Add template {{random[:len]}} with optional length specifier

Signed-off-by: DL6ER <[email protected]>

Author: DL6ER

README.md

@@ -96,6 +96,15 @@ Additional printer support comes from [matmair/brother_ql-inventree](https://git
 -   Dockerized
 -   Devcontainer for ease of development/contributing
 
+### Supported templates
+
+-   `{{counter}}` — Inserts the current counter value (automatically increments when printing multiple labels at the same time).
+-   `{{datetime:<format>}}` — Inserts the current date and time, e.g. `%H:%M:%S %d.%m.%Y` (see [strftime](https://strftime.org/)).
+-   `{{uuid}}` — Inserts a random UUID (Universally Unique Identifier).
+-   `{{short-uuid}}` — Inserts a shortened version of a UUID.
+-   `{{env:var}}` — Inserts the value of the environment variable `var`.
+-   `{{random[:<len>]}}` — Inserts a random string of optional length `len` (defaulting to 64).
+
 ## Docker Compose
 
 You may also use the example [`docker-compose.yml`](./docker-compose.yml) file provided in this repository to quickly get started with Docker Compose:

app/labeldesigner/label.py

@@ -8,6 +8,8 @@
 from barcode.writer import ImageWriter
 import datetime
 import re
+import random
+import string
 
 logger = logging.getLogger(__name__)
 
@@ -175,6 +177,9 @@ def process_templates(self):
         # {{counter}} by an incrementing counter
         self.text = self.input_text.copy()
         for line in self.text:
+            if len(line['text']) > 500:
+                logger.warning("Text line is very long (> 500 characters), this may lead to long processing times.")
+
             # Replace {{counter}} with current counter value
             line['text'] = line['text'].replace("{{counter}}", str(self._counter))
 
@@ -186,9 +191,7 @@ def datetime_replacer(match):
                 else:
                     now = datetime.datetime.now()
                 return now.strftime(fmt)
-            # Performance issue mitigation
-            if len(line['text']) < 100:
-                line['text'] = re.sub(r"\{\{datetime:([^}]+)\}\}", datetime_replacer, line['text'])
+            line['text'] = re.sub(r"\{\{datetime:([^}]+)\}\}", datetime_replacer, line['text'])
 
             # Replace {{uuid}} with a new UUID
             if "{{uuid}}" in line['text']:
@@ -202,9 +205,13 @@ def datetime_replacer(match):
             def env_replacer(match):
                 var_name = match.group(1)
                 return os.getenv(var_name, "")
-            # Performance issue mitigation
-            if len(line['text']) < 100:
-                line['text'] = re.sub(r"\{\{env:([^}]+)\}\}", env_replacer, line['text'])
+            line['text'] = re.sub(r"\{\{env:([^}]+)\}\}", env_replacer, line['text'])
+
+            # Replace {{random[:len]}} with random string of optional length <len>
+            def random_replacer(match):
+                length = int(match.group(1)) if match.group(1) else 64
+                return ''.join(random.choices(string.ascii_letters + string.digits + string.punctuation, k=length))
+            line['text'] = re.sub(r"\{\{random(?:\:(\d+))?\}\}", random_replacer, line['text'])
 
         # Increment counter
         self._counter += 1

app/labeldesigner/templates/labeldesigner.html

@@ -360,8 +360,8 @@ <h6>Additional Font Options:</h6>
                             </li>
                             <li><code>{{'{{uuid'}}}}</code> — Inserts a random UUID (Universally Unique Identifier).</li>
                             <li><code>{{'{{short-uuid'}}}}</code> — Inserts a shortened version of a UUID.</li>
-                            <li><code>{{'{{env:var}}'}}</code> — Inserts the value of the environment variable <code>var</code>.
-                            </li>
+                            <li><code>{{'{{env:var}}'}}</code> — Inserts the value of the environment variable <code>var</code>.</li>
+                            <li><code>{{'{{random[:len]}}'}}</code> — Inserts a random string of optional length <code>len</code> (defaulting to 64).</li>
                         </ul>
                         <span class="text-muted">Templates are replaced at print time.</span>
                     </div>