XIP/backend/src/lib/stats.ts

import { redis } from "./redis";
import { prisma } from "./prisma";

/**
 * XIP live stats.
 *
 * Two kinds of metrics:
 *  - PERSISTENT totals, stored in Redis (survive restarts): messages, replies,
 *    characters sent, letters typed (even if never sent), unique IPs, longest message.
 *  - LIVE metrics, kept in process memory (sliding windows): letters/sec, messages/min.
 *
 * The number of connected tabs and the "currently typing" count are owned by the
 * realtime module and injected when building a snapshot.
 */

const K = {
  messages: "xip:stat:messages",
  replies: "xip:stat:replies",
  charsSent: "xip:stat:chars_sent",
  lettersTyped: "xip:stat:letters_typed",
  longest: "xip:stat:longest",
  ips: "xip:hll:ips",
  initialized: "xip:stat:initialized",
  creditsSpent: "xip:money:credits_spent", // centi-credits spent (set by wallet/catalog)
  impressionsTotal: "xip:money:impressions_total", // ad impressions (set by lib/ads)
} as const;

// Satirical CPM: "€" earned per 1000 ad impressions.
const FAKE_CPM = 12.5;

// ── Sliding-window live metrics (per process) ──────────────────────────────
const LETTERS_WINDOW_MS = 4000; // smoothing window for letters/sec
const MSGS_WINDOW_MS = 60000; // messages per minute

let letterEvents: { ts: number; n: number }[] = [];
let messageEvents: number[] = [];

function prune(now: number): void {
  letterEvents = letterEvents.filter((e) => now - e.ts <= LETTERS_WINDOW_MS);
  messageEvents = messageEvents.filter((ts) => now - ts <= MSGS_WINDOW_MS);
}

export function getLettersPerSec(): number {
  const now = Date.now();
  prune(now);
  const total = letterEvents.reduce((sum, e) => sum + e.n, 0);
  return total / (LETTERS_WINDOW_MS / 1000);
}

export function getMsgsPerMin(): number {
  const now = Date.now();
  prune(now);
  return messageEvents.length;
}

// ── First-boot backfill ─────────────────────────────────────────────────────

/**
 * Seed the persistent counters from the database the first time the server runs
 * (guarded by a Redis sentinel, so it's a no-op on hot reloads / restarts).
 * Without this, totals would show 0 while seeded messages are already visible.
 * letters_typed is intentionally NOT backfilled — it has no DB source.
 */
export async function initStats(): Promise<void> {
  const first = await redis.set(K.initialized, "1", "NX").catch(() => null);
  if (first !== "OK") return; // already initialized

  try {
    const rows = await prisma.$queryRaw<
      { messages: bigint; replies: bigint; chars: bigint; longest: bigint }[]
    >`
      SELECT
        COUNT(*)                                       AS messages,
        COUNT(*) FILTER (WHERE "parentId" IS NOT NULL) AS replies,
        COALESCE(SUM(LENGTH(content)), 0)              AS chars,
        COALESCE(MAX(LENGTH(content)), 0)              AS longest
      FROM messages
    `;
    const r = rows[0];
    if (r) {
      const pipe = redis.pipeline();
      pipe.set(K.messages, String(Number(r.messages)));
      pipe.set(K.replies, String(Number(r.replies)));
      pipe.set(K.charsSent, String(Number(r.chars)));
      pipe.set(K.longest, String(Number(r.longest)));
      await pipe.exec();
    }

    const ips = await prisma.message.findMany({
      distinct: ["authorIp"],
      select: { authorIp: true },
    });
    if (ips.length > 0) {
      await redis.pfadd(K.ips, ...ips.map((m) => m.authorIp));
    }
    console.log("📊  Stats backfilled from database.");
  } catch (err) {
    // Non-fatal: release the sentinel so a later boot can retry.
    await redis.del(K.initialized).catch(() => {});
    console.warn("⚠️  Stats backfill failed:", (err as Error).message);
  }
}

// ── Mutations ──────────────────────────────────────────────────────────────

/** Record a freshly created message (top-level or reply). */
export async function recordMessage(
  contentLength: number,
  isReply: boolean
): Promise<void> {
  messageEvents.push(Date.now());
  const pipe = redis.pipeline();
  pipe.incr(K.messages);
  pipe.incrby(K.charsSent, contentLength);
  if (isReply) pipe.incr(K.replies);
  // Track longest message (read-modify-write is fine; contention is negligible).
  pipe.get(K.longest);
  const res = await pipe.exec().catch(() => null);
  if (res) {
    const current = Number(res[res.length - 1]?.[1] ?? 0);
    if (contentLength > current) {
      await redis.set(K.longest, String(contentLength)).catch(() => {});
    }
  }
}

/** Record letters typed (sent or not). Feeds both the persistent total and letters/sec. */
export async function recordLettersTyped(delta: number): Promise<void> {
  if (!Number.isFinite(delta) || delta <= 0) return;
  const n = Math.min(delta, 1000); // guard against bogus client payloads
  letterEvents.push({ ts: Date.now(), n });
  await redis.incrby(K.lettersTyped, n).catch(() => {});
}

/** Register an IP in the HyperLogLog of unique visitors. */
export async function recordIp(ip: string): Promise<void> {
  if (!ip) return;
  await redis.pfadd(K.ips, ip).catch(() => {});
}

// ── Snapshot ─────────────────────────────────────────────────────────────

export interface StatsSnapshot {
  // live
  connectedTabs: number;
  typingNow: number;
  lettersPerSec: number;
  msgsPerMin: number;
  // totals
  messages: number;
  replies: number;
  charsSent: number;
  lettersTyped: number;
  uniqueIps: number;
  longestMsg: number;
  // derived
  abandonRate: number; // % of typed letters that were never sent
  avgLength: number; // average sent-message length
  moneyExtorted: number; // fake "€": impressions×CPM + credits spent
}

export async function buildSnapshot(live: {
  connectedTabs: number;
  typingNow: number;
}): Promise<StatsSnapshot> {
  const [messages, replies, charsSent, lettersTyped, longest, uniqueIps, creditsSpent, impressions] =
    await Promise.all([
      redis.get(K.messages).catch(() => "0"),
      redis.get(K.replies).catch(() => "0"),
      redis.get(K.charsSent).catch(() => "0"),
      redis.get(K.lettersTyped).catch(() => "0"),
      redis.get(K.longest).catch(() => "0"),
      redis.pfcount(K.ips).catch(() => 0),
      redis.get(K.creditsSpent).catch(() => "0"),
      redis.get(K.impressionsTotal).catch(() => "0"),
    ]);

  const nMessages = Number(messages ?? 0);
  const nCharsSent = Number(charsSent ?? 0);
  const nLettersTyped = Number(lettersTyped ?? 0);

  const abandonRate =
    nLettersTyped > 0
      ? Math.max(0, Math.min(100, ((nLettersTyped - nCharsSent) / nLettersTyped) * 100))
      : 0;
  const avgLength = nMessages > 0 ? nCharsSent / nMessages : 0;

  // Fake revenue: ad impressions × CPM + credits spent (centi-credits → "€").
  const moneyExtorted =
    (Number(impressions ?? 0) / 1000) * FAKE_CPM + Number(creditsSpent ?? 0) / 100;

  return {
    connectedTabs: live.connectedTabs,
    typingNow: live.typingNow,
    lettersPerSec: getLettersPerSec(),
    msgsPerMin: getMsgsPerMin(),
    messages: nMessages,
    replies: Number(replies ?? 0),
    charsSent: nCharsSent,
    lettersTyped: nLettersTyped,
    uniqueIps: Number(uniqueIps ?? 0),
    longestMsg: Number(longest ?? 0),
    abandonRate,
    avgLength,
    moneyExtorted,
  };
}