neo4j: save and load edges separately from nodes.

[nit.git] / lib / neo4j / neo4j.nit

# This file is part of NIT ( http://www.nitlanguage.org ).
#
# 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
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

# Neo4j connector through its JSON REST API using curl.
#
# For ease of use and testing this module provide a wrapper to the `neo4j` command:
#
#     # Start the Neo4j server
#     var srv = new Neo4jServer
#     assert srv.start_quiet
#
# In order to connect to Neo4j you need a connector:
#
#    # Create new Neo4j client
#    var client = new Neo4jClient("http://localhost:7474")
#    assert client.is_ok
#
# The fundamental units that form a graph are nodes and relationships.
#
# Nodes are used to represent entities stored in base:
#
#    # Create a disconnected node
#    var andres = new NeoNode
#    andres["name"] = "Andres"
#    # Connect the node to Neo4j
#    client.save_node(andres)
#    assert andres.is_linked
#    #
#    # Create a second node
#    var kate = new NeoNode
#    kate["name"] = "Kate"
#    client.save_node(kate)
#    assert kate.is_linked
#
# Relationships between nodes are a key part of a graph database.
# They allow for finding related data. Just like nodes, relationships can have properties.
#
#    # Create a relationship
#    var loves = new NeoEdge(andres, "LOVES", kate)
#    client.save_edge(loves)
#    assert loves.is_linked
#
# Nodes can also be loaded fron Neo4j:
#
#    # Get a node from DB and explore edges
#    var url = andres.url.to_s
#    var from = client.load_node(url)
#    assert from["name"].to_s == "Andres"
#    var to = from.out_nodes("LOVES").first             # follow the first LOVES relationship
#    assert to["name"].to_s == "Kate"
#
# For more details, see http://docs.neo4j.org/chunked/milestone/rest-api.html
module neo4j

import curl_json

# Handles Neo4j server start and stop command
#
# `neo4j` binary must be in `PATH` in order to work
class Neo4jServer

        # Start the local Neo4j server instance
        fun start: Bool do
                sys.system("neo4j start console")
                return true
        end

        # Like `start` but redirect the console output to `/dev/null`
        fun start_quiet: Bool do
                sys.system("neo4j start console > /dev/null")
                return true
        end

        # Stop the local Neo4j server instance
        fun stop: Bool do
                sys.system("neo4j stop")
                return true
        end

        # Like `stop` but redirect the console output to `/dev/null`
        fun stop_quiet: Bool do
                sys.system("neo4j stop > /dev/null")
                return true
        end
end

# `Neo4jClient` is needed to communicate through the REST API
#
#    var client = new Neo4jClient("http://localhost:7474")
#    assert client.is_ok
class Neo4jClient

        # Neo4j REST services baseurl
        var base_url: String
        # REST service to get node data
        private var node_url: String
        # REST service to batch
        private var batch_url: String
        # REST service to send cypher requests
        private var cypher_url: String

        private var curl = new Curl

        init(base_url: String) do
                self.base_url = base_url
                var root = service_root
                if not root isa JsonObject then
                        print "Neo4jClientError: cannot connect to server at {base_url}"
                        abort
                end
                self.node_url = root["node"].to_s
                self.batch_url = root["batch"].to_s
                self.cypher_url = root["cypher"].to_s
        end

        fun service_root: Jsonable do return get("{base_url}/db/data")

        # Is the connection with the Neo4j server ok?
        fun is_ok: Bool do return service_root isa JsonObject

        # Empty the graph
        fun clear_graph do
                cypher(new CypherQuery.from_string("MATCH (n) OPTIONAL MATCH n-[r]-() DELETE r, n"))
        end

        # Last errors
        var errors = new Array[String]

        # Nodes view stored locally
        private var local_nodes = new HashMap[String, nullable NeoNode]

        # Save the node in base
        #
        #     var client = new Neo4jClient("http://localhost:7474")
        #     #
        #     # Create a node
        #     var andres = new NeoNode
        #     andres["name"] = "Andres"
        #     client.save_node(andres)
        #     assert andres.is_linked
        #
        # Once linked, nodes cannot be created twice:
        #
        #     var oldurl = andres.url
        #     client.save_node(andres) # do nothing
        #     assert andres.url == oldurl
        fun save_node(node: NeoNode): Bool do
                if node.is_linked then return true
                node.neo = self
                var batch = new NeoBatch(self)
                batch.save_node(node)
                # batch.create_edges(node.out_edges)
                var errors = batch.execute
                if not errors.is_empty then
                        errors.add_all errors
                        return false
                end
                local_nodes[node.url.to_s] = node
                return true
        end

        # Load a node from base
        # Data, labels and edges will be loaded lazily.
        fun load_node(url: String): NeoNode do
                if local_nodes.has_key(url) then
                        var node = local_nodes[url]
                        if node != null then return node
                end
                var node = new NeoNode.from_neo(self, url)
                local_nodes[url] = node
                return node
        end

        # Remove the entity from base
        fun delete_node(node: NeoNode): Bool do
                if not node.is_linked then return false
                var url = node.url.to_s
                delete(url)
                local_nodes[url] = null
                node.url = null
                return true
        end

        # Edges view stored locally
        private var local_edges = new HashMap[String, nullable NeoEdge]

        # Save the edge in base
        # From and to nodes will be created.
        #
        #     var client = new Neo4jClient("http://localhost:7474")
        #     #
        #     var andres = new NeoNode
        #     var kate = new NeoNode
        #     var edge = new NeoEdge(andres, "LOVES", kate)
        #     client.save_edge(edge)
        #     assert andres.is_linked
        #     assert kate.is_linked
        #     assert edge.is_linked
        fun save_edge(edge: NeoEdge): Bool do
                if edge.is_linked then return true
                edge.neo = self
                edge.from.out_edges.add edge
                edge.to.in_edges.add edge
                var batch = new NeoBatch(self)
                batch.save_edge(edge)
                var errors = batch.execute
                if not errors.is_empty then
                        errors.add_all errors
                        return false
                end
                local_edges[edge.url.to_s] = edge
                return true
        end

        # Load a edge from base
        # Data will be loaded lazily.
        fun load_edge(url: String): NeoEdge do
                if local_edges.has_key(url) then
                        var node = local_edges[url]
                        if node != null then return node
                end
                var edge = new NeoEdge.from_neo(self, url)
                local_edges[url] = edge
                return edge
        end

        # Remove the edge from base
        fun delete_edge(edge: NeoEdge): Bool do
                if not edge.is_linked then return false
                var url = edge.url.to_s
                delete(url)
                local_edges[url] = null
                edge.url = null
                return true
        end

        # Retrieve all nodes with specified `lbl`
        fun nodes_with_label(lbl: String): Array[NeoNode] do
                var res = get("{base_url}/db/data/label/{lbl}/nodes")
                var nodes = new Array[NeoNode]
                var batch = new NeoBatch(self)
                for obj in res.as(JsonArray) do
                        var node = new NeoNode.from_json(self, obj.as(JsonObject))
                        batch.load_node(node)
                        nodes.add node
                end
                batch.execute
                return nodes
        end

        # Perform a `CypherQuery`
        # see: CypherQuery
        fun cypher(query: CypherQuery): Jsonable do
                return post("{cypher_url}", query.to_json)
        end

        # GET JSON data from `url`
        fun get(url: String): Jsonable do
                var request = new JsonGET(url, curl)
                var response = request.execute
                return parse_response(response)
        end

        # POST `params` to `url`
        fun post(url: String, params: Jsonable): Jsonable do
                var request = new JsonPOST(url, curl)
                request.data = params
                var response = request.execute
                return parse_response(response)
        end

        # PUT `params` at `url`
        fun put(url: String, params: Jsonable): Jsonable do
                var request = new JsonPUT(url, curl)
                request.data = params
                var response = request.execute
                return parse_response(response)
        end

        # DELETE `url`
        fun delete(url: String): Jsonable do
                var request = new JsonDELETE(url, curl)
                var response = request.execute
                return parse_response(response)
        end

        # Parse the cURL `response` as a JSON string
        private fun parse_response(response: CurlResponse): Jsonable do
                if response isa CurlResponseSuccess then
                        if response.body_str.is_empty then
                                return new JsonObject
                        else
                                var str = response.body_str
                                var res = str.to_jsonable
                                if res == null then
                                        # empty response wrap it in empty object
                                        return new JsonObject
                                else if res isa JsonObject and res.has_key("exception") then
                                        var error = "Neo4jError::{res["exception"] or else "null"}"
                                        var msg = ""
                                        if res.has_key("message") then
                                                msg = res["message"].to_s
                                        end
                                        return new JsonError(error, msg.to_json)
                                else
                                        return res
                                end
                        end
                else if response isa CurlResponseFailed then
                        return new JsonError("Curl error", "{response.error_msg} ({response.error_code})")
                else
                        return new JsonError("Curl error", "Unexpected response '{response}'")
                end
        end
end

# A Cypher query for Neo4j REST API
#
# The Neo4j REST API allows querying with Cypher.
# The results are returned as a list of string headers (columns), and a data part,
# consisting of a list of all rows, every row consisting of a list of REST representations
# of the field value - Node, Relationship, Path or any simple value like String.
#
# Example:
#
#    var client = new Neo4jClient("http://localhost:7474")
#    var query = new CypherQuery
#    query.nmatch("(n)-[r:LOVES]->(m)")
#    query.nwhere("n.name=\"Andres\"")
#    query.nreturn("m.name")
#    var res = client.cypher(query).as(JsonObject)
#    assert res["data"].as(JsonArray).first.as(JsonArray).first == "Kate"
#
# For more details, see: http://docs.neo4j.org/chunked/milestone/rest-api-cypher.html
class CypherQuery
        # Query string to perform
        private var query: String

        # `params` to embed in the query like in prepared statements
        var params = new JsonObject

        init do
                self.query = ""
        end

        # init the query from a query string
        init from_string(query: String) do
                self.query = query
        end

        # init the query with parameters
        init with_params(params: JsonObject) do
                self.params = params
        end

        # Add a `CREATE` statement to the query
        fun ncreate(query: String): CypherQuery do
                self.query = "{self.query}CREATE {query} "
                return self
        end

        # Add a `START` statement to the query
        fun nstart(query: String): CypherQuery do
                self.query = "{self.query}START {query} "
                return self
        end

        # Add a `MATCH` statement to the query
        fun nmatch(query: String): CypherQuery do
                self.query = "{self.query}MATCH {query} "
                return self
        end

        # Add a `WHERE` statement to the query
        fun nwhere(query: String): CypherQuery do
                self.query = "{self.query}WHERE {query} "
                return self
        end

        # Add a `AND` statement to the query
        fun nand(query: String): CypherQuery do
                self.query = "{self.query}AND {query} "
                return self
        end

        # Add a `RETURN` statement to the query
        fun nreturn(query: String): CypherQuery do
                self.query = "{self.query}RETURN {query} "
                return self
        end

        # Translate the query to JSON
        fun to_json: JsonObject do
                var obj = new JsonObject
                obj["query"] = query
                if not params.is_empty then
                        obj["params"] = params
                end
                return obj
        end

        redef fun to_s do return to_json.to_s
end

# The fundamental units that form a graph are nodes and relationships.
#
# Entities can have two states:
#
# * linked: the NeoEntity references an existing node or edge in Neo4j
# * unlinked: the NeoEntity is not yet created in Neo4j
#
# If the entity is initialized unlinked from neo4j:
#
#    # Create a disconnected node
#    var andres = new NeoNode
#    andres["name"] = "Andres"
#    # At this point, the node is not linked
#    assert not andres.is_linked
#
# Then we can link the entity to the base:
#
#     # Init client
#     var client = new Neo4jClient("http://localhost:7474")
#     client.save_node(andres)
#     # The node is now linked
#     assert andres.is_linked
#
# Entities can also be loaded from Neo4j:
#
#     # Get a node from Neo4j
#     var url = andres.url.to_s
#     var node = client.load_node(url)
#     assert node.is_linked
#
# When working in connected mode, all reading operations are executed lazily on the base:
#
#     # Get the node `name` property
#     assert node["name"] == "Andres"   # loaded lazily from base
abstract class NeoEntity
        # Neo4j client connector
        private var neo: Neo4jClient

        # Entity unique URL in Neo4j REST API
        var url: nullable String

        # Temp id used in batch mode to update the entity
        private var batch_id: nullable Int = null

        # Load the entity from base
        private init from_neo(neo: Neo4jClient, url: String) do
                self.neo = neo
                self.url = url
        end

        # Init entity from JSON representation
        private init from_json(neo: Neo4jClient, obj: JsonObject) do
                self.neo = neo
                self.url = obj["self"].to_s
                self.internal_properties = obj["data"].as(JsonObject)
        end

        # Create a empty (and not-connected) entity
        init do
                self.internal_properties = new JsonObject
        end

        # Is the entity linked to a Neo4j database?
        fun is_linked: Bool do return url != null

        # In Neo4j, both nodes and relationships can contain properties.
        # Properties are key-value pairs where the key is a string.
        # Property values are JSON formatted.
        #
        # Properties are loaded lazily
        fun properties: JsonObject do return internal_properties or else load_properties

        private var internal_properties: nullable JsonObject = null

        private fun load_properties: JsonObject do
                var obj = neo.get("{url.to_s}/properties").as(JsonObject)
                internal_properties = obj
                return obj
        end

        # Get the entity `id` if connected to base
        fun id: nullable Int do
                if url == null then return null
                return url.split("/").last.to_i
        end

        # Get the entity property at `key`
        fun [](key: String): nullable Jsonable do
                if not properties.has_key(key) then return null
                return properties[key]
        end

        # Set the entity property `value` at `key`
        fun []=(key: String, value: nullable Jsonable) do properties[key] = value

        # Is the property `key` set?
        fun has_key(key: String): Bool do return properties.has_key(key)

        # Translate `self` to JSON
        fun to_json: JsonObject do return properties
end

# Nodes are used to represent entities stored in base.
# Apart from properties and relationships (edges),
# nodes can also be labeled with zero or more labels.
#
# A label is a `String` that is used to group nodes into sets.
# All nodes labeled with the same label belongs to the same set.
# A node may be labeled with any number of labels, including none,
# making labels an optional addition to the graph.
#
# Creating new nodes:
#
#    var client = new Neo4jClient("http://localhost:7474")
#    #
#    var andres = new NeoNode
#    andres.labels.add "Person"
#    andres["name"] = "Andres"
#    andres["age"] = 22
#    client.save_node(andres)
#    assert andres.is_linked
#
# Get nodes from Neo4j:
#
#    var url = andres.url.to_s
#    var node = client.load_node(url)
#    assert node["name"] == "Andres"
#    assert node["age"].to_s.to_i       == 22
class NeoNode
        super NeoEntity

        private var internal_labels: nullable Array[String] = null
        private var internal_in_edges: nullable List[NeoEdge] = null
        private var internal_out_edges: nullable List[NeoEdge] = null

        init do
                super
                self.internal_labels = new Array[String]
                self.internal_in_edges = new List[NeoEdge]
                self.internal_out_edges = new List[NeoEdge]
        end

        redef fun to_s do
                var tpl = new FlatBuffer
                tpl.append "\{"
                tpl.append "labels: [{labels.join(", ")}],"
                tpl.append "data: {to_json}"
                tpl.append "\}"
                return tpl.write_to_string
        end

        # A label is a `String` that is used to group nodes into sets.
        # A node may be labeled with any number of labels, including none.
        # All nodes labeled with the same label belongs to the same set.
        #
        # Many database queries can work with these sets instead of the whole graph,
        # making queries easier to write and more efficient.
        #
        # Labels are loaded lazily
        fun labels: Array[String] do return internal_labels or else load_labels

        private fun load_labels: Array[String] do
                var labels = new Array[String]
                var res = neo.get("{url.to_s}/labels")
                if res isa JsonArray then
                        for val in res do labels.add val.to_s
                end
                internal_labels = labels
                return labels
        end

        # Get the list of `NeoEdge` pointing to `self`
        #
        # Edges are loaded lazily
        fun in_edges: List[NeoEdge] do return internal_in_edges or else load_in_edges

        private fun load_in_edges: List[NeoEdge] do
                var edges = new List[NeoEdge]
                var res = neo.get("{url.to_s}/relationships/in").as(JsonArray)
                for obj in res do
                        edges.add(new NeoEdge.from_json(neo, obj.as(JsonObject)))
                end
                internal_in_edges = edges
                return edges
        end

        # Get the list of `NeoEdge` pointing from `self`
        #
        # Edges are loaded lazily
        fun out_edges: List[NeoEdge] do return internal_out_edges or else load_out_edges

        private fun load_out_edges: List[NeoEdge] do
                var edges = new List[NeoEdge]
                var res = neo.get("{url.to_s}/relationships/out")
                for obj in res.as(JsonArray) do
                        edges.add(new NeoEdge.from_json(neo, obj.as(JsonObject)))
                end
                internal_out_edges = edges
                return edges
        end

        # Get nodes pointed by `self` following a `rel_type` edge
        fun out_nodes(rel_type: String): Array[NeoNode] do
                var res = new Array[NeoNode]
                for edge in out_edges do
                        if edge.rel_type == rel_type then res.add edge.to
                end
                return res
        end

        # Get nodes pointing to `self` following a `rel_type` edge
        fun in_nodes(rel_type: String): Array[NeoNode] do
                var res = new Array[NeoNode]
                for edge in in_edges do
                        if edge.rel_type == rel_type then res.add edge.from
                end
                return res
        end
end

# A relationship between two nodes.
# Relationships between nodes are a key part of a graph database.
# They allow for finding related data. Just like nodes, relationships can have properties.
#
# Create a relationship:
#
#    var client = new Neo4jClient("http://localhost:7474")
#    # Create nodes
#    var andres = new NeoNode
#    andres["name"] = "Andres"
#    var kate = new NeoNode
#    kate["name"] = "Kate"
#    # Create a relationship of type `LOVES`
#    var loves = new NeoEdge(andres, "LOVES", kate)
#    client.save_edge(loves)
#    assert loves.is_linked
#
# Get an edge from DB:
#
#    var url = loves.url.to_s
#    var edge = client.load_edge(url)
#    assert edge.from["name"].to_s == "Andres"
#    assert edge.to["name"].to_s == "Kate"
class NeoEdge
        super NeoEntity

        private var internal_from: nullable NeoNode
        private var internal_to: nullable NeoNode
        private var internal_type: nullable String
        private var internal_from_url: nullable String
        private var internal_to_url: nullable String

        init(from: NeoNode, rel_type: String, to: NeoNode) do
                self.internal_from = from
                self.internal_to = to
                self.internal_type = rel_type
        end

        redef init from_neo(neo, url) do
                super
                var obj = neo.get(url).as(JsonObject)
                self.internal_type = obj["type"].to_s
                self.internal_from_url = obj["start"].to_s
                self.internal_to_url = obj["end"].to_s
        end

        redef init from_json(neo, obj) do
                super
                self.internal_type = obj["type"].to_s
                self.internal_from_url = obj["start"].to_s
                self.internal_to_url = obj["end"].to_s
        end

        # Get `from` node
        fun from: NeoNode do return internal_from or else load_from

        private fun load_from: NeoNode do
                var node = neo.load_node(internal_from_url.to_s)
                internal_from = node
                return node
        end

        # Get `to` node
        fun to: NeoNode do return internal_to or else load_to

        private fun load_to: NeoNode do
                var node = neo.load_node(internal_to_url.to_s)
                internal_to = node
                return node
        end

        # Get edge type
        fun rel_type: nullable String do return internal_type

        redef fun to_json do
                var obj = new JsonObject
                if to.is_linked then
                        obj["to"] = to.url
                else
                        obj["to"] = "\{{to.batch_id.to_s}\}"
                end
                obj["type"] = rel_type
                obj["data"] = properties
                return obj
        end
end

# Batches are used to perform multiple operations on the REST API in one cURL request.
# This can significantly improve performance for large insert and update operations.
#
# see: http://docs.neo4j.org/chunked/milestone/rest-api-batch-ops.html
#
# This service is transactional.
# If any of the operations performed fails (returns a non-2xx HTTP status code),
# the transaction will be rolled back and all changes will be undone.
#
# Example:
#
#    var client = new Neo4jClient("http://localhost:7474")
#    #
#    var node1 = new NeoNode
#    var node2 = new NeoNode
#    var edge = new NeoEdge(node1, "TO", node2)
#    #
#    var batch = new NeoBatch(client)
#    batch.save_node(node1)
#    batch.save_node(node2)
#    batch.save_edge(edge)
#    batch.execute
#    #
#    assert node1.is_linked
#    assert node2.is_linked
#    assert edge.is_linked
class NeoBatch

        # Neo4j client connector
        var client: Neo4jClient

        # Jobs to perform in this batch
        #
        # The batch service expects an array of job descriptions as input,
        # each job description describing an action to be performed via the normal server API.
        var jobs = new HashMap[Int, NeoJob]

        # Append a new job to the batch in JSON Format
        # see `NeoJob`
        fun new_job(nentity: NeoEntity): NeoJob do
                var id = jobs.length
                var job = new NeoJob(id, nentity)
                jobs[id] = job
                return job
        end

        # Load a node in batch mode also load labels, data and edges
        fun load_node(node: NeoNode) do
                var job = new_job(node)
                job.action = load_node_data_action
                job.method = "GET"
                if node.id != null then
                        job.to = "/node/{node.id.to_s}"
                else
                        job.to = "\{{node.batch_id.to_s}\}"
                end
                job = new_job(node)
                job.action = load_node_labels_action
                job.method = "GET"
                if node.id != null then
                        job.to = "/node/{node.id.to_s}/labels"
                else
                        job.to = "\{{node.batch_id.to_s}\}/labels"
                end
        end

        # Load in and out edges into node
        fun load_node_edges(node: NeoNode) do
                var job = new_job(node)
                job.action = load_node_in_edges_action
                job.method = "GET"
                if node.id != null then
                        job.to = "/node/{node.id.to_s}/relationships/in"
                else
                        job.to = "\{{node.batch_id.to_s}\}/relationships/in"
                end
                job = new_job(node)
                job.action = load_node_out_edges_action
                job.method = "GET"
                if node.id != null then
                        job.to = "/node/{node.id.to_s}/relationships/out"
                else
                        job.to = "\{{node.batch_id.to_s}\}/relationships/out"
                end
        end

        # Create a node in batch mode also create labels and edges
        fun save_node(node: NeoNode) do
                if node.id != null or node.batch_id != null then return
                # create node
                var job = new_job(node)
                node.batch_id = job.id
                job.action = create_node_action
                job.method = "POST"
                job.to = "/node"
                job.body = node.properties
                # add labels
                job = new_job(node)
                job.method = "POST"
                job.to = "\{{node.batch_id.to_s}\}/labels"
                job.body = new JsonArray.from(node.labels)
                # add edges
                #save_edges(node.out_edges)
        end

        # Create multiple nodes
        # also create labels and edges
        fun save_nodes(nodes: Collection[NeoNode]) do for node in nodes do save_node(node)

        # Create an edge
        # nodes `edge.from` and `edge.to` will be created if not in base
        fun save_edge(edge: NeoEdge) do
                if edge.id != null or edge.batch_id != null then return
                # create nodes
                save_node(edge.from)
                save_node(edge.to)
                # create edge
                var job = new_job(edge)
                edge.batch_id = job.id
                job.action = create_edge_action
                job.method = "POST"
                if edge.from.id != null then
                        job.to = "/node/{edge.from.id.to_s}/relationships"
                else
                        job.to = "\{{edge.from.batch_id.to_s}\}/relationships"
                end
                job.body = edge.to_json
        end

        # Create multiple edges
        fun save_edges(edges: Collection[NeoEdge]) do for edge in edges do save_edge(edge)

        # Execute the batch and update local nodes
        fun execute: List[JsonError] do
                var request = new JsonPOST(client.batch_url, client.curl)
                # request.headers["X-Stream"] = "true"
                var json_jobs = new JsonArray
                for job in jobs.values do json_jobs.add job.to_json
                request.data = json_jobs
                var response = request.execute
                var res = client.parse_response(response)
                return finalize_batch(res)
        end

        # Associate data from response in original nodes and edges
        private fun finalize_batch(response: Jsonable): List[JsonError] do
                var errors = new List[JsonError]
                if not response isa JsonArray then
                        errors.add(new JsonError("Neo4jError", "Unexpected batch response format"))
                        return errors
                end
                # print " {res.length} jobs executed"
                for res in response do
                        if not res isa JsonObject then
                                errors.add(new JsonError("Neo4jError", "Unexpected job format in batch response"))
                                continue
                        end
                        var id = res["id"].as(Int)
                        var job = jobs[id]
                        if job.action == create_node_action then
                                var node = job.entity.as(NeoNode)
                                node.batch_id = null
                                node.url = res["location"].to_s
                        else if job.action == create_edge_action then
                                var edge = job.entity.as(NeoEdge)
                                edge.batch_id = null
                                edge.url = res["location"].to_s
                        else if job.action == load_node_data_action then
                                var node = job.entity.as(NeoNode)
                                node.internal_properties = res["body"].as(JsonObject)["data"].as(JsonObject)
                        else if job.action == load_node_labels_action then
                                var node = job.entity.as(NeoNode)
                                var labels = new Array[String]
                                for l in res["body"].as(JsonArray) do labels.add l.to_s
                                node.internal_labels = labels
                        else if job.action == load_node_in_edges_action then
                                var node = job.entity.as(NeoNode)
                                var edges = res["body"].as(JsonArray)
                                node.internal_in_edges = new List[NeoEdge]
                                for edge in edges do
                                        node.internal_in_edges.add client.load_edge(edge.as(JsonObject)["self"].to_s)
                                end
                        else if job.action == load_node_out_edges_action then
                                var node = job.entity.as(NeoNode)
                                var edges = res["body"].as(JsonArray)
                                node.internal_out_edges = new List[NeoEdge]
                                for edge in edges do
                                        node.internal_out_edges.add client.load_edge(edge.as(JsonObject)["self"].to_s)
                                end
                        end
                end
                return errors
        end

        # JobActions
        # TODO replace with enum

        private fun create_node_action: Int do return 1
        private fun create_edge_action: Int do return 2
        private fun load_node_data_action: Int do return 3
        private fun load_node_labels_action: Int do return 4
        private fun load_node_in_edges_action: Int do return 5
        private fun load_node_out_edges_action: Int do return 6
end

# A job that can be executed in a `NeoBatch`
# This is a representation of a neo job in JSON Format
#
# Each job description should contain a `to` attribute, with a value relative to the data API root
# (so http://localhost:7474/db/data/node becomes just /node), and a `method` attribute containing
# HTTP verb to use.
#
# Optionally you may provide a `body` attribute, and an `id` attribute to help you keep track
# of responses, although responses are guaranteed to be returned in the same order the job
# descriptions are received.
class NeoJob
        # The job uniq `id`
        var id: Int
        # Entity targeted by the job
        var entity: NeoEntity

        init(id: Int, entity: NeoEntity) do
                self.id = id
                self.entity = entity
        end

        # What kind of action do the job
        # used to attach responses to original Neo objets
        private var action: nullable Int = null

        # Job HTTP method: `GET`, `POST`, `PUT`, `DELETE`...
        var method: String
        # Job service target: `/node`, `/labels` etc...
        var to: String
        # Body to send with the job service request
        var body: nullable Jsonable = null

        # JSON formated job
        fun to_json: JsonObject do
                var job = new JsonObject
                job["id"] = id
                job["method"] = method
                job["to"] = to
                if not body == null then
                        job["body"] = body
                end
                return job
        end
end