package httpapi

import (
	"net/netip"
	"strings"
	"time"

	"evobgp/internal/birdfmt"
	"evobgp/internal/store"
)

type speakerBGPLive struct {
	SpeakerID           string
	Label               string
	Sessions            []birdfmt.BGPSession
	Error               string
	Polled              bool
	ObservedAt          time.Time
	ReceivedAt          time.Time
	LastSuccessAt       time.Time
	Source              string
	ObservationOverride *liveObservation
}

type liveObservation struct {
	ObservedAt    *string `json:"observed_at"`
	ReceivedAt    *string `json:"received_at"`
	LastSuccessAt *string `json:"last_success_at"`
	ExpiresAt     *string `json:"expires_at,omitempty"`
	Source        string  `json:"source"`
	Quality       string  `json:"quality"`
	ErrorCode     string  `json:"error_code,omitempty"`
}

func liveTime(t time.Time) *string {
	if t.IsZero() {
		return nil
	}
	v := t.UTC().Format(time.RFC3339Nano)
	return &v
}

func (v speakerBGPLive) observed() bool {
	return v.Polled || v.Error != "" || len(v.Sessions) > 0
}

func (v speakerBGPLive) successful() bool {
	return v.observed() && v.Error == ""
}

func (v speakerBGPLive) observation() liveObservation {
	if v.ObservationOverride != nil {
		return *v.ObservationOverride
	}
	o := liveObservation{ObservedAt: liveTime(v.ObservedAt), ReceivedAt: liveTime(v.ReceivedAt), LastSuccessAt: liveTime(v.LastSuccessAt), Source: v.Source, Quality: "unknown"}
	if o.Source == "" {
		o.Source = "none"
	}
	switch {
	case v.successful():
		o.Quality = "ok"
	case v.Error != "" && !v.LastSuccessAt.IsZero():
		o.Quality = "stale"
		o.ErrorCode = liveErrorCode(v.Error)
	case v.Error != "":
		o.Quality = "unreachable"
		o.ErrorCode = liveErrorCode(v.Error)
	default:
		o.ErrorCode = "not_polled"
	}
	return o
}

func liveErrorCode(err string) string {
	if strings.Contains(strings.ToLower(err), "not configured") || strings.Contains(strings.ToLower(err), "missing") {
		return "not_configured"
	}
	return "poll_failed"
}

type peerSessionOnSpeaker struct {
	SpeakerID   string          `json:"speaker_id"`
	Label       string          `json:"label"`
	State       string          `json:"state"`
	PollError   string          `json:"poll_error,omitempty"`
	Observation liveObservation `json:"observation"`
}

type liveSpeakerPoll struct {
	SpeakerID    string          `json:"speaker_id"`
	Label        string          `json:"label"`
	OK           bool            `json:"ok"`
	SessionCount *int            `json:"session_count"`
	PollError    string          `json:"poll_error,omitempty"`
	Observation  liveObservation `json:"observation"`
}

func speakerDisplayLabel(sp *store.Speaker) string {
	if sp == nil {
		return ""
	}
	meta := store.ParseSpeakerMeta(sp.MetaJSON)
	host := strings.TrimSpace(meta.AgentDomain)
	if host == "" {
		host = strings.TrimSpace(sp.Endpoint)
	}
	if strings.EqualFold(strings.TrimSpace(sp.Role), "master") {
		if host != "" {
			return "CP · " + host
		}
		return "CP (master)"
	}
	if host != "" {
		return host
	}
	return sp.ID
}

func liveSpeakerPollJSON(views []speakerBGPLive) []liveSpeakerPoll {
	out := make([]liveSpeakerPoll, 0, len(views))
	for _, v := range views {
		var sessionCount *int
		if v.successful() {
			count := len(v.Sessions)
			sessionCount = &count
		}
		out = append(out, liveSpeakerPoll{
			SpeakerID:    v.SpeakerID,
			Label:        v.Label,
			OK:           v.successful(),
			SessionCount: sessionCount,
			PollError:    v.Error,
			Observation:  v.observation(),
		})
	}
	return out
}

func findPeerSession(sessions []birdfmt.BGPSession, protoName string, neighbor netip.Addr, hasNeighbor bool) *birdfmt.BGPSession {
	for i := range sessions {
		if peerSessionMatches(sessions[i], protoName, neighbor, hasNeighbor) {
			return &sessions[i]
		}
	}
	return nil
}

func matchPeerOnSpeakers(peer *store.BGPPeer, views []speakerBGPLive) (
	bestState string,
	connectedID string,
	connectedLabel string,
	establishedOn []peerSessionOnSpeaker,
	on []peerSessionOnSpeaker,
	mismatch bool,
) {
	if peer == nil {
		return "", "", "", nil, nil, false
	}
	neighbor, hasNeighbor := store.ParsePeerNeighbor(peer.Neighbor)
	protoName := birdfmt.PeerProtocolName(peer.ID)

	for _, v := range views {
		if !v.successful() {
			on = append(on, peerSessionOnSpeaker{
				SpeakerID:   v.SpeakerID,
				Label:       v.Label,
				PollError:   v.Error,
				Observation: v.observation(),
			})
			continue
		}
		sess := findPeerSession(v.Sessions, protoName, neighbor, hasNeighbor)
		if sess == nil {
			on = append(on, peerSessionOnSpeaker{
				SpeakerID:   v.SpeakerID,
				Label:       v.Label,
				State:       "absent",
				Observation: v.observation(),
			})
			continue
		}
		hit := peerSessionOnSpeaker{
			SpeakerID:   v.SpeakerID,
			Label:       v.Label,
			State:       sess.State,
			Observation: v.observation(),
		}
		on = append(on, hit)
		if strings.EqualFold(strings.TrimSpace(sess.State), "Established") {
			establishedOn = append(establishedOn, hit)
		}
		if bestState == "" || sessionStateRank(sess.State) > sessionStateRank(bestState) {
			bestState = sess.State
		}
	}

	if len(establishedOn) > 0 {
		bestState = "Established"
		labels := make([]string, 0, len(establishedOn))
		for _, e := range establishedOn {
			labels = append(labels, e.Label)
		}
		connectedLabel = strings.Join(labels, ", ")
		if len(establishedOn) == 1 {
			connectedID = establishedOn[0].SpeakerID
		}
	} else if len(on) == 1 && on[0].PollError == "" && on[0].State != "" {
		connectedID = on[0].SpeakerID
		connectedLabel = on[0].Label
	}

	if peer.SpeakerID != nil && strings.TrimSpace(*peer.SpeakerID) != "" && len(establishedOn) > 0 {
		want := strings.TrimSpace(*peer.SpeakerID)
		found := false
		for _, e := range establishedOn {
			if strings.EqualFold(strings.TrimSpace(e.SpeakerID), want) {
				found = true
				break
			}
		}
		mismatch = !found
	}
	return bestState, connectedID, connectedLabel, establishedOn, on, mismatch
}

func peerSessionMatches(sess birdfmt.BGPSession, protoName string, neighbor netip.Addr, hasNeighbor bool) bool {
	if strings.EqualFold(strings.TrimSpace(sess.Name), protoName) {
		return true
	}
	if !hasNeighbor || strings.TrimSpace(sess.Neighbor) == "" {
		return false
	}
	peerAddr, ok := store.ParsePeerNeighbor(sess.Neighbor)
	if !ok {
		return false
	}
	return peerAddr == neighbor
}

func sessionStateRank(state string) int {
	switch strings.ToLower(strings.TrimSpace(state)) {
	case "established":
		return 100
	case "openconfirm", "opensent":
		return 80
	case "active", "connect":
		return 60
	case "idle":
		return 20
	default:
		return 10
	}
}

func applyPeerLiveFields(row map[string]any, peer *store.BGPPeer, views []speakerBGPLive) {
	expected := expectedPeerViews(peer, views)
	state, _, _, _, _, _ := matchPeerOnSpeakers(peer, expected)
	_, connID, connLabel, establishedOn, on, mismatch := matchPeerOnSpeakers(peer, views)
	row["session_on_speakers"] = on
	row["established_on_speakers"] = establishedOn
	row["session_conflict"] = false
	row["session_mismatch"] = mismatch
	row["last_known_session_state"] = row["session_state"]
	row["session_state"] = nil
	if state != "" {
		row["session_state"] = state
	}
	if state == "" && len(expected) > 0 && allSpeakerPollsSuccessful(expected) {
		row["session_state"] = "absent"
	}
	row["live_observation"] = peerLiveObservation(expected)
	if connLabel != "" {
		row["connected_speaker_label"] = connLabel
	}
	row["connected_speaker_id"] = peerLiveSpeakerIDOrNull(connID)
}

func expectedPeerViews(peer *store.BGPPeer, views []speakerBGPLive) []speakerBGPLive {
	if peer == nil || peer.SpeakerID == nil || strings.TrimSpace(*peer.SpeakerID) == "" {
		return views
	}
	want := strings.TrimSpace(*peer.SpeakerID)
	expected := make([]speakerBGPLive, 0, 1)
	for _, v := range views {
		if strings.EqualFold(v.SpeakerID, want) {
			expected = append(expected, v)
		}
	}
	return expected
}

func allSpeakerPollsSuccessful(views []speakerBGPLive) bool {
	for _, v := range views {
		if !v.successful() {
			return false
		}
	}
	return true
}

func peerLiveObservation(views []speakerBGPLive) liveObservation {
	if len(views) == 0 {
		return speakerBGPLive{}.observation()
	}
	result := liveObservation{Source: views[0].Source, Quality: "unknown"}
	if result.Source == "" {
		result.Source = "none"
	}
	var latestObserved, latestReceived, latestSuccess time.Time
	allOK, allFailed, anyStale := true, true, false
	for _, v := range views {
		o := v.observation()
		if v.ObservedAt.After(latestObserved) {
			latestObserved = v.ObservedAt
		}
		if v.ReceivedAt.After(latestReceived) {
			latestReceived = v.ReceivedAt
		}
		if v.LastSuccessAt.After(latestSuccess) {
			latestSuccess = v.LastSuccessAt
		}
		allOK = allOK && v.successful()
		allFailed = allFailed && o.Quality == "unreachable"
		anyStale = anyStale || o.Quality == "stale"
		if result.ErrorCode == "" && o.ErrorCode != "" {
			result.ErrorCode = o.ErrorCode
		}
		if o.ExpiresAt != nil {
			expires, err := time.Parse(time.RFC3339Nano, *o.ExpiresAt)
			if err == nil {
				previous := time.Time{}
				if result.ExpiresAt != nil {
					previous, _ = time.Parse(time.RFC3339Nano, *result.ExpiresAt)
				}
				if previous.IsZero() || expires.Before(previous) {
					result.ExpiresAt = o.ExpiresAt
				}
			}
		}
	}
	result.ObservedAt = liveTime(latestObserved)
	result.ReceivedAt = liveTime(latestReceived)
	result.LastSuccessAt = liveTime(latestSuccess)
	if len(views) > 1 {
		result.Source = "mixed"
	}
	switch {
	case allOK:
		result.Quality = "ok"
		result.ErrorCode = ""
	case anyStale:
		result.Quality = "stale"
	case allFailed:
		result.Quality = "unreachable"
	}
	return result
}

func peerLiveSpeakerIDOrNull(id string) any {
	if strings.TrimSpace(id) == "" {
		return nil
	}
	return id
}