'''
BSD Licence
Copyright (c) 2015, Science & Technology Facilities Council (STFC)
All rights reserved.

Redistribution and use in source and binary forms, with or without modification,
are permitted provided that the following conditions are met:

    * Redistributions of source code must retain the above copyright notice,
        this list of conditions and the following disclaimer.
    * Redistributions in binary form must reproduce the above copyright notice,
        this list of conditions and the following disclaimer in the
        documentation and/or other materials provided with the distribution.
    * Neither the name of the Science & Technology Facilities Council (STFC)
        nor the names of its contributors may be used to endorse or promote
        products derived from this software without specific prior written
        permission.

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ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
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(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
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SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.


Contents:
This module contains pre-formatted queries of the triple store.

'''
from rdflib.graph import Graph


def _collect_all(graph, cache_graph, uri_ref, depth=1):
    if depth == None:
        depth = 1
    for res in graph.triples((uri_ref, None, None)):
        cache_graph.add(res)
        if depth > 1:
            new_depth = depth
            if new_depth > 1:  # decrease the depth by one
                new_depth = new_depth - 1
            _collect_all(graph, cache_graph, res[2], new_depth)


def extract_subject(graph, subject, depth):
    """
    Extracts from graph and describes, if exists, the specified subject
    - Graph **graph**
        the graph to search in
    - URIRef **uriRef**
        the subject to describe
    - integer **depth**
        how deep should the subject's properties be described

    **return** an rdflib.Graph containing the subject details
    """
    tmp_g = Graph()
    for res in graph.triples((subject, None, None)):
        tmp_g.add(res)
        if depth is None or depth > 0:
            _collect_all(graph, tmp_g, res[2], depth)
    return tmp_g

