import-bug-from-debian: split big main function into smaller ones

This allows better understanding of the various parts of the code, by
naming important parts and defining boundaries on the used variables.

import-bug-from-debian

@@ -40,9 +40,7 @@ Logger = getLogger()
 ATTACHMENT_MAX_SIZE = 2000
 
 
-def main():
-    bug_re = re.compile(r"bug=(\d+)")
-
+def parse_args():
     parser = argparse.ArgumentParser()
     parser.add_argument(
         "-b",
@@ -72,28 +70,15 @@ def main():
         "--no-conf", action="store_true", help="Don't read config files or environment variables."
     )
     parser.add_argument("bugs", nargs="+", help="Bug number(s) or URL(s)")
-    options = parser.parse_args()
+    return parser.parse_args()
 
-    config = UDTConfig(options.no_conf)
-    if options.lpinstance is None:
-        options.lpinstance = config.get_value("LPINSTANCE")
 
-    if options.dry_run:
-        launchpad = Launchpad.login_anonymously("ubuntu-dev-tools")
-        options.verbose = True
-    else:
-        launchpad = Launchpad.login_with("ubuntu-dev-tools", options.lpinstance)
-
-    if options.verbose:
-        Logger.setLevel(logging.DEBUG)
-
-    debian = launchpad.distributions["debian"]
-    ubuntu = launchpad.distributions["ubuntu"]
-    lp_debbugs = launchpad.bug_trackers.getByName(name="debbugs")
+def get_bug_numbers(bug_list):
+    bug_re = re.compile(r"bug=(\d+)")
 
     bug_nums = []
 
-    for bug_num in options.bugs:
+    for bug_num in bug_list:
         if bug_num.startswith("http"):
             # bug URL
             match = bug_re.search(bug_num)
@@ -105,40 +90,29 @@ def main():
         bug_num = int(bug_num)
         bug_nums.append(bug_num)
 
-    bugs = debianbts.get_status(bug_nums)
+    return bug_nums
 
-    if not bugs:
-        Logger.error("Cannot find any of the listed bugs")
-        sys.exit(1)
 
-    err = False
-    for bug in bugs:
-        ubupackage = package = bug.source
-        if options.package:
-            ubupackage = options.package
-        bug_num = bug.bug_num
-        subject = bug.subject
-        log = debianbts.get_bug_log(bug_num)
-        message = log[0]["message"]
-        attachments = []
-        if message.is_multipart():
+def walk_multipart_message(message):
     summary = ""
+    attachments = []
     i = 1
     for part in message.walk():
         content_type = part.get_content_type()
+
         if content_type.startswith("multipart/"):
             # we're already iterating on multipart items
             # let's just skip the multipart extra metadata
             continue
         if content_type == "application/pgp-signature":
-                    # we don't want to import pgp signature
+            # we're not interested in importing pgp signatures
             continue
 
         if part.is_attachment():
             attachments.append((i, part))
         elif content_type.startswith("image/"):
-                    # images here are not attachment, they are inline, but Launchpad can't handle
-                    # that, so let's add them as attachments
+            # images here are not attachment, they are inline, but Launchpad can't handle that,
+            # so let's add them as attachments
             summary += f"Message part #{i}\n"
             summary += f"[inline image '{part.get_filename()}']\n\n"
             attachments.append((i, part))
@@ -158,6 +132,27 @@ Faulty message part:
 {part}"""
             )
         i += 1
+
+    return summary, attachments
+
+
+def process_bugs(bugs, launchpad, package, dry_run=True, browserless=False):
+    debian = launchpad.distributions["debian"]
+    ubuntu = launchpad.distributions["ubuntu"]
+    lp_debbugs = launchpad.bug_trackers.getByName(name="debbugs")
+
+    err = False
+    for bug in bugs:
+        ubupackage = package = bug.source
+        if package:
+            ubupackage = package
+        bug_num = bug.bug_num
+        subject = bug.subject
+        log = debianbts.get_bug_log(bug_num)
+        message = log[0]["message"]
+        attachments = []
+        if message.is_multipart():
+            summary, attachments = walk_multipart_message(message)
         else:
             summary = log[0]["message"].get_payload()
 
@@ -193,7 +188,7 @@ Faulty message part:
             else:
                 Logger.debug("[data]")
 
-        if options.dry_run:
+        if dry_run:
             Logger.info("Dry-Run: not creating Ubuntu bug.")
             continue
 
@@ -210,17 +205,42 @@ Faulty message part:
                 comment=f"Imported from Debian bug http://bugs.debian.org/{bug_num}",
             )
         d_sp = debian.getSourcePackage(name=package)
-        if d_sp is None and options.package:
-            d_sp = debian.getSourcePackage(name=options.package)
+        if d_sp is None and package:
+            d_sp = debian.getSourcePackage(name=package)
         d_task = u_bug.addTask(target=d_sp)
         d_watch = u_bug.addWatch(remote_bug=bug_num, bug_tracker=lp_debbugs)
         d_task.bug_watch = d_watch
         d_task.lp_save()
         Logger.info("Opened %s", u_bug.web_link)
-        if not options.browserless:
+        if not browserless:
             webbrowser.open(u_bug.web_link)
 
-    if err:
+    return err
+
+
+def main():
+    options = parse_args()
+
+    config = UDTConfig(options.no_conf)
+    if options.lpinstance is None:
+        options.lpinstance = config.get_value("LPINSTANCE")
+
+    if options.dry_run:
+        launchpad = Launchpad.login_anonymously("ubuntu-dev-tools")
+        options.verbose = True
+    else:
+        launchpad = Launchpad.login_with("ubuntu-dev-tools", options.lpinstance)
+
+    if options.verbose:
+        Logger.setLevel(logging.DEBUG)
+
+    bugs = debianbts.get_status(get_bug_numbers(options.bugs))
+
+    if not bugs:
+        Logger.error("Cannot find any of the listed bugs")
+        sys.exit(1)
+
+    if process_bugs(bugs, launchpad, options.package, options.dry_run, options.browserless):
         sys.exit(1)