console_conf: run as recovery chooser when --recovery-chooser-mode is provided

Add support for --recover-chooser-mode command line argument. When provided, run
as a recovery chooser, rather than as a regular console-conf instance.

Signed-off-by: Maciej Borzecki <maciej.zenon.borzecki@canonical.com>

Makefile

@@ -33,6 +33,12 @@ i18n:
 dryrun: probert i18n
 	$(MAKE) ui-view DRYRUN="--dry-run --bootloader uefi"
 
+dryrun-console-conf:
+	$(MAKE) ui-view-console-conf DRYRUN="--dry-run"
+
+ui-view-console-conf:
+	$(PYTHON) -m console_conf.cmd.tui $(DRYRUN) $(MACHARGS)
+
 ui-view:
 	$(PYTHON) -m subiquity $(DRYRUN) $(MACHARGS)
 

console_conf/cmd/tui.py

@@ -16,10 +16,11 @@
 
 import argparse
 import sys
+import os
 import logging
 from subiquitycore.log import setup_logger
 from subiquitycore import __version__ as VERSION
-from console_conf.core import ConsoleConf
+from console_conf.core import ConsoleConf, RecoveryChooser
 
 
 class ClickAction(argparse.Action):
@@ -53,6 +54,10 @@ def parse_options(argv):
     parser.add_argument('--click', metavar="PAT", action=ClickAction,
                         help='Synthesize a click on a button matching PAT')
     parser.add_argument('--answers')
+    parser.add_argument('--recovery-chooser-mode', action='store_true',
+                        dest='chooser_systems',
+                        help=('Run as a recovery chooser interacting with the '
+                              'calling process over stdin/stdout streams'))
     return parser.parse_args(argv)
 
 
@@ -69,9 +74,30 @@ def main():
     logger.info("Starting console-conf v{}".format(VERSION))
     logger.info("Arguments passed: {}".format(sys.argv))
 
-    interface = ConsoleConf(opts)
+    if opts.chooser_systems:
+        # when running as a chooser, the stdin/stdout streams are set up by the
+        # process that runs us, attempt to restore the tty in/out by looking at
+        # stderr
+        chooser_input, chooser_output = restore_std_streams_from(sys.stderr)
+        interface = RecoveryChooser(opts, chooser_input, chooser_output)
+    else:
+        interface = ConsoleConf(opts)
+
     interface.run()
 
 
+def restore_std_streams_from(from_file):
+    """
+    Attempt to restore the original sys.std{in,out} streams by inspecting the
+    tty that stderr is hooked up to. Returns the chooser input/output streams.
+    """
+    tty = os.ttyname(from_file.fileno())
+    # we have tty now
+    chooser_input, chooser_output = sys.stdin, sys.stdout
+    sys.stdin = open(tty, 'r')
+    sys.stdout = open(tty, 'w')
+    return chooser_input, chooser_output
+
+
 if __name__ == '__main__':
     sys.exit(main())