package whisper

import (
	"crypto/ecdsa"
	"errors"
	"sync"
	"time"

	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/crypto"
	"github.com/ethereum/go-ethereum/crypto/ecies"
	"github.com/ethereum/go-ethereum/event/filter"
	"github.com/ethereum/go-ethereum/logger"
	"github.com/ethereum/go-ethereum/p2p"
	"gopkg.in/fatih/set.v0"
)

const (
	statusMsg      = 0x0
	envelopesMsg   = 0x01
	whisperVersion = 0x02
)

type MessageEvent struct {
	To      *ecdsa.PrivateKey
	From    *ecdsa.PublicKey
	Message *Message
}

const DefaultTtl = 50 * time.Second

var wlogger = logger.NewLogger("SHH")

type Whisper struct {
	protocol p2p.Protocol
	filters  *filter.Filters

	mmu      sync.RWMutex
	messages map[common.Hash]*Envelope
	expiry   map[uint32]*set.SetNonTS

	quit chan struct{}

	keys map[string]*ecdsa.PrivateKey
}

func New() *Whisper {
	whisper := &Whisper{
		messages: make(map[common.Hash]*Envelope),
		filters:  filter.New(),
		expiry:   make(map[uint32]*set.SetNonTS),
		quit:     make(chan struct{}),
		keys:     make(map[string]*ecdsa.PrivateKey),
	}
	whisper.filters.Start()

	// p2p whisper sub protocol handler
	whisper.protocol = p2p.Protocol{
		Name:    "shh",
		Version: uint(whisperVersion),
		Length:  2,
		Run:     whisper.msgHandler,
	}

	return whisper
}

func (self *Whisper) Version() uint {
	return self.protocol.Version
}

func (self *Whisper) Start() {
	wlogger.Infoln("Whisper started")
	go self.update()
}

func (self *Whisper) Stop() {
	close(self.quit)
}

func (self *Whisper) Send(envelope *Envelope) error {
	return self.add(envelope)
}

func (self *Whisper) NewIdentity() *ecdsa.PrivateKey {
	key, err := crypto.GenerateKey()
	if err != nil {
		panic(err)
	}

	self.keys[string(crypto.FromECDSAPub(&key.PublicKey))] = key

	return key
}

func (self *Whisper) HasIdentity(key *ecdsa.PublicKey) bool {
	return self.keys[string(crypto.FromECDSAPub(key))] != nil
}

func (self *Whisper) GetIdentity(key *ecdsa.PublicKey) *ecdsa.PrivateKey {
	return self.keys[string(crypto.FromECDSAPub(key))]
}

// func (self *Whisper) RemoveIdentity(key *ecdsa.PublicKey) bool {
// 	k := string(crypto.FromECDSAPub(key))
// 	if _, ok := self.keys[k]; ok {
// 		delete(self.keys, k)
// 		return true
// 	}
// 	return false
// }

func (self *Whisper) Watch(opts Filter) int {
	return self.filters.Install(filter.Generic{
		Str1: string(crypto.FromECDSAPub(opts.To)),
		Str2: string(crypto.FromECDSAPub(opts.From)),
		Data: bytesToMap(opts.Topics),
		Fn: func(data interface{}) {
			opts.Fn(data.(*Message))
		},
	})
}

func (self *Whisper) Unwatch(id int) {
	self.filters.Uninstall(id)
}

func (self *Whisper) Messages(id int) (messages []*Message) {
	filter := self.filters.Get(id)
	if filter != nil {
		for _, e := range self.messages {
			if msg, key := self.open(e); msg != nil {
				f := createFilter(msg, e.Topics, key)
				if self.filters.Match(filter, f) {
					messages = append(messages, msg)
				}
			}
		}
	}

	return
}

// Main handler for passing whisper messages to whisper peer objects
func (self *Whisper) msgHandler(peer *p2p.Peer, ws p2p.MsgReadWriter) error {
	wpeer := NewPeer(self, peer, ws)
	// initialise whisper peer (handshake/status)
	if err := wpeer.init(); err != nil {
		return err
	}
	// kick of the main handler for broadcasting/managing envelopes
	go wpeer.start()
	defer wpeer.stop()

	// Main *read* loop. Writing is done by the peer it self.
	for {
		msg, err := ws.ReadMsg()
		if err != nil {
			return err
		}

		var envelopes []*Envelope
		if err := msg.Decode(&envelopes); err != nil {
			peer.Infoln(err)
			continue
		}

		for _, envelope := range envelopes {
			if err := self.add(envelope); err != nil {
				// TODO Punish peer here. Invalid envelope.
				peer.Debugln(err)
			}
			wpeer.addKnown(envelope)
		}
	}
}

// takes care of adding envelopes to the messages pool. At this moment no sanity checks are being performed.
func (self *Whisper) add(envelope *Envelope) error {
	if !envelope.valid() {
		return errors.New("invalid pow provided for envelope")
	}

	self.mmu.Lock()
	defer self.mmu.Unlock()

	hash := envelope.Hash()
	self.messages[hash] = envelope
	if self.expiry[envelope.Expiry] == nil {
		self.expiry[envelope.Expiry] = set.NewNonTS()
	}

	if !self.expiry[envelope.Expiry].Has(hash) {
		self.expiry[envelope.Expiry].Add(hash)
		go self.postEvent(envelope)
	}

	wlogger.DebugDetailf("added whisper envelope %x\n", envelope)

	return nil
}

func (self *Whisper) update() {
	expire := time.NewTicker(800 * time.Millisecond)
out:
	for {
		select {
		case <-expire.C:
			self.expire()
		case <-self.quit:
			break out
		}
	}
}

func (self *Whisper) expire() {
	self.mmu.Lock()
	defer self.mmu.Unlock()

	now := uint32(time.Now().Unix())
	for then, hashSet := range self.expiry {
		if then > now {
			continue
		}

		hashSet.Each(func(v interface{}) bool {
			delete(self.messages, v.(common.Hash))
			return true
		})
		self.expiry[then].Clear()
	}
}

func (self *Whisper) envelopes() (envelopes []*Envelope) {
	self.mmu.RLock()
	defer self.mmu.RUnlock()

	envelopes = make([]*Envelope, len(self.messages))
	i := 0
	for _, envelope := range self.messages {
		envelopes[i] = envelope
		i++
	}

	return
}

func (self *Whisper) postEvent(envelope *Envelope) {
	if message, key := self.open(envelope); message != nil {
		self.filters.Notify(createFilter(message, envelope.Topics, key), message)
	}
}

func (self *Whisper) open(envelope *Envelope) (*Message, *ecdsa.PrivateKey) {
	for _, key := range self.keys {
		if message, err := envelope.Open(key); err == nil || (err != nil && err == ecies.ErrInvalidPublicKey) {
			message.To = &key.PublicKey

			return message, key
		}
	}

	return nil, nil
}

func (self *Whisper) Protocol() p2p.Protocol {
	return self.protocol
}

func createFilter(message *Message, topics [][]byte, key *ecdsa.PrivateKey) filter.Filter {
	return filter.Generic{
		Str1: string(crypto.FromECDSAPub(&key.PublicKey)), Str2: string(crypto.FromECDSAPub(message.Recover())),
		Data: bytesToMap(topics),
	}
}
