
	}
	d.interestedEvents = make(map[string]*pb.Interest)
	return d, nil
}

// Stop stops this handler
func (d *handler) Stop() error {
	d.deregisterAll()
	d.interestedEvents = nil
	return nil
}

func getInterestKey(interest pb.Interest) string {
	var key string
	switch interest.EventType {
	case pb.EventType_BLOCK:
		key = "/" + strconv.Itoa(int(pb.EventType_BLOCK))
	case pb.EventType_REJECTION:
		key = "/" + strconv.Itoa(int(pb.EventType_REJECTION))
	case pb.EventType_CHAINCODE:
		key = "/" + strconv.Itoa(int(pb.EventType_CHAINCODE)) + "/" + interest.GetChaincodeRegInfo().ChaincodeId + "/" + interest.GetChaincodeRegInfo().EventName
	default:
		logger.Errorf("unknown interest type %s", interest.EventType)
	}

	return key
}

func (d *handler) register(iMsg []*pb.Interest) error {
	// Could consider passing interest array to registerHandler
	// and only lock once for entire array here
	for _, v := range iMsg {
		if err := registerHandler(v, d); err != nil {
			logger.Errorf("could not register %s: %s", v, err)
			continue
		}
		d.interestedEvents[getInterestKey(*v)] = v
	}

	return nil
}

func (d *handler) deregister(iMsg []*pb.Interest) error {
	for _, v := range iMsg {
		if err := deRegisterHandler(v, d); err != nil {
			logger.Errorf("could not deregister %s", v)
			continue
		}
		delete(d.interestedEvents, getInterestKey(*v))
	}
	return nil
}

func (d *handler) deregisterAll() {
	for k, v := range d.interestedEvents {
		if err := deRegisterHandler(v, d); err != nil {
			logger.Errorf("could not deregister %s", v)
			continue
		}
		delete(d.interestedEvents, k)
	}
}

// HandleMessage handles the Openchain messages for the Peer.
func (d *handler) HandleMessage(msg *pb.SignedEvent) error {
	evt, err := validateEventMessage(msg)
	if err != nil {
		return fmt.Errorf("event message must be properly signed by an identity from the same organization as the peer: [%s]", err)
	}

	switch evt.Event.(type) {
	case *pb.Event_Register:
		eventsObj := evt.GetRegister()
		if err := d.register(eventsObj.Events); err != nil {
			return fmt.Errorf("could not register events %s", err)
		}
	case *pb.Event_Unregister:
		eventsObj := evt.GetUnregister()
		if err := d.deregister(eventsObj.Events); err != nil {
			return fmt.Errorf("could not unregister events %s", err)
		}
	case nil:
	default:
		return fmt.Errorf("invalide type from client %T", evt.Event)
	}
	//TODO return supported events.. for now just return the received msg
	if err := d.ChatStream.Send(evt); err != nil {
		return fmt.Errorf("error sending response to %v:  %s", msg, err)
	}

	return nil
}

// SendMessage sends a message to the remote PEER through the stream
func (d *handler) SendMessage(msg *pb.Event) error {
	err := d.ChatStream.Send(msg)
	if err != nil {
		return fmt.Errorf("error Sending message through ChatStream: %s", err)
	}
	return nil
}

// Validates event messages by validating the Creator and verifying
// the signature. Returns the unmarshaled Event object
// Validation of the creator identity's validity is done by checking with local MSP to ensure the
// submitter is a member in the same organization as the peer
//
// TODO: ideally this should also check each channel's "Readers" policy to ensure the identity satisfies
// each channel's access control policy. This step is necessary because the registered listener is going
// to get read access to all channels by receiving Block events from all channels.
// However, this is not being done for v1.0 due to complexity concerns and the need to complex a stable,
// minimally viable release. Eventually events will be made channel-specific, at which point this method
// should be revisited
func validateEventMessage(signedEvt *pb.SignedEvent) (*pb.Event, error) {
	logger.Debugf("ValidateEventMessage starts for signed event %p", signedEvt)

	// messages from the client for registering and unregistering must be signed
	// and accompanied by the signing certificate in the "Creator" field
	evt := &pb.Event{}
	err := proto.Unmarshal(signedEvt.EventBytes, evt)
	if err != nil {
		return nil, fmt.Errorf("error unmarshaling the event bytes in the SignedEvent: %s", err)
	}

	localMSP := mgmt.GetLocalMSP()
	principalGetter := mgmt.NewLocalMSPPrincipalGetter()

	// Load MSPPrincipal for policy
	principal, err := principalGetter.Get(mgmt.Members)
	if err != nil {
		return nil, fmt.Errorf("failed getting local MSP principal [member]: [%s]", err)
	}

	id, err := localMSP.DeserializeIdentity(evt.Creator)
	if err != nil {
		return nil, fmt.Errorf("failed deserializing event creator: [%s]", err)
	}

	// Verify that event's creator satisfies the principal
	err = id.SatisfiesPrincipal(principal)
	if err != nil {
		return nil, fmt.Errorf("failed verifying the creator satisfies local MSP's [member] principal: [%s]", err)
	}

	// Verify the signature
	err = id.Verify(signedEvt.EventBytes, signedEvt.Signature)
	if err != nil {
		return nil, fmt.Errorf("failed verifying the event signature: %s", err)
	}

	return evt, nil
}