# Provides services to save and load data for the android platform
class SharedPreferences
	protected var shared_preferences: NativeSharedPreferences
	protected var editor: NativeSharedPreferencesEditor

	# Automatically commits every saving/removing instructions (`true` by default)
	var auto_commit = true

	protected init(app: App, file_name: String, mode: Int)
	do
		sys.jni_env.push_local_frame(1)
		setup(file_name.to_java_string, mode, app.native_context)
		sys.jni_env.pop_local_frame
	end

	# Restricts file access to the current application
	init privately(app: App, file_name: String)
	do
		self.init(app, file_name, private_mode)
	end

	# File access mode
	private fun private_mode: Int in "Java" `{ return Context.MODE_PRIVATE; `}

	private fun set_vars(shared_pref: NativeSharedPreferences, editor: NativeSharedPreferencesEditor)
	do
		self.shared_preferences = shared_pref.new_global_ref
		self.editor = editor.new_global_ref
	end

	private fun setup(file_name: JavaString, mode: Int, context: NativeContext) import set_vars in "Java" `{
		SharedPreferences sp;

		// Uses default SharedPreferences if file_name is an empty String
		if (file_name.equals("")) {
			Activity activity = (Activity)context;
			sp = activity.getPreferences((int)mode);
		} else {
			sp = context.getSharedPreferences(file_name, (int)mode);
		}

		SharedPreferences.Editor editor = sp.edit();

		SharedPreferences_set_vars(self, sp, editor);
	`}

	private fun commit_if_auto do if auto_commit then self.commit

	# Returns true if there's an entry corresponding the given key
	fun has(key: String): Bool
	do
		sys.jni_env.push_local_frame(2)
		var return_value = shared_preferences.contains(key.to_java_string)
		sys.jni_env.pop_local_frame
		return return_value
	end

	# Returns a `HashMap` containing all entries or `null` if there's no entries
	#
	# User has to manage local stack deallocation himself
	#
	# ~~~nitish
	# var foo = new HashMap[JavaString, JavaObject]
	# # ...
	# for key, value in foo do
	#	  key.delete_local_ref
	#	  value.delete_local_ref
	# end
	# ~~~
	# *You should use Nit getters instead and get each value one by one*
	fun all: nullable HashMap[JavaString, JavaObject]
	do
		var hashmap = shared_preferences.get_all
		if hashmap.is_empty then return null
		return hashmap
	end

	# Returns the `Bool` value corresponding the given key or `def_value` if none
	# or if the value isn't of correct type
	fun bool(key: String, def_value: Bool): Bool
	do
		sys.jni_env.push_local_frame(2)
		var return_value = shared_preferences.get_boolean(key.to_java_string, def_value)
		sys.jni_env.pop_local_frame
		return return_value
	end

	# Returns the `Float` value corresponding the given key or `def_value` if none
	# or if the value isn't of correct type
	fun float(key: String, def_value: Float): Float
	do
		sys.jni_env.push_local_frame(2)
		var return_value = shared_preferences.get_float(key.to_java_string, def_value)
		sys.jni_env.pop_local_frame
		return return_value
	end

	# Returns the `Int` value corresponding the given key or `def_value` if none
	# or if the value isn't of correct type
	# Be aware of possible `def_value` integer overflow as the Nit `Int` corresponds
	# to Java `long`
	fun int(key: String, def_value: Int): Int
	do
		sys.jni_env.push_local_frame(2)
		var return_value = shared_preferences.get_int(key.to_java_string, def_value)
		sys.jni_env.pop_local_frame
		return return_value
	end

	# Returns the `Int` value corresponding the given key or `def_value` if none
	# or if the value isn't of correct type
	# Calls `getLong(key, value)` java method
	# Nit `Int` is equivalent to Java `long` so that no integer overflow will occur
	fun long(key: String, def_value: Int): Int
	do
		sys.jni_env.push_local_frame(2)
		var return_value = shared_preferences.get_long(key.to_java_string, def_value)
		sys.jni_env.pop_local_frame
		return return_value
	end

	# Returns the `String` value corresponding the given key or `def_value` if none
	# or if the value isn't of correct type
	fun string(key: String, def_value: String): String
	do
		sys.jni_env.push_local_frame(3)
		var java_return_value = shared_preferences.get_string(key.to_java_string,
			def_value.to_java_string)
		var nit_return_value = java_return_value.to_s
		sys.jni_env.pop_local_frame
		return nit_return_value
	end

	# Clears all the dictionnary entries in the specified file or the default file
	# if none specified at instanciation
	# Returns `self` allowing fluent programming
	fun clear: SharedPreferences
	do
		editor.clear
		commit_if_auto
		return self
	end

	# If auto_commit is `false`, has to be called to save the data to persistant memory
	fun commit: Bool
	do
		sys.jni_env.push_local_frame(1)
		var return_value = editor.commit
		sys.jni_env.pop_local_frame
		return return_value
	end

	# Set a key-value pair using a `Bool` value
	# Returns `self` allowing fluent programming
	fun add_bool(key: String, value: Bool): SharedPreferences
	do
		sys.jni_env.push_local_frame(1)
		editor.put_boolean(key.to_java_string, value)
		sys.jni_env.pop_local_frame
		commit_if_auto
		return self
	end

	# Set a key-value pair using a `Float` value
	# Returns `self` allowing fluent programming
	#
	# Be aware of possible loss of precision as Nit `Float` corresponds to Java `double`
	# and the methods stores a Java `float`
	fun add_float(key: String, value: Float): SharedPreferences
	do
		sys.jni_env.push_local_frame(1)
		editor.put_float(key.to_java_string, value)
		sys.jni_env.pop_local_frame
		commit_if_auto
		return self
	end

	# Set a key-value pair using a `Int` type value
	# Returns `self` allowing fluent programming
	#
	# Be aware of possible integer overflow as the Nit `Int` corresponds to Java `long`
	# and the methods stores a Java `int`
	# *You might want to use add_long instead*
	fun add_int(key: String, value: Int): SharedPreferences
	do
		sys.jni_env.push_local_frame(1)
		editor.put_int(key.to_java_string, value)
		sys.jni_env.pop_local_frame
		commit_if_auto
		return self
	end

	# Set a key-value pair using a `Int` type value
	# Returns `self` allowing fluent programming
	fun add_long(key: String, value: Int): SharedPreferences
	do
		sys.jni_env.push_local_frame(1)
		editor.put_long(key.to_java_string, value)
		sys.jni_env.pop_local_frame
		commit_if_auto
		return self
	end

	# Set a key-value pair using a `String` type value
	# Returns `self` allowing fluent programming
	fun add_string(key: String, value: String): SharedPreferences
	do
		sys.jni_env.push_local_frame(2)
		editor.put_string(key.to_java_string, value.to_java_string)
		sys.jni_env.pop_local_frame
		commit_if_auto
		return self
	end

	# Removes the corresponding entry in the file
	# Returns `self` allowing fluent programming
	fun remove(key: String): SharedPreferences
	do
		sys.jni_env.push_local_frame(1)
		editor.remove(key.to_java_string)
		sys.jni_env.pop_local_frame
		commit_if_auto
		return self
	end

	# Deallocate global references allocated by the SharedPreferences instance
	fun destroy
	do
		self.shared_preferences.delete_global_ref
		self.editor.delete_global_ref
	end

	# Store `value` as a serialized Json string
	fun []=(key: String, value: nullable Serializable)
	do
		var serialized_string = new StringWriter
		var serializer = new JsonSerializer(serialized_string)
		serializer.serialize(value)

		add_string(key, serialized_string.to_s)
		commit_if_auto
	end

	# Retrieve an `Object` stored via `[]=` function
	#
	# Returns `null` if there's no serialized object corresponding to the given key
	# Make sure that the serialized object is `serialize` or that it redefines
	# the appropriate methods. Refer to `Serializable` documentation for further details
	fun [](key: String): nullable Object
	do
		var serialized_string = self.string(key, "")

		if serialized_string == "" then return null

		var deserializer = new JsonDeserializer(serialized_string)
		var deserialized = deserializer.deserialize

		var errors = deserializer.errors
		if errors.not_empty then
			# An update may have broken the versioning compatibility
			print_error "{class_name} error at deserialization: {errors.join(", ")}"
			return null # Let's be safe
		end

		return deserialized
	end
end