/**
 * Auto-rotating proxy pool.
 *
 * Reads proxies from a text file (format: host:port:username:password),
 * rotates through them round-robin, and tracks failures so unhealthy
 * proxies are skipped.
 */

import { readFileSync, existsSync } from "node:fs";

// --- Types -------------------------------------------------------------------

export interface ProxyEntry {
	host: string;
	port: number;
	username: string;
	password: string;
}

// --- ProxyPool ---------------------------------------------------------------

const POOL_PREFIX = "[proxy-pool]";

function logPool(msg: string, extra?: Record<string, unknown>): void {
	const ts = new Date().toISOString().slice(11, 23);
	const parts = [`${POOL_PREFIX} ${ts}`, msg];
	if (extra) {
		for (const [k, v] of Object.entries(extra)) {
			parts.push(`${k}=${v ?? "null"}`);
		}
	}
	console.log(parts.join(" "));
}

export class ProxyPool {
	private proxies: ProxyEntry[] = [];
	private currentIndex = 0;
	private failureThreshold = 3;
	/** host:port -> consecutive failure count */
	private failures = new Map<string, number>();

	// -- Load --------------------------------------------------------------------

	/**
	 * Load proxies from a file at `filePath`.
	 *
	 * Expected format -- one proxy per line:
	 *   host:port:username:password
	 *
	 * Lines starting with `#` are ignored as comments.
	 */
	load(filePath: string): void {
		if (!existsSync(filePath)) {
			console.warn(`[proxy-pool] File not found: ${filePath}`);
			return;
		}

		const text = readFileSync(filePath, "utf-8");
		const lines = text
			.split("\n")
			.map((l: string) => l.trim())
			.filter(Boolean);

		const parsed: ProxyEntry[] = [];
		for (const line of lines) {
			if (line.startsWith("#")) continue;

			const parts = line.split(":");
			if (parts.length < 2) continue;

			const host = parts[0]!;
			const port = Number.parseInt(parts[1]!, 10);
			if (!Number.isFinite(port)) continue;

			parsed.push({
				host,
				port,
				username: parts[2] ?? "",
				password: parts.slice(3).join(":") ?? "",
			});
		}

		this.proxies = parsed;
		this.currentIndex = 0;
		this.failures.clear();

		logPool(`loaded ${this.proxies.length} proxies from ${filePath}`);
	}

	/**
	 * Convenience -- load from a path or skip.
	 * Returns `true` if proxies were loaded.
	 */
	tryLoad(filePath?: string): boolean {
		if (filePath) this.load(filePath);
		return this.proxies.length > 0;
	}

	// -- Access ------------------------------------------------------------------

	/** Total number of proxies in the pool. */
	get size(): number {
		return this.proxies.length;
	}

	/**
	 * Return the current proxy entry.
	 * Returns `null` if pool is empty.
	 */
	getCurrent(): ProxyEntry | null {
		if (this.proxies.length === 0) return null;
		return this.proxies[this.currentIndex] ?? null;
	}

	/**
	 * Return the proxy URL string for `fetch()`'s `proxy` option.
	 *
	 * Format: `http://username:password@host:port`
	 * Returns `null` when the pool is empty.
	 */
	getProxyUrl(): string | null {
		const entry = this.getCurrent();
		if (!entry) return null;
		const url = this.formatProxyUrl(entry);
		logPool(`getProxyUrl -> ${entry.host}:${entry.port}`, { index: this.currentIndex });
		return url;
	}

	/** Build a `http://user:pass@host:port` URL from an entry. */
	private formatProxyUrl(entry: ProxyEntry): string {
		const auth = entry.username
			? `${encodeURIComponent(entry.username)}:${encodeURIComponent(entry.password)}@`
			: "";
		return `http://${auth}${entry.host}:${entry.port}`;
	}

	// -- Rotation ----------------------------------------------------------------

	/**
	 * Advance to the next proxy (round-robin, wraps around).
	 * Returns the new current proxy or `null` if the pool is empty.
	 */
	rotate(): ProxyEntry | null {
		if (this.proxies.length === 0) return null;
		const oldIndex = this.currentIndex;
		this.currentIndex = (this.currentIndex + 1) % this.proxies.length;
		const entry = this.proxies[this.currentIndex] ?? null;
		logPool(`rotate ${oldIndex} -> ${this.currentIndex}`, { host: entry?.host });
		return entry;
	}

	/**
	 * Mark the **current** proxy as failed.  Increments the failure count;
	 * when the count reaches the threshold a warning is logged.
	 *
	 * NOTE: This no longer calls `rotate()` automatically -- the caller is
	 * responsible for deciding when to rotate.  Previously this was conflated
	 * and caused double-rotation bugs in retry loops.
	 */
	markFailed(threshold?: number): void {
		const entry = this.getCurrent();
		if (!entry) return;

		const key = `${entry.host}:${entry.port}`;
		const count = (this.failures.get(key) ?? 0) + 1;
		this.failures.set(key, count);

		const th = threshold ?? this.failureThreshold;
		logPool(`markFailed ${key} (${count}/${th})`);
		if (count >= th) {
			console.warn(
				`[proxy-pool] Proxy ${key} failed ${count}/${th} times -- skipping`,
			);
		}
	}

	/** Check if the current proxy has exceeded the failure threshold. */
	isFailed(threshold?: number): boolean {
		const entry = this.getCurrent();
		if (!entry) return true;
		const key = `${entry.host}:${entry.port}`;
		const failed = (this.failures.get(key) ?? 0) >= (threshold ?? this.failureThreshold);
		if (failed) logPool(`isFailed true for ${key}`);
		return failed;
	}

	/** Reset the failure counter for the current proxy. */
	markSuccess(): void {
		const entry = this.getCurrent();
		if (!entry) return;
		this.failures.delete(`${entry.host}:${entry.port}`);
		logPool(`markSuccess ${entry.host}:${entry.port}`);
	}

	/** Set the failure count that triggers a permanent skip. */
	setFailureThreshold(n: number): void {
		this.failureThreshold = n;
	}
}

// --- SessionProxyPool ---------------------------------------------------------

interface SessionInfo {
	proxyIndex: number;
	failures: number;
}

/**
 * Session-based sticky proxy allocation on top of ProxyPool.
 *
 * Each session gets one sticky proxy until:
 * - The session is released (cleanup)
 * - The proxy exceeds the failure threshold (auto-rotate to next avail)
 * - The session explicitly calls release()
 *
 * New sessions are assigned to the least-loaded proxy (fewest active sessions).
 */
export class SessionProxyPool {
	private pool: ProxyPool;
	private sessions = new Map<string, SessionInfo>();
	/** proxyIndex -> set of session IDs currently using it */
	private proxyUsage = new Map<number, Set<string>>();
	private failureThreshold: number;

	/**
	 * @param poolOrPath Existing ProxyPool or file path to load from.
	 */
	constructor(poolOrPath?: ProxyPool | string) {
		if (poolOrPath instanceof ProxyPool) {
			this.pool = poolOrPath;
		} else {
			this.pool = new ProxyPool();
			if (poolOrPath) this.pool.load(poolOrPath);
		}
		this.failureThreshold = 3;
		logPool(`SessionProxyPool created, poolSize=${this.pool.size}`);
	}

	/** Number of available proxies in the underlying pool. */
	get size(): number {
		return this.pool.size;
	}

	/** Number of active sessions. */
	get activeSessions(): number {
		return this.sessions.size;
	}

	// -- Session management -------------------------------------------------------

	/**
	 * Assign a sticky proxy to a session. Returns the proxy URL, or null if empty.
	 *
	 * If the session already has a proxy, returns the same one (resume).
	 * Otherwise picks the least-loaded proxy.
	 */
	acquire(sessionId: string): string | null {
		if (this.pool.size === 0) return null;

		const existing = this.sessions.get(sessionId);
		if (existing !== undefined) {
			logPool(`acquire existing session=${sessionId.slice(0, 8)} proxyIndex=${existing.proxyIndex}`);
			return this.formatProxyUrlAtIndex(existing.proxyIndex);
		}

		const index = this.pickLeastUsedIndex();
		if (index === -1) return null;

		this.sessions.set(sessionId, { proxyIndex: index, failures: 0 });

		let usedBy = this.proxyUsage.get(index);
		if (!usedBy) {
			usedBy = new Set();
			this.proxyUsage.set(index, usedBy);
		}
		usedBy.add(sessionId);

		const entry = this.poolEntryAtIndex(index);
		logPool(`acquire session=${sessionId.slice(0, 8)} -> proxyIndex=${index} host=${entry?.host} activeSessions=${this.activeSessions}`);
		return this.formatProxyUrlAtIndex(index);
	}

	/** Return the current proxy URL for a session (no rotation), or null. */
	getProxyUrl(sessionId: string): string | null {
		const info = this.sessions.get(sessionId);
		if (!info) return null;
		const entry = this.poolEntryAtIndex(info.proxyIndex);
		logPool(`getProxyUrl session=${sessionId.slice(0, 8)} proxyIndex=${info.proxyIndex} host=${entry?.host}`);
		return this.formatProxyUrlAtIndex(info.proxyIndex);
	}

	/** Remove a session from all tracking. */
	release(sessionId: string): void {
		const info = this.sessions.get(sessionId);
		if (!info) return;

		const usedBy = this.proxyUsage.get(info.proxyIndex);
		if (usedBy) {
			usedBy.delete(sessionId);
			if (usedBy.size === 0) this.proxyUsage.delete(info.proxyIndex);
		}

		this.sessions.delete(sessionId);
		const entry = this.poolEntryAtIndex(info.proxyIndex);
		logPool(`release session=${sessionId.slice(0, 8)} proxyIndex=${info.proxyIndex} host=${entry?.host} activeSessions=${this.activeSessions}`);
	}

	/**
	 * Increment failure count for this session's proxy.
	 *
	 * If failures >= threshold, auto-rotate to a different proxy.
	 * Also marks the old proxy as failed in the underlying ProxyPool.
	 *
	 * @returns true if the session was rotated to a new proxy.
	 */
	markFailed(sessionId: string): boolean {
		const info = this.sessions.get(sessionId);
		if (!info) return false;

		info.failures += 1;
		logPool(`markFailed session=${sessionId.slice(0, 8)} proxyIndex=${info.proxyIndex} failures=${info.failures}/${this.failureThreshold}`);

		if (info.failures < this.failureThreshold) return false;

		const oldIndex = info.proxyIndex;
		const oldEntry = this.poolEntryAtIndex(oldIndex);

		// Mark in underlying pool (public API only works on currentIndex)
		const savedIdx = (this.pool as any).currentIndex as number;
		(this.pool as any).currentIndex = oldIndex;
		this.pool.markFailed(this.failureThreshold);
		(this.pool as any).currentIndex = savedIdx;

		// Remove session from old proxy usage tracking
		const usedBy = this.proxyUsage.get(oldIndex);
		if (usedBy) {
			usedBy.delete(sessionId);
			if (usedBy.size === 0) this.proxyUsage.delete(oldIndex);
		}

		// Pick next available proxy
		const newIndex = this.pickLeastUsedIndex();
		if (newIndex === -1 || newIndex === oldIndex) {
			// Single-proxy pool or none available — reset failures, stay put
			this.sessions.set(sessionId, { proxyIndex: oldIndex, failures: 0 });
			logPool(`markFailed no alternative, staying on oldIndex=${oldIndex} host=${oldEntry?.host}`);
			return false;
		}

		this.sessions.set(sessionId, { proxyIndex: newIndex, failures: 0 });

		let newUsedBy = this.proxyUsage.get(newIndex);
		if (!newUsedBy) {
			newUsedBy = new Set();
			this.proxyUsage.set(newIndex, newUsedBy);
		}
		newUsedBy.add(sessionId);

		const newEntry = this.poolEntryAtIndex(newIndex);
		logPool(`markFailed rotated session=${sessionId.slice(0, 8)} ${oldEntry?.host} -> ${newEntry?.host}`);
		return true;
	}

	/** Reset failure count for this session's proxy. */
	markSuccess(sessionId: string): void {
		const info = this.sessions.get(sessionId);
		if (!info) return;
		info.failures = 0;
		logPool(`markSuccess session=${sessionId.slice(0, 8)} proxyIndex=${info.proxyIndex}`);
	}

	// -- Internals ----------------------------------------------------------------

	/** Get the ProxyEntry at a given index. Forward reference to local type. */
	private poolEntryAtIndex(index: number): ProxyEntry | null {
		return (this.pool as any).proxies[index] ?? null;
	}

	/** Build proxy URL string by index. */
	private formatProxyUrlAtIndex(index: number): string | null {
		const entry = this.poolEntryAtIndex(index);
		if (!entry) return null;
		const auth = entry.username
			? `${encodeURIComponent(entry.username)}:${encodeURIComponent(entry.password)}@`
			: "";
		return `http://${auth}${entry.host}:${entry.port}`;
	}

	/** Return the index of the proxy with the fewest active sessions, or -1. */
	private pickLeastUsedIndex(): number {
		if (this.pool.size === 0) return -1;

		let bestIndex = 0;
		let bestCount = Infinity;

		for (let i = 0; i < this.pool.size; i++) {
			const count = this.proxyUsage.get(i)?.size ?? 0;
			logPool(`pickLeastUsed proxy[${i}] count=${count}`);
			if (count < bestCount) {
				bestCount = count;
				bestIndex = i;
			}
		}

		logPool(`pickLeastUsed selected index=${bestIndex} count=${bestCount}`);
		return bestIndex;
	}

	/** Override the failure threshold (default 3). */
	setFailureThreshold(n: number): void {
		this.failureThreshold = n;
	}
}