import { NextRequest, NextResponse } from "next/server";
import { readFileSync, existsSync } from "fs";
import { auth } from "@/lib/auth";
import { memo } from "@/lib/cache";

export const dynamic = "force-dynamic";

const ANALYTICS_FILE = "/home/minecraft/server/analytics.jsonl";

type MetricEntry = {
  ts: string;
  tps: number;
  ramUsedMB: number;
  ramTotalMB: number;
  cpuPercent: number;
  playersOnline: number;
  players: string[];
};

function readWindow(hours: number): MetricEntry[] {
  const cutoff = new Date(Date.now() - hours * 60 * 60 * 1000).toISOString();
  const raw = readFileSync(ANALYTICS_FILE, "utf8");

  // Reverse scan: walk from the end, collect until we pass cutoff.
  const out: MetricEntry[] = [];
  let end = raw.length;
  while (end > 0) {
    const start = raw.lastIndexOf("\n", end - 1);
    const line = raw.slice(start + 1, end).trim();
    end = start;
    if (!line) continue;
    try {
      const entry = JSON.parse(line) as MetricEntry;
      if (entry.ts < cutoff) break; // file is append-ordered by time
      out.push(entry);
    } catch {}
  }
  return out.reverse();
}

export async function GET(req: NextRequest) {
  const session = await auth();
  if (!session) {
    return NextResponse.json({ error: "Unauthorized" }, { status: 403 });
  }

  const hours = Math.min(
    parseInt(req.nextUrl.searchParams.get("hours") || "6"),
    48
  );

  if (!existsSync(ANALYTICS_FILE)) {
    return NextResponse.json([]);
  }

  try {
    const entries = memo(`analytics:${hours}`, 30_000, () => readWindow(hours));
    return NextResponse.json(entries, {
      headers: { "Cache-Control": "private, max-age=30" },
    });
  } catch (e) {
    return NextResponse.json(
      { error: (e as Error).message },
      { status: 500 }
    );
  }
}