Move preview to external file

1 files changed, 36 insertions, 0 deletions

diff --git a/cli/cli.py b/cli/cli.py
index 7a5c4bd0..ed2680f4 100644
--- a/cli/cli.py
+++ b/cli/cli.py
@@ -11,6 +11,8 @@ import fileinput
 
 import time
 
+import signal
+
 from config.config import *
 
 from utils import utils
@@ -319,3 +321,37 @@ def gen_deploy(args):
 
     generators.generate_blog(fresh=True)
     deploy(None)
+
+
+def preview(args):
+    """Serve the blog and auto regenerate upon changes."""
+
+    # pylint: disable=unused-argument
+
+    server_process = utils.HTTPServerProcess(BUILDDIR)
+    server_process.start()
+    sys.stderr.write("watching for changes\n")
+    sys.stderr.write("send SIGINT to stop\n")
+
+    # install a SIGINT handler only for this process
+    sigint_raised = False
+
+    def sigint_mitigator(signum, frame):
+        """Translate SIGINT to setting the sigint_raised flag."""
+        nonlocal sigint_raised
+        sigint_raised = True
+
+    signal.signal(signal.SIGINT, sigint_mitigator)
+
+    # Watch and auto-regen.
+    # No need to actually implement watch separately, since
+    # generate_blog(fresh=False, report_total_errors=False) already
+    # watches for modifications and only regens upon changes, and it is
+    # completely silent when there's no change.
+    while not sigint_raised:
+        generators.generate_blog(fresh=False, report_total_errors=False)
+        time.sleep(0.5)
+
+    sys.stderr.write("\nSIGINT received, cleaning up...\n")
+    server_process.join()
+    return 0