// Copyright (C) MongoDB, Inc. 2017-present.
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may
// not use this file except in compliance with the License. You may obtain
// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
// NOTE: This documentation should be kept in line with the Example* test functions.
// Package mongo provides a MongoDB Driver API for Go.
//
// Basic usage of the driver starts with creating a Client from a connection
// string. To do so, call Connect:
//
// ctx, cancel := context.WithTimeout(context.Background(), 20*time.Second)
// defer cancel()
// client, err := mongo.Connect(ctx, options.Client().ApplyURI("mongodb://foo:bar@localhost:27017"))
// if err != nil { return err }
//
// This will create a new client and start monitoring the MongoDB server on localhost.
// The Database and Collection types can be used to access the database:
//
// collection := client.Database("baz").Collection("qux")
//
// A Collection can be used to query the database or insert documents:
//
// res, err := collection.InsertOne(context.Background(), bson.M{"hello": "world"})
// if err != nil { return err }
// id := res.InsertedID
//
// Several methods return a cursor, which can be used like this:
//
// cur, err := collection.Find(context.Background(), bson.D{})
// if err != nil { log.Fatal(err) }
// defer cur.Close(context.Background())
// for cur.Next(context.Background()) {
// // To decode into a struct, use cursor.Decode()
// result := struct{
// Foo string
// Bar int32
// }{}
// err := cur.Decode(&result)
// if err != nil { log.Fatal(err) }
// // do something with result...
//
// // To get the raw bson bytes use cursor.Current
// raw := cur.Current
// // do something with raw...
// }
// if err := cur.Err(); err != nil {
// return err
// }
//
// Cursor.All will decode all of the returned elements at once:
//
// var results []struct{
// Foo string
// Bar int32
// }
// if err = cur.All(context.Background(), &results); err != nil {
// log.Fatal(err)
// }
// // do something with results...
//
// Methods that only return a single document will return a *SingleResult, which works
// like a *sql.Row:
//
// result := struct{
// Foo string
// Bar int32
// }{}
// filter := bson.D{{"hello", "world"}}
// err := collection.FindOne(context.Background(), filter).Decode(&result)
// if err != nil { return err }
// // do something with result...
//
// All Client, Collection, and Database methods that take parameters of type interface{}
// will return ErrNilDocument if nil is passed in for an interface{}.
//
// Additional examples can be found under the examples directory in the driver's repository and
// on the MongoDB website.
//
// # Error Handling
//
// Errors from the MongoDB server will implement the ServerError interface, which has functions to check for specific
// error codes, labels, and message substrings. These can be used to check for and handle specific errors. Some methods,
// like InsertMany and BulkWrite, can return an error representing multiple errors, and in those cases the ServerError
// functions will return true if any of the contained errors satisfy the check.
//
// There are also helper functions to check for certain specific types of errors:
//
// IsDuplicateKeyError(error)
// IsNetworkError(error)
// IsTimeout(error)
//
// # Potential DNS Issues
//
// Building with Go 1.11+ and using connection strings with the "mongodb+srv"[1] scheme is unfortunately
// incompatible with some DNS servers in the wild due to the change introduced in
// https://github.com/golang/go/issues/10622. You may receive an error with the message "cannot unmarshal DNS message"
// while running an operation when using DNS servers that non-compliantly compress SRV records. Old versions of kube-dns
// and the native DNS resolver (systemd-resolver) on Ubuntu 18.04 are known to be non-compliant in this manner. We suggest
// using a different DNS server (8.8.8.8 is the common default), and, if that's not possible, avoiding the "mongodb+srv"
// scheme.
//
// # Client Side Encryption
//
// Client-side encryption is a new feature in MongoDB 4.2 that allows specific data fields to be encrypted. Using this
// feature requires specifying the "cse" build tag during compilation:
//
// go build -tags cse
//
// Note: Auto encryption is an enterprise- and Atlas-only feature.
//
// The libmongocrypt C library is required when using client-side encryption. Specific versions of libmongocrypt
// are required for different versions of the Go Driver:
//
// - Go Driver v1.2.0 requires libmongocrypt v1.0.0 or higher
//
// - Go Driver v1.5.0 requires libmongocrypt v1.1.0 or higher
//
// - Go Driver v1.8.0 requires libmongocrypt v1.3.0 or higher
//
// - Go Driver v1.10.0 requires libmongocrypt v1.5.0 or higher.
// There is a severe bug when calling RewrapManyDataKey with libmongocrypt versions less than 1.5.2.
// This bug may result in data corruption.
// Please use libmongocrypt 1.5.2 or higher when calling RewrapManyDataKey.
//
// - Go Driver v1.12.0 requires libmongocrypt v1.8.0 or higher.
//
// To install libmongocrypt, follow the instructions for your
// operating system:
//
// 1. Linux: follow the instructions listed at
// https://github.com/mongodb/libmongocrypt#installing-libmongocrypt-from-distribution-packages to install the correct
// deb/rpm package.
//
// 2. Mac: Follow the instructions listed at https://github.com/mongodb/libmongocrypt#installing-libmongocrypt-on-macos
// to install packages via brew and compile the libmongocrypt source code.
//
// 3. Windows:
//
// mkdir -p c:/libmongocrypt/bin
// mkdir -p c:/libmongocrypt/include
//
// // Run the curl command in an empty directory as it will create new directories when unpacked.
// curl https://s3.amazonaws.com/mciuploads/libmongocrypt/windows/latest_release/libmongocrypt.tar.gz --output libmongocrypt.tar.gz
// tar -xvzf libmongocrypt.tar.gz
//
// cp ./bin/mongocrypt.dll c:/libmongocrypt/bin
// cp ./include/mongocrypt/*.h c:/libmongocrypt/include
// export PATH=$PATH:/cygdrive/c/libmongocrypt/bin
//
// libmongocrypt communicates with the mongocryptd process or mongo_crypt shared library for automatic encryption.
// See AutoEncryptionOpts.SetExtraOptions for options to configure use of mongocryptd or mongo_crypt.
//
// [1] See https://www.mongodb.com/docs/manual/reference/connection-string/#dns-seedlist-connection-format
package mongo