[cli] First draft implementation of "convert" command, which builds a simple graph of reader+writer and executes it.

bonobo/commands/convert.py

@@ -0,0 +1,61 @@
+import mimetypes
+
+import bonobo
+
+SHORTCUTS = {
+    'plain': 'text/plain',
+    'txt': 'text/plain',
+    'text': 'text/plain',
+    'csv': 'text/csv',
+    'json': 'application/json',
+}
+
+REGISTRY = {
+    'text/plain': (bonobo.FileReader, bonobo.FileWriter),
+    'text/csv': (bonobo.CsvReader, bonobo.CsvWriter),
+    'application/json': (bonobo.JsonReader, bonobo.JsonWriter),
+}
+
+
+def resolve_factory(name, filename, factory_type):
+    """
+    Try to resolve which transformation factory to use for this filename. User eventually provided a name, which has
+    priority, otherwise we try to detect it using the mimetype detection on filename.
+
+    """
+    if name is None:
+        name = mimetypes.guess_type(filename)[0]
+
+    if name in SHORTCUTS:
+        name = SHORTCUTS[name]
+
+    if not name in REGISTRY:
+        raise RuntimeError('Could not resolve {factory_type} factory for {filename} ({name}). Try providing it explicitely using -{opt} <format>.'.format(name=name, filename=filename, factory_type=factory_type, opt=factory_type[0]))
+
+    if factory_type == 'reader':
+        return REGISTRY[name][0]
+    elif factory_type == 'writer':
+        return REGISTRY[name][1]
+    else:
+        raise ValueError('Invalid factory type.')
+
+def execute(input, output, reader=None, reader_options=None, writer=None, writer_options=None, options=None):
+    reader = resolve_factory(reader, input, 'reader')(input)
+    writer = resolve_factory(writer, output, 'writer')(output)
+
+    graph = bonobo.Graph()
+    graph.add_chain(reader, writer)
+
+    return bonobo.run(graph, services={
+            'fs': bonobo.open_fs(),
+        })
+
+def register(parser):
+    parser.add_argument('input')
+    parser.add_argument('output')
+    parser.add_argument('--reader', '-r')
+    parser.add_argument('--writer', '-w')
+    parser.add_argument('--reader-option', '-ro', dest='reader_options')
+    parser.add_argument('--writer-option', '-wo', dest='writer_options')
+    parser.add_argument('--option', '-o', dest='options')
+    return execute