Add queue completion method, add Printer discovery and types

src/printers.py

@@ -3,16 +3,129 @@ A collection of Printers.
 
 It has methods to discover printers, and provides an interface for the methods expected from printers.
 """
-
-from printer import Printer
+from collections.abc import Mapping, Set
+import usb.core
+import usb.util
+from printer import Printer, EscPosPrinter, BrotherPrinter, PrinterType
 
 class Printers():
     """
-    A collection of Printers
+    Finds and creates a set of Printer that can be used by the Workers to print.
     """
-    def __init__(self, name, age):
-        self.name = name
-        self.age = age
+    def __init__(self, app):
+        """
+        Discover printers connected to the computer and return a Collection of Printer()
+        """
+        self.app = app
+        self.printers = self._discover_printers()
 
-    def _discover_printers(self):
-        pass
+    def _discover_printers(self) -> Set[Printer]:
+        """
+        Gets connected USB printer devices using the pyusb library.
+
+        We analyse the USB devices, get the ones that match
+        the printer class ( 7 ) and for Brother and EPSON printers,
+        try to create a Printer object that can be used by the Worker class
+        to execute prints.
+
+        Returns a set of Printer
+        """
+
+        self.app.logger.debug("Discovering USB Devices connected to this system")
+
+        printers = set()
+
+        # Find all connected USB devices
+        devices = usb.core.find(find_all=True,custom_match=_FindClass(7))
+        if not devices:
+            self.app.logger.warning("No USB devices of class 7 ( printers ) found or pyusb could not access the bus.")
+            raise RuntimeError("No USB devices of class 7 ( printers ) found or pyusb could not access the bus.")
+
+        for dev in devices:
+            # Attempt to get the manufacturer and product strings
+            try:
+                manufacturer = usb.util.get_string(dev, dev.iManufacturer)
+            except Exception:
+                manufacturer = "Unknown"
+
+            try:
+                product = usb.util.get_string(dev, dev.iProduct)
+            except Exception:
+                product = "Unknown"
+            self.app.logger.debug("Looking at %s %s (%s:%s)", manufacturer, product, hex(dev.idVendor), hex(dev.idProduct))
+
+            if manufacturer == "EPSON":
+                try:
+                    # We create a new EscPosPrinter()
+                    self.app.logger.debug("Trying to creat a new EPSON printer")
+                    prid = dev.idProduct
+                    vendir = dev.idVendor
+                    escpos_printer = EscPosPrinter(self.app, vendor_id=vendir, device_id=prid)
+                except Exception as e:
+                    raise e
+
+                # If the object creation is successfull, we add it to the list of Printers
+                printers.add(escpos_printer)
+                self.app.logger.debug("Found a %s printer" % manufacturer )
+
+                # We already found the type of printer,
+                # we don't need an extra comparaison.
+                continue
+
+            # or a Brother Printer
+            if manufacturer == "Brother":
+                try:
+                    # We create a new BrotherPrinter()
+                    self.app.logger.debug("Trying to creat a new BROTHER printer")
+                    prid = dev.idProduct
+                    vendir = dev.idVendor
+                    brother_printer = BrotherPrinter(self.app, vendor_id=vendir,device_id=prid)
+                except Exception as e:
+                    self.app.logger.error("Could not create a %s printer class with %s:%s" % product, dev.idVendor, dev.idProduct)
+                    raise e
+
+                # If the object creation is successfull, we add it to the list of Printers
+                printers.add(brother_printer)
+                self.app.logger.debug("Found a %s printer" % manufacturer )
+
+        self.app.logger.debug("Found %s printers" % len(printers))
+        return printers
+
+    def any(self) -> Printer:
+        """
+        Return a dict key: UUID, value: Printer, with any connected printer.
+        """
+        if len(self.printers) > 0:
+            for i in self.printers:
+                return i
+        else:
+            raise RuntimeError("No printers available")
+
+    def get_printer(self, printer_type):
+        """
+        Return a specific printer
+
+        printer_type -- a printer type
+        """
+        return NotImplementedError()
+
+
+class _FindClass():
+    def __init__(self, class_):
+        self._class = class_
+    def __call__(self, device):
+        # first, let's check the device
+        if device.bDeviceClass == self._class:
+            return True
+        # ok, transverse all devices to find an
+        # interface that matches our class
+        for cfg in device:
+            # find_descriptor: what's it?
+            intf = usb.util.find_descriptor(
+                                        cfg,
+                                        bInterfaceClass=self._class
+                                )
+            if intf is not None:
+                return True
+
+        return False