if (process.env.NODE_ENV !== "test")
    require("server-only");
import crypto from "node:crypto";
import getPool from "@/lib/server/db";
import { apiError } from "@/lib/server/errors";

type LimitInput = {
    key: string;
    limit: number;
    windowMs: number;
    scope: string;
};

let ensureTablePromise: Promise<void> | null = null;
let lastCleanupAtMs = 0;

async function ensureRateLimitsTable() {
    if (!ensureTablePromise) {
        ensureTablePromise = (async () => {
            const pool = getPool();
            await pool.query(`
                create table if not exists rate_limits(
                  key text primary key,
                  window_start timestamptz not null,
                  count integer not null default 0,
                  updated_at timestamptz not null default now()
                )
            `);
            await pool.query("create index if not exists rate_limits_updated_at_idx on rate_limits(updated_at)");
        })();
    }
    await ensureTablePromise;
}

function normalizeSegment(value: string, fallbackUnknown = true) {
    const trimmed = value.trim().toLowerCase().slice(0, 256);
    if (!trimmed) return fallbackUnknown ? "unknown" : "";
    const safe = trimmed.replace(/[^a-z0-9:._-]/g, "_");
    if (safe.length <= 96) return safe;
    return `sha256:${crypto.createHash("sha256").update(safe).digest("hex")}`;
}

async function cleanupStaleRateLimits() {
    const nowMs = Date.now();
    if (nowMs - lastCleanupAtMs < 10 * 60 * 1000) return;
    lastCleanupAtMs = nowMs;
    const pool = getPool();
    await pool.query("delete from rate_limits where updated_at < now() - interval '2 days'");
}

function normalizeWindowStart(nowMs: number, windowMs: number) {
    const bucketStart = Math.floor(nowMs / windowMs) * windowMs;
    return new Date(bucketStart);
}

async function consumeRateLimit(input: LimitInput) {
    await ensureRateLimitsTable();
    await cleanupStaleRateLimits();
    const now = Date.now();
    const windowStart = normalizeWindowStart(now, input.windowMs);
    const pool = getPool();
    const { rows } = await pool.query<{ count: number }>(
        `insert into rate_limits(key, window_start, count, updated_at)
         values($1, $2, 1, now())
         on conflict (key) do update
         set count = case
             when rate_limits.window_start = excluded.window_start then rate_limits.count + 1
             else 1
         end,
         window_start = case
             when rate_limits.window_start = excluded.window_start then rate_limits.window_start
             else excluded.window_start
         end,
         updated_at = now()
         returning count`,
        [input.key, windowStart]
    );
    const count = Number(rows[0]?.count || 0);
    if (count > input.limit) {
        apiError("RATE_LIMITED", {
            scope: input.scope,
            limit: input.limit,
            windowMs: input.windowMs
        });
    }
}

export async function enforceAuthRateLimit(input: {
    route: "login" | "register";
    ip?: string | null;
    identifier?: string | null;
    ipLimit?: number;
    identifierLimit?: number;
    windowMs?: number;
}) {
    const scope = normalizeSegment(`auth:${input.route}`);
    const ip = normalizeSegment(String(input.ip || "unknown"));
    const windowMs = input.windowMs ?? (15 * 60 * 1000);
    await consumeRateLimit({
        key: `${scope}:ip:${ip}`,
        scope,
        limit: input.ipLimit ?? 20,
        windowMs
    });

    const identifier = normalizeSegment(String(input.identifier || ""), false);
    if (identifier) {
        await consumeRateLimit({
            key: `${scope}:identifier:${identifier}`,
            scope,
            limit: input.identifierLimit ?? 10,
            windowMs
        });
    }
}

export async function enforceUserWriteRateLimit(input: { userId: number; scope: string; limit?: number; windowMs?: number }) {
    const scope = normalizeSegment(input.scope);
    await consumeRateLimit({
        key: `write:user:${input.userId}:scope:${scope}`,
        scope,
        limit: input.limit ?? 120,
        windowMs: input.windowMs ?? (15 * 60 * 1000)
    });
}