const UserSchema = new mongoose.Schema({
  fullname: {
    type: String, // Data Type
    min:6,
    max:12,
    required: [true, "Please enter your fullname"], // Required with error
    trim: true,
  },
  followersCount: {
    type: Number,
    default: 0,
  },
  followers: [{ type: mongoose.Schema.ObjectId, ref: "User" }], // Array of Object Ids and ref to schema
  createdAt: {
    type: Date,
    default: Date.now,
  },
  drink: {
    type: String,
    enum: ['Coffee', 'Tea', 'Water',]
  }
}
  
 module.exports = mongoose.model("User", UserSchema);

const query = Band.findOne({name: "Guns N' Roses"});
assert.ok(!(query instanceof Promise));

// A query is not a fully-fledged promise, but it does have a `.then()`.
query.then(function (doc) {
  // use doc
});

// `.exec()` gives you a fully-fledged promise
const promise = query.exec(); //or use await on promise
assert.ok(promise instanceof Promise);

promise.then(function (doc) {
  // use doc
});

// ---------------------------------- Find -----------------------------------------
User.find({ author : bob._id }).exec()
// ------------------------------- Find in list --------------------------------------------
User.find()
    .where("_id")
    .in(following.concat([req.user.id]))
    .exec();
// -------------------------------Find and Populate--------------------------------------------
Post.find()
    .populate({
      path: "comments",
      select: "text",
      populate: { path: "user", select: "avatar fullname username" },  // Two level populate
    })
    .populate({ path: "user", select: "avatar fullname username" })
    .sort("-createdAt")
    .where("_id")
    .in(postIds)
    .lean()   // Lean menas POJO
    .exec();
// ------------------------------  Find Regex ---------------------------------------------
  const regex = new RegExp(req.query.username, "i");
  const users = await User.find({ username: regex });
// -------------------------------- Find One -------------------------------------------
User.findOne({ title: 'Bob goes sledding' })
	.select("-password")
  .populate('author')
  .exec()
// --------------------------------Find by Id -------------------------------------------
User.findById(bob._id)
.populate({ path: "posts", select: "files commentsCount likesCount" })
    .populate({ path: "savedPosts", select: "files commentsCount likesCount" })
    .populate({ path: "followers", select: "avatar username fullname" })
    .populate({ path: "following", select: "avatar username fullname" })
    .lean()  //Enabling the lean option tells Mongoose to skip instantiating a full Mongoose document and just give you the POJO (So you cannot use Save() and other document methods)
    .exec();
// --------------------------------Find By Id and update -------------------------------------------
User.findByIdAndUpdate(req.params.id, {
    $push: { followers: req.user.id },
    $inc: { followersCount: 1 },
  });

// -----------------------------Find by Id and Update with options -------------------------------------
User.findByIdAndUpdate(
    req.user.id,
    {
      $set: { ...fieldsToUpdate, website, bio },
    },
    {
      new: true,
      runValidators: true,
    }
  ).select("avatar username fullname email bio website");

// ----------------------------Find and Pull ----------------------------------------------
User.findByIdAndUpdate(req.user.id, {
    $pull: { posts: req.params.id },
    $inc: { postCount: -1 },
  });


// -------------------------------Find and Populate exec -----------------------------------------
  let post = await Post.create({ caption, files, tags, user });

  await User.findByIdAndUpdate(req.user.id, {
    $push: { posts: post._id },
    $inc: { postCount: 1 },
  });

  post = await post
    .populate({ path: "user", select: "avatar username fullname" })
    .execPopulate(); // execPopulate is used to explicitly execute populate on query

// ---------------------------------------------------------------------------
  let post = await Post.create({ caption, files, tags, user });

  await User.findByIdAndUpdate(req.user.id, {
    $push: { posts: post._id },
    $inc: { postCount: 1 },
  });

  post = await post
    .populate({ path: "user", select: "avatar username fullname" })
    .execPopulate(); // execPopulate is used to explicitly execute populate on query