use logging to control output verbosity

Use the logging module to control what output is printed to the
console.

Add some additional debugging information to the rule evaluation module.

Change-Id: I3b83bdd90c33cdddf36946d01a32e799d4a95e31
Signed-off-by: Doug Hellmann <doug@doughellmann.com>

whereto/app.py

@@ -19,6 +19,8 @@ from __future__ import print_function
 
 import argparse
 import io
+import logging
+import sys
 
 from whereto import parser
 from whereto import rules
@@ -124,10 +126,19 @@ argument_parser.add_argument(
     default=0,
     help='how many hops are allowed',
 )
+argument_parser.add_argument(
+    '-v', '--verbose',
+    dest='verbosity',
+    default=[1],
+    action='append_const',
+    const=1,
+    help='increase the verbosity by one level',
+)
 argument_parser.add_argument(
     '-q', '--quiet',
-    action='store_true',
-    default=False,
+    action='store_const',
+    dest='verbosity',
+    const=[],
     help='run quietly',
 )
 argument_parser.add_argument(
@@ -140,34 +151,43 @@ argument_parser.add_argument(
 )
 
 
-def report(msg):
-    print('whereto: {}'.format(msg))
-
-
 def show_test_and_matches(msg, test, matches):
-    report(
+    logging.error(
         '{} on line {}: {} should produce {} {}'.format(
             msg, test[0], test[1], test[2], test[3])
     )
     path = test[1]
     for linenum, code, new_path in matches:
-        print('whereto:   {} -> {} {} [line {}]'.format(
+        logging.error('   {} -> {} {} [line {}]'.format(
             path, code, new_path, linenum))
 
 
 def main():
     args = argument_parser.parse_args()
 
+    verbosity = sum(args.verbosity)
+    if verbosity < 1:
+        log_level = logging.WARNING
+    elif verbosity == 1:
+        log_level = logging.INFO
+    else:
+        log_level = logging.DEBUG
+
+    logging.basicConfig(
+        level=log_level,
+        format='whereto %(levelname)s: %(message)s',
+        stream=sys.stdout,
+    )
+    log = logging.getLogger()
+
     ruleset = rules.RuleSet()
 
-    if not args.quiet:
-        print('whereto: reading redirects from {}'.format(args.htaccess_file))
+    log.debug('reading redirects from {}'.format(args.htaccess_file))
     with io.open(args.htaccess_file, 'r', encoding='utf-8') as f:
         for linenum, params in parser.parse_rules(f):
             ruleset.add(linenum, *params)
 
-    if not args.quiet:
-        print('whereto: reading tests from {}'.format(args.htaccess_file))
+    log.debug('reading tests from {}'.format(args.htaccess_file))
     with io.open(args.test_file, 'r', encoding='utf-8') as f:
         tests = [
             (linenum,) + tuple(params)
@@ -210,15 +230,14 @@ def main():
         )
 
     if untested:
-        if not args.quiet:
-            print('')
+        log.debug('')
         for linenum in sorted(untested):
             if not args.quiet:
-                report('Untested rule: {}'.format(ruleset[linenum]))
+                logging.error('Untested rule: {}'.format(ruleset[linenum]))
             if args.error_untested:
                 failures += 1
 
     if failures:
-        report('{} failures'.format(failures))
+        logging.error('{} failures'.format(failures))
         return 1
     return 0

whereto/rules.py

@@ -15,9 +15,13 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
+import logging
 import re
 
 
+LOG = logging.getLogger()
+
+
 class Rule(object):
     "Base class for rules."
 
@@ -118,8 +122,11 @@ class RuleSet(object):
             try:
                 m = rule.match(path)
             except Exception as e:
-                print('Failed to evaluate {} against {}: {}'.format(
+                LOG.warning('Failed to evaluate {} against {}: {}'.format(
                     rule, path, e))
             else:
                 if m is not None:
+                    LOG.debug(
+                        'Matched "{}" for path "{}" producing {}'.format(
+                            rule, path, m))
                     return (rule.linenum,) + m