udev-device-plug-handler: Handle Canon LiDE400

When this scanner is plugged in, we want to start `scanimage` in batch
mode with button support, scanning into a pre-defined directory. Since
plug and unplug might happen multiple times a day and batch mode
overwrites files with the same name, we use date and time to define
directory and filename.

udev-device-plug-handler/udev-device-plug-handler

@@ -1,5 +1,7 @@
 #!/usr/bin/env python3
+from datetime import datetime
 import inspect
+from pathlib import Path
 import subprocess
 from typing import Dict, List, Optional, Union
 
@@ -96,6 +98,61 @@ class UsbLogitechG930(KnownDevice):
         print("Handled Logitech G930 Headset")
 
 
+class CanonLIDE400(KnownDevice):
+    """Represents our 2023-bought Canon flatbed scanner"""
+    UDEV_PROPS = {'PRODUCT': '4a9/1912/100'}
+
+    __process = None
+
+    @staticmethod
+    def check_available() -> bool:
+        cmd = "lsusb | grep 'LiDE 400'"
+        cp = subprocess.run(cmd, shell=True, stdout=subprocess.DEVNULL)
+        return cp.returncode == 0
+
+    @staticmethod
+    def handle_bind(device: Optional[pyudev.Device] = None) -> None:
+        if CanonLIDE400.__process is not None:
+            # in theory, uplugging the Scanner should have terminated/killed the process, but if something went wrong,
+            # we just try to kill it and proceed
+            CanonLIDE400.__process.kill()
+
+        now = datetime.now()
+        directory = Path('/srv/paperless/later/scanned/') / now.strftime('%Y-%m-%d')
+        # directory = Path('/home/joker/tmp/scanned/') / now.strftime('%Y-%m-%d')
+        directory.mkdir(exist_ok=True)
+
+        # TODO read config from ~/.config/udev-device-plug-handler/
+        # How should that look like? Directory list of arguments? Would be easiest and we just default to something.
+        # Could be nice to read the directory from there, too.
+        cmd = [
+            'scanimage',
+            '-d', 'pixma:04A91912_4B9054',
+            '-l', '0mm',
+            '-t', '0mm',
+            '-x', '210mm',
+            '-y', '297mm',
+            '--mode=Color',
+            '--resolution', '300dpi',
+            '--button-controlled=yes',
+            # '-p',  # progress
+            f"--batch=scan_{now.strftime('%H%M%S')}_%04d.pnm"
+        ]
+        CanonLIDE400.__process = subprocess.Popen(cmd, stdout=subprocess.DEVNULL, cwd=directory)
+        print("Handled Canon LiDE 400")
+
+    @staticmethod
+    def handle_remove(device: pyudev.Device) -> None:
+        if CanonLIDE400.__process is not None:
+            p = CanonLIDE400.__process
+            p.terminate()
+            try:
+                p.wait(timeout=3)
+            except subprocess.TimeoutExpired:
+                p.kill()
+        print("Handled Canon LiDE 400 unplug")
+
+
 @click.command()
 @click.option('--debug', is_flag=True, help='Show all device changes instead of only handled.')
 def main(debug: bool) -> None: