feat: add dynamic printer configuration manager

Co-authored-by: aider (openai/DeepSeek-V3.2-Thinking) <aider@aider.chat>

inventory-backend/app/services/print/print_config.py

@@ -0,0 +1,61 @@
+import json
+import os
+from pathlib import Path
+
+class PrintConfigManager:
+    CONFIG_FILENAME = 'printer_config.json'
+    DEFAULT_CONFIG = {
+        'label_printer': {'ip': '192.168.9.221', 'port': 9100},
+        'network_printer': {'ip': '192.168.9.250', 'port': 9100}
+    }
+
+    @classmethod
+    def _get_config_path(cls):
+        # Determine the path relative to this file's directory
+        current_dir = Path(__file__).parent
+        return current_dir / cls.CONFIG_FILENAME
+
+    @classmethod
+    def get_config(cls, printer_type='label_printer'):
+        """
+        Retrieve configuration for a given printer type.
+        Returns a dict with 'ip' and 'port'.
+        """
+        config_path = cls._get_config_path()
+        if not config_path.exists():
+            # Write default config if not exists
+            cls.save_config(cls.DEFAULT_CONFIG)
+            config = cls.DEFAULT_CONFIG
+        else:
+            try:
+                with open(config_path, 'r', encoding='utf-8') as f:
+                    config = json.load(f)
+            except Exception as e:
+                print(f"Error reading printer config: {e}")
+                config = cls.DEFAULT_CONFIG
+        # Return specific printer config, falling back to default for that type
+        printer_config = config.get(printer_type, cls.DEFAULT_CONFIG.get(printer_type))
+        # Ensure it's a dict with ip and port
+        if not printer_config or 'ip' not in printer_config:
+            printer_config = cls.DEFAULT_CONFIG.get(printer_type, {'ip': '127.0.0.1', 'port': 9100})
+        return printer_config
+
+    @classmethod
+    def save_config(cls, new_config):
+        """
+        Save entire config dictionary to file.
+        new_config should be a dict with keys 'label_printer' and/or 'network_printer'.
+        """
+        config_path = cls._get_config_path()
+        try:
+            # If file exists, merge existing with new
+            existing = {}
+            if config_path.exists():
+                with open(config_path, 'r', encoding='utf-8') as f:
+                    existing = json.load(f)
+            existing.update(new_config)
+            with open(config_path, 'w', encoding='utf-8') as f:
+                json.dump(existing, f, indent=2)
+        except Exception as e:
+            print(f"Error saving printer config: {e}")
+            raise