1 files changed, 75 insertions, 0 deletions
diff --git a/bsfs/front/builder.py b/bsfs/front/builder.py
new file mode 100644
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+++ b/bsfs/front/builder.py
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+"""
+
+Part of the BlackStar filesystem (bsfs) module.
+A copy of the license is provided with the project.
+Author: Matthias Baumgartner, 2022
+"""
+# imports
+import typing
+
+# bsfs imports
+from bsfs.graph import Graph
+from bsfs.triple_store import TripleStoreBase, SparqlStore
+from bsfs.utils import URI, errors
+
+# exports
+__all__: typing.Sequence[str] = (
+    'build_graph',
+    )
+
+# constants
+_graph_classes = {
+    'Graph': Graph,
+    }
+
+_backend_classes = {
+    'SparqlStore': SparqlStore,
+    }
+
+
+## code ##
+
+def build_backend(cfg: typing.Any) -> TripleStoreBase:
+    """Build and return a backend from user-provided config."""
+    # essential checks
+    if not isinstance(cfg, dict):
+        raise TypeError(cfg)
+    if len(cfg) != 1:
+        raise errors.ConfigError(f'expected a single key that identifies the backend class, found {list(cfg)}')
+    # unpack from config
+    name = next(iter(cfg))
+    args = cfg[name]
+    # check name
+    if name not in _backend_classes:
+        raise errors.ConfigError(f'{name} is not a valid triple store class name')
+    # build and return backend
+    cls = _backend_classes[name]
+    return cls.Open(**args)
+
+
+def build_graph(cfg: typing.Any) -> Graph:
+    """Build and return a Graph from user-provided config."""
+    # essential checks
+    if not isinstance(cfg, dict):
+        raise TypeError(cfg)
+    if len(cfg) != 1:
+        raise errors.ConfigError(f'expected a single key that identifies the graph class, found {list(cfg)}')
+    # unpack from config
+    name = next(iter(cfg))
+    args = cfg[name]
+    # check name
+    if name not in _graph_classes:
+        raise errors.ConfigError(f'{name} is not a valid graph class name')
+    # check user argument
+    if 'user' not in args:
+        raise errors.ConfigError('required argument "user" is not provided')
+    user = URI(args['user'])
+    # check backend argument
+    if 'backend' not in args:
+        raise errors.ConfigError('required argument "backend" is not provided')
+    backend = build_backend(args['backend'])
+    # build and return graph
+    cls = _graph_classes[name]
+    return cls(backend, user)
+
+## EOF ##