// Copyright 2026 Beacon Contributors
// SPDX-License-Identifier: AGPL-3.0-or-later

// Package ingest subscribes to a single MeshCore MQTT broker and drives the
// observation pipeline described in the design doc.
//
// Call Start() once per broker in a dedicated goroutine. Both broker instances
// share the same *hub.Hub and *DB handle so dedup and fan-out are centralised.
//
// Pipeline per incoming /packets message:
//  1. Parse topic → extract IATA + publisher pubkey
//  2. Decode hex payload via meshcore-go PacketFromBytes
//  3. Compute content-based packet hash (PacketHash)
//  4. Upsert observers + observer_brokers + iata_codes
//  5. Upsert packets row (ON CONFLICT bump last_heard_at)
//  6. Insert packet_observations (ON CONFLICT DO NOTHING for cross-broker dedup)
//  7. Match transport codes against known scopes (TRANSPORT_FLOOD/DIRECT only)
//  8. If INSERT succeeded: capability detection, payload-type side effects, fan-out
//
// Pipeline per incoming /status message:
//  1. Parse topic → extract publisher pubkey
//  2. Upsert observers row (status_metadata, last_status_at, observer_type, etc.)
//  3. Fan out observerStatus event to hub
//
// Pipeline per incoming /neighbors message (sent every 12-368h if mqtt.neighbors
// is enabled on the observer):
//  1. Parse topic → extract IATA + publisher pubkey
//  2. Record the observer's own "self" region scope (always known, unconditional write)
//  3. For each reported zero-hop neighbor: resolve both sides via GetNodeByPubkey
//     (skip the entry if either the observer or the neighbor has no node row yet --
//     i.e. hasn't advertised) and upsert a node_neighbors edge. Absence from the
//     report means nothing (10KB message cap can truncate a highly-connected node's
//     list), so this never deletes existing edges. A neighbor's region_scope is only
//     written when status == "responded"; "timeout" (OTA scope queries are flaky)
//     leaves any previously known scope untouched.
package ingest

import (
	"context"
	"crypto/rand"
	"encoding/binary"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"log/slog"
	"strconv"
	"strings"
	"sync/atomic"
	"time"

	mqtt "github.com/eclipse/paho.mqtt.golang"
	"github.com/google/uuid"

	"github.com/MeshCore-Beacon/beacon-server/internal/api"
	"github.com/MeshCore-Beacon/beacon-server/internal/borders"
	"github.com/MeshCore-Beacon/beacon-server/internal/hub"
	"github.com/MeshCore-Beacon/beacon-server/internal/keystore"
	"github.com/MeshCore-Beacon/beacon-server/internal/scopestore"
)

// Config holds the connection parameters for one broker.
type Config struct {
	// LocalBorders is the same live classifier used by node API reads.
	LocalBorders *borders.Live
	// BrokerName is a short human-readable label ("mqtt1", "mqtt2") used in
	// log messages and stored in packet_observations.source_broker.
	BrokerName string

	// URL is the full broker WebSocket URL, e.g. "wss://mqtt1.meshcore.ca/mqtt"
	URL string

	Username string
	Password string

	// AllowedIATAs is a pre-computed set of IATA codes derived from the ingest
	// filter config. If non-nil, packets from IATAs not in this set are dropped.
	// Build this set at startup from IngestFilterConfig using iatadb.
	AllowedIATAs map[string]struct{}

	// TelemetryResolution controls how frequently telemetry snapshots are stored.
	// Status messages within the same window are deduplicated via ON CONFLICT.
	// Defaults to 1 hour if zero.
	TelemetryResolution time.Duration
}

// DB is the minimal database interface the ingest pipeline depends on.
// Wire in your real *pgxpool.Pool implementation here.
type DB interface {
	// UpsertObserver upserts the observers row keyed on pubkey, and returns
	// the Observer ID, Display Name and an error if any.
	UpsertObserver(ctx context.Context, pubkey []byte, iata string) (uuid.UUID, string, error)

	// UpsertObserverBroker records that this observer was seen on brokerName.
	UpsertObserverBroker(ctx context.Context, observerID uuid.UUID, brokerName string, isPacket bool) error

	// UpsertIATA auto-creates an iata_codes row if it doesn't exist yet.
	UpsertIATA(ctx context.Context, iata string) error

	// UpsertPacket inserts or bumps the packets row. Returns (isNew, error).
	UpsertPacket(ctx context.Context, p UpsertPacketParams) (bool, error)

	// SetPacketDecrypted marks a packet as decrypted in the DB
	SetPacketDecrypted(ctx context.Context, hash []byte) error

	// InsertObservation inserts a packet_observations row and returns the packet's
	// observation count; inserted=false means ON CONFLICT DO NOTHING fired.
	InsertObservation(ctx context.Context, o InsertObservationParams) (inserted bool, observationCount int64, err error)

	// SetNodeCapability flips supports_multibyte_paths or supports_multibyte_traces
	// for a node, never downgrading an existing TRUE.
	SetNodeCapability(ctx context.Context, nodeID uuid.UUID, paths, traces bool) error

	// SetNodeDefaultScope records the most recent scope attached to a node advert
	// scopes are matched against configured regional transport scopes
	SetNodeDefaultScope(ctx context.Context, nodeID uuid.UUID, scopeID int32) error

	// UpsertNode upserts a nodes row from an advert payload.
	UpsertNode(ctx context.Context, n UpsertNodeParams, r RadioSettings) (uuid.UUID, error)

	// GetNodeByPubkey returns the node ID for a given public key, or an
	// error (sql.ErrNoRows-equivalent) if no node exists yet for that key.
	// Used for observer-sourced neighbor writes (e.g. DISCOVER_RESP), where
	// the observer's own node may not exist until it has advertised.
	GetNodeByPubkey(ctx context.Context, pubkey []byte) (uuid.UUID, error)

	// GetNodesByIDs returns resolved node details (name, pubkey, coords) for a set of node
	// IDs. Used with GetNodeByPubkey to resolve an ADVERT's exact-match source endpoint.
	GetNodesByIDs(ctx context.Context, ids []uuid.UUID) (map[uuid.UUID]*api.ResolvedNode, error)

	// UpsertNodeIATA upserts a node_iatas row.
	UpsertNodeIATA(ctx context.Context, nodeID uuid.UUID, iata string) error

	// UpsertNodeShortID upserts a node_short_ids row for path resolution.
	UpsertNodeShortID(ctx context.Context, nodeID uuid.UUID, iata string, prefix4 []byte) error

	// InsertChannelMessage stores a decrypted group text message. Returns the inserted message, nil for a duplicate, and an error.
	InsertChannelMessage(ctx context.Context, m InsertChannelMessageParams) (*InsertedChannelMessage, error)

	// UpdateObserverStatus updates the observer row from a /status message. Returns the OberserID
	// and any error.
	UpdateObserverStatus(ctx context.Context, p UpdateObserverStatusParams) (uuid.UUID, error)

	// GetObserverLastIATA returns the IATA of the observer's most recent packet, or "" if none.
	GetObserverLastIATA(ctx context.Context, observerID uuid.UUID) (string, error)

	// InsertObserverTelemetry stores a telemetry snapshot for an observer.
	// The caller should truncate reportedAt to the configured resolution before calling.
	InsertObserverTelemetry(ctx context.Context, observerID uuid.UUID, reportedAt time.Time, batteryMV *int32, txAirSecs, rxAirSecs *float32, noiseFloor float32, uptimeSeconds int64, queueLen, debugFlags, recvErrors *int32) error

	// GetObserverRadio returns the current radio settings for the given observer.
	GetObserverRadio(ctx context.Context, observerID uuid.UUID) (RadioSettings, error)

	// IsObserverByPubkey returns true if the given public key belongs to a known observer.
	IsObserverByPubkey(ctx context.Context, pubkey []byte) bool

	// GetObserverScopes returns the list of scope names associated with the given observer.
	GetObserverScopes(ctx context.Context, observerID uuid.UUID) ([]string, error)

	// ResolvePathHashes returns a list of node UUIDs for the given path hash prefixes and IATA.
	ResolvePathHashes(ctx context.Context, iata string, hashes [][]byte) (map[string][]api.ResolvedPathEntry, error)
	ResolveTracePathHashes(ctx context.Context, iata string, hashes [][]byte) (map[string][]api.ResolvedPathEntry, error)

	// ResolveEndpointHashes matches one-byte logical endpoints, including companions.
	ResolveEndpointHashes(ctx context.Context, iata string, hashes [][]byte) (map[string][]api.ResolvedPathEntry, error)

	// UpsertChannel upserts a channel row by (hash, keyFingerprint) and returns its integer ID.
	// Pass nil keyFingerprint to record a hash-only row when the key is unknown.
	UpsertChannel(ctx context.Context, channelHash []byte, keyFingerprint []byte, name string, hashtag string) (int, error)

	// UpsertChannelHashOnly upserts a hash-only channel row for cases where the
	// channel key is unknown. Uses the partial unique index to ensure only one
	// hash-only row exists per channel hash. The return value is the channel ID
	// but can be safely ignored since unknown-key channels have no messages.
	UpsertChannelHashOnly(ctx context.Context, channelHash []byte) (int, error)

	// ListUndecryptedGroupTextPackets returns GRP_TXT packets never successfully decrypted --
	// used by BackfillChannelMessages to retry them against the current keystore at boot.
	ListUndecryptedGroupTextPackets(ctx context.Context) ([]UndecryptedPacket, error)

	// ListUndecryptedGroupTextPacketsByHash limits that scan to channels that just gained a key.
	ListUndecryptedGroupTextPacketsByHash(ctx context.Context, hashes [][]byte) ([]UndecryptedPacket, error)

	// UpsertChannelIATA upserts a channel_iatas row.
	UpsertChannelIATA(ctx context.Context, channelHash []byte, iata string, heardAt time.Time) error

	// RecordTrace records one hearing of a TRACE packet in trace_iatas and trace_tags.
	RecordTrace(ctx context.Context, h TraceHearing) error

	// GetTransportScopeByName returns the ID of a transport scope by its normalized name.
	GetTransportScopeByName(ctx context.Context, name string) (int32, error)

	// UpsertObserverScope records or updates a scope association for an observer.
	// Called when a TRANSPORT_FLOOD packet is observed, linking the observer to
	// the matched regional transport scope.
	UpsertObserverScope(ctx context.Context, observerID uuid.UUID, scopeID int32) error

	// UpsertKnownRoute stores a fully resolved path where all hops have high confidence.
	UpsertKnownRoute(ctx context.Context, nodeIDs []uuid.UUID, hashPrefix [][]byte, iata string, hopCount int32) error

	// UpsertNodeNeighbor records or updates a neighbor relationship between two nodes.
	// nodeID is the advertising node, neighborID is the first-hop forwarder.
	// snr is optional (nil when no signal reading is available, the common case).
	// regionScope is optional (nil when there's no fresh OTA-queried scope to
	// record for this neighbor, e.g. a /neighbors report entry with a failed query).
	UpsertNodeNeighbor(ctx context.Context, nodeID, neighborID uuid.UUID, iata string, snr *float32, regionScope *string) error

	// UpdateObserverRegionScope records the observer's own OTA-reported region
	// scope, from the "self" field of a /neighbors report.
	UpdateObserverRegionScope(ctx context.Context, observerID uuid.UUID, regionScope string) error
}

// ChannelKeyStore is a read-only view of the channel keys loaded from config.
type ChannelKeyStore interface {
	// GetKey returns all known key entries for the given channel hash byte.
	// Returns nil if no keys are known for this hash.
	GetKey(channelHash []byte) []keystore.Entry
}

// ScopeStore provides transport scope key lookup for matching TRANSPORT_FLOOD packets.
type ScopeStore interface {
	Entries() []scopestore.Entry
}

// Worker holds the dependencies for one broker's ingest loop.
type Worker struct {
	log              *slog.Logger
	cfg              Config
	db               DB
	hub              *hub.Hub
	keys             ChannelKeyStore
	scopes           ScopeStore
	client           atomic.Pointer[mqtt.Client] // read by /brokers while Start sets it
	capabilities     capabilityCache
	onNodeUpsert     func(ctx context.Context, nodeID uuid.UUID)
	onObserverUpsert func(ctx context.Context, observerID uuid.UUID)
}

// New creates an ingest Worker. Call Start() to connect and begin processing.
func New(cfg Config, db DB, h *hub.Hub, keys ChannelKeyStore, scopes ScopeStore) *Worker {
	return &Worker{cfg: cfg, db: db, hub: h, keys: keys, scopes: scopes,
		log: slog.Default().With("component", "ingest", "broker", cfg.BrokerName)}
}

// Start connects to the broker and blocks until ctx is cancelled. It
// reconnects automatically on transient failures using paho's built-in
// reconnect logic.
//
// Intended usage: go worker.Start(ctx)
func (w *Worker) Start(ctx context.Context) {
	if w.cfg.URL == "" {
		return
	}
	queue := newMessageQueue(8, 2048, 32<<20, func(ctx context.Context, msg mqtt.Message) {
		w.handleMessageContext(ctx, msg)
	})
	reportDrops := func() {
		if n := queue.takeDropped(); n > 0 {
			w.log.Error("ingest queue full, messages dropped", "count", n)
		}
	}
	defer func() {
		drainCtx, cancel := context.WithTimeout(context.Background(), 20*time.Second)
		defer cancel()
		if err := queue.close(drainCtx); err != nil {
			w.log.Warn("ingest shutdown timed out", "error", err)
		}
		reportDrops()
		w.log.Info("stopped")
	}()

	// Isolate workers across deployments; Paho reuses this ID on reconnect.
	// Keep it alphanumeric and within MQTT 3.1's 23-character client ID limit.
	// Auto-ack: sessions are clean, so deferring acks only throttled the broker's inflight window.
	opts := mqtt.NewClientOptions().
		AddBroker(w.cfg.URL).
		SetClientID(rand.Text()[:23]).
		SetUsername(w.cfg.Username).
		SetPassword(w.cfg.Password).
		SetAutoReconnect(true).
		SetMaxReconnectInterval(30 * time.Second).
		SetKeepAlive(30 * time.Second).
		SetPingTimeout(10 * time.Second).
		SetConnectTimeout(15 * time.Second).
		SetWriteTimeout(10 * time.Second).
		SetConnectRetry(true).
		SetConnectRetryInterval(5 * time.Second).
		SetOnConnectHandler(func(c mqtt.Client) {
			w.log.Info("connected")
			w.subscribe(c, queue)
		}).
		SetConnectionLostHandler(func(_ mqtt.Client, err error) {
			w.log.Warn("connection lost, will reconnect", "error", err)
		})

	client := mqtt.NewClient(opts)
	w.client.Store(&client)

	token := client.Connect()
	ticker := time.NewTicker(5 * time.Second)
	defer ticker.Stop()
	connected := token.Done()
	for {
		select {
		case <-connected:
			if err := token.Error(); err != nil {
				w.log.Error("initial connect failed", "error", err)
			}
			connected = nil
		case <-ticker.C:
			reportDrops()
		case <-ctx.Done():
			client.Disconnect(500)
			return
		}
	}

}

func (w *Worker) BrokerName() string {
	return w.cfg.BrokerName
}

func (w *Worker) IsConnected() bool {
	c := w.client.Load()
	if c == nil {
		return false
	}
	return (*c).IsConnected()
}

func (w *Worker) SetCacheInvalidators(onNode, onObserver func(ctx context.Context, id uuid.UUID)) {
	w.onNodeUpsert = onNode
	w.onObserverUpsert = onObserver
}

// subscribe registers the wildcard topic handler after (re)connect.
func (w *Worker) subscribe(client mqtt.Client, queue *messageQueue) {
	// meshcore/{IATA}/{pubkey}/packets
	// meshcore/{IATA}/{pubkey}/status
	// We do NOT subscribe to /internal (Role 2 access).
	tok := client.Subscribe("meshcore/#", 1, func(_ mqtt.Client, msg mqtt.Message) {
		queue.enqueue(msg)
	})
	if tok.Wait() && tok.Error() != nil {
		w.log.Error("subscribe error", "error", tok.Error())
	}
}

// isValidIATA reports whether s is 3 uppercase ASCII letters, matching the
// iata_codes.iata CHAR(3) column. MQTT topic segments are attacker/observer
// controlled and must be validated before touching the DB.
func isValidIATA(s string) bool {
	if len(s) != 3 {
		return false
	}
	for i := 0; i < 3; i++ {
		if s[i] < 'A' || s[i] > 'Z' {
			return false
		}
	}
	return true
}

// isValidPubkeyHex reports whether s is a 32-byte public key in hex.
func isValidPubkeyHex(s string) bool {
	if len(s) != 64 {
		return false
	}
	_, err := hex.DecodeString(s)
	return err == nil
}

// handleMessage dispatches incoming MQTT messages by subtopic.
// Each message is processed with a 30s timeout to prevent slow DB calls
// from holding a processing worker indefinitely.
func (w *Worker) handleMessage(msg mqtt.Message) {
	w.handleMessageContext(context.Background(), msg)
}

func (w *Worker) handleMessageContext(parent context.Context, msg mqtt.Message) {
	// Topic shape: meshcore/{IATA}/{pubkey}/{subtopic}
	parts := strings.SplitN(msg.Topic(), "/", 4)
	if len(parts) != 4 || parts[0] != "meshcore" {
		return
	}
	iata, pubkeyHex, subtopic := parts[1], parts[2], parts[3]

	// iata_codes.iata is CHAR(3); anything else would fail the DB insert
	// downstream, so reject malformed topic segments here instead.
	if !isValidIATA(iata) {
		w.log.Debug("dropped packet with malformed IATA", "iata", iata, "topic", msg.Topic())
		return
	}
	if !isValidPubkeyHex(pubkeyHex) {
		w.log.Debug("dropped message with malformed observer pubkey", "pubkey", pubkeyHex, "topic", msg.Topic())
		return
	}

	// Drop packets from IATAs outside the configured geographic filter.
	if w.cfg.AllowedIATAs != nil {
		if _, ok := w.cfg.AllowedIATAs[iata]; !ok {
			if w.log.Enabled(context.Background(), slog.LevelDebug) {
				w.log.Debug(fmt.Sprintf("dropped packet from %s (not in allowed IATAs)", iata))
			}
			return
		}
	}

	ctx, cancel := context.WithTimeout(parent, 30*time.Second)
	defer cancel()

	switch subtopic {
	case "packets":
		w.handlePacket(ctx, iata, pubkeyHex, msg.Payload())
	case "status":
		w.handleStatus(ctx, pubkeyHex, msg.Payload())
	case "neighbors":
		w.handleNeighbors(ctx, iata, pubkeyHex, msg.Payload())
		// "internal" is intentionally not handled (Role 2 access)
	}
}

func (w *Worker) broadcast(eventType hub.EventType, iata string, payloadType uint8, channelHash string, payload any) {
	b, err := json.Marshal(payload)
	if err != nil {
		w.log.Error(fmt.Sprintf("failed to marshal %s event", eventType), "error", err)
		return
	}
	w.hub.Broadcast(hub.Event{
		Type:        eventType,
		Payload:     b,
		IATA:        iata,
		PayloadType: payloadType,
		ChannelHash: channelHash,
	})
}

// broadcastPacketObservation marshals evt once as-is (the default
// payload every packetObservation subscriber gets) and once with
// resolvedPath populated (delivered only to connections that opted in via
// the "configure" WS message; see hub.Client.ResolvePath). resolvedPath is
// passed in rather than computed here because the caller already has the
// path-hash resolution results in hand from other per-packet work (known
// route detection, capability detection) — this adds no extra DB calls.
// Repeats go through the hub's drop-first path.
func (w *Worker) broadcastPacketObservation(iata string, payloadType uint8, evt packetObservationEvent, resolvedPath []api.ResolvedHop, observerKey string, repeat bool) {
	base, err := json.Marshal(evt)
	if err != nil {
		w.log.Error("failed to marshal packetObservation event", "error", err)
		return
	}
	out := hub.Event{
		Type:        hub.EventPacketObservation,
		Payload:     base,
		IATA:        iata,
		PayloadType: payloadType,
		RouteType:   evt.Packet.RouteType,
		ObserverID:  evt.Observation.ObserverID,
	}
	evt.Observation.ResolvedPath = resolvedPath
	if out.PayloadResolved, err = json.Marshal(evt); err != nil {
		w.log.Error("failed to marshal packetObservation event (resolved variant)", "error", err)
		out.PayloadResolved = nil
	}
	if w.hub.ObserverKeyWanted() {
		evt.Observation.ObserverPublicKey = observerKey
		if out.PayloadResolvedWithKey, err = json.Marshal(evt); err != nil {
			w.log.Error("failed to marshal packetObservation event (resolved key variant)", "error", err)
			out.PayloadResolvedWithKey = nil
		}
		evt.Observation.ResolvedPath = nil
		if out.PayloadWithKey, err = json.Marshal(evt); err != nil {
			w.log.Error("failed to marshal packetObservation event (key variant)", "error", err)
			out.PayloadWithKey = nil
		}
	}
	if repeat {
		w.hub.BroadcastRepeat(out)
		return
	}
	w.hub.Broadcast(out)
}

// parseNumber handles RSSI and SNR fields that different observer types send as
// either a bare JSON number (e.g. -108) or a quoted string (e.g. "-108").
// Returns 0 if the value is missing or unparseable.
func parseNumber(raw json.RawMessage) float64 {
	if len(raw) == 0 {
		return 0
	}
	// try unquoted number first
	var f float64
	if err := json.Unmarshal(raw, &f); err == nil {
		return f
	}
	// try quoted string
	var s string
	if err := json.Unmarshal(raw, &s); err == nil {
		f, _ = strconv.ParseFloat(s, 64)
		return f
	}
	return 0
}

func inferObserverType(source, clientVersion string) string {
	if source != "" {
		return normalizeObserverType(source)
	}
	if clientVersion != "" {
		return clientVersion // use raw version string for custom firmware observers
	}
	return ""
}

func normalizeObserverType(source string) string {
	if source == "" {
		return ""
	}
	s := source
	// strip org/path prefix e.g. "meshcore-dev/meshcore-ha" → "meshcore-ha"
	if i := strings.LastIndex(s, "/"); i >= 0 {
		s = s[i+1:]
	}
	// strip version suffix e.g. "meshcoretomqtt:1.1.0" → "meshcoretomqtt"
	if i := strings.Index(s, ":"); i >= 0 {
		s = s[:i]
	}
	// strip build suffix e.g. "meshcoretomqtt/1.1.0.0-622ce04" → "meshcoretomqtt"
	if i := strings.Index(s, "/"); i >= 0 {
		s = s[:i]
	}
	if s == "" {
		return source // fall back to raw if parsing produced nothing
	}
	return s
}

func uint32ToBytes(v uint32) []byte {
	b := make([]byte, 4)
	binary.LittleEndian.PutUint32(b, v)
	return b
}