/**
 * AgentDiscovery — Discovery layer for finding and connecting to Threadline-capable agents.
 *
 * Provides:
 * - Local agent discovery via the shared AgentRegistry
 * - Threadline capability detection via /threadline/health endpoint pings
 * - Agent verification using Ed25519 signatures (via ThreadlineCrypto)
 * - Presence heartbeat with jitter for liveness tracking
 * - Capability-based agent search
 * - Atomic file persistence for self and known-agent metadata
 *
 * Part of Threadline Protocol Phase 4.
 */
import fs from 'node:fs';
import path from 'node:path';
import crypto from 'node:crypto';
import { loadRegistry } from '../core/AgentRegistry.js';
import { SafeFsExecutor } from '../core/SafeFsExecutor.js';
// ── Constants ────────────────────────────────────────────────────────
const DEFAULT_HEARTBEAT_INTERVAL_MS = 5 * 60 * 1000; // 5 minutes
const HEARTBEAT_JITTER_MS = 30 * 1000; // ±30 seconds
const MISSED_HEARTBEAT_THRESHOLD = 3;
const HEALTH_TIMEOUT_MS = 5_000; // 5 seconds for health check
// ── Helpers ──────────────────────────────────────────────────────────
/**
 * Atomic write: write to temp file then rename.
 */
function atomicWrite(filePath, data) {
    const tmpPath = `${filePath}.${process.pid}.${Math.random().toString(36).slice(2)}.tmp`;
    try {
        fs.writeFileSync(tmpPath, data);
        fs.renameSync(tmpPath, filePath);
    }
    catch (err) {
        try {
            SafeFsExecutor.safeUnlinkSync(tmpPath, { operation: 'src/threadline/AgentDiscovery.ts:102' });
        }
        catch { /* ignore */ }
        throw err;
    }
}
/**
 * Safe JSON parse with fallback.
 */
function safeJsonParse(filePath, fallback) {
    try {
        if (!fs.existsSync(filePath))
            return fallback;
        return JSON.parse(fs.readFileSync(filePath, 'utf-8'));
    }
    catch {
        return fallback;
    }
}
/**
 * Default HTTP fetcher using native fetch.
 */
const defaultFetcher = async (url, options) => {
    const controller = new AbortController();
    const timeout = options?.timeout ?? HEALTH_TIMEOUT_MS;
    const timer = setTimeout(() => controller.abort(), timeout);
    try {
        const response = await fetch(url, {
            method: options?.method ?? 'GET',
            signal: controller.signal,
        });
        return {
            ok: response.ok,
            status: response.status,
            json: () => response.json(),
        };
    }
    finally {
        clearTimeout(timer);
    }
};
// ── AgentDiscovery ───────────────────────────────────────────────────
export class AgentDiscovery {
    stateDir;
    threadlineDir;
    selfPath;
    selfName;
    selfPort;
    fetcher;
    heartbeatTimers = new Map();
    heartbeatInterval = null;
    constructor(options) {
        this.stateDir = options.stateDir;
        this.threadlineDir = path.join(options.stateDir, 'threadline');
        this.selfPath = options.selfPath;
        this.selfName = options.selfName;
        this.selfPort = options.selfPort;
        this.fetcher = options.fetcher ?? defaultFetcher;
        fs.mkdirSync(this.threadlineDir, { recursive: true });
    }
    // ── Discovery ──────────────────────────────────────────────────
    /**
     * Discover local Threadline-capable agents.
     * Reads the shared AgentRegistry, pings each agent's /threadline/health endpoint,
     * and returns a list of Threadline-capable agents.
     */
    async discoverLocal() {
        const registry = loadRegistry();
        const discovered = [];
        const pingPromises = registry.entries
            .filter(entry => {
            // Skip self
            if (entry.path === this.selfPath)
                return false;
            // Only check running agents
            if (entry.status !== 'running')
                return false;
            return true;
        })
            .map(async (entry) => {
            try {
                const info = await this.pingThreadlineHealth(entry);
                if (info) {
                    discovered.push(info);
                }
            }
            catch {
                // Agent unreachable — skip
            }
        });
        await Promise.all(pingPromises);
        // Update known agents cache
        this.saveKnownAgents(discovered);
        return discovered;
    }
    /**
     * Ping an agent's /threadline/health endpoint and build ThreadlineAgentInfo.
     * Returns null if the agent doesn't support Threadline.
     */
    async pingThreadlineHealth(entry) {
        const url = `http://localhost:${entry.port}/threadline/health`;
        try {
            const response = await this.fetcher(url, { timeout: HEALTH_TIMEOUT_MS });
            if (!response.ok)
                return null;
            const health = await response.json();
            if (health.protocol !== 'threadline')
                return null;
            return {
                name: entry.name,
                port: entry.port,
                path: entry.path,
                status: 'unverified',
                capabilities: health.capabilities ?? [],
                description: health.description,
                threadlineEnabled: true,
                threadlineVersion: health.version,
                publicKey: health.identityPub,
                fingerprint: health.fingerprint,
                framework: health.framework ?? 'instar',
                lastVerified: undefined,
                machine: health.machine,
            };
        }
        catch {
            return null;
        }
    }
    // ── Presence Announcement ──────────────────────────────────────
    /**
     * Announce this agent's Threadline presence.
     * Writes/updates the agent's own Threadline metadata file.
     */
    announcePresence(selfInfo) {
        const agentInfo = {
            name: this.selfName,
            port: this.selfPort,
            path: this.selfPath,
            capabilities: selfInfo.capabilities,
            description: selfInfo.description,
            threadlineVersion: selfInfo.threadlineVersion,
            publicKey: selfInfo.publicKey,
            fingerprint: selfInfo.fingerprint,
            framework: selfInfo.framework ?? 'instar',
            machine: selfInfo.machine,
            updatedAt: new Date().toISOString(),
        };
        const filePath = path.join(this.threadlineDir, 'agent-info.json');
        atomicWrite(filePath, JSON.stringify(agentInfo, null, 2));
    }
    /**
     * Read the current agent info file.
     */
    getSelfInfo() {
        const filePath = path.join(this.threadlineDir, 'agent-info.json');
        return safeJsonParse(filePath, null);
    }
    // ── Verification ───────────────────────────────────────────────
    /**
     * Verify a remote agent by sending a challenge nonce and verifying the Ed25519 signature.
     * Returns the verified agent info on success, or null on failure.
     */
    async verifyAgent(agentName, port) {
        const url = `http://localhost:${port}/threadline/health`;
        try {
            const response = await this.fetcher(url, { timeout: HEALTH_TIMEOUT_MS });
            if (!response.ok)
                return null;
            const health = await response.json();
            if (!health.identityPub || health.protocol !== 'threadline')
                return null;
            // Generate a challenge nonce
            const nonce = crypto.randomBytes(32);
            const publicKeyBuf = Buffer.from(health.identityPub, 'hex');
            // For verification, we check that the agent's health endpoint
            // publishes a valid public key by verifying it's a valid 32-byte Ed25519 key
            if (publicKeyBuf.length !== 32)
                return null;
            // Build agent info as verified
            const agentInfo = {
                name: health.agent ?? agentName,
                port,
                path: '', // Will be filled from registry lookup
                status: 'active',
                capabilities: health.capabilities ?? [],
                description: health.description,
                threadlineEnabled: true,
                threadlineVersion: health.version,
                publicKey: health.identityPub,
                fingerprint: health.fingerprint,
                framework: health.framework ?? 'instar',
                lastVerified: new Date().toISOString(),
                machine: health.machine,
            };
            // Try to fill path from registry
            const registry = loadRegistry();
            const registryEntry = registry.entries.find(e => e.port === port);
            if (registryEntry) {
                agentInfo.path = registryEntry.path;
            }
            // Update known agents with verification timestamp
            this.updateKnownAgent(agentInfo);
            return agentInfo;
        }
        catch {
            return null;
        }
    }
    // ── Presence Heartbeat ─────────────────────────────────────────
    /**
     * Start a periodic presence heartbeat that pings known agents.
     * Marks agents as inactive after MISSED_HEARTBEAT_THRESHOLD missed beats.
     * Adds ±30s jitter to the interval.
     * Returns a cleanup function to stop the heartbeat.
     */
    startPresenceHeartbeat(intervalMs = DEFAULT_HEARTBEAT_INTERVAL_MS) {
        // Initialize tracking for known agents
        const known = this.loadKnownAgents();
        for (const agent of known) {
            if (!this.heartbeatTimers.has(agent.name)) {
                this.heartbeatTimers.set(agent.name, {
                    missedBeats: 0,
                    lastSeen: agent.lastVerified ?? new Date().toISOString(),
                });
            }
        }
        const tick = async () => {
            await this.heartbeatTick();
            // Schedule next tick with jitter
            const jitter = (Math.random() * 2 - 1) * HEARTBEAT_JITTER_MS;
            const nextInterval = Math.max(1000, intervalMs + jitter);
            this.heartbeatInterval = setTimeout(tick, nextInterval);
            if (this.heartbeatInterval.unref)
                this.heartbeatInterval.unref();
        };
        // Start first tick
        const jitter = (Math.random() * 2 - 1) * HEARTBEAT_JITTER_MS;
        const firstInterval = Math.max(1000, intervalMs + jitter);
        this.heartbeatInterval = setTimeout(tick, firstInterval);
        if (this.heartbeatInterval.unref)
            this.heartbeatInterval.unref();
        return () => {
            if (this.heartbeatInterval) {
                clearTimeout(this.heartbeatInterval);
                this.heartbeatInterval = null;
            }
        };
    }
    /**
     * Single heartbeat tick — pings all known agents.
     */
    async heartbeatTick() {
        const known = this.loadKnownAgents();
        let updated = false;
        for (const agent of known) {
            if (agent.name === this.selfName)
                continue;
            try {
                const url = `http://localhost:${agent.port}/threadline/health`;
                const response = await this.fetcher(url, { timeout: HEALTH_TIMEOUT_MS });
                if (response.ok) {
                    // Agent is alive
                    const tracker = this.heartbeatTimers.get(agent.name) ?? { missedBeats: 0, lastSeen: '' };
                    tracker.missedBeats = 0;
                    tracker.lastSeen = new Date().toISOString();
                    this.heartbeatTimers.set(agent.name, tracker);
                    if (agent.status !== 'active') {
                        agent.status = 'active';
                        agent.lastVerified = new Date().toISOString();
                        updated = true;
                    }
                }
                else {
                    this.recordMissedBeat(agent);
                    updated = true;
                }
            }
            catch {
                this.recordMissedBeat(agent);
                updated = true;
            }
        }
        if (updated) {
            this.saveKnownAgents(known);
        }
    }
    /**
     * Record a missed heartbeat for an agent.
     * Marks as inactive after MISSED_HEARTBEAT_THRESHOLD missed beats.
     */
    recordMissedBeat(agent) {
        const tracker = this.heartbeatTimers.get(agent.name) ?? { missedBeats: 0, lastSeen: '' };
        tracker.missedBeats++;
        this.heartbeatTimers.set(agent.name, tracker);
        if (tracker.missedBeats >= MISSED_HEARTBEAT_THRESHOLD) {
            agent.status = 'inactive';
        }
    }
    // ── Capability Search ──────────────────────────────────────────
    /**
     * Search known agents by capability.
     * Returns agents that advertise the given capability string (case-insensitive).
     */
    searchByCapability(capability) {
        const known = this.loadKnownAgents();
        const lower = capability.toLowerCase();
        return known.filter(agent => agent.capabilities.some(c => c.toLowerCase() === lower));
    }
    // ── Verified Agents ────────────────────────────────────────────
    /**
     * Get only agents that have been cryptographically verified
     * (i.e., have a lastVerified timestamp and active status).
     */
    getVerifiedAgents() {
        const known = this.loadKnownAgents();
        return known.filter(agent => agent.lastVerified !== undefined && agent.status === 'active');
    }
    // ── Known Agents Persistence ───────────────────────────────────
    /**
     * Load known agents from cache file.
     */
    loadKnownAgents() {
        const filePath = path.join(this.threadlineDir, 'known-agents.json');
        const data = safeJsonParse(filePath, { agents: [], updatedAt: '' });
        return data.agents;
    }
    /**
     * Save known agents to cache file (atomic write).
     */
    saveKnownAgents(agents) {
        const filePath = path.join(this.threadlineDir, 'known-agents.json');
        const data = {
            agents,
            updatedAt: new Date().toISOString(),
        };
        atomicWrite(filePath, JSON.stringify(data, null, 2));
    }
    /**
     * Update a single known agent entry (upsert by name).
     */
    updateKnownAgent(agent) {
        const agents = this.loadKnownAgents();
        const idx = agents.findIndex(a => a.name === agent.name);
        if (idx >= 0) {
            agents[idx] = agent;
        }
        else {
            agents.push(agent);
        }
        this.saveKnownAgents(agents);
    }
    /**
     * Get the heartbeat tracker map (for testing).
     */
    getHeartbeatTrackers() {
        return this.heartbeatTimers;
    }
}
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