patman: Add a library to handle logging and progress

When tools want to display information of varying levels of importance, it
helps to provide the user with control over the verbosity of these messages.
Progress messages work best if they are displayed and then removed from the
display when no-longer relevant.

Add a new tout library (terminal out) to handle these tasks.

Signed-off-by: Simon Glass <sjg@chromium.org>

tools/patman/tout.py

@@ -0,0 +1,166 @@
+# Copyright (c) 2016 Google, Inc
+#
+# SPDX-License-Identifier:            GPL-2.0+
+#
+# Terminal output logging.
+#
+
+import sys
+
+import terminal
+
+# Output verbosity levels that we support
+ERROR = 0
+WARNING = 1
+NOTICE = 2
+INFO = 3
+DEBUG = 4
+
+"""
+This class handles output of progress and other useful information
+to the user. It provides for simple verbosity level control and can
+output nothing but errors at verbosity zero.
+
+The idea is that modules set up an Output object early in their years and pass
+it around to other modules that need it. This keeps the output under control
+of a single class.
+
+Public properties:
+    verbose: Verbosity level: 0=silent, 1=progress, 3=full, 4=debug
+"""
+def __enter__():
+    return
+
+def __exit__(unused1, unused2, unused3):
+    """Clean up and remove any progress message."""
+    ClearProgress()
+    return False
+
+def UserIsPresent():
+    """This returns True if it is likely that a user is present.
+
+    Sometimes we want to prompt the user, but if no one is there then this
+    is a waste of time, and may lock a script which should otherwise fail.
+
+    Returns:
+        True if it thinks the user is there, and False otherwise
+    """
+    return stdout_is_tty and verbose > 0
+
+def ClearProgress():
+    """Clear any active progress message on the terminal."""
+    if verbose > 0 and stdout_is_tty:
+        _stdout.write('\r%s\r' % (" " * len (_progress)))
+        _stdout.flush()
+
+def Progress(msg, warning=False, trailer='...'):
+    """Display progress information.
+
+    Args:
+        msg: Message to display.
+        warning: True if this is a warning."""
+    ClearProgress()
+    if verbose > 0:
+        _progress = msg + trailer
+        if stdout_is_tty:
+            col = _color.YELLOW if warning else _color.GREEN
+            _stdout.write('\r' + _color.Color(col, _progress))
+            _stdout.flush()
+        else:
+            _stdout.write(_progress + '\n')
+
+def _Output(level, msg, color=None):
+    """Output a message to the terminal.
+
+    Args:
+        level: Verbosity level for this message. It will only be displayed if
+                this as high as the currently selected level.
+        msg; Message to display.
+        error: True if this is an error message, else False.
+    """
+    if verbose >= level:
+        ClearProgress()
+        if color:
+            msg = _color.Color(color, msg)
+        _stdout.write(msg + '\n')
+
+def DoOutput(level, msg):
+    """Output a message to the terminal.
+
+    Args:
+        level: Verbosity level for this message. It will only be displayed if
+                this as high as the currently selected level.
+        msg; Message to display.
+    """
+    _Output(level, msg)
+
+def Error(msg):
+    """Display an error message
+
+    Args:
+        msg; Message to display.
+    """
+    _Output(0, msg, _color.RED)
+
+def Warning(msg):
+    """Display a warning message
+
+    Args:
+        msg; Message to display.
+    """
+    _Output(1, msg, _color.YELLOW)
+
+def Notice(msg):
+    """Display an important infomation message
+
+    Args:
+        msg; Message to display.
+    """
+    _Output(2, msg)
+
+def Info(msg):
+    """Display an infomation message
+
+    Args:
+        msg; Message to display.
+    """
+    _Output(3, msg)
+
+def Debug(msg):
+    """Display a debug message
+
+    Args:
+        msg; Message to display.
+    """
+    _Output(4, msg)
+
+def UserOutput(msg):
+    """Display a message regardless of the current output level.
+
+    This is used when the output was specifically requested by the user.
+    Args:
+        msg; Message to display.
+    """
+    _Output(0, msg)
+
+def Init(_verbose=WARNING, stdout=sys.stdout):
+    """Initialize a new output object.
+
+    Args:
+        verbose: Verbosity level (0-4).
+        stdout: File to use for stdout.
+    """
+    global verbose, _progress, _color, _stdout, stdout_is_tty
+
+    verbose = _verbose
+    _progress = ''                    # Our last progress message
+    _color = terminal.Color()
+    _stdout = stdout
+
+    # TODO(sjg): Move this into Chromite libraries when we have them
+    stdout_is_tty = hasattr(sys.stdout, 'isatty') and sys.stdout.isatty()
+
+def Uninit():
+    ClearProgress()
+
+Init()