add .env.example and update README for environment variable configuration

videoplayer.py

@@ -11,12 +11,18 @@ play videos from different camera views.
 
 import os
 import re
+
+from dotenv import load_dotenv
 from flask import Flask, render_template, send_from_directory, abort
 
+# Load variables from a .env file if present (does not override real env vars)
+load_dotenv()
+
 app = Flask(__name__)
 
 # Root TeslaCam directory containing RecentClips, SavedClips, SentryClips, etc.
-TESLACAM_DIRECTORY = '/mnt/TeslaCam'
+# Override via the TESLACAM_DIRECTORY environment variable (see .env.example).
+TESLACAM_DIRECTORY = os.environ.get('TESLACAM_DIRECTORY', '/mnt/TeslaCam')
 
 # Regular expression matching TeslaCam filenames: YYYY-MM-DD_HH-MM-SS-${camera_view}.mp4
 VIDEO_FILENAME_REGEX = re.compile(
@@ -132,5 +138,11 @@ def serve_video(filepath):
 
 
 if __name__ == '__main__':
-    host = '0.0.0.0'
-    app.run(debug=True, host=host, port=5000)
+    # Local dev server. For production, run behind a WSGI server instead, e.g.:
+    #   gunicorn -w 4 -b 0.0.0.0:5000 'videoplayer:app'
+    # or
+    #   waitress-serve --host=0.0.0.0 --port=5000 videoplayer:app
+    host = os.environ.get('FLASK_RUN_HOST', '0.0.0.0')
+    port = int(os.environ.get('FLASK_RUN_PORT', '5000'))
+    debug = os.environ.get('FLASK_DEBUG', '0').lower() in ('1', 'true', 'yes')
+    app.run(debug=debug, host=host, port=port)