import { randomUUID } from "node:crypto";
import { getConfig } from "./config.js";
import { getDb } from "./db.js";

const COOKIE_NAME = "arena_visitor_id";
const COOKIE_MAX_AGE_SECONDS = 60 * 60 * 24 * 365 * 2;
const DEFAULT_COLLECTION_NAME = "visitors";
const USER_AGENT_LIMIT = 500;

let indexesReady;

export async function visitorRoutes(fastify) {
  fastify.post("/check", async (request, reply) => {
    return recordVisitor(request, reply);
  });

  fastify.get("/stats", async () => {
    const collection = await getVisitorCollection();
    await ensureVisitorIndexes(collection);

    return {
      uniqueVisitors: await collection.countDocuments(),
    };
  });
}

async function recordVisitor(request, reply) {
  const collection = await getVisitorCollection();
  await ensureVisitorIndexes(collection);

  let visitorId = readCookie(request, COOKIE_NAME);
  const hadValidCookie = isValidVisitorId(visitorId);

  if (!hadValidCookie) {
    visitorId = randomUUID();
  }

  const now = new Date();
  const userAgent = String(request.headers["user-agent"] || "").slice(0, USER_AGENT_LIMIT);
  const result = await collection.updateOne(
    { _id: visitorId },
    {
      $setOnInsert: {
        _id: visitorId,
        firstSeenAt: now,
        firstUserAgent: userAgent,
      },
      $set: {
        lastSeenAt: now,
        lastUserAgent: userAgent,
      },
      $inc: {
        visits: 1,
      },
    },
    { upsert: true },
  );

  if (!hadValidCookie || result.upsertedCount > 0) {
    writeVisitorCookie(reply, visitorId);
  }

  return {
    isNewVisitor: result.upsertedCount > 0,
    uniqueVisitors: await collection.countDocuments(),
    checkedAt: now.toISOString(),
  };
}

async function getVisitorCollection() {
  const db = await getDb();
  return db.collection(getConfig().MONGODB_VISITOR_COLLECTION || DEFAULT_COLLECTION_NAME);
}

async function ensureVisitorIndexes(collection) {
  if (!indexesReady) {
    indexesReady = collection.createIndex({ lastSeenAt: -1 });
  }

  return indexesReady;
}

function readCookie(request, name) {
  const cookieHeader = request.headers.cookie;

  if (!cookieHeader) {
    return "";
  }

  const cookies = cookieHeader.split(";").map((cookie) => cookie.trim());
  const matchedCookie = cookies.find((cookie) => cookie.startsWith(`${name}=`));

  if (!matchedCookie) {
    return "";
  }

  try {
    return decodeURIComponent(matchedCookie.slice(name.length + 1));
  } catch {
    return "";
  }
}

function writeVisitorCookie(reply, visitorId) {
  const secureFlag = getConfig().COOKIE_SECURE ? "; Secure" : "";

  reply.header(
    "Set-Cookie",
    `${COOKIE_NAME}=${encodeURIComponent(visitorId)}; Path=/; Max-Age=${COOKIE_MAX_AGE_SECONDS}; SameSite=Lax; HttpOnly${secureFlag}`,
  );
}

function isValidVisitorId(value) {
  return /^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i.test(
    value,
  );
}