Implement continuous Python Daemon

1 files changed, 43 insertions, 10 deletions

diff --git a/python/birdscan/__main__.py b/python/birdscan/__main__.py
index 71ba294..862ec1b 100644
--- a/python/birdscan/__main__.py
+++ b/python/birdscan/__main__.py
@@ -10,25 +10,58 @@ This is the main executable of the birdscan package.
 
 import sys
 import time
+import socket
+import argparse
 
 
 def main():
     """Main function of this module"""
 
-    if len(sys.argv) == 2:  # check if argument is given (--debug)
-        time.sleep(1)
-        sys.stdout.write("ok\n")
-    else:
+    # parse command line args
+    parser = argparse.ArgumentParser()
+    parser.add_argument("-d", "--debug", action="store_true", help="For use in development environment")
+    parser.add_argument("-s", "--socket", default="/dev/null", type=str, help="Unix domain socket path for IPC")
+    args = parser.parse_args()
+
+    # prepare camera if on production system
+    if not args.debug:
         from picamera import PiCamera
         camera = PiCamera()
         camera.resolution = "3280x2464"
         camera.start_preview()
-        # Camera warm-up time
-        time.sleep(2)
-        camera.capture("/var/lib/birdscan/{}.jpg".format(
-            time.strftime("%Y-%m-%d_%H-%M-%S", time.localtime()))
-        )
-        sys.stdout.write("ok\n")
+    time.sleep(2)  # camera warm-up time
+
+    # connect to IPC socket
+    sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+    sock.connect(args.socket)
+    sock.send("picamera\n".encode())  # register this service
+
+    # main loop for Python background service
+    while True:
+        cmd = read_line(sock)
+        if cmd == "single_picture":
+            if args.debug:
+                time.sleep(1)
+                sock.send("single_picture_taken\n".encode())
+            else:
+                camera.capture("/var/lib/birdscan/{}.jpg".format(
+                    time.strftime("%Y-%m-%d_%H-%M-%S", time.localtime()))
+                )
+                sock.send("single_picture_taken\n".encode())
+        elif cmd == "":
+            pass
+        else:
+            sock.send("unknown_command\n".encode())
+
+def read_line(socket):
+    data = b""
+    while True:
+        byte = socket.recv(1)
+        if byte == b"\n":
+            break
+        else:
+            data += byte
+    return data.decode()
 
 
 if __name__ == "__main__":