Toot toot, it's the refactor tractor

- Introduces the concept of a "BarcodeHandler"
- Re-uses most of the code
- Custom handlers for barcode success / failure

lib/barcode.dart

@@ -3,10 +3,6 @@ import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
 import 'package:font_awesome_flutter/font_awesome_flutter.dart';
 
-//import 'package:qr_utils/qr_utils.dart';
-//import 'package:flutter_barcode_scanner/flutter_barcode_scanner.dart';
-//import 'package:barcode_scan/barcode_scan.dart';
-
 import 'package:qr_code_scanner/qr_code_scanner.dart';
 
 import 'package:InvenTree/inventree/stock.dart';
@@ -22,179 +18,288 @@ import 'package:InvenTree/widget/stock_detail.dart';
 import 'dart:convert';
 
 
-class InvenTreeQRView extends StatefulWidget {
+class BarcodeHandler {
+  /**
+   * Class which "handles" a barcode, by communicating with the InvenTree server,
+   * and handling match / unknown / error cases.
+   *
+   * Override functionality of this class to perform custom actions,
+   * based on the response returned from the InvenTree server
+   */
 
-  InvenTreeQRView({Key key}) : super(key: key);
+    BarcodeHandler();
 
-  @override
+    QRViewController _controller;
-  State<StatefulWidget> createState() => _QRViewState();
+    BuildContext _context;
-}
 
 
-class _QRViewState extends State<InvenTreeQRView> {
+    Future<void> onBarcodeMatched(Map<String, dynamic> data) {
+      // Called when the server "matches" a barcode
+      // Override this function
+    }
 
-  QRViewController _controller;
+    Future<void> onBarcodeUnknown(Map<String, dynamic> data) {
+      // Called when the server does not know about a barcode
+      // Override this function
+    }
 
-  BuildContext context;
+    Future<void> onBarcodeUnhandled(Map<String, dynamic> data) {
+      // Called when the server returns an unhandled response
+      showErrorDialog(
+          _context,
+          "Response Data",
+          data.toString(),
+          error: "Unknown Response",
+          onDismissed: () {
+            _controller.resumeCamera();
+          }
+      );
+    }
 
-  _QRViewState() : super();
+    Future<void> processBarcode(BuildContext context, QRViewController _controller, String barcode) {
+      this._context = context;
+      this._controller = _controller;
 
-  final GlobalKey qrKey = GlobalKey(debugLabel: 'QR');
+      print("Scanned barcode data: ${barcode}");
+      showProgressDialog(context, "Scanning", "Sending barcode data to server");
 
-  // Callback when the server repsonds with a match for the barcode
+      // Send barcode request to server
-  Future<void> onBarcodeMatched(Map<String, dynamic> response) {
+      InvenTreeAPI().post(
+          "barcode/",
+          body: {
+            "barcode": barcode
+          }
+      ).then((var response) {
+        hideProgressDialog(context);
+
+        if (response.statusCode != 200) {
+          showErrorDialog(
+            context,
+            "Status Code: ${response.statusCode}",
+            "${response.body
+                .toString()
+                .split('\n')
+                .first}",
+            onDismissed: () {
+              _controller.resumeCamera();
+            },
+            error: "Server Error",
+            icon: FontAwesomeIcons.server,
+          );
+
+          return;
+        }
+
+        // Decode the response
+        final Map<String, dynamic> data = json.decode(response.body);
+
+        if (data.containsKey('error')) {
+          onBarcodeUnknown(data);
+        } else if (data.containsKey('success')) {
+          onBarcodeMatched(data);
+        } else {
+          onBarcodeUnhandled(data);
+        }
+      }).timeout(
+          Duration(seconds: 5)
+      ).catchError((error) {
+        hideProgressDialog(context);
+        showErrorDialog(
+            context,
+            "Error",
+            error.toString(),
+            onDismissed: () {
+              _controller.resumeCamera();
+            }
+        );
+        return;
+      });
+    }
+}
+
+
+class BarcodeScanHandler extends BarcodeHandler {
+  /**
+   * Class for general barcode scanning.
+   * Scan *any* barcode without context, and then redirect app to correct view
+   */
+
+  @override
+  Future<void> onBarcodeUnknown(Map<String, dynamic> data) {
+    showErrorDialog(
+        _context,
+        data['error'] ?? '',
+        data['plugin'] ?? 'No barcode plugin information',
+        error: "Barcode Error",
+        icon: FontAwesomeIcons.barcode,
+        onDismissed: () {
+          _controller.resumeCamera();
+        }
+    );
+  }
+
+  @override
+  Future<void> onBarcodeMatched(Map<String, dynamic> data) {
     int pk;
 
     print("Handle barcode:");
-    print(response);
+    print(data);
 
     // A stocklocation has been passed?
-    if (response.containsKey('stocklocation')) {
+    if (data.containsKey('stocklocation')) {
 
-      pk = response['stocklocation']['pk'] as int ?? null;
+      pk = data['stocklocation']['pk'] as int ?? null;
 
       if (pk != null) {
-        InvenTreeStockLocation().get(context, pk).then((var loc) {
+        InvenTreeStockLocation().get(_context, pk).then((var loc) {
           if (loc is InvenTreeStockLocation) {
-            Navigator.of(context).pop();
+            Navigator.of(_context).pop();
-            Navigator.push(context, MaterialPageRoute(builder: (context) => LocationDisplayWidget(loc)));
+            Navigator.push(_context, MaterialPageRoute(builder: (context) => LocationDisplayWidget(loc)));
           }
         });
       } else {
         // TODO - Show an error here!
       }
 
-    } else if (response.containsKey('stockitem')) {
+    } else if (data.containsKey('stockitem')) {
 
-      pk = response['stockitem']['pk'] as int ?? null;
+      pk = data['stockitem']['pk'] as int ?? null;
 
       if (pk != null) {
-        InvenTreeStockItem().get(context, pk).then((var item) {
+        InvenTreeStockItem().get(_context, pk).then((var item) {
-          Navigator.of(context).pop();
+          Navigator.of(_context).pop();
-          Navigator.push(context, MaterialPageRoute(builder: (context) => StockDetailWidget(item)));
+          Navigator.push(_context, MaterialPageRoute(builder: (context) => StockDetailWidget(item)));
         });
       } else {
         // TODO - Show an error here!
       }
-    } else if (response.containsKey('part')) {
+    } else if (data.containsKey('part')) {
 
-      pk = response['part']['pk'] as int ?? null;
+      pk = data['part']['pk'] as int ?? null;
 
       if (pk != null) {
-        InvenTreePart().get(context, pk).then((var part) {
+        InvenTreePart().get(_context, pk).then((var part) {
-          Navigator.of(context).pop();
+          Navigator.of(_context).pop();
-          Navigator.push(context, MaterialPageRoute(builder: (context) => PartDetailWidget(part)));
+          Navigator.push(_context, MaterialPageRoute(builder: (context) => PartDetailWidget(part)));
         });
       } else {
         // TODO - Show an error here!
       }
     } else {
       showDialog(
-          context: context,
+          context: _context,
           child: SimpleDialog(
             title: Text("Unknown response"),
             children: <Widget>[
               ListTile(
                 title: Text("Response data"),
-                subtitle: Text(response.toString()),
+                subtitle: Text(data.toString()),
               )
             ],
           )
       );
     }
   }
+}
+
+
+class StockItemBarcodeAssignmentHandler extends BarcodeHandler {
+  /**
+   * Barcode handler for assigning a new barcode to a stock item
+   */
+
+  final InvenTreeStockItem item;
+
+  StockItemBarcodeAssignmentHandler(this.item);
 
-  // Callback when the server responds with no match for the barcode
+  @override
-  Future<void> onBarcodeUnknown(Map<String, dynamic> response) {
+  Future<void> onBarcodeMatched(Map<String, dynamic> data) {
+    // If the barcode is known, we can't asisgn it to the stock item!
     showErrorDialog(
-        context,
+      _context,
-        response['error'] ?? '',
+      "Barcode in Use",
-        response['plugin'] ?? 'No barcode plugin information',
+      "Barcode is already known",
-        error: "Barcode Error",
+      onDismissed: () {
-        icon: FontAwesomeIcons.barcode,
+        _controller.resumeCamera();
-        onDismissed: () {
+      }
-          _controller.resumeCamera();
-        }
     );
   }
 
-  // Callback when the server responds with an unhandled response
+  @override
-  Future<void> onBarcodeUnhandled(Map<String, dynamic> response) {
+  Future<void> onBarcodeUnknown(Map<String, dynamic> data) {
-    showErrorDialog(
+    // If the barcode is unknown, we *can* assign it to the stock item!
-        context,
+
-        "Response Data",
+    if (!data.containsKey("hash")) {
-        response.toString(),
+      showErrorDialog(
-        error: "Unknown Response",
+        _context,
+        "Missing Data",
+        "Missing hash data from server",
         onDismissed: () {
-        _controller.resumeCamera();
+          _controller.resumeCamera();
         }
-    );
+      );
+    } else {
+      // Send the 'hash' code as the UID for the stock item
+      item.update(
+        _context,
+        values: {
+          "uid": data['hash'],
+        }
+      ).then((result) {
+        if (result) {
+          showInfoDialog(
+              _context,
+              "Barcode Set",
+              "Barcode assigned to stock item",
+              onDismissed: () {
+                _controller.dispose();
+                Navigator.of(_context).pop();
+              }
+          );
+        } else {
+          showErrorDialog(
+            _context,
+            "Server Error",
+            "Could not assign barcode",
+            onDismissed: () {
+              _controller.resumeCamera();
+            }
+          );
+        }
+      });
+    }
   }
+}
 
-  Future<void> processBarcode(String barcode) async {
-    if (barcode == null || barcode.isEmpty) {
-      return;
-    }
 
-    print("Scanned: ${barcode}");
+class InvenTreeQRView extends StatefulWidget {
-    showProgressDialog(context, "Querying server", "Sending barcode data to server");
 
-    InvenTreeAPI().post("barcode/", body: {"barcode": barcode}).then((var response) {
+  final BarcodeHandler _handler;
-      hideProgressDialog(context);
 
-      print("Response:");
+  InvenTreeQRView(this._handler, {Key key}) : super(key: key);
-      print(response.body);
 
-      if (response.statusCode != 200) {
+  @override
+  State<StatefulWidget> createState() => _QRViewState(_handler);
+}
 
-        showErrorDialog(
-          context,
-          "Status Code: ${response.statusCode}",
-          "${response.body.toString().split('\n').first}",
-          onDismissed: () {
-            _controller.resumeCamera();
-          },
-          error: "Server Error",
-          icon: FontAwesomeIcons.server,
-        );
 
-        return;
+class _QRViewState extends State<InvenTreeQRView> {
-      }
 
-      // Decode the response
+  QRViewController _controller;
-      final Map<String, dynamic> body = json.decode(response.body);
 
-      // "Error" contained in response
+  final BarcodeHandler _handler;
-      if (body.containsKey('error')) {
-        onBarcodeUnknown(body);
-      } else if (body.containsKey('success')) {
-        onBarcodeMatched(body);
-      } else {
-        onBarcodeUnhandled(body);
-      }
 
-    }).timeout(
+  BuildContext context;
-        Duration(seconds: 5)
-    ).catchError((error) {
-      hideProgressDialog(context);
-      showErrorDialog(
-        context,
-        "Error",
-        error.toString(),
-        onDismissed: () {
-          _controller.resumeCamera();
-        }
-      );
-      return;
-    });
 
-  }
+  _QRViewState(this._handler) : super();
+
+  final GlobalKey qrKey = GlobalKey(debugLabel: 'QR');
 
   void _onViewCreated(QRViewController controller) {
     _controller = controller;
     controller.scannedDataStream.listen((scandata) {
       _controller?.pauseCamera();
-      processBarcode(scandata);
+      _handler.processBarcode(context, _controller, scandata);
     });
   }
 
@@ -236,7 +341,7 @@ class _QRViewState extends State<InvenTreeQRView> {
 
 Future<void> scanQrCode(BuildContext context) async {
 
-  Navigator.push(context, MaterialPageRoute(builder: (context) => InvenTreeQRView()));
+  Navigator.push(context, MaterialPageRoute(builder: (context) => InvenTreeQRView(BarcodeScanHandler())));
 
   return;
 }

lib/inventree/stock.dart

@@ -168,6 +168,8 @@ class InvenTreeStockItem extends InvenTreeModel {
     return false;
   }
 
+  String get uid => jsondata['uid'] ?? '';
+
   int get partId => jsondata['part'] ?? -1;
 
   int get trackingItemCount => jsondata['tracking_items'] as int ?? 0;

lib/widget/dialogs.dart

@@ -9,6 +9,28 @@ void showMessage(BuildContext context, String message) {
   ));
 }
 
+Future<void> showInfoDialog(BuildContext context, String title, String description, {IconData icon = FontAwesomeIcons.info, String info = "Info", Function onDismissed}) async {
+  showDialog(
+    context: context,
+    child: SimpleDialog(
+      title: ListTile(
+        title: Text(info),
+        leading: FaIcon(icon),
+      ),
+      children: <Widget>[
+        ListTile(
+          title: Text(title),
+          subtitle: Text(description)
+        )
+      ]
+    )
+  ).then((value) {
+    if (onDismissed != null) {
+      onDismissed();
+    }
+  });
+}
+
 Future<void> showErrorDialog(BuildContext context, String title, String description, {IconData icon = FontAwesomeIcons.exclamationCircle, String error = "Error", Function onDismissed}) async {
   showDialog(
     context: context,

lib/widget/stock_detail.dart

@@ -1,5 +1,6 @@
 
 
+import 'package:InvenTree/barcode.dart';
 import 'package:InvenTree/inventree/stock.dart';
 import 'package:InvenTree/inventree/part.dart';
 import 'package:InvenTree/widget/dialogs.dart';
@@ -374,9 +375,22 @@ class _StockItemDisplayState extends RefreshableState<StockDetailWidget> {
             trailing: Text("${item.quantity}"),
           )
       );
-
     }
 
+    tiles.add(
+      ListTile(
+        title: Text("Add Barcode"),
+        leading: FaIcon(FontAwesomeIcons.qrcode),
+        onTap: () {
+          Navigator.push(
+            context,
+            MaterialPageRoute(builder: (context) => InvenTreeQRView(StockItemBarcodeAssignmentHandler(item)))  
+          );
+          //Navigator.push(context, MaterialPageRoute(builder: (context) => AssignBarcodeToStockItemView(item)));
+        },
+      )
+    );
+
     // Location information
     if ((item.locationId > 0) && (item.locationName != null) && (item.locationName.isNotEmpty)) {
       tiles.add(