// Bhylu MongoDB 8.0.12 lab: $unwind
// Run only against your separate authenticated loopback learning instance.
async function main() {
  if (process.env.BHYLU_MONGO_LAB !== "YES")
    throw new Error("Set BHYLU_MONGO_LAB=YES for a private lab");
  const raw = process.env.BHYLU_MONGO_URI;
  if (!raw)
    throw new Error("Set BHYLU_MONGO_URI privately; do not commit credentials");
  const address = new URL(raw);
  if (
    address.protocol !== "mongodb:" ||
    address.hostname !== "127.0.0.1" ||
    !address.port ||
    address.port === "27017"
  )
    throw new Error("Use a private loopback MongoDB on a non-default port");
  const marker = new ObjectId().toString(),
    dbName = "bhylu_mongo_" + marker;
  const connection = new Mongo(raw);
  const db = connection.getDB(dbName);
  let owned = false;
  const emit = (value) => print(JSON.stringify(value));
  try {
    if ((await db.getCollectionNames()).length)
      throw new Error("Refusing an existing database");
    await db.createCollection("_bhylu_owner");
    await db.getCollection("_bhylu_owner").insertOne({ _id: marker });
    owned = true;
    await db.getCollection("kits").insertMany([
      {
        _id: "K1",
        label: "Birdwatch pack",
        category: "observation",
        available: 3,
        condition: "ready",
        location: { room: "North", shelf: 2 },
        tags: ["outdoor", "compact"],
        notes: null,
        checks: [
          { kind: "lens", passed: true },
          { kind: "strap", passed: false },
        ],
      },
      {
        _id: "K2",
        label: "Stream sampler",
        category: "sampling",
        available: 1,
        condition: "ready",
        location: { room: "South", shelf: 1 },
        tags: ["outdoor", "washable"],
        checks: [
          { kind: "lens", passed: false },
          { kind: "strap", passed: true },
        ],
      },
      {
        _id: "K3",
        label: "Soil survey set",
        category: "sampling",
        available: 0,
        condition: "repair",
        location: { room: "North", shelf: 3 },
        tags: ["washable"],
        notes: "Replace pouch",
        checks: [],
      },
      {
        _id: "K4",
        label: "Weather logger",
        category: "observation",
        available: 2,
        condition: "ready",
        location: { room: "South", shelf: 2 },
        tags: [],
        notes: null,
        checks: [],
      },
    ]);
    await db.getCollection("members").insertMany([
      { _id: "M1", name: "Asha", area: "North" },
      { _id: "M2", name: "Dev", area: "South" },
      { _id: "M3", name: "Noor", area: "West" },
    ]);
    await db.getCollection("loans").insertMany([
      {
        _id: "L1",
        kitId: "K1",
        memberId: "M1",
        quantity: 1,
        status: "returned",
        openedAt: new Date("2026-01-10T09:00:00Z"),
      },
      {
        _id: "L2",
        kitId: "K1",
        memberId: "M2",
        quantity: 2,
        status: "open",
        openedAt: new Date("2026-01-11T09:00:00Z"),
      },
      {
        _id: "L3",
        kitId: "K2",
        memberId: "M1",
        quantity: 1,
        status: "open",
        openedAt: new Date("2026-01-11T10:00:00Z"),
      },
      {
        _id: "L4",
        kitId: "K3",
        memberId: "M2",
        quantity: 1,
        status: "returned",
        openedAt: new Date("2026-01-10T11:00:00Z"),
      },
      {
        _id: "L5",
        kitId: "K4",
        memberId: null,
        quantity: 1,
        status: "planned",
        openedAt: new Date("2026-01-12T09:00:00Z"),
      },
    ]);
    const kits = db.getCollection("kits"),
      loans = db.getCollection("loans"),
      members = db.getCollection("members");
    // Lesson commands begin here.
    emit(
      await kits
        .aggregate([
          { $unwind: "$tags" },
          { $group: { _id: "$tags", kits: { $sum: 1 } } },
          { $sort: { _id: 1 } },
        ])
        .toArray(),
    );
  } finally {
    if (owned) {
      const owner = await db
        .getCollection("_bhylu_owner")
        .findOne({ _id: marker });
      if (!owner || !/^bhylu_mongo_[a-f0-9]{24}$/.test(dbName))
        throw new Error("Refusing cleanup without matching ownership marker");
      await db.dropDatabase();
    }
    // The noninteractive mongosh process closes its connection when it exits.
  }
}
main().catch((error) => {
  console.error(error.message);
  exit(1);
});