Refactor LogPrinter to make it immutable and remove logic from the constructor.

Signed-off-by: Daniel Nephin <dnephin@gmail.com>

compose/cli/log_printer.py

@@ -4,8 +4,6 @@ from __future__ import unicode_literals
 import sys
 from itertools import cycle
 
-from six import next
-
 from . import colors
 from .multiplexer import Multiplexer
 from .utils import split_buffer
@@ -13,82 +11,75 @@ from compose import utils
 
 
 class LogPrinter(object):
-    # TODO: move logic to run
+    """Print logs from many containers to a single output stream."""
+
     def __init__(self, containers, output=sys.stdout, monochrome=False):
         self.containers = containers
-        self.prefix_width = self._calculate_prefix_width(containers)
-        self.generators = self._make_log_generators(monochrome)
         self.output = utils.get_output_stream(output)
+        self.monochrome = monochrome
 
     def run(self):
-        mux = Multiplexer(self.generators)
+        if not self.containers:
-        for line in mux.loop():
+            return
+
+        prefix_width = max_name_width(self.containers)
+        generators = list(self._make_log_generators(self.monochrome, prefix_width))
+        for line in Multiplexer(generators).loop():
             self.output.write(line)
 
-    # TODO: doesn't use self, remove from class
+    def _make_log_generators(self, monochrome, prefix_width):
-    def _calculate_prefix_width(self, containers):
-        """
-        Calculate the maximum width of container names so we can make the log
-        prefixes line up like so:
-
-        db_1  | Listening
-        web_1 | Listening
-        """
-        prefix_width = 0
-        for container in containers:
-            prefix_width = max(prefix_width, len(container.name_without_project))
-        return prefix_width
-
-    def _make_log_generators(self, monochrome):
-        color_fns = cycle(colors.rainbow())
-        generators = []
-
         def no_color(text):
             return text
 
-        for container in self.containers:
+        if monochrome:
-            if monochrome:
+            color_funcs = cycle([no_color])
-                color_fn = no_color
+        else:
-            else:
+            color_funcs = cycle(colors.rainbow())
-                color_fn = next(color_fns)
-            generators.append(self._make_log_generator(container, color_fn))
 
-        return generators
+        for color_func, container in zip(color_funcs, self.containers):
-
+            generator_func = get_log_generator(container)
-    def _make_log_generator(self, container, color_fn):
+            prefix = color_func(build_log_prefix(container, prefix_width))
-        prefix = color_fn(self._generate_prefix(container))
+            yield generator_func(container, prefix, color_func)
-
-        if container.has_api_logs:
-            return build_log_generator(container, prefix, color_fn)
-        return build_no_log_generator(container, prefix, color_fn)
-
-    def _generate_prefix(self, container):
-        """
-        Generate the prefix for a log line without colour
-        """
-        name = container.name_without_project
-        padding = ' ' * (self.prefix_width - len(name))
-        return ''.join([name, padding, ' | '])
 
 
-def build_no_log_generator(container, prefix, color_fn):
+def build_log_prefix(container, prefix_width):
+    return container.name_without_project.ljust(prefix_width) + ' | '
+
+
+def max_name_width(containers):
+    """Calculate the maximum width of container names so we can make the log
+    prefixes line up like so:
+
+    db_1  | Listening
+    web_1 | Listening
+    """
+    return max(len(container.name_without_project) for container in containers)
+
+
+def get_log_generator(container):
+    if container.has_api_logs:
+        return build_log_generator
+    return build_no_log_generator
+
+
+def build_no_log_generator(container, prefix, color_func):
     """Return a generator that prints a warning about logs and waits for
     container to exit.
     """
     yield "{} WARNING: no logs are available with the '{}' log driver\n".format(
         prefix,
         container.log_driver)
-    yield color_fn(wait_on_exit(container))
+    yield color_func(wait_on_exit(container))
 
 
-def build_log_generator(container, prefix, color_fn):
+def build_log_generator(container, prefix, color_func):
     # Attach to container before log printer starts running
     stream = container.attach(stdout=True, stderr=True,  stream=True, logs=True)
     line_generator = split_buffer(stream, u'\n')
 
     for line in line_generator:
         yield prefix + line
-    yield color_fn(wait_on_exit(container))
+    yield color_func(wait_on_exit(container))
 
 
 def wait_on_exit(container):