--- /dev/null
+# This file is part of NIT ( http://www.nitlanguage.org ).
+#
+# This file is free software, which comes along with NIT. This software is
+# distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
+# without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+# PARTICULAR PURPOSE. You can modify it is you want, provided this header
+# is kept unaltered, and a notification of the changes is added.
+# You are allowed to redistribute it and sell it, alone or is a part of
+# another product.
+
+# Provides JSON as a mean to store graphs.
+module neo4j::graph::json_graph_store
+
+import graph
+
+# Save or load a graph using a JSON document.
+#
+# The graph (or the specified part of it) is stored as a JSON object with the
+# following properties:
+#
+# * `"nodes"`: An array with all nodes. Each node is an object with the
+# following properties:
+# * `"labels"`: An array of all applied labels.
+# * `"properties"`: An object mapping each defined property to its value.
+# * `"edges"`: An array with all relationships. Each relationship is an object
+# with the following properties:
+# * `"type"`: The type (`String`) of the relationship.
+# * `"properties"`: An object mapping each defined property to its value.
+# * `"from"`: The local ID of the source node.
+# * `"to"`: The local ID of the destination node.
+#
+# ~~~nit
+# import neo4j::graph::sequential_id
+#
+# var graph = new NeoGraph(new SequentialNodeCollection("nid"))
+# var a = new NeoNode
+# a.labels.add "Foo"
+# a["answer"] = 42
+# a["Ultimate question of"] = new JsonArray.from(["life",
+# "the Universe", "and Everything."])
+# graph.nodes.register a
+# var b = graph.create_node
+# b.labels.add "Foo"
+# b.labels.add "Bar"
+# graph.edges.add new NeoEdge(a, "BAZ", b)
+#
+# var ostream = new StringOStream
+# var store = new JsonGraphStore(graph)
+# store.ostream = ostream
+# store.save
+# assert ostream.to_s == """{"nodes":[""" + """
+# {"labels":["Foo"],"properties":{"answer":42,""" + """
+# "Ultimate question of":["life","the Universe","and Everything."],""" + """
+# "nid":1}},""" + """
+# {"labels":["Foo","Bar"],"properties":{"nid":2}}],""" + """
+# "edges":[{"type":"BAZ","properties":{},"from":1,"to":2}]}"""
+#
+# graph.nodes.clear
+# graph.edges.clear
+# store.istream = new StringIStream(ostream.to_s)
+# store.load
+# assert 1 == graph.edges.length
+# for edge in graph.edges do
+# assert "BAZ" == edge.rel_type
+# assert a.labels == edge.from.labels
+# for k, v in a.properties do assert v == edge.from.properties[k]
+# assert b.labels == edge.to.labels
+# for k, v in b.properties do assert v == edge.to.properties[k]
+# end
+# assert 2 == graph.nodes.length
+# ~~~
+class JsonGraphStore
+ super GraphStore
+
+ # The stream to use for `load`.
+ var istream: nullable IStream = null is writable
+
+ # The stream to use for `save` and `save_part`.
+ var ostream: nullable OStream = null is writable
+
+ # Use the specified `IOStream`.
+ init from_io(graph: NeoGraph, iostream: IOStream) do
+ init(graph)
+ istream = iostream
+ ostream = iostream
+ end
+
+ # Use the specified string to load the graph.
+ init from_string(graph: NeoGraph, string: String) do
+ init(graph)
+ istream = new StringIStream(string)
+ end
+
+ redef fun isolated_save do return true
+
+ redef fun load do
+ var istream = self.istream
+ assert istream isa IStream
+ fire_started
+ graph.load_json(istream.read_all)
+ fire_done
+ end
+
+ redef fun save_part(nodes, edges) do
+ var ostream = self.ostream
+ assert ostream isa OStream
+ fire_started
+ ostream.write(graph.to_json)
+ fire_done
+ end
+end
+
+redef class NeoGraph
+ super Jsonable
+
+ # Retrieve the graph from the specified JSON document.
+ #
+ # For the expected format, see `JsonGraphStore`.
+ #
+ # ~~~nit
+ # import neo4j::graph::sequential_id
+ #
+ # var graph = new NeoGraph(new SequentialNodeCollection("node_id"))
+ # var a = new NeoNode
+ # a.labels.add "Foo"
+ # a["answer"] = 42
+ # a["Ultimate question of"] = new JsonArray.from(["life",
+ # "the Universe", "and Everything."])
+ # graph.nodes.register a
+ # var b = graph.create_node
+ # b.labels.add "Foo"
+ # b.labels.add "Bar"
+ # graph.edges.add new NeoEdge(a, "BAZ", b)
+ #
+ # graph = new NeoGraph.from_json(
+ # new SequentialNodeCollection("node_id"), graph.to_json)
+ # assert 1 == graph.edges.length
+ # for edge in graph.edges do
+ # assert "BAZ" == edge.rel_type
+ # assert a.labels == edge.from.labels
+ # for k, v in a.properties do assert v == edge.from.properties[k]
+ # assert b.labels == edge.to.labels
+ # for k, v in b.properties do assert v == edge.to.properties[k]
+ # end
+ # assert 2 == graph.nodes.length
+ # ~~~
+ init from_json(nodes: NeoNodeCollection, t: Text) do
+ from_json_object(nodes, t.parse_json.as(JsonObject))
+ end
+
+ # Retrieve the graph from the specified JSON object.
+ #
+ # For the expected format, see `JsonGraphStore`.
+ init from_json_object(nodes: NeoNodeCollection, o: JsonObject) do
+ init(nodes)
+ load_json_object(o)
+ end
+
+ # Retrieve a part of the graph from the specified JSON document.
+ #
+ # For the expected format, see `JsonGraphStore`.
+ fun load_json(t: Text) do
+ load_json_object(t.parse_json.as(JsonObject))
+ end
+
+ # Retrieve a part of the graph from the specified JSON object.
+ #
+ # For the expected format, see `JsonGraphStore`.
+ fun load_json_object(o: JsonObject) do
+ var json_nodes = o["nodes"].as(JsonArray)
+ for json_node in json_nodes do
+ assert json_node isa JsonObject
+ var node = new NeoNode.from_json_object(json_node)
+ nodes.add node
+ end
+
+ var json_edges = o["edges"].as(JsonArray)
+ for json_edge in json_edges do
+ assert json_edge isa JsonObject
+ var from = nodes[nodes.id_from_jsonable(json_edge["from"])]
+ var to = nodes[nodes.id_from_jsonable(json_edge["to"])]
+ var rel_type = json_edge["type"].as(String)
+ var json_properties = json_edge["properties"].as(JsonObject)
+ var edge = new NeoEdge(from, rel_type, to)
+ edge.properties.recover_with(json_properties)
+ edges.add edge
+ end
+ end
+
+ redef fun to_json do return to_json_by_append
+
+ # Append the JSON representation of `self` to the specified buffer.
+ #
+ # For a description of the format, see `JsonGraphStore`.
+ #
+ # SEE: `to_json`
+ redef fun append_json(b) do
+ b.append "\{\"nodes\":["
+ append_entities_json(nodes, b)
+ b.append "],\"edges\":["
+ append_entities_json(edges, b)
+ b.append "]\}"
+ end
+
+ # Encode `self` in JSON.
+ #
+ # For a description of the format, see `JsonGraphStore`.
+ #
+ # SEE: `append_json`
+ private fun append_entities_json(entities: Collection[NeoEntity],
+ b: Buffer) do
+ var i = entities.iterator
+ if i.is_ok then
+ i.item.append_json_for(self, b)
+ i.next
+ for entity in i do
+ b.add ','
+ entity.append_json_for(self, b)
+ end
+ end
+ end
+end
+
+redef class NeoNodeCollection
+ # Convert the specified JSON value into a local ID.
+ fun id_from_jsonable(id: nullable Jsonable): ID_TYPE do return id.as(ID_TYPE)
+end
+
+redef class NeoEntity
+
+ # Append the JSON representation of the entity to the specified buffer.
+ fun append_json_for(graph: NeoGraph, buffer: Buffer) is abstract
+end
+
+# Make `NeoNode` `Jsonable`.
+redef class NeoNode
+ super Jsonable
+
+ # Retrieve the node from the specified JSON value.
+ #
+ # Note: Here, the `"id"` is optional and ignored.
+ #
+ # SEE: `JsonGraph`
+ #
+ # var node = new NeoNode.from_json("""
+ # {
+ # "labels": ["foo", "Bar"],
+ # "properties": {
+ # "baz": 42
+ # }
+ # }
+ # """)
+ # assert ["foo", "Bar"] == node.labels
+ # assert 42 == node["baz"]
+ init from_json(t: Text) do
+ from_json_object(t.parse_json.as(JsonObject))
+ end
+
+ # Retrieve the node from the specified JSON value.
+ #
+ # Note: Here, the `"id"` is optional and ignored.
+ #
+ # SEE: `JsonGraph`
+ init from_json_object(o: JsonObject) do
+ init
+ var labels = o["labels"].as(JsonArray)
+ for lab in labels do self.labels.add(lab.as(String))
+ var json_properties = o["properties"].as(JsonObject)
+ properties.recover_with(json_properties)
+ end
+
+ redef fun to_json do return to_json_by_append
+
+ # Append the JSON representation of the node to the specified buffer.
+ #
+ # SEE: `JsonGraph`
+ redef fun append_json(b) do
+ b.append "\{\"labels\":["
+ var i = labels.iterator
+ if i.is_ok then
+ i.item.append_json(b)
+ i.next
+ for lab in i do
+ b.add ','
+ lab.append_json(b)
+ end
+ end
+ b.append "],\"properties\":"
+ properties.append_json(b)
+ b.add '}'
+ end
+
+ redef fun to_s do return to_json
+
+ # Append the JSON representation of the node to the specified buffer.
+ redef fun append_json_for(graph: NeoGraph, buffer: Buffer) do
+ append_json(buffer)
+ end
+end
+
+redef class NeoEdge
+
+ # Append the JSON representation of the relationship to the specified buffer.
+ #
+ # Use the IDs specfied by `graph.nodes`.
+ redef fun append_json_for(graph: NeoGraph, buffer: Buffer) do
+ buffer.append "\{\"type\":"
+ rel_type.append_json(buffer)
+ buffer.append ",\"properties\":"
+ properties.append_json(buffer)
+ buffer.append ",\"from\":"
+ graph.nodes.id_of(from).append_json(buffer)
+ buffer.append ",\"to\":"
+ graph.nodes.id_of(to).append_json(buffer)
+ buffer.append "}"
+ end
+end
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