1 files changed, 75 insertions, 0 deletions
diff --git a/cliff/display.py b/cliff/display.py
new file mode 100644
index 0000000..14497fe
--- /dev/null
+++ b/cliff/display.py
@@ -0,0 +1,75 @@
+"""Application base class for displaying data.
+"""
+import abc
+import logging
+
+import pkg_resources
+
+from .command import Command
+
+
+LOG = logging.getLogger(__name__)
+
+
+class DisplayCommandBase(Command):
+    """Command base class for displaying data about a single object.
+    """
+    __metaclass__ = abc.ABCMeta
+
+    def __init__(self, app, app_args):
+        super(DisplayCommandBase, self).__init__(app, app_args)
+        self.load_formatter_plugins()
+
+    @abc.abstractproperty
+    def formatter_namespace(self):
+        "String specifying the namespace to use for loading formatter plugins."
+
+    @abc.abstractproperty
+    def formatter_default(self):
+        "String specifying the name of the default formatter."
+
+    def load_formatter_plugins(self):
+        self.formatters = {}
+        for ep in pkg_resources.iter_entry_points(self.formatter_namespace):
+            try:
+                self.formatters[ep.name] = ep.load()()
+            except Exception as err:
+                LOG.error(err)
+                if self.app_args.debug:
+                    raise
+        return
+
+    def get_parser(self, prog_name):
+        parser = super(DisplayCommandBase, self).get_parser(prog_name)
+        formatter_group = parser.add_argument_group(
+            title='output formatters',
+            description='output formatter options',
+            )
+        formatter_choices = sorted(self.formatters.keys())
+        formatter_default = self.formatter_default
+        if formatter_default not in formatter_choices:
+            formatter_default = formatter_choices[0]
+        formatter_group.add_argument(
+            '-f', '--format',
+            dest='formatter',
+            action='store',
+            choices=formatter_choices,
+            default=formatter_default,
+            help='the output format to use, defaults to %s' % formatter_default,
+            )
+        for name, formatter in sorted(self.formatters.items()):
+            formatter.add_argument_group(parser)
+        return parser
+
+    @abc.abstractmethod
+    def get_data(self, parsed_args):
+        """Return a two-part tuple with a tuple of column names
+        and a tuple of values.
+        """
+
+    @abc.abstractmethod
+    def run(self, parsed_args):
+        column_names, data = self.get_data(parsed_args)
+        formatter = self.formatters[parsed_args.formatter]
+        formatter.emit_one(column_names, data, self.app.stdout, parsed_args)
+        return 0