fix(cli): lazy settings fetch and full device erase

Download settings only for --show or when applying edits; skip upload
when unchanged; erase entire device root including settings.json.

Co-authored-by: Cursor <cursoragent@cursor.com>

cli.py

@@ -2,8 +2,10 @@
 """
 LED Bar Configuration CLI Tool
 
-Command-line interface for downloading, editing, and uploading settings.json
-to/from MicroPython devices via mpremote.
+Command-line interface for editing settings.json on MicroPython devices via mpremote.
+Settings are downloaded from the device only when displaying (--show) or when applying
+setting changes; uploads occur only when something changed. Use --erase to clear the
+device filesystem (including settings).
 """
 
 import json
@@ -279,10 +281,13 @@ def main() -> None:
         formatter_class=argparse.RawDescriptionHelpFormatter,
         epilog="""
 Examples:
-  # Download and print current settings
+  # Show help (no device I/O)
   %(prog)s
 
-  # Download, edit device name and brightness, then upload
+  # Show current settings.json from device (read-only)
+  %(prog)s --show
+
+  # Edit device name and brightness, then upload only if values changed
   %(prog)s -n "LED-Strip-1" -b 128
 
   # Set multiple parameters
@@ -500,7 +505,7 @@ Examples:
         "-e", "--erase",
         dest="erase_all",
         action="store_true",
-        help="Erase all code on the device (delete all files except settings.json)"
+        help="Erase the device filesystem: delete all files and directories at device root (including settings.json and presets.json)",
     )
 
     parser.add_argument(
@@ -516,6 +521,9 @@ Examples:
     )
 
     try:
+        if len(sys.argv) <= 1:
+            parser.print_help()
+            return
         args = parser.parse_args()
         ordered_actions = _get_ordered_actions(sys.argv)
     except ValueError as e:
@@ -631,14 +639,12 @@ Examples:
 
         elif action_name == 'erase_all':
             try:
-                print(f"Erasing all code on device {port}...", file=sys.stderr)
+                print(f"Erasing device filesystem on {port}...", file=sys.stderr)
                 conn = DeviceConnection(port)
                 items = conn.list_files('')
                 for name, is_dir, size in items:
-                    if name == "settings.json":
-                        continue
                     conn.delete(name)
-                print("Erase complete.", file=sys.stderr)
+                print("Erase complete (device root is empty).", file=sys.stderr)
             except Exception as e:
                 print(f"Error erasing device: {e}", file=sys.stderr)
                 sys.exit(1)
@@ -735,40 +741,86 @@ Examples:
         # Clamp into single-byte range; store as int in settings.json
         edits["id"] = max(0, min(255, args.device_id))
 
-    # 1. Download: get current settings from device
-    try:
-        print(f"Downloading settings from {args.port}...", file=sys.stderr)
-        settings = download_settings(args.port)
-        print("Settings downloaded successfully.", file=sys.stderr)
-    except Exception as e:
-        if "timeout" in str(e).lower() or "connection" in str(e).lower():
-            print(f"Error: Connection timeout. Check device connection on {args.port}", file=sys.stderr)
-        else:
-            print(f"Error downloading settings: {e}", file=sys.stderr)
-        sys.exit(1)
+    settings_work = args.show or bool(edits)
+
+    if settings_work:
+        try:
+            print(f"Downloading settings from {args.port}...", file=sys.stderr)
+            settings = download_settings(args.port)
+            print("Settings downloaded successfully.", file=sys.stderr)
+        except Exception as e:
+            if "timeout" in str(e).lower() or "connection" in str(e).lower():
+                print(
+                    f"Error: Connection timeout. Check device connection on {args.port}",
+                    file=sys.stderr,
+                )
+            else:
+                print(f"Error downloading settings: {e}", file=sys.stderr)
+            sys.exit(1)
+
+        if args.show:
+            print_settings(settings)
+            if not edits and args.preset is None:
+                return
+
+        changed_edits: Dict[str, Any] = {}
+        for key, value in edits.items():
+            if settings.get(key) != value:
+                changed_edits[key] = value
+
+        if edits and not changed_edits:
+            print("No settings changes detected; skipping settings upload.", file=sys.stderr)
+
+        if changed_edits:
+            print(f"Applying {len(changed_edits)} setting change(s)...", file=sys.stderr)
+            settings.update(changed_edits)
 
-    # If --show only, print and exit (unless presets or settings are being written)
-    if args.show:
         print_settings(settings)
-        if not edits and args.preset is None:
-            return
 
-    # 2. Edit: only apply/upload settings when values actually change
-    changed_edits: Dict[str, Any] = {}
-    for key, value in edits.items():
-        if settings.get(key) != value:
-            changed_edits[key] = value
+        if args.preset is not None:
+            pattern = args.pattern if args.pattern is not None else "on"
+            try:
+                print(f"Downloading presets from {args.port}...", file=sys.stderr)
+                presets_data = download_presets(args.port)
+                entry = presets_data.get(args.preset)
+                if not isinstance(entry, dict):
+                    entry = {}
+                entry["p"] = pattern
+                presets_data[args.preset] = entry
+                print(
+                    f"Writing preset {args.preset!r} (pattern={pattern}) to {PRESETS_REMOTE}...",
+                    file=sys.stderr,
+                )
+                upload_presets(args.port, presets_data, reset=not bool(edits))
+                print("Presets uploaded successfully.", file=sys.stderr)
+                if not edits:
+                    print("Device will reset.", file=sys.stderr)
+            except Exception as e:
+                if "timeout" in str(e).lower() or "connection" in str(e).lower():
+                    print(
+                        f"Error: Connection timeout. Check device connection on {args.port}",
+                        file=sys.stderr,
+                    )
+                else:
+                    print(f"Error uploading presets: {e}", file=sys.stderr)
+                sys.exit(1)
 
-    if edits and not changed_edits:
-        print("No settings changes detected; skipping settings upload.", file=sys.stderr)
+        if changed_edits:
+            try:
+                print(f"\nUploading settings to {args.port}...", file=sys.stderr)
+                upload_settings(args.port, settings)
+                print("Settings uploaded successfully. Device will reset.", file=sys.stderr)
+            except Exception as e:
+                if "timeout" in str(e).lower() or "connection" in str(e).lower():
+                    print(
+                        f"Error: Connection timeout. Check device connection on {args.port}",
+                        file=sys.stderr,
+                    )
+                else:
+                    print(f"Error uploading settings: {e}", file=sys.stderr)
+                sys.exit(1)
+        return
 
-    if changed_edits:
-        print(f"Applying {len(changed_edits)} setting change(s)...", file=sys.stderr)
-        settings.update(changed_edits)
-
-    print_settings(settings)
-
-    # 3a. Presets file (led-driver presets.json)
     if args.preset is not None:
         pattern = args.pattern if args.pattern is not None else "on"
         try:
@@ -783,29 +835,24 @@ Examples:
                 f"Writing preset {args.preset!r} (pattern={pattern}) to {PRESETS_REMOTE}...",
                 file=sys.stderr,
             )
-            upload_presets(args.port, presets_data, reset=not bool(edits))
+            upload_presets(args.port, presets_data, reset=True)
             print("Presets uploaded successfully.", file=sys.stderr)
-            if not edits:
-                print("Device will reset.", file=sys.stderr)
+            print("Device will reset.", file=sys.stderr)
         except Exception as e:
             if "timeout" in str(e).lower() or "connection" in str(e).lower():
-                print(f"Error: Connection timeout. Check device connection on {args.port}", file=sys.stderr)
+                print(
+                    f"Error: Connection timeout. Check device connection on {args.port}",
+                    file=sys.stderr,
+                )
             else:
                 print(f"Error uploading presets: {e}", file=sys.stderr)
             sys.exit(1)
+        return
 
-    # 3b. Settings upload (resets device)
-    if changed_edits:
-        try:
-            print(f"\nUploading settings to {args.port}...", file=sys.stderr)
-            upload_settings(args.port, settings)
-            print("Settings uploaded successfully. Device will reset.", file=sys.stderr)
-        except Exception as e:
-            if "timeout" in str(e).lower() or "connection" in str(e).lower():
-                print(f"Error: Connection timeout. Check device connection on {args.port}", file=sys.stderr)
-            else:
-                print(f"Error uploading settings: {e}", file=sys.stderr)
-            sys.exit(1)
+    if ordered_actions:
+        return
+
+    parser.print_help()
 
 
 if __name__ == "__main__":