import { CID } from "multiformats";
import type { Helia } from "@helia/interface";
import type { BlockMap } from "@atproto/repo";
import type Database from "better-sqlite3";
import { encode as cborEncode, decode as cborDecode } from "./cbor-compat.js";
import { SqliteBlockstore } from "./sqlite-blockstore.js";
import { SqliteDatastore } from "./sqlite-datastore.js";
import type { RateLimiter } from "./rate-limiter.js";
import { DEFAULT_RATE_LIMIT_CONFIG } from "./rate-limiter.js";

/** Maximum gossipsub message size (8 KB). Messages larger than this are dropped before decoding. */
const MAX_GOSSIPSUB_MESSAGE_SIZE = 8192;

/**
 * Pure storage: put, get, has blocks by CID string.
 * No networking, no peer identity — just content-addressed bytes.
 */
export interface BlockStore {
	putBlock(cidStr: string, bytes: Uint8Array): Promise<void>;
	getBlock(cidStr: string): Promise<Uint8Array | null>;
	hasBlock(cidStr: string): Promise<boolean>;
	putBlocks(blocks: BlockMap): Promise<void>;
	deleteBlock(cidStr: string): Promise<void>;
}

/**
 * Lightweight gossipsub notification for a repo commit.
 * Contains only metadata — actual blocks are fetched via existing sync mechanisms.
 */
export interface CommitNotification {
	did: string;
	commit: string;
	rev: string;
	time: string;
	peer: string;
}

export type CommitNotificationHandler = (notification: CommitNotification) => void | Promise<void>;

export const COMMIT_TOPIC_PREFIX = "/p2pds/commits/1/";

export function commitTopic(did: string): string {
	return `${COMMIT_TOPIC_PREFIX}${did}`;
}

/**
 * Lightweight gossipsub notification for a peer identity change.
 * Published when a peer's multiaddrs or PeerID changes.
 */
export interface IdentityNotification {
	did: string;
	peerId: string;
	multiaddrs: string[];
	time: string;
}

export type IdentityNotificationHandler = (notification: IdentityNotification) => void | Promise<void>;

export const IDENTITY_TOPIC_PREFIX = "/p2pds/identity/1/";

export function identityTopic(did: string): string {
	return `${IDENTITY_TOPIC_PREFIX}${did}`;
}

/**
 * P2P networking: content routing, peer identity, connectivity, gossipsub.
 * Separated from storage so transports can be swapped independently.
 */
export interface NetworkService {
	provideBlocks(cidStrs: string[]): Promise<void>;
	publishCommitNotification(
		did: string,
		commitCid: string,
		rev: string,
	): Promise<void>;
	onCommitNotification(handler: CommitNotificationHandler): void;
	subscribeCommitTopics(dids: string[]): void;
	unsubscribeCommitTopics(dids: string[]): void;
	getPeerId(): string | null;
	getMultiaddrs(): string[];
	getConnectionCount(): number;
	getRemoteAddrs(peerId: string): string[];
	publishIdentityNotification(did: string, peerId: string, multiaddrs: string[]): Promise<void>;
	onIdentityNotification(handler: IdentityNotificationHandler): void;
	subscribeIdentityTopics(dids: string[]): void;
	unsubscribeIdentityTopics(dids: string[]): void;
	provideForDid(did: string): Promise<void>;
	findProvidersForDid(did: string): Promise<string[]>;
}

export interface IpfsConfig {
	db: Database.Database;
	networking: boolean;
}

/**
 * IpfsService encapsulates all Helia/IPFS functionality.
 *
 * Implements both BlockStore (storage) and NetworkService (P2P networking).
 * When networking is enabled, a full Helia node is created (libp2p + bitswap + DHT + gossipsub).
 * When networking is disabled, only a local FsBlockstore is used (for testing).
 *
 * All methods no-op gracefully if the service hasn't started yet.
 * String-based CID interface at the boundary — decouples from @atproto's CID class.
 */
export class IpfsService implements BlockStore, NetworkService {
	private helia: Helia | null = null;
	private blockstore: SqliteBlockstore | null = null;
	private config: IpfsConfig;
	private running = false;
	private commitHandlers: CommitNotificationHandler[] = [];
	private identityHandlers: IdentityNotificationHandler[] = [];
	private subscribedTopics: Set<string> = new Set();
	private rateLimiter: RateLimiter | null = null;

	constructor(config: IpfsConfig) {
		this.config = config;
	}

	/**
	 * Set a rate limiter for gossipsub message rate limiting.
	 * Called from server.ts after construction.
	 */
	setRateLimiter(limiter: RateLimiter): void {
		this.rateLimiter = limiter;
	}

	async start(): Promise<void> {
		this.blockstore = new SqliteBlockstore(this.config.db);

		if (this.config.networking) {
			const { createHelia } = await import("helia");
			const { tcp } = await import("@libp2p/tcp");
			const { noise } = await import("@chainsafe/libp2p-noise");
			const { yamux } = await import("@chainsafe/libp2p-yamux");
			const { identify } = await import("@libp2p/identify");
			const { autoNAT } = await import("@libp2p/autonat");
			const { kadDHT, removePrivateAddressesMapper } = await import("@libp2p/kad-dht");
			const { bootstrap } = await import("@libp2p/bootstrap");
			const { ping } = await import("@libp2p/ping");
			const datastore = new SqliteDatastore(this.config.db);

			// libp2p config: direct peer connections + lightweight diagnostics.
			// - Amino DHT in client mode: queries the public IPFS DHT for content
			//   routing and PLC log discovery, but doesn't serve DHT queries.
			// - AutoNAT: asks connected peers to dial us back, confirming reachability.
			// - Bootstrap: connects to standard IPFS bootstrap peers on startup.
			// Cast SQLite stores to Helia's expected interfaces.
			// Our implementations are duck-type compatible but use Promise
			// returns instead of AwaitGenerator, which Helia handles fine at runtime.
			this.helia = await createHelia({
				libp2p: {
					addresses: { listen: ["/ip4/0.0.0.0/tcp/0"] },
					transports: [tcp()],
					connectionEncrypters: [noise()],
					streamMuxers: [yamux()],
					services: {
						identify: identify(),
						ping: ping(),
						autoNAT: autoNAT(),
						aminoDHT: kadDHT({
							protocol: "/ipfs/kad/1.0.0",
							peerInfoMapper: removePrivateAddressesMapper,
							clientMode: true,
						}),
					},
					peerDiscovery: [
						bootstrap({
							list: [
								"/dnsaddr/bootstrap.libp2p.io/p2p/QmNnooDu7bfjPFoTZYxMNLWUQJyrVwtbZg5gBMjTezGAJN",
								"/dnsaddr/bootstrap.libp2p.io/p2p/QmQCU2EcMqAqQPR2i9bChDtGNJchTbq5TbXJJ16u19uLTa",
							],
						}),
					],
					connectionManager: {
						maxConnections: 10,
						maxIncomingPendingConnections: 3,
						inboundConnectionThreshold: 2,
					},
				},
				blockstore: this.blockstore as any,
				datastore: datastore as any,
			});
		}

		this.running = true;
	}

	async stop(): Promise<void> {
		if (this.helia) {
			await this.helia.stop();
			this.helia = null;
		}
		this.blockstore = null;
		this.running = false;
		this.subscribedTopics.clear();
	}

	async putBlock(cidStr: string, bytes: Uint8Array): Promise<void> {
		if (!this.blockstore) return;
		const cid = CID.parse(cidStr);
		if (this.helia) {
			await this.helia.blockstore.put(cid, bytes);
		} else {
			await this.blockstore.put(cid, bytes);
		}
	}

	async putBlocks(blocks: BlockMap): Promise<void> {
		if (!this.blockstore) return;
		const internalMap = (
			blocks as unknown as { map: Map<string, Uint8Array> }
		).map;
		if (!internalMap) return;
		for (const [cidStr, bytes] of internalMap) {
			await this.putBlock(cidStr, bytes);
		}
	}

	async getBlock(cidStr: string): Promise<Uint8Array | null> {
		if (!this.blockstore) return null;
		try {
			const cid = CID.parse(cidStr);
			// Both Helia's blockstore and SqliteBlockstore return AsyncGenerator<Uint8Array>
			const gen = this.helia
				? this.helia.blockstore.get(cid, { offline: true })
				: this.blockstore.get(cid);
			const chunks: Uint8Array[] = [];
			for await (const chunk of gen) {
				chunks.push(chunk);
			}
			if (chunks.length === 0) return null;
			if (chunks.length === 1) return chunks[0]!;
			const total = chunks.reduce((acc, c) => acc + c.length, 0);
			const result = new Uint8Array(total);
			let offset = 0;
			for (const c of chunks) {
				result.set(c, offset);
				offset += c.length;
			}
			return result;
		} catch {
			return null;
		}
	}

	async hasBlock(cidStr: string): Promise<boolean> {
		if (!this.blockstore) return false;
		try {
			const cid = CID.parse(cidStr);
			if (this.helia) {
				return await this.helia.blockstore.has(cid);
			}
			return await this.blockstore.has(cid);
		} catch {
			return false;
		}
	}

	async deleteBlock(cidStr: string): Promise<void> {
		if (!this.blockstore) return;
		try {
			const cid = CID.parse(cidStr);
			if (this.helia) {
				await this.helia.blockstore.delete(cid);
			} else {
				await this.blockstore.delete(cid);
			}
		} catch {
			// No-op if block doesn't exist
		}
	}

	/**
	 * Announce blocks to the DHT. Fire-and-forget, non-blocking.
	 * Only works when networking is enabled.
	 */
	async provideBlocks(cidStrs: string[]): Promise<void> {
		if (!this.helia) return;
		for (const cidStr of cidStrs) {
			try {
				const cid = CID.parse(cidStr);
				await this.helia.routing.provide(cid);
			} catch {
				// fire-and-forget: log but don't throw
			}
		}
	}

	/**
	 * Publish a commit notification via gossipsub.
	 * CBOR-encodes { did, commit, rev, time, peer } and publishes to the DID's topic.
	 * No-op when networking is disabled.
	 */
	async publishCommitNotification(
		did: string,
		commitCid: string,
		rev: string,
	): Promise<void> {
		if (!this.helia) return;
		const pubsub = (this.helia.libp2p.services as Record<string, unknown>).pubsub as
			{ publish(topic: string, data: Uint8Array): Promise<unknown> } | undefined;
		if (!pubsub) return;

		const notification: CommitNotification = {
			did,
			commit: commitCid,
			rev,
			time: new Date().toISOString(),
			peer: this.helia.libp2p.peerId.toString(),
		};

		const data = cborEncode(notification);
		await pubsub.publish(commitTopic(did), data);
	}

	/**
	 * Register a handler for incoming commit notifications.
	 * Multiple handlers can be registered; all are called for each notification.
	 */
	onCommitNotification(handler: CommitNotificationHandler): void {
		this.commitHandlers.push(handler);
	}

	/**
	 * Subscribe to gossipsub topics for the given DIDs.
	 * No-op when networking is disabled.
	 */
	subscribeCommitTopics(dids: string[]): void {
		if (!this.helia) return;
		const pubsub = (this.helia.libp2p.services as Record<string, unknown>).pubsub as
			{ subscribe(topic: string): void } | undefined;
		if (!pubsub) return;

		for (const did of dids) {
			const topic = commitTopic(did);
			if (!this.subscribedTopics.has(topic)) {
				pubsub.subscribe(topic);
				this.subscribedTopics.add(topic);
			}
		}
	}

	/**
	 * Unsubscribe from gossipsub topics for the given DIDs.
	 * No-op when networking is disabled.
	 */
	unsubscribeCommitTopics(dids: string[]): void {
		if (!this.helia) return;
		const pubsub = (this.helia.libp2p.services as Record<string, unknown>).pubsub as
			{ unsubscribe(topic: string): void } | undefined;
		if (!pubsub) return;

		for (const did of dids) {
			const topic = commitTopic(did);
			if (this.subscribedTopics.has(topic)) {
				pubsub.unsubscribe(topic);
				this.subscribedTopics.delete(topic);
			}
		}
	}

	/**
	 * Publish an identity notification via gossipsub.
	 * CBOR-encodes { did, peerId, multiaddrs, time } and publishes to the DID's identity topic.
	 */
	async publishIdentityNotification(
		did: string,
		peerId: string,
		multiaddrs: string[],
	): Promise<void> {
		if (!this.helia) return;
		const pubsub = (this.helia.libp2p.services as Record<string, unknown>).pubsub as
			{ publish(topic: string, data: Uint8Array): Promise<unknown> } | undefined;
		if (!pubsub) return;

		const notification: IdentityNotification = {
			did,
			peerId,
			multiaddrs,
			time: new Date().toISOString(),
		};

		const data = cborEncode(notification);
		await pubsub.publish(identityTopic(did), data);
	}

	/**
	 * Register a handler for incoming identity notifications.
	 */
	onIdentityNotification(handler: IdentityNotificationHandler): void {
		this.identityHandlers.push(handler);
	}

	/**
	 * Subscribe to identity gossipsub topics for the given DIDs.
	 */
	subscribeIdentityTopics(dids: string[]): void {
		if (!this.helia) return;
		const pubsub = (this.helia.libp2p.services as Record<string, unknown>).pubsub as
			{ subscribe(topic: string): void } | undefined;
		if (!pubsub) return;

		for (const did of dids) {
			const topic = identityTopic(did);
			if (!this.subscribedTopics.has(topic)) {
				pubsub.subscribe(topic);
				this.subscribedTopics.add(topic);
			}
		}
	}

	/**
	 * Unsubscribe from identity gossipsub topics for the given DIDs.
	 */
	unsubscribeIdentityTopics(dids: string[]): void {
		if (!this.helia) return;
		const pubsub = (this.helia.libp2p.services as Record<string, unknown>).pubsub as
			{ unsubscribe(topic: string): void } | undefined;
		if (!pubsub) return;

		for (const did of dids) {
			const topic = identityTopic(did);
			if (this.subscribedTopics.has(topic)) {
				pubsub.unsubscribe(topic);
				this.subscribedTopics.delete(topic);
			}
		}
	}

	/**
	 * Set up the gossipsub message handler.
	 * Listens for "message" events, CBOR-decodes, and dispatches to all registered handlers.
	 */
	private setupGossipsubHandler(): void {
		if (!this.helia) return;
		const pubsub = (this.helia.libp2p.services as Record<string, unknown>).pubsub as
			{ addEventListener(event: string, handler: (evt: unknown) => void): void } | undefined;
		if (!pubsub) return;

		pubsub.addEventListener("message", (evt: unknown) => {
			try {
				const detail = (evt as { detail: { topic: string; data: Uint8Array } }).detail;

				// Drop oversized messages before decoding
				if (detail.data.length > MAX_GOSSIPSUB_MESSAGE_SIZE) {
					return;
				}

				// Per-topic rate limiting via the shared RateLimiter
				if (this.rateLimiter) {
					const isCommit = detail.topic.startsWith(COMMIT_TOPIC_PREFIX);
					const isIdentity = detail.topic.startsWith(IDENTITY_TOPIC_PREFIX);
					if (isCommit || isIdentity) {
						const rule = isCommit
							? DEFAULT_RATE_LIMIT_CONFIG.gossipsubCommit
							: DEFAULT_RATE_LIMIT_CONFIG.gossipsubIdentity;
						const result = this.rateLimiter.check("gossipsub", detail.topic, rule);
						if (!result.allowed) return; // silently drop
					}
				}

				if (detail.topic.startsWith(COMMIT_TOPIC_PREFIX)) {
					const notification = cborDecode(detail.data) as CommitNotification;
					if (
						typeof notification.did !== "string" ||
						typeof notification.commit !== "string" ||
						typeof notification.rev !== "string"
					) {
						return;
					}

					for (const handler of this.commitHandlers) {
						try {
							const result = handler(notification);
							if (result && typeof (result as Promise<void>).catch === "function") {
								(result as Promise<void>).catch(() => {});
							}
						} catch {
							// Individual handler errors don't affect other handlers
						}
					}
				} else if (detail.topic.startsWith(IDENTITY_TOPIC_PREFIX)) {
					const notification = cborDecode(detail.data) as IdentityNotification;
					if (
						typeof notification.did !== "string" ||
						typeof notification.peerId !== "string" ||
						!Array.isArray(notification.multiaddrs)
					) {
						return;
					}

					for (const handler of this.identityHandlers) {
						try {
							const result = handler(notification);
							if (result && typeof (result as Promise<void>).catch === "function") {
								(result as Promise<void>).catch(() => {});
							}
						} catch {
							// Individual handler errors don't affect other handlers
						}
					}
				}
			} catch {
				// Malformed messages are silently dropped
			}
		});
	}

	getMultiaddrs(): string[] {
		if (!this.helia) return [];
		return this.helia.libp2p.getMultiaddrs().map(ma => ma.toString());
	}

	getPeerId(): string | null {
		if (!this.helia) return null;
		return this.helia.libp2p.peerId.toString();
	}

	getConnectionCount(): number {
		if (!this.helia) return 0;
		return this.helia.libp2p.getConnections().length;
	}

	getRemoteAddrs(peerId: string): string[] {
		if (!this.helia) return [];
		return this.helia.libp2p
			.getConnections()
			.filter((conn) => conn.remotePeer.toString() === peerId)
			.map((conn) => conn.remoteAddr.toString());
	}

	/**
	 * Announce this node as a provider for a DID's PLC log via the DHT.
	 * Computes a deterministic CID from the DID and calls routing.provide().
	 */
	async provideForDid(did: string): Promise<void> {
		if (!this.helia) return;
		try {
			const { computeDiscoveryCid } = await import("./identity/plc-mirror.js");
			const cidStr = await computeDiscoveryCid(did);
			const cid = CID.parse(cidStr);
			await this.helia.routing.provide(cid);
		} catch {
			// fire-and-forget
		}
	}

	/**
	 * Find providers for a DID's PLC log via the DHT.
	 * Returns multiaddrs of peers that have announced they hold this DID's log.
	 */
	async findProvidersForDid(did: string): Promise<string[]> {
		if (!this.helia) return [];
		try {
			const { computeDiscoveryCid } = await import("./identity/plc-mirror.js");
			const cidStr = await computeDiscoveryCid(did);
			const cid = CID.parse(cidStr);
			const providers: string[] = [];
			for await (const provider of this.helia.routing.findProviders(cid)) {
				for (const ma of provider.multiaddrs) {
					providers.push(ma.toString());
				}
				if (providers.length >= 10) break;
			}
			return providers;
		} catch {
			return [];
		}
	}

	/**
	 * Delete all blocks from the underlying blockstore.
	 * Used during full disconnect to wipe the node clean.
	 */
	clearBlockstore(): void {
		if (this.blockstore) {
			this.blockstore.clear();
		}
	}

	/**
	 * Get dialability diagnostics: listening addrs, public addrs, NAT status,
	 * and HTTP reachability (if PUBLIC_URL is configured).
	 */
	async getDialability(publicUrl?: string): Promise<{
		listeningAddrs: string[];
		publicAddrs: string[];
		natStatus: "unknown" | "public" | "private";
		httpReachable: boolean | null;
	}> {
		const allAddrs = this.getMultiaddrs();
		const publicAddrs = allAddrs.filter((a) => !isPrivateMultiaddr(a));

		// Determine NAT status from multiaddr analysis
		// getMultiaddrs() includes addresses confirmed by identify/autoNAT
		let natStatus: "unknown" | "public" | "private" = "unknown";
		if (this.helia) {
			// If we have public addresses in our advertised multiaddrs,
			// that indicates we're publicly reachable
			if (publicAddrs.length > 0) {
				natStatus = "public";
			} else if (allAddrs.length > 0) {
				natStatus = "private";
			}
		}

		// Check HTTP reachability
		let httpReachable: boolean | null = null;
		if (publicUrl) {
			try {
				const res = await fetch(publicUrl + "/health", {
					signal: AbortSignal.timeout(5000),
				});
				httpReachable = res.ok;
			} catch {
				httpReachable = false;
			}
		}

		return { listeningAddrs: allAddrs, publicAddrs, natStatus, httpReachable };
	}

	isRunning(): boolean {
		return this.running;
	}

	/**
	 * Get the underlying libp2p node, if networking is enabled.
	 * Typed as `unknown` at the boundary to avoid importing libp2p types
	 * into this module. Callers cast to `Libp2p` when needed.
	 */
	getLibp2p(): unknown | null {
		return this.helia?.libp2p ?? null;
	}

	/**
	 * Dial a specific multiaddr to establish a connection.
	 * No-op when networking is disabled.
	 */
	async dial(multiaddr: string): Promise<void> {
		if (!this.helia) return;
		const { multiaddr: ma } = await import("@multiformats/multiaddr");
		await this.helia.libp2p.dial(ma(multiaddr));
	}
}

/**
 * Check if a multiaddr string contains a private/loopback IP address.
 * Filters: 127.x.x.x, 10.x.x.x, 192.168.x.x, 172.16-31.x.x, ::1, fe80::
 */
function isPrivateMultiaddr(addr: string): boolean {
	// Extract the IP from the multiaddr (e.g. /ip4/10.0.0.1/tcp/4001 → 10.0.0.1)
	const ip4Match = addr.match(/\/ip4\/([\d.]+)/);
	if (ip4Match) {
		const ip = ip4Match[1]!;
		if (ip.startsWith("127.")) return true;
		if (ip.startsWith("10.")) return true;
		if (ip.startsWith("192.168.")) return true;
		// 172.16.0.0 - 172.31.255.255
		const parts = ip.split(".");
		if (parts[0] === "172") {
			const second = parseInt(parts[1]!, 10);
			if (second >= 16 && second <= 31) return true;
		}
		return false;
	}

	const ip6Match = addr.match(/\/ip6\/([a-fA-F0-9:]+)/);
	if (ip6Match) {
		const ip = ip6Match[1]!.toLowerCase();
		if (ip === "::1") return true;
		if (ip.startsWith("fe80")) return true;
		if (ip === "::") return true;
		return false;
	}

	// dnsaddr and other non-IP addrs are considered public
	return false;
}