Added paper message generator

LXMF/LXMessage.py

@@ -2,6 +2,7 @@ import RNS
 import RNS.vendor.umsgpack as msgpack
 
 import time
+import base64
 
 from .LXMF import APP_NAME
 
@@ -22,7 +23,8 @@ class LXMessage:
     OPPORTUNISTIC      = 0x01
     DIRECT             = 0x02
     PROPAGATED         = 0x03
-    valid_methods      = [OPPORTUNISTIC, DIRECT, PROPAGATED]
+    PAPER              = 0x05
+    valid_methods      = [OPPORTUNISTIC, DIRECT, PROPAGATED, PAPER]
 
     SOURCE_UNKNOWN     = 0x01
     SIGNATURE_INVALID  = 0x02
@@ -76,6 +78,12 @@ class LXMessage:
     ENCRYPTION_DESCRIPTION_EC  = "Curve25519"
     ENCRYPTION_DESCRIPTION_UNENCRYPTED = "Unencrypted"
 
+    # Constants for QR/URL encoding LXMs
+    URL_PROTO_SPECIFIER = "lxm"
+    QR_ERROR_CORRECTION = "ERROR_CORRECT_L"
+    QR_MAX_STORAGE = 2953
+    PAPER_MDU = ((QR_MAX_STORAGE-(len(URL_PROTO_SPECIFIER)+len("://")))*6)//8
+
     def __str__(self):
         if self.hash != None:
             return "<LXMessage "+RNS.hexrep(self.hash, delimit=False)+">"
@@ -196,6 +204,7 @@ class LXMessage:
                 self.timestamp = time.time()
 
             self.propagation_packed = None
+            self.paper_packed = None
 
             self.payload = [self.timestamp, self.title, self.content, self.fields]
 
@@ -263,6 +272,19 @@ class LXMessage:
                     self.method = self.desired_method
                     self.representation = LXMessage.RESOURCE
 
+            elif self.desired_method == LXMessage.PAPER:
+                paper_content_limit = LXMessage.PAPER_MDU
+
+                encrypted_data = self.__destination.encrypt(self.packed[LXMessage.DESTINATION_LENGTH:])
+                self.paper_packed = msgpack.packb(self.packed[:LXMessage.DESTINATION_LENGTH]+encrypted_data)
+
+                content_size = len(self.paper_packed)
+                if content_size <= paper_content_limit:
+                    self.method = self.desired_method
+                    self.representation = LXMessage.PAPER
+                else:
+                    raise TypeError("LXMessage desired paper delivery method, but content exceeds paper message maximum size.")
+
         else:
             raise ValueError("Attempt to re-pack LXMessage "+str(self)+" that was already packed")
 
@@ -327,6 +349,16 @@ class LXMessage:
             else:
                 self.transport_encrypted = False
                 self.transport_encryption = LXMessage.ENCRYPTION_DESCRIPTION_UNENCRYPTED
+        elif self.method == LXMessage.PAPER:
+            if self.__destination.type == RNS.Destination.SINGLE:
+                self.transport_encrypted = True
+                self.transport_encryption = LXMessage.ENCRYPTION_DESCRIPTION_EC
+            elif self.__destination.type == RNS.Destination.GROUP:
+                self.transport_encrypted = True
+                self.transport_encryption = LXMessage.ENCRYPTION_DESCRIPTION_AES
+            else:
+                self.transport_encrypted = False
+                self.transport_encryption = LXMessage.ENCRYPTION_DESCRIPTION_UNENCRYPTED
         else:
             self.transport_encrypted = False
             self.transport_encryption = LXMessage.ENCRYPTION_DESCRIPTION_UNENCRYPTED
@@ -351,6 +383,16 @@ class LXMessage:
             except Exception as e:
                     RNS.log("An error occurred in the external delivery callback for "+str(message), RNS.LOG_ERROR)
 
+    def __mark_paper_generated(self, receipt = None):
+        RNS.log("Paper message generation succeeded for "+str(self), RNS.LOG_DEBUG)
+        self.state = LXMessage.PAPER
+
+        if self.__delivery_callback != None and callable(self.__delivery_callback):
+            try:
+                self.__delivery_callback(self)
+            except Exception as e:
+                    RNS.log("An error occurred in the external delivery callback for "+str(message), RNS.LOG_ERROR)
+
     def __resource_concluded(self, resource):
         if resource.status == RNS.Resource.COMPLETE:
             self.__mark_delivered()
@@ -441,6 +483,56 @@ class LXMessage:
             RNS.log("Error while writing LXMF message to file \""+str(file_path)+"\". The contained exception was: "+str(e), RNS.LOG_ERROR)
             return None
 
+    def as_url(self, finalise=True):
+        self.determine_transport_encryption()
+        if not self.packed:
+            self.pack()
+
+        if self.desired_method == LXMessage.PAPER and self.paper_packed != None:
+            # Encode packed LXM with URL-safe base64 and remove padding
+            encoded_bytes = base64.urlsafe_b64encode(self.paper_packed)
+
+            # Add protocol specifier and return
+            lxm_url = LXMessage.URL_PROTO_SPECIFIER+"://"+encoded_bytes.decode("utf-8").replace("=","")
+
+            # TODO: Remove
+            # RNS.log(str(len(lxm_url))+" byte LXM URL: "+str(lxm_url), RNS.LOG_EXTREME)
+
+            if finalise:
+                self.__mark_paper_generated()
+            
+            return lxm_url
+
+        else:
+            raise TypeError("Attempt to represent LXM with non-paper delivery method as URL")
+
+    def as_qr(self):
+        self.determine_transport_encryption()
+        if not self.packed:
+            self.pack()
+
+        if self.desired_method == LXMessage.PAPER and self.paper_packed != None:
+            import importlib
+            if importlib.util.find_spec('qrcode') != None:
+                import qrcode
+
+                qr = qrcode.make(
+                    error_correction = qrcode.constants.__dict__[LXMessage.QR_ERROR_CORRECTION],
+                    border = 1,
+                    data = self.as_url(finalise=False),
+                )
+
+                self.__mark_paper_generated()
+
+                return qr
+
+            else:
+                RNS.log("Generating QR-code representanions of LXMs requires the \"qrcode\" module to be installed.", RNS.LOG_CRITICAL)
+                RNS.log("You can install it with the command: python3 -m pip install qrcode", RNS.LOG_CRITICAL)
+                return None
+
+        else:
+            raise TypeError("Attempt to represent LXM with non-paper delivery method as QR-code")
 
     @staticmethod
     def unpack_from_bytes(lxmf_bytes):