# All the nodes in a `NeoGraph`.
#
# An identification scheme can be defined throught the `register` and `add`
# methods. The `id_property` attribute defines where the local ID (that is the
# ID managed by the collection) is stored in each node.
abstract class NeoNodeCollection
	super SimpleCollection[NeoNode]

	# The type of the local IDs.
	type ID_TYPE: Serializable

	# The property of the nodes that hold the local ID.
	var id_property: String

	# Retrieve the node that has the specified local id.
	#
	# Note: The default implementation uses `get_or_null`.
	fun [](id: ID_TYPE): NeoNode do
		var n = get_or_null(id)
		assert n isa NeoNode
		return n
	end

	# Retrieve the node that has the specified local id, or return `null`.
	#
	# Note: The default implementation uses `iterator`.
	fun get_or_null(id: ID_TYPE): nullable NeoNode do
		for n in self do
			if id_of(n) == id then return n
		end
		return null
	end

	# There is a node that has the specified local id?
	#
	# Note: The default implementation uses `get_or_null`.
	fun has_id(id: ID_TYPE): Bool do return get_or_null(id) isa NeoNode

	# Return the local ID of the node.
	fun id_of(node: NeoNode): ID_TYPE do return node[id_property].as(ID_TYPE)

	# Set the local ID of the specified node.
	#
	# Just update the property at `property_id`. Do not check anything.
	protected fun id_of=(node: NeoNode, id: ID_TYPE) do
		node[id_property] = id
	end

	# Enlarge the collection to have at least the specified capacity.
	#
	# The capacity is specified in number of nodes. Used to minimize the
	# number of times the collection need to be resized when adding nodes
	# in batches.
	#
	# Do nothing by default.
	fun enlarge(cap: Int) do end

	# Add the specified node to the graph and set its local ID.
	#
	# SEE: `add`
	# SEE: `create_node`
	fun register(node: NeoNode) is abstract

	# Add the specified node to the graph assuming that its local ID is already set.
	#
	# SEE: `create_node`
	# SEE: `register`
	redef fun add(node) is abstract

	# Add a new node to the graph and return it.
	#
	# Set the local ID of the node before returning it.
	#
	# SEE: `add`
	# SEE: `register`
	fun create_node: NeoNode do
		var node = new NeoNode
		register(node)
		return node
	end

	# Remove the node with the specified local ID.
	fun remove_at(id: ID_TYPE) is abstract

	# Remove the specified node.
	#
	# The local ID is used instead of `==` to seek the node.
	fun remove_node(node: NeoNode) do
		remove_at(id_of(node))
	end

	redef fun clear do
		for node in self do remove_node(node)
	end

	redef fun remove(node) do
		for n in self do
			if node == n then
				remove_node(n)
				return
			end
		end
	end

	redef fun remove_all(node) do
		for n in self do
			if node == n then remove_node(n)
		end
	end

	# Optimize the collection, possibly by rewritting it.
	#
	# The local ID of the elements may be changed by this method.
	fun compact do end
end