// SPDX-FileCopyrightText: 2023 The Pion community <https://pion.ly>
// SPDX-License-Identifier: MIT

//go:build !js
// +build !js

package webrtc

import (
	"fmt"
	"strings"
	"sync"
	"sync/atomic"
	"time"

	"github.com/pion/ice/v4"
	"github.com/pion/logging"
	"github.com/pion/stun/v3"
)

// ICEGatherer gathers local host, server reflexive and relay
// candidates, as well as enabling the retrieval of local Interactive
// Connectivity Establishment (ICE) parameters which can be
// exchanged in signaling.
type ICEGatherer struct {
	lock  sync.RWMutex
	log   logging.LeveledLogger
	state ICEGathererState

	validatedServers []*stun.URI
	gatherPolicy     ICETransportPolicy

	agent *ice.Agent

	onLocalCandidateHandler atomic.Value // func(candidate *ICECandidate)
	onStateChangeHandler    atomic.Value // func(state ICEGathererState)

	// Used for GatheringCompletePromise
	onGatheringCompleteHandler atomic.Value // func()

	api *API

	// Used to set the corresponding media stream identification tag and media description index
	// for ICE candidates generated by this gatherer.
	sdpMid        atomic.Value  // string
	sdpMLineIndex atomic.Uint32 // uint16
}

// ICEAddressRewriteMode controls whether a rule replaces or appends candidates.
type ICEAddressRewriteMode byte

const (
	ICEAddressRewriteModeUnspecified ICEAddressRewriteMode = iota
	ICEAddressRewriteReplace
	ICEAddressRewriteAppend
)

func (r ICEAddressRewriteMode) toICE() ice.AddressRewriteMode {
	return ice.AddressRewriteMode(r)
}

// ICEAddressRewriteRule represents a rule for remapping candidate addresses.
type ICEAddressRewriteRule struct {
	External        []string
	Local           string
	Iface           string
	CIDR            string
	AsCandidateType ICECandidateType
	Mode            ICEAddressRewriteMode
	Networks        []NetworkType
}

func (r ICEAddressRewriteRule) toICE() ice.AddressRewriteRule {
	candidateType := r.AsCandidateType.toICE()
	mode := r.Mode.toICE()
	networks := toICENetworkTypes(r.Networks)

	rule := ice.AddressRewriteRule{
		External:        append([]string(nil), r.External...),
		Local:           r.Local,
		Iface:           r.Iface,
		CIDR:            r.CIDR,
		AsCandidateType: candidateType,
		Mode:            mode,
		Networks:        networks,
	}

	return rule
}

// NewICEGatherer creates a new NewICEGatherer.
// This constructor is part of the ORTC API. It is not
// meant to be used together with the basic WebRTC API.
func (api *API) NewICEGatherer(opts ICEGatherOptions) (*ICEGatherer, error) {
	var validatedServers []*stun.URI
	if len(opts.ICEServers) > 0 {
		for _, server := range opts.ICEServers {
			url, err := server.urls()
			if err != nil {
				return nil, err
			}
			validatedServers = append(validatedServers, url...)
		}
	}

	return &ICEGatherer{
		state:            ICEGathererStateNew,
		gatherPolicy:     opts.ICEGatherPolicy,
		validatedServers: validatedServers,
		api:              api,
		log:              api.settingEngine.LoggerFactory.NewLogger("ice"),
		sdpMid:           atomic.Value{},
		sdpMLineIndex:    atomic.Uint32{},
	}, nil
}

func (g *ICEGatherer) createAgent() error {
	g.lock.Lock()
	defer g.lock.Unlock()

	if g.agent != nil || g.State() != ICEGathererStateNew {
		return nil
	}

	options, err := g.buildAgentOptions()
	if err != nil {
		return err
	}

	agent, err := ice.NewAgentWithOptions(options...)
	if err != nil {
		return err
	}

	g.agent = agent

	return nil
}

func (g *ICEGatherer) buildAgentOptions() ([]ice.AgentOption, error) {
	candidateTypes := g.resolveCandidateTypes()
	nat1To1CandiTyp := g.resolveNAT1To1CandidateType()
	mDNSMode := g.sanitizedMDNSMode()

	options := g.baseAgentOptions(mDNSMode)
	if len(candidateTypes) > 0 {
		options = append(options, ice.WithCandidateTypes(candidateTypes))
	}

	options = append(options, g.credentialOptions()...)

	rewriteOptions, err := g.addressRewriteOptions(nat1To1CandiTyp)
	if err != nil {
		return nil, err
	}
	options = append(options, rewriteOptions...)
	options = append(options, g.timeoutOptions()...)
	options = append(options, g.miscOptions()...)
	options = append(options, g.renominationOptions()...)

	requestedNetworkTypes := g.api.settingEngine.candidates.ICENetworkTypes
	if len(requestedNetworkTypes) == 0 {
		requestedNetworkTypes = supportedNetworkTypes()
	}

	return append(options, ice.WithNetworkTypes(toICENetworkTypes(requestedNetworkTypes))), nil
}

func (g *ICEGatherer) resolveCandidateTypes() []ice.CandidateType {
	if g.api.settingEngine.candidates.ICELite {
		return []ice.CandidateType{ice.CandidateTypeHost}
	}

	switch g.gatherPolicy {
	case ICETransportPolicyRelay:
		return []ice.CandidateType{ice.CandidateTypeRelay}
	case ICETransportPolicyNoHost:
		return []ice.CandidateType{ice.CandidateTypeServerReflexive, ice.CandidateTypeRelay}
	default:
	}

	return nil
}

func (g *ICEGatherer) resolveNAT1To1CandidateType() ice.CandidateType {
	switch g.api.settingEngine.candidates.NAT1To1IPCandidateType {
	case ICECandidateTypeHost:
		return ice.CandidateTypeHost
	case ICECandidateTypeSrflx:
		return ice.CandidateTypeServerReflexive
	default:
		return ice.CandidateTypeUnspecified
	}
}

func (g *ICEGatherer) sanitizedMDNSMode() ice.MulticastDNSMode {
	mode := g.api.settingEngine.candidates.MulticastDNSMode
	if mode == ice.MulticastDNSModeDisabled || mode == ice.MulticastDNSModeQueryAndGather {
		return mode
	}

	return ice.MulticastDNSModeQueryOnly
}

func (g *ICEGatherer) baseAgentOptions(mDNSMode ice.MulticastDNSMode) []ice.AgentOption {
	return []ice.AgentOption{
		ice.WithICELite(g.api.settingEngine.candidates.ICELite),
		ice.WithUrls(g.validatedServers),
		ice.WithPortRange(g.api.settingEngine.ephemeralUDP.PortMin, g.api.settingEngine.ephemeralUDP.PortMax),
		ice.WithLoggerFactory(g.api.settingEngine.LoggerFactory),
		ice.WithInterfaceFilter(g.api.settingEngine.candidates.InterfaceFilter),
		ice.WithIPFilter(g.api.settingEngine.candidates.IPFilter),
		ice.WithNet(g.api.settingEngine.net),
		ice.WithMulticastDNSMode(mDNSMode),
		ice.WithTCPMux(g.api.settingEngine.iceTCPMux),
		ice.WithUDPMux(g.api.settingEngine.iceUDPMux),
		ice.WithProxyDialer(g.api.settingEngine.iceProxyDialer),
		ice.WithBindingRequestHandler(g.api.settingEngine.iceBindingRequestHandler),
	}
}

func (g *ICEGatherer) credentialOptions() []ice.AgentOption {
	ufrag := g.api.settingEngine.candidates.UsernameFragment
	pass := g.api.settingEngine.candidates.Password
	if ufrag == "" && pass == "" {
		return nil
	}

	return []ice.AgentOption{
		ice.WithLocalCredentials(g.api.settingEngine.candidates.UsernameFragment, g.api.settingEngine.candidates.Password),
	}
}

func (g *ICEGatherer) addressRewriteOptions(candidateType ice.CandidateType) ([]ice.AgentOption, error) {
	rules := g.api.settingEngine.candidates.addressRewriteRules
	nat1To1IPs := g.api.settingEngine.candidates.NAT1To1IPs
	if len(rules) > 0 && len(nat1To1IPs) > 0 {
		return nil, errAddressRewriteWithNAT1To1
	}

	if len(rules) > 0 {
		return []ice.AgentOption{ice.WithAddressRewriteRules(rules...)}, nil
	}

	if len(nat1To1IPs) == 0 {
		return nil, nil
	}

	return []ice.AgentOption{
		ice.WithAddressRewriteRules(
			legacyNAT1To1AddressRewriteRules(
				nat1To1IPs,
				candidateType,
			)...,
		),
	}, nil
}

func (g *ICEGatherer) timeoutOptions() []ice.AgentOption {
	opts := make([]ice.AgentOption, 0, 8)

	if g.api.settingEngine.timeout.ICEDisconnectedTimeout != nil {
		opts = append(opts, ice.WithDisconnectedTimeout(*g.api.settingEngine.timeout.ICEDisconnectedTimeout))
	}
	if g.api.settingEngine.timeout.ICEFailedTimeout != nil {
		opts = append(opts, ice.WithFailedTimeout(*g.api.settingEngine.timeout.ICEFailedTimeout))
	}
	if g.api.settingEngine.timeout.ICEKeepaliveInterval != nil {
		opts = append(opts, ice.WithKeepaliveInterval(*g.api.settingEngine.timeout.ICEKeepaliveInterval))
	}
	if g.api.settingEngine.timeout.ICEHostAcceptanceMinWait != nil {
		opts = append(opts, ice.WithHostAcceptanceMinWait(*g.api.settingEngine.timeout.ICEHostAcceptanceMinWait))
	}
	if g.api.settingEngine.timeout.ICESrflxAcceptanceMinWait != nil {
		opts = append(opts, ice.WithSrflxAcceptanceMinWait(*g.api.settingEngine.timeout.ICESrflxAcceptanceMinWait))
	}
	if g.api.settingEngine.timeout.ICEPrflxAcceptanceMinWait != nil {
		opts = append(opts, ice.WithPrflxAcceptanceMinWait(*g.api.settingEngine.timeout.ICEPrflxAcceptanceMinWait))
	}
	if g.api.settingEngine.timeout.ICERelayAcceptanceMinWait != nil {
		opts = append(opts, ice.WithRelayAcceptanceMinWait(*g.api.settingEngine.timeout.ICERelayAcceptanceMinWait))
	}
	if g.api.settingEngine.timeout.ICESTUNGatherTimeout != nil {
		opts = append(opts, ice.WithSTUNGatherTimeout(*g.api.settingEngine.timeout.ICESTUNGatherTimeout))
	}

	return opts
}

func (g *ICEGatherer) miscOptions() []ice.AgentOption {
	opts := make([]ice.AgentOption, 0, 4)

	if g.api.settingEngine.candidates.MulticastDNSHostName != "" {
		opts = append(opts, ice.WithMulticastDNSHostName(g.api.settingEngine.candidates.MulticastDNSHostName))
	}

	if g.api.settingEngine.candidates.IncludeLoopbackCandidate {
		opts = append(opts, ice.WithIncludeLoopback())
	}

	if g.api.settingEngine.iceDisableActiveTCP {
		opts = append(opts, ice.WithDisableActiveTCP())
	}

	if g.api.settingEngine.iceMaxBindingRequests != nil {
		opts = append(opts, ice.WithMaxBindingRequests(*g.api.settingEngine.iceMaxBindingRequests))
	}

	return opts
}

func (g *ICEGatherer) renominationOptions() []ice.AgentOption {
	renom := g.api.settingEngine.renomination
	if !renom.enabled && !renom.automatic {
		return nil
	}

	generator := renom.generator
	opts := []ice.AgentOption{
		ice.WithRenomination(func() uint32 {
			return generator()
		}),
	}

	if renom.automatic {
		interval := time.Duration(0)
		if renom.automaticInterval != nil {
			interval = *renom.automaticInterval
		}

		opts = append(opts, ice.WithAutomaticRenomination(interval))
	}

	return opts
}

func legacyNAT1To1AddressRewriteRules(ips []string, candidateType ice.CandidateType) []ice.AddressRewriteRule {
	catchAll := make([]string, 0, len(ips))
	rules := make([]ice.AddressRewriteRule, 0, len(ips)+1)

	for _, ip := range ips {
		splits := strings.SplitN(ip, "/", 2)

		if len(splits) == 2 {
			rules = append(rules, ice.AddressRewriteRule{
				External:        []string{splits[0]},
				Local:           splits[1],
				AsCandidateType: candidateType,
			})
			catchAll = append(catchAll, splits[0])
		} else {
			catchAll = append(catchAll, ip)
		}
	}

	if len(catchAll) > 0 {
		rules = append(rules, ice.AddressRewriteRule{
			External:        catchAll,
			AsCandidateType: candidateType,
		})
	}

	return rules
}

// Gather ICE candidates.
func (g *ICEGatherer) Gather() error { //nolint:cyclop
	if err := g.createAgent(); err != nil {
		return err
	}

	agent := g.getAgent()
	// it is possible agent had just been closed
	if agent == nil {
		return fmt.Errorf("%w: unable to gather", errICEAgentNotExist)
	}

	g.setState(ICEGathererStateGathering)
	if err := agent.OnCandidate(func(candidate ice.Candidate) {
		onLocalCandidateHandler := func(*ICECandidate) {}
		if handler, ok := g.onLocalCandidateHandler.Load().(func(candidate *ICECandidate)); ok && handler != nil {
			onLocalCandidateHandler = handler
		}

		onGatheringCompleteHandler := func() {}
		if handler, ok := g.onGatheringCompleteHandler.Load().(func()); ok && handler != nil {
			onGatheringCompleteHandler = handler
		}

		sdpMid := ""

		if mid, ok := g.sdpMid.Load().(string); ok {
			sdpMid = mid
		}

		sdpMLineIndex := uint16(g.sdpMLineIndex.Load()) //nolint:gosec // G115

		if candidate != nil {
			c, err := newICECandidateFromICE(candidate, sdpMid, sdpMLineIndex)
			if err != nil {
				g.log.Warnf("Failed to convert ice.Candidate: %s", err)

				return
			}
			onLocalCandidateHandler(&c)
		} else {
			g.setState(ICEGathererStateComplete)

			onGatheringCompleteHandler()
			onLocalCandidateHandler(nil)
		}
	}); err != nil {
		return err
	}

	return agent.GatherCandidates()
}

// set media stream identification tag and media description index for this gatherer.
func (g *ICEGatherer) setMediaStreamIdentification(mid string, mLineIndex uint16) {
	g.sdpMid.Store(mid)
	g.sdpMLineIndex.Store(uint32(mLineIndex))
}

// Close prunes all local candidates, and closes the ports.
func (g *ICEGatherer) Close() error {
	return g.close(false /* shouldGracefullyClose */)
}

// GracefulClose prunes all local candidates, and closes the ports. It also waits
// for any goroutines it started to complete. This is only safe to call outside of
// ICEGatherer callbacks or if in a callback, in its own goroutine.
func (g *ICEGatherer) GracefulClose() error {
	return g.close(true /* shouldGracefullyClose */)
}

func (g *ICEGatherer) close(shouldGracefullyClose bool) error {
	g.lock.Lock()
	defer g.lock.Unlock()

	if g.agent == nil {
		return nil
	}
	if shouldGracefullyClose {
		if err := g.agent.GracefulClose(); err != nil {
			return err
		}
	} else {
		if err := g.agent.Close(); err != nil {
			return err
		}
	}

	g.agent = nil
	g.setState(ICEGathererStateClosed)

	return nil
}

// GetLocalParameters returns the ICE parameters of the ICEGatherer.
func (g *ICEGatherer) GetLocalParameters() (ICEParameters, error) {
	if err := g.createAgent(); err != nil {
		return ICEParameters{}, err
	}

	agent := g.getAgent()
	// it is possible agent had just been closed
	if agent == nil {
		return ICEParameters{}, fmt.Errorf("%w: unable to get local parameters", errICEAgentNotExist)
	}

	frag, pwd, err := agent.GetLocalUserCredentials()
	if err != nil {
		return ICEParameters{}, err
	}

	return ICEParameters{
		UsernameFragment: frag,
		Password:         pwd,
		ICELite:          false,
	}, nil
}

// GetLocalCandidates returns the sequence of valid local candidates associated with the ICEGatherer.
func (g *ICEGatherer) GetLocalCandidates() ([]ICECandidate, error) {
	if err := g.createAgent(); err != nil {
		return nil, err
	}

	agent := g.getAgent()
	// it is possible agent had just been closed
	if agent == nil {
		return nil, fmt.Errorf("%w: unable to get local candidates", errICEAgentNotExist)
	}

	iceCandidates, err := agent.GetLocalCandidates()
	if err != nil {
		return nil, err
	}

	sdpMid := ""
	if mid, ok := g.sdpMid.Load().(string); ok {
		sdpMid = mid
	}

	sdpMLineIndex := uint16(g.sdpMLineIndex.Load()) //nolint:gosec // G115

	return newICECandidatesFromICE(iceCandidates, sdpMid, sdpMLineIndex)
}

// OnLocalCandidate sets an event handler which fires when a new local ICE candidate is available
// Take note that the handler will be called with a nil pointer when gathering is finished.
func (g *ICEGatherer) OnLocalCandidate(f func(*ICECandidate)) {
	g.onLocalCandidateHandler.Store(f)
}

// OnStateChange fires any time the ICEGatherer changes.
func (g *ICEGatherer) OnStateChange(f func(ICEGathererState)) {
	g.onStateChangeHandler.Store(f)
}

// State indicates the current state of the ICE gatherer.
func (g *ICEGatherer) State() ICEGathererState {
	return atomicLoadICEGathererState(&g.state)
}

func (g *ICEGatherer) setState(s ICEGathererState) {
	atomicStoreICEGathererState(&g.state, s)

	if handler, ok := g.onStateChangeHandler.Load().(func(state ICEGathererState)); ok && handler != nil {
		handler(s)
	}
}

func (g *ICEGatherer) getAgent() *ice.Agent {
	g.lock.RLock()
	defer g.lock.RUnlock()

	return g.agent
}

func (g *ICEGatherer) collectStats(collector *statsReportCollector) {
	agent := g.getAgent()
	if agent == nil {
		return
	}

	collector.Collecting()
	go func(collector *statsReportCollector, agent *ice.Agent) {
		for _, candidatePairStats := range agent.GetCandidatePairsStats() {
			collector.Collecting()

			stats, err := toICECandidatePairStats(candidatePairStats)
			if err != nil {
				g.log.Error(err.Error())
				collector.Done()

				continue
			}

			collector.Collect(stats.ID, stats)
		}

		for _, candidateStats := range agent.GetLocalCandidatesStats() {
			collector.Collecting()

			networkType, err := getNetworkType(candidateStats.NetworkType)
			if err != nil {
				g.log.Error(err.Error())
			}

			candidateType, err := getCandidateType(candidateStats.CandidateType)
			if err != nil {
				g.log.Error(err.Error())
			}

			stats := ICECandidateStats{
				Timestamp:     statsTimestampFrom(candidateStats.Timestamp),
				ID:            candidateStats.ID,
				Type:          StatsTypeLocalCandidate,
				IP:            candidateStats.IP,
				Port:          int32(candidateStats.Port), //nolint:gosec // G115, no overflow, port
				Protocol:      networkType.Protocol(),
				CandidateType: candidateType,
				Priority:      int32(candidateStats.Priority), //nolint:gosec
				URL:           candidateStats.URL,
				RelayProtocol: candidateStats.RelayProtocol,
				Deleted:       candidateStats.Deleted,
			}
			collector.Collect(stats.ID, stats)
		}

		for _, candidateStats := range agent.GetRemoteCandidatesStats() {
			collector.Collecting()
			networkType, err := getNetworkType(candidateStats.NetworkType)
			if err != nil {
				g.log.Error(err.Error())
			}

			candidateType, err := getCandidateType(candidateStats.CandidateType)
			if err != nil {
				g.log.Error(err.Error())
			}

			stats := ICECandidateStats{
				Timestamp:     statsTimestampFrom(candidateStats.Timestamp),
				ID:            candidateStats.ID,
				Type:          StatsTypeRemoteCandidate,
				IP:            candidateStats.IP,
				Port:          int32(candidateStats.Port), //nolint:gosec // G115, no overflow, port
				Protocol:      networkType.Protocol(),
				CandidateType: candidateType,
				Priority:      int32(candidateStats.Priority), //nolint:gosec // G115
				URL:           candidateStats.URL,
				RelayProtocol: candidateStats.RelayProtocol,
			}
			collector.Collect(stats.ID, stats)
		}
		collector.Done()
	}(collector, agent)
}

func (g *ICEGatherer) getSelectedCandidatePairStats() (ICECandidatePairStats, bool) {
	agent := g.getAgent()
	if agent == nil {
		return ICECandidatePairStats{}, false
	}

	selectedCandidatePairStats, isAvailable := agent.GetSelectedCandidatePairStats()
	if !isAvailable {
		return ICECandidatePairStats{}, false
	}

	stats, err := toICECandidatePairStats(selectedCandidatePairStats)
	if err != nil {
		g.log.Error(err.Error())

		return ICECandidatePairStats{}, false
	}

	return stats, true
}