# The MongoClient is used to connect to the mongo server and send queries.
#
# Usage:
#
# ~~~
# var uri = "mongodb://mongo:27017/"
# var client = new MongoClient(uri)
# assert client.server_uri == uri
# ~~~
class MongoClient
	super FinalizableOnce

	# Server URI.
	var server_uri: String

	private var native: NativeMongoClient is noinit

	init do native = new NativeMongoClient(server_uri.to_cstring)

	# Gets server data.
	#
	# Returns `null` if an error occured. See `last_error`.
	#
	# ~~~
	# var client = new MongoClient("mongodb://mongo:27017/")
	# assert client.server_status["process"] == "mongod"
	# ~~~
	fun server_status: nullable JsonObject do
		var nbson = native.server_status
		if nbson == null then return null
		var bson = new BSON(nbson)
		var res = new JsonObject.from_bson(bson)
		return res
	end

	# Lists available database names.
	#
	# ~~~
	# var client = new MongoClient("mongodb://mongo:27017/")
	# var db_suffix = "NIT_TESTING_ID".environ
	# var db_name = "test_{db_suffix}"
	# var db = client.database(db_name)
	# db.collection("test").insert(new JsonObject)
	# assert client.database_names.has(db_name)
	# ~~~
	fun database_names: Array[String] do
		var res = new Array[String]
		var nas = native.database_names
		if nas == null then return res
		var i = 0
		var name = nas[i]
		while not name.address_is_null do
			res.add name.to_s
			name.free
			i += 1
			name = nas[i]
		end
		return res
	end

	# Loads or creates a database from its `name`.
	#
	# Database are automatically created on the MongoDB server upon insertion of
	# the first document into a collection.
	# There is no need to create a database manually.
	#
	# ~~~
	# var client = new MongoClient("mongodb://mongo:27017/")
	# var db_suffix = "NIT_TESTING_ID".environ
	# var db_name = "test_{db_suffix}"
	# var db = client.database(db_name)
	# assert db.name == db_name
	# ~~~
	fun database(name: String): MongoDb do return new MongoDb(self, name)

	# Close the connexion and destroy the instance.
	#
	# The reference should not be used beyond this point!
	fun close do finalize_once

	redef fun finalize_once do native.destroy

	# Last error raised by mongoc.
	fun last_error: nullable MongoError do
		var last_error = sys.last_mongoc_error
		if last_error == null then return null
		return new MongoError(last_error)
	end

	# Last auto generated id.
	private fun last_id: nullable MongoObjectId do
		var last_id = sys.last_mongoc_id
		if last_id == null then return null
		return new MongoObjectId.with_native(last_id)
	end

	# Set the last generated id or `null` to unset once used.
	private fun last_id=(id: nullable MongoObjectId) do
		if id == null then
			sys.last_mongoc_id = null
		else
			sys.last_mongoc_id = id.native
		end
	end
end