package common

import (
	"errors"
	"sync"
	"time"

	pp "github.com/libp2p/go-libp2p/core/peer"
	"github.com/libp2p/go-libp2p/core/protocol"
)

type Score struct {
	FirstContacted time.Time
	UptimeTracker  *UptimeTracker
	LastFillRate   float64
	Score          float64
	// IsSeed marks indexers that came from the IndexerAddresses static config.
	// Seeds are sticky: they are never evicted by the score threshold alone.
	// A seed is only removed when: (a) heartbeat fails, or (b) it sends
	// SuggestMigrate and the node already has MinIndexer non-seed alternatives.
	IsSeed bool
	// challenge bookkeeping (2-3 peers per batch, raw data returned by indexer)
	hbCount          int // heartbeats sent since last challenge batch
	nextChallenge    int // send challenges when hbCount reaches this (rand 1-10)
	challengeTotal   int // number of own-PeerID challenges sent (ground truth)
	challengeCorrect int // own PeerID found AND lastSeen within 2×interval
	// fill rate consistency: cross-check reported fillRate vs peerCount/maxNodes
	fillChecked    int
	fillConsistent int
	// BornAt stability
	LastBornAt    time.Time
	bornAtChanges int
	// DHT challenge
	dhtChecked      int
	dhtSuccess      int
	dhtBatchCounter int
	// Peer witnesses
	witnessChecked    int
	witnessConsistent int
}

// computeNodeSideScore computes the node's quality assessment of an indexer from raw metrics.
// All ratios are in [0,1]; result is in [0,100].
//   - uptimeRatio      : gap-aware fraction of lifetime the indexer was reachable
//   - challengeAccuracy: own-PeerID challenges answered correctly (found + recent lastSeen)
//   - latencyScore     : 1 - RTT/maxRTT, clamped [0,1]
//   - fillScore        : 1 - fillRate — prefer less-loaded indexers
//   - fillConsistency  : fraction of ticks where peerCount/maxNodes ≈ fillRate (±10%)
func (s *Score) ComputeNodeSideScore(latencyScore float64) float64 {
	uptime := s.UptimeTracker.UptimeRatio()
	challengeAccuracy := 1.0
	if s.challengeTotal > 0 {
		challengeAccuracy = float64(s.challengeCorrect) / float64(s.challengeTotal)
	}
	fillScore := 1.0 - s.LastFillRate
	fillConsistency := 1.0
	if s.fillChecked > 0 {
		fillConsistency = float64(s.fillConsistent) / float64(s.fillChecked)
	}
	witnessConsistency := 1.0
	if s.witnessChecked > 0 {
		witnessConsistency = float64(s.witnessConsistent) / float64(s.witnessChecked)
	}
	dhtSuccessRate := 1.0
	if s.dhtChecked > 0 {
		dhtSuccessRate = float64(s.dhtSuccess) / float64(s.dhtChecked)
	}
	base := ((0.20 * uptime) +
		(0.20 * challengeAccuracy) +
		(0.15 * latencyScore) +
		(0.10 * fillScore) +
		(0.10 * fillConsistency) +
		(0.15 * witnessConsistency) +
		(0.10 * dhtSuccessRate)) * 100
	// BornAt stability: each unexpected BornAt change penalises by 30%.
	bornAtPenalty := 1.0 - 0.30*float64(s.bornAtChanges)
	if bornAtPenalty < 0 {
		bornAtPenalty = 0
	}
	return base * bornAtPenalty
}

type Directory struct {
	MuAddr   sync.RWMutex
	MuScore  sync.RWMutex
	MuStream sync.RWMutex
	Addrs    map[string]*pp.AddrInfo
	Scores   map[string]*Score
	Nudge    chan struct{}
	Streams  ProtocolStream
}

func (d *Directory) ExistsScore(a string) bool {
	d.MuScore.RLock()
	defer d.MuScore.RUnlock()
	for addr, ai := range d.Scores {
		if ai != nil && (a == addr) {
			return true
		}
	}
	return false
}

func (d *Directory) GetScore(a string) *Score {
	d.MuScore.RLock()
	defer d.MuScore.RUnlock()
	for addr, s := range d.Scores {
		if s != nil && (a == addr) {
			sCopy := *s
			return &sCopy
		}
	}
	return nil
}

func (d *Directory) GetScores() map[string]*Score {
	d.MuScore.RLock()
	defer d.MuScore.RUnlock()
	score := map[string]*Score{}
	for addr, s := range d.Scores {
		score[addr] = s
	}
	return score
}

func (d *Directory) DeleteScore(a string) {
	d.MuScore.RLock()
	defer d.MuScore.RUnlock()
	score := map[string]*Score{}
	for addr, s := range d.Scores {
		if a != addr {
			score[addr] = s
		}
	}
	d.Scores = score
}

func (d *Directory) SetScore(addr string, score *Score) *pp.AddrInfo {
	d.MuScore.Lock()
	defer d.MuScore.Unlock()
	d.Scores[addr] = score
	return nil
}

func (d *Directory) ExistsAddr(addrOrId string) bool {
	d.MuAddr.RLock()
	defer d.MuAddr.RUnlock()
	for addr, ai := range d.Addrs {
		if ai != nil && (addrOrId == ai.ID.String() || addrOrId == addr) {
			return true
		}
	}
	return false
}

func (d *Directory) GetAddr(addrOrId string) *pp.AddrInfo {
	d.MuAddr.RLock()
	defer d.MuAddr.RUnlock()
	for addr, ai := range d.Addrs {
		if ai != nil && (addrOrId == ai.ID.String() || addrOrId == addr) {
			aiCopy := *ai
			return &aiCopy
		}
	}
	return nil
}

func (d *Directory) DeleteAddr(a string) {
	d.MuAddr.RLock()
	defer d.MuAddr.RUnlock()
	addrs := map[string]*pp.AddrInfo{}
	for addr, s := range d.Addrs {
		if a != addr {
			addrs[addr] = s
		}
	}
	d.Addrs = addrs
}

func (d *Directory) SetAddr(addr string, info *pp.AddrInfo) *pp.AddrInfo {
	d.MuAddr.Lock()
	defer d.MuAddr.Unlock()
	d.Addrs[addr] = info
	return nil
}

func (d *Directory) GetAddrIDs() []pp.ID {
	d.MuAddr.RLock()
	defer d.MuAddr.RUnlock()
	indexers := make([]pp.ID, 0, len(d.Addrs))
	for _, ai := range d.Addrs {
		if ai != nil {
			indexers = append(indexers, ai.ID)
		}
	}
	return Shuffle(indexers)
}

func (d *Directory) GetAddrsStr() []string {
	d.MuAddr.RLock()
	defer d.MuAddr.RUnlock()
	indexers := make([]string, 0, len(d.Addrs))
	for s, ai := range d.Addrs {
		if ai != nil {
			indexers = append(indexers, s)
		}
	}

	return Shuffle(indexers)
}

type Entry struct {
	Addr string
	Info *pp.AddrInfo
}

func (d *Directory) GetAddrs() []Entry {
	d.MuAddr.RLock()
	defer d.MuAddr.RUnlock()
	indexers := make([]Entry, 0, len(d.Addrs))
	for addr, ai := range d.Addrs {
		if ai != nil {
			indexers = append(indexers, Entry{
				Addr: addr,
				Info: ai,
			})
		}
	}
	return Shuffle(indexers)
}

// NudgeIndexerHeartbeat signals the indexer heartbeat goroutine to fire immediately.
func (d *Directory) NudgeIt() {
	select {
	case d.Nudge <- struct{}{}:
	default: // nudge already pending, skip
	}
}

type ProtocolStream map[protocol.ID]map[pp.ID]*Stream

func (ps ProtocolStream) Get(protocol protocol.ID) map[pp.ID]*Stream {
	if ps[protocol] == nil {
		ps[protocol] = map[pp.ID]*Stream{}
	}

	return ps[protocol]
}

func (ps ProtocolStream) GetPerID(protocol protocol.ID, peerID pp.ID) *Stream {
	if ps[protocol] == nil {
		ps[protocol] = map[pp.ID]*Stream{}
	}
	return ps[protocol][peerID]
}

func (ps ProtocolStream) Add(protocol protocol.ID, peerID *pp.ID, s *Stream) error {
	if ps[protocol] == nil {
		ps[protocol] = map[pp.ID]*Stream{}
	}
	if peerID != nil {
		if s != nil {
			ps[protocol][*peerID] = s
		} else {
			return errors.New("unable to add stream : stream missing")
		}
	}
	return nil
}

func (ps ProtocolStream) Delete(protocol protocol.ID, peerID *pp.ID) {
	if streams, ok := ps[protocol]; ok {
		if peerID != nil && streams[*peerID] != nil && streams[*peerID].Stream != nil {
			streams[*peerID].Stream.Close()
			delete(streams, *peerID)
		} else {
			for _, s := range ps {
				for _, v := range s {
					if v.Stream != nil {
						v.Stream.Close()
					}
				}
			}
			delete(ps, protocol)
		}
	}
}

var Indexers = &Directory{
	Addrs:   map[string]*pp.AddrInfo{},
	Scores:  map[string]*Score{},
	Nudge:   make(chan struct{}, 1),
	Streams: ProtocolStream{},
}