lib/neo4j/graph/graph.nit

   1 # This file is part of NIT ( http://www.nitlanguage.org ).
   2 #
   3 # This file is free software, which comes along with NIT. This software is
   4 # distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
   5 # without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
   6 # PARTICULAR PURPOSE. You can modify it is you want, provided this header
   7 # is kept unaltered, and a notification of the changes is added.
   8 # You are allowed to redistribute it and sell it, alone or is a part of
   9 # another product.
  10
  11 # Provides an interface for services on a Neo4j graphs.
  12 module neo4j::graph::graph
  13
  14 import neo4j
  15 import progression
  16
  17 # A Neo4j graph with a local identification scheme for its nodes.
  18 #
  19 # An identification scheme can be defined by subclassing `NeoNodeCollection`.
  20 #
  21 # `GraphStore` can be subclassed to add ways to save or load a graph. The
  22 # storing mechanisms may use `nodes.id_of` to identify the nodes in the graph
  23 # while encoding the relationships.
  24 class NeoGraph
  25         # All the nodes in the graph.
  26         var nodes: NeoNodeCollection
  27
  28         # All the relationships in the graph.
  29         var edges: SimpleCollection[NeoEdge] = new Array[NeoEdge]
  30
  31         # Add a new node to the graph and return it.
  32         #
  33         # Set the local ID of the node before returning it.
  34         #
  35         # SEE: `NeoNodeCollection.add`
  36         # SEE: `NeoNodeCollection.create_node`
  37         # SEE: `NeoNodeCollection.register`
  38         fun create_node: NeoNode do return nodes.create_node
  39 end
  40
  41 # All the nodes in a `NeoGraph`.
  42 #
  43 # An identification scheme can be defined throught the `register` and `add`
  44 # methods. The `id_property` attribute defines where the local ID (that is the
  45 # ID managed by the collection) is stored in each node.
  46 abstract class NeoNodeCollection
  47         super SimpleCollection[NeoNode]
  48
  49         # The type of the local IDs.
  50         type ID_TYPE: Jsonable
  51
  52         # The property of the nodes that hold the local ID.
  53         var id_property: String
  54
  55         # Retrieve the node that has the specified local id.
  56         #
  57         # Note: The default implementation uses `get_or_null`.
  58         fun [](id: ID_TYPE): NeoNode do
  59                 var n = get_or_null(id)
  60                 assert n isa NeoNode
  61                 return n
  62         end
  63
  64         # Retrieve the node that has the specified local id, or return `null`.
  65         #
  66         # Note: The default implementation uses `iterator`.
  67         fun get_or_null(id: ID_TYPE): nullable NeoNode do
  68                 for n in self do
  69                         if id_of(n) == id then return n
  70                 end
  71                 return null
  72         end
  73
  74         # There is a node that has the specified local id?
  75         #
  76         # Note: The default implementation uses `get_or_null`.
  77         fun has_id(id: ID_TYPE): Bool do return get_or_null(id) isa NeoNode
  78
  79         # Return the local ID of the node.
  80         fun id_of(node: NeoNode): ID_TYPE do return node[id_property].as(ID_TYPE)
  81
  82         # Set the local ID of the specified node.
  83         #
  84         # Just update the property at `property_id`. Do not check anything.
  85         protected fun id_of=(node: NeoNode, id: ID_TYPE) do
  86                 node[id_property] = id
  87         end
  88
  89         # Enlarge the collection to have at least the specified capacity.
  90         #
  91         # The capacity is specified in number of nodes. Used to minimize the
  92         # number of times the collection need to be resized when adding nodes
  93         # in batches.
  94         #
  95         # Do nothing by default.
  96         fun enlarge(cap: Int) do end
  97
  98         # Add the specified node to the graph and set its local ID.
  99         #
 100         # SEE: `add`
 101         # SEE: `create_node`
 102         fun register(node: NeoNode) is abstract
 103
 104         # Add the specified node to the graph assuming that its local ID is already set.
 105         #
 106         # SEE: `create_node`
 107         # SEE: `register`
 108         redef fun add(node: NeoNode) is abstract
 109
 110         # Add a new node to the graph and return it.
 111         #
 112         # Set the local ID of the node before returning it.
 113         #
 114         # SEE: `add`
 115         # SEE: `register`
 116         fun create_node: NeoNode do
 117                 var node = new NeoNode
 118                 register(node)
 119                 return node
 120         end
 121
 122         # Remove the node with the specified local ID.
 123         fun remove_at(id: ID_TYPE) is abstract
 124
 125         # Remove the specified node.
 126         #
 127         # The local ID is used instead of `==` to seek the node.
 128         fun remove_node(node: NeoNode) do
 129                 remove_at(id_of(node))
 130         end
 131
 132         redef fun clear do
 133                 for node in self do remove_node(node)
 134         end
 135
 136         redef fun remove(node: NeoNode) do
 137                 for n in self do
 138                         if node == n then
 139                                 remove_node(n)
 140                                 return
 141                         end
 142                 end
 143         end
 144
 145         redef fun remove_all(node: NeoNode) do
 146                 for n in self do
 147                         if node == n then remove_node(n)
 148                 end
 149         end
 150
 151         # Optimize the collection, possibly by rewritting it.
 152         #
 153         # The local ID of the elements may be changed by this method.
 154         fun compact do end
 155 end
 156
 157 # A mean to save and load a Neo4j graph.
 158 abstract class GraphStore
 159         super Trackable
 160
 161         # The graph to save or load.
 162         var graph: NeoGraph
 163
 164         # Can we save the graph without conflict?
 165         fun isolated_save: Bool is abstract
 166
 167         # Load the graph (or a part of it).
 168         #
 169         # Do not reset the graph.
 170         fun load is abstract
 171
 172         # Save the graph.
 173         fun save do save_part(graph.nodes, graph.edges)
 174
 175         # Save the specified part of the graph.
 176         #
 177         # Assume that for each relationship specified, both ends are already saved
 178         # or are specified in the same call to this method.
 179         fun save_part(nodes: Collection[NeoNode],
 180                         edges: Collection[NeoEdge]) is abstract
 181 end