kete/prompt: interleave the logs in a better way with the prompt

We overwrite the current formatter to display or not
the prompt depending if we are in the prompt or not.

To prevent races between the background events and our
current configuration, we acquire/release the lock on
the current handler.

tools/tuhi-kete.py

@@ -24,9 +24,13 @@ import threading
 import time
 import svgwrite
 
-logging.basicConfig(format='%(levelname)s: %(message)s',
-                    level=logging.INFO)
+
+log_format = '%(levelname)s: %(message)s'
+logger_handler = logging.StreamHandler()
+logger_handler.setFormatter(logging.Formatter(log_format))
 logger = logging.getLogger('tuhi-kete')
+logger.addHandler(logger_handler)
+logger.setLevel(logging.INFO)
 
 TUHI_DBUS_NAME = 'org.freedesktop.tuhi1'
 ORG_FREEDESKTOP_TUHI1_MANAGER = 'org.freedesktop.tuhi1.Manager'
@@ -490,6 +494,24 @@ class Printer(Worker):
             print(d)
 
 
+class TuhiKeteShellLogHandler(logging.StreamHandler):
+    def __init__(self):
+        super(TuhiKeteShellLogHandler, self).__init__(sys.stdout)
+        self.setFormatter(logging.Formatter(log_format))
+
+    def set_normal_mode(self):
+        self.acquire()
+        self.setFormatter(logging.Formatter(log_format))
+        self.terminator = '\n'
+        self.release()
+
+    def set_prompt_mode(self, prompt):
+        self.acquire()
+        self.setFormatter(logging.Formatter('\r{}'.format(log_format)))
+        self.terminator = '\n{}'.format(prompt)
+        self.release()
+
+
 class TuhiKeteShell(cmd.Cmd):
     intro = 'Tuhi shell control'
     prompt = 'tuhi> '
@@ -498,6 +520,9 @@ class TuhiKeteShell(cmd.Cmd):
         super(TuhiKeteShell, self).__init__(completekey, stdin, stdout)
         self._manager = manager
         self._workers = []
+        self._log_handler = TuhiKeteShellLogHandler()
+        logger.removeHandler(logger_handler)
+        logger.addHandler(self._log_handler)
 
     def emptyline(self):
         # make sure we do not re-enter the last typed command
@@ -514,6 +539,17 @@ class TuhiKeteShell(cmd.Cmd):
             worker.stop()
         return True
 
+    def precmd(self, line):
+        # Restore the logger facility to something sane:
+        self._log_handler.set_normal_mode()
+        return line
+
+    def postcmd(self, stop, line):
+        # overwrite the logger facility to remove the current prompt and append
+        # a new one
+        self._log_handler.set_prompt_mode(self.prompt)
+        return stop
+
     def run(self, init=None):
         try:
             self.cmdloop(init)