Added Combined new/edit and view product screen

Similarily to categories and rooms,
the edit product screen is reused as a new-room screen,
which is especially easy, because the user is unable to select
the product id themselves.
NOTE: the dynamic value-unit input is still missing some "subunits"

The view product screen has links to the edit product page,
the view parent page (if available) and a not yet functional
view children screen.
NOTE: The parent product display should be restricted in width,
and the screen is missing value/unit information.

lib/backend/room.dart

@@ -127,32 +127,32 @@ class RoomIcon {
   String get text {
     switch (type.toLowerCase()) {
       case 'love':
-      return 'Friends';
+        return 'Friends';
       case 'sports':
-      return 'Sports';
+        return 'Sports';
       case 'pets':
-      return 'Pets';
+        return 'Pets';
       case 'vacation':
-      return 'Vacation';
+        return 'Vacation';
       case 'gifts':
-      return 'Gifts';
+        return 'Gifts';
       case 'groceries':
-      return 'Groceries';
+        return 'Groceries';
       case 'fashion':
-      return 'Clothing';
+        return 'Clothing';
       case 'art':
-      return 'Arts & Crafts';
+        return 'Arts & Crafts';
       case 'tech':
-      return 'Electronics';
+        return 'Electronics';
       case 'home':
-      return 'Home supplies';
+        return 'Home supplies';
       case 'family':
-      return 'Family';
+        return 'Family';
       case 'social':
-      return 'Social';
+        return 'Social';
       case 'other':
       default:
-      return 'Other';
+        return 'Other';
     }
   }
 
@@ -161,44 +161,44 @@ class RoomIcon {
     String path = "";
     switch (type.toLowerCase()) {
       case 'love':
-      path = 'undraw/undraw_couple.svg';
+        path = 'undraw/undraw_couple.svg';
-      break;
+        break;
       case 'sports':
-      path = 'undraw/undraw_greek_freak.svg';
+        path = 'undraw/undraw_greek_freak.svg';
-      break;
+        break;
       case 'pets':
-      path = 'undraw/undraw_dog.svg';
+        path = 'undraw/undraw_dog.svg';
-      break;
+        break;
       case 'vacation':
-      path = 'undraw/undraw_trip.svg';
+        path = 'undraw/undraw_trip.svg';
-      break;
+        break;
       case 'gifts':
-      path = 'undraw/undraw_gifts.svg';
+        path = 'undraw/undraw_gifts.svg';
-      break;
+        break;
       case 'groceries':
-      path = 'undraw/undraw_gone_shopping.svg';
+        path = 'undraw/undraw_gone_shopping.svg';
-      break;
+        break;
       case 'fashion':
-      path = 'undraw/undraw_jewelry.svg';
+        path = 'undraw/undraw_jewelry.svg';
-      break;
+        break;
       case 'art':
-      path = 'undraw/undraw_sculpting.svg';
+        path = 'undraw/undraw_sculpting.svg';
-      break;
+        break;
       case 'tech':
-      path = 'undraw/undraw_progressive_app.svg';
+        path = 'undraw/undraw_progressive_app.svg';
-      break;
+        break;
       case 'home':
-      path = 'undraw/undraw_under_construction.svg';
+        path = 'undraw/undraw_under_construction.svg';
-      break;
+        break;
       case 'family':
-      path = 'undraw/undraw_family.svg';
+        path = 'undraw/undraw_family.svg';
-      break;
+        break;
       case 'social':
-      path = 'undraw/undraw_pizza_sharing.svg';
+        path = 'undraw/undraw_pizza_sharing.svg';
-      break;
+        break;
       case 'other':
       default:
-      path = 'undraw/undraw_file_manager.svg';
+        path = 'undraw/undraw_file_manager.svg';
     }
 
     return asset(path);
@@ -214,7 +214,7 @@ class Room {
   RoomVisibility? visibility = RoomVisibility.private;
 
   Room(
-    {required this.id,
+      {required this.id,
       required this.serverTag,
       this.name = "",
       this.description = "",
@@ -263,12 +263,12 @@ class Room {
 
   factory Room.fromMap(Map<String, dynamic> map) {
     return Room(
-      id: map['id'],
+        id: map['id'],
-      serverTag: map['server'],
+        serverTag: map['server'],
-      name: map['name'],
+        name: map['name'],
-      description: map['description'] ?? '',
+        description: map['description'] ?? '',
-      icon: RoomIcon(type: map['icon'] ?? 'Other'),
+        icon: RoomIcon(type: map['icon'] ?? 'Other'),
-      visibility: RoomVisibility(map['visibility'] ?? 0));
+        visibility: RoomVisibility(map['visibility'] ?? 0));
   }
 
   Map<String, dynamic> toMap() {
@@ -284,12 +284,12 @@ class Room {
 
   factory Room.fromJSON(dynamic json) {
     return Room(
-      id: json['name'],
+        id: json['name'],
-      serverTag: json['server'],
+        serverTag: json['server'],
-      name: json['title'],
+        name: json['title'],
-      description: json['description'],
+        description: json['description'],
-      icon: RoomIcon(type: json['icon']),
+        icon: RoomIcon(type: json['icon']),
-      visibility: RoomVisibility(json['visibility']));
+        visibility: RoomVisibility(json['visibility']));
   }
 
   Future<void> toDisk() async {
@@ -308,7 +308,7 @@ class Room {
   }
 
   static Future<Room> fromDisk(
-    {required String id, required String serverTag}) async {
+      {required String id, required String serverTag}) async {
     final db = Localstore.instance;
     final raw = await db.collection('rooms').doc('$id@$serverTag').get();
     return Room.fromMap(raw!);
@@ -321,13 +321,13 @@ class RoomMember {
   final bool isAdmin;
 
   const RoomMember(
-    {required this.id, required this.serverTag, required this.isAdmin});
+      {required this.id, required this.serverTag, required this.isAdmin});
 
   factory RoomMember.fromJSON(dynamic json) {
     return RoomMember(
-      id: json['name'],
+        id: json['name'],
-      serverTag: json['server'],
+        serverTag: json['server'],
-      isAdmin: json['admin'] == 1);
+        isAdmin: json['admin'] == 1);
   }
 
   String get humanReadableName {
@@ -342,40 +342,39 @@ class RoomInfo {
   final int permissions;
 
   const RoomInfo(
-    {required this.permissions,
+      {required this.permissions,
       required this.owner,
       required this.isAdmin,
       required this.isOwner});
 
   factory RoomInfo.fromJSON(dynamic json) {
     return RoomInfo(
-      permissions: json['rights'],
+        permissions: json['rights'],
-      owner: json['owner'],
+        owner: json['owner'],
-      isAdmin: json['isAdmin'],
+        isAdmin: json['isAdmin'],
-      isOwner: json['isOwner']);
+        isOwner: json['isOwner']);
   }
 }
 
 class RoomCategory {
-  final int id;
+  final int? id;
   final String name;
   final ColorSwatch<int> color;
 
   const RoomCategory(
-    {required this.id, required this.name, required this.color});
+      {required this.id, required this.name, required this.color});
 
   factory RoomCategory.fromJSON(dynamic json) {
     return RoomCategory(
-      id: json['id'],
+        id: json['id'],
-      name: json['title'],
+        name: json['title'],
-      color: colorFromString(json['color']));
+        color: colorFromString(json['color']));
   }
   factory RoomCategory.other(BuildContext context) {
     return RoomCategory(
-      id: -1,
+        id: null,
-      name: AppLocalizations.of(context)!.categoryNameOther,
+        name: AppLocalizations.of(context)!.categoryNameOther,
-      color: Colors.grey
+        color: Colors.grey);
-    );
   }
 
   static List<ColorSwatch<int>> listColors() {
@@ -399,31 +398,31 @@ class RoomCategory {
 ColorSwatch<int> colorFromString(String text) {
   switch (text.toLowerCase()) {
     case 'red-acc':
-    return Colors.redAccent;
+      return Colors.redAccent;
     case 'green-acc':
-    return Colors.greenAccent;
+      return Colors.greenAccent;
     case 'yellow-acc':
-    return Colors.yellowAccent;
+      return Colors.yellowAccent;
     case 'blue-acc':
-    return Colors.blueAccent;
+      return Colors.blueAccent;
     case 'aqua-acc':
-    return Colors.tealAccent;
+      return Colors.tealAccent;
     case 'purple-acc':
-    return Colors.purpleAccent;
+      return Colors.purpleAccent;
 
     case 'red':
-    return Colors.red;
+      return Colors.red;
     case 'green':
-    return Colors.green;
+      return Colors.green;
     case 'yellow':
-    return Colors.yellow;
+      return Colors.yellow;
     case 'blue':
-    return Colors.blue;
+      return Colors.blue;
     case 'aqua':
-    return Colors.teal;
+      return Colors.teal;
     case 'purple':
     default:
-    return Colors.purple;
+      return Colors.purple;
   }
 }
 
@@ -487,7 +486,7 @@ class RoomProduct {
   int? parent;
 
   RoomProduct(
-    {required this.id,
+      {required this.id,
       required this.name,
       this.description = '',
       this.category = -1,
@@ -498,14 +497,14 @@ class RoomProduct {
 
   factory RoomProduct.fromJSON(dynamic json) {
     return RoomProduct(
-      id: json['listProdID'],
+        id: json['listProdID'],
-      name: json['title'],
+        name: json['title'],
-      description: json['description'],
+        description: json['description'],
-      category: json['category'],
+        category: json['category'],
-      defaultUnit: json['defUnit'],
+        defaultUnit: json['defUnit'],
-      defaultValue: json['defValue'],
+        defaultValue: json['defValue'],
-      ean: json['ean'],
+        ean: json['ean'],
-      parent: json['parent']);
+        parent: json['parent']);
   }
 }
 
@@ -524,7 +523,7 @@ class RoomItem {
   int? link;
 
   RoomItem(
-    {required this.id,
+      {required this.id,
       required this.name,
       this.description = '',
       this.state = 0,
@@ -535,24 +534,24 @@ class RoomItem {
 
   factory RoomItem.fromJSON(dynamic json) {
     return RoomItem(
-      id: json['listItemID'],
+        id: json['listItemID'],
-      name: json['title'],
+        name: json['title'],
-      description: json['description'],
+        description: json['description'],
-      category: json['listCatID'],
+        category: json['listCatID'],
-      state: json['state'],
+        state: json['state'],
-      unit: json['unit'],
+        unit: json['unit'],
-      value: json['value'],
+        value: json['value'],
-      link: json['listProdID']);
+        link: json['listProdID']);
   }
 
   RoomItem clone() {
     return RoomItem(
-      id: id,
+        id: id,
-      name: name,
+        name: name,
-      description: description,
+        description: description,
-      category: category,
+        category: category,
-      unit: unit,
+        unit: unit,
-      value: value,
+        value: value,
-      link: link);
+        link: link);
   }
 }

lib/components/category_chip.dart

@@ -0,0 +1,16 @@
+import 'package:flutter/material.dart';
+import 'package:outbag_app/backend/room.dart';
+
+class CategoryChip extends StatelessWidget {
+  final RoomCategory? category;
+
+  const CategoryChip({super.key, this.category});
+
+  @override
+  Widget build(BuildContext context) {
+    return ActionChip(
+      avatar: Icon(Icons.square_rounded, color: category?.color ?? RoomCategory.other(context).color),
+      label: Text(category?.name ?? RoomCategory.other(context).name),
+    );
+  }
+}

lib/components/category_picker.dart

@@ -1,19 +1,19 @@
 import 'package:flutter/material.dart';
 import 'package:outbag_app/backend/room.dart';
-import 'package:flutter_gen/gen_l10n/app_localizations.dart';
 
 class CategoryPicker extends StatelessWidget {
-  List<RoomCategory> categories = [];
+  final List<RoomCategory> categories;
-  int? selected;
+  final int? selected;
-  bool enabled = true;
+  final bool enabled;
-  Function(int?)? onSelect;
+  final Function(int?)? onSelect;
 
   // hint and label may differ depending on the screen
-  String? hint;
+  final String? hint;
-  String? label;
+  final String? label;
 
-  CategoryPicker(
+  const CategoryPicker(
-    {required this.categories,
+    {super.key,
+      required this.categories,
       this.selected,
       this.onSelect,
       this.hint,
@@ -24,34 +24,35 @@ class CategoryPicker extends StatelessWidget {
   Widget build(BuildContext context) {
     return Padding(
       padding: const EdgeInsets.all(8),
-      child: DropdownMenu<int?>(
+      child: DropdownButtonFormField<int?>(
-        initialSelection: selected,
+        hint: hint==null?null:Text(hint!),
-        enabled: enabled,
+        decoration: InputDecoration(
-        hintText: hint,
+          label: label==null?null:Text(label!),
-        label: (label!=null)?Text(label!):null,
+          border: const OutlineInputBorder(),
-        onSelected: ((id) {
+          prefixIcon: const Icon(Icons.category)
-            if (onSelect != null) {
+        ),
-              onSelect!(id);
+        value: selected,
-            }
+        items: [
-        }),
+          ...categories,
-        dropdownMenuEntries: [
+          RoomCategory.other(context)
-          // entry for every categry
+        ].map((category)=>DropdownMenuItem<int?>(
-          ...categories.map((category) => DropdownMenuEntry(
+            value: category.id,
-              value: category.id,
+            child: Row(
-              label: category.name,
+              mainAxisAlignment: MainAxisAlignment.spaceBetween,
-              trailingIcon: Icon(
+              crossAxisAlignment: CrossAxisAlignment.center,
-                Icons.square_rounded,
+              children: [
-                color: category.color,
+                Text(category.name),
-          ))),
+                Icon(Icons.square_rounded,
-          // entry for default ("other") category
+                  color:category.color,
-          DropdownMenuEntry(
+                  size: 32)
-            value: null,
+              ]
-            label: AppLocalizations.of(context)!.categoryNameOther,
+            ),
-            trailingIcon: Icon(
+        )).toList(),
-              Icons.square_rounded,
+        onChanged: enabled?(cid) {
-              color: RoomCategory.other(context).color,
+          if (onSelect != null) {
-          ))
+            onSelect!(cid);
-        ],
+          }
+        }:null,
     ));
   }
 }

lib/components/product_picker.dart

@@ -3,20 +3,23 @@ import 'package:outbag_app/backend/room.dart';
 import 'package:flutter_gen/gen_l10n/app_localizations.dart';
 
 class ProductPicker extends StatelessWidget {
-  List<RoomProduct> products = [];
+  final List<RoomProduct> products;
-  int? selected;
+  final int? selected;
-  bool enabled = true;
+  final bool enabled;
-  Function(int?)? onSelect;
+  final Function(int?)? onSelect;
 
   // hint and label may differ depending on the screen
-  String? hint;
+  final String? hint;
-  String? label;
+  final String? label;
+  final String? help;
 
-  ProductPicker(
+  const ProductPicker(
-    {required this.products,
+    {super.key,
+      required this.products,
       this.selected,
       this.onSelect,
       this.hint,
+      this.help,
       this.label,
       this.enabled = true});
 
@@ -24,28 +27,31 @@ class ProductPicker extends StatelessWidget {
   Widget build(BuildContext context) {
     return Padding(
       padding: const EdgeInsets.all(8),
-      child: DropdownMenu<int?>(
+      child: DropdownButtonFormField<int?>(
-        initialSelection: selected,
+        hint: hint == null ? null : Text(hint!),
-        label: (label!=null)?Text(label!):null,
+        decoration: InputDecoration(
-        hintText: hint,
+          label: label == null ? null : Text(label!),
-        enabled: enabled,
+          border: const OutlineInputBorder(),
-        onSelected: ((id) {
+          prefixIcon: const Icon(Icons.inventory_2),
-            if (onSelect != null) {
+          helperText: help),
-              onSelect!(id);
+        value: selected,
-            }
+        items: [
-        }),
+          // "no product" entry
-        dropdownMenuEntries: [
+          DropdownMenuItem<int?>(
-          // entry for no product
-          DropdownMenuEntry(
             value: null,
-            label: AppLocalizations.of(context)!.productNameNone,
+            child: Text(AppLocalizations.of(context)!.productNameNone),
           ),
-          // entry for every product
+          // other products
-          ...products.map((product) => DropdownMenuEntry(
+          ...products.map((product) => DropdownMenuItem<int?>(
-              value: product.id,
+              value: product.id, child: Text(product.name)))
-              label: product.name,
-          )),
         ],
+        onChanged: enabled
+        ? (pid) {
+          if (onSelect != null) {
+            onSelect!(pid);
+          }
+        }
+        : null,
     ));
   }
 }

lib/components/value_unit_input.dart

@@ -0,0 +1,331 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_gen/gen_l10n/app_localizations.dart';
+
+enum UnitType { text, amount, mass, volume, length, area }
+
+class Unit {
+  UnitType type = UnitType.text;
+
+  Unit(this.type);
+
+  factory Unit.fromId(int id) {
+    switch (id) {
+      case 1:
+        return Unit(UnitType.amount);
+      case 2:
+        return Unit(UnitType.mass);
+      case 3:
+        return Unit(UnitType.volume);
+      case 4:
+        return Unit(UnitType.length);
+      case 5:
+        return Unit(UnitType.area);
+      case 0:
+      default:
+        return Unit(UnitType.text);
+    }
+  }
+
+  String name(BuildContext context) {
+    final trans = AppLocalizations.of(context);
+
+    if (type == UnitType.text) {
+      return trans!.unitText;
+    } else if (type == UnitType.amount) {
+      return trans!.unitAmount;
+    } else if (type == UnitType.mass) {
+      return trans!.unitMass;
+    } else if (type == UnitType.volume) {
+      return trans!.unitVolume;
+    } else if (type == UnitType.length) {
+      return trans!.unitLength;
+    } else if (type == UnitType.area) {
+      return trans!.unitArea;
+    }
+
+    return trans!.unitText;
+  }
+
+  int get id {
+    if (type == UnitType.text) {
+      return 0;
+    } else if (type == UnitType.amount) {
+      return 1;
+    } else if (type == UnitType.mass) {
+      return 2;
+    } else if (type == UnitType.volume) {
+      return 3;
+    } else if (type == UnitType.length) {
+      return 4;
+    } else if (type == UnitType.area) {
+      return 5;
+    }
+
+    return 0;
+  }
+
+  static List<Unit> list() {
+    return [
+      Unit.fromId(0),
+      Unit.fromId(1),
+      Unit.fromId(2),
+      Unit.fromId(3),
+      Unit.fromId(4),
+      Unit.fromId(5),
+    ];
+  }
+
+  List<SubUnit> get subUnits {
+    if (type == UnitType.text) {
+      // NOTE: plain text does not need subunits
+      return [];
+    } else if (type == UnitType.amount) {
+      // NOTE: amount does not need subunits
+      return [];
+    } else if (type == UnitType.mass) {
+      // TODO: add subunits (with conversion)
+      return [SubUnit.def('kg'), SubUnit.nth('g', 1 / 1000)];
+    } else if (type == UnitType.volume) {
+      // TODO: add subunits (with conversion)
+      return [SubUnit.def('l')];
+    } else if (type == UnitType.length) {
+      // TODO: add subunits (with conversion)
+      return [SubUnit.def('m')];
+    } else if (type == UnitType.area) {
+      // TODO: add subunits (with conversion)
+      return [SubUnit.def('m²')];
+    }
+
+    return [];
+  }
+
+  int? get defaultSubUnit {
+    if (type == UnitType.text) {
+      // NOTE: plain text does not need subunits
+      return null;
+    } else if (type == UnitType.amount) {
+      // NOTE: amount does not need subunits
+      return null;
+    } else if (type == UnitType.mass) {
+      return 0;
+    } else if (type == UnitType.volume) {
+      return 0;
+    } else if (type == UnitType.length) {
+      return 0;
+    } else if (type == UnitType.area) {
+      return 0;
+    }
+
+    return null;
+  }
+
+  TextInputType get recommendedType {
+    if (type == UnitType.text) {
+      return TextInputType.text;
+    } else {
+      return TextInputType.number;
+    }
+  }
+}
+
+class SubUnit {
+  final String name;
+  // function to convert from default subunit to this subunit
+  final String Function(String value) convertTo;
+  // function to convert from this subunit to default subunit
+  final String Function(String value) convertFrom;
+
+  const SubUnit({
+    required this.name,
+    required this.convertTo,
+    required this.convertFrom,
+  });
+
+  @override
+  bool operator ==(Object other) {
+    if (runtimeType != other.runtimeType) {
+      return false;
+    }
+
+    return name.hashCode == other.hashCode;
+  }
+
+  @override
+  int get hashCode {
+    return name.hashCode;
+  }
+
+  factory SubUnit.def(String name) {
+    return SubUnit(name: name, convertTo: (v) => v, convertFrom: (v) => v);
+  }
+  factory SubUnit.nth(String name, double fact) {
+    return SubUnit(
+        name: name,
+        convertTo: (v) {
+          try {
+            final double number = double.parse(v);
+            return (number * fact).toString();
+          } catch (_) {
+            return v;
+          }
+        },
+        convertFrom: (v) {
+          try {
+            final double number = double.parse(v);
+            return (number / fact).toString();
+          } catch (_) {
+            return v;
+          }
+        });
+  }
+}
+
+class DynamicValueUnitInput extends StatefulWidget {
+  final int initialUnit;
+  final String initialValue;
+  final Function(String)? onValueChange;
+  final Function(int)? onUnitChange;
+
+  const DynamicValueUnitInput(
+      {super.key,
+      required this.initialUnit,
+      required this.initialValue,
+      this.onValueChange,
+      this.onUnitChange});
+
+  @override
+  State<StatefulWidget> createState() => _DynamicValueUnitInputState();
+}
+
+class _DynamicValueUnitInputState extends State<DynamicValueUnitInput> {
+  Unit unit = Unit.fromId(0);
+  bool enabled = true;
+  TextEditingController controller = TextEditingController();
+  SubUnit? sub;
+
+  @override
+  void initState() {
+    super.initState();
+
+    controller = TextEditingController(text: widget.initialValue);
+    unit = Unit.fromId(widget.initialUnit);
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Wrap(children: [
+      // unit type picker
+      Padding(
+          padding: const EdgeInsets.all(8),
+          child: DropdownMenu<int>(
+            label: Text(AppLocalizations.of(context)!.selectUnitTypeLabel),
+            enabled: enabled,
+            initialSelection: unit.id,
+            onSelected: (unit) {
+              if (unit == null) {
+                return;
+              }
+
+              final u = Unit.fromId(unit);
+              SubUnit? s;
+              if (u.defaultSubUnit != null) {
+                s = u.subUnits[u.defaultSubUnit!];
+              }
+              // NOTE: we could run this here as well,
+              // but at least to me it seems more natural without it
+              // convertSubunit(s);
+
+              if (widget.onUnitChange != null) {
+                widget.onUnitChange!(unit);
+              }
+
+              setState(() {
+                this.unit = u;
+                sub = s;
+              });
+            },
+            dropdownMenuEntries: Unit.list()
+                .map((unit) => DropdownMenuEntry(
+                    value: unit.id, label: unit.name(context)))
+                .toList(),
+          )),
+
+      // (optional) subunit selector
+      ...(unit.defaultSubUnit != null)
+          ? [
+              Padding(
+                  padding: const EdgeInsets.all(8),
+                  child: DropdownButtonFormField<SubUnit>(
+                    hint: Text(AppLocalizations.of(context)!.selectUnitLabel),
+                    decoration: InputDecoration(
+                        label:
+                            Text(AppLocalizations.of(context)!.selectUnitLabel),
+                        border: const OutlineInputBorder()),
+                    value: sub,
+                    items: unit.subUnits
+                        .map((sub) =>
+                            DropdownMenuItem(value: sub, child: Text(sub.name)))
+                        .toList(),
+                    onChanged: (sub) {
+                      // there is no way to select nothing
+                      if (sub == null) {
+                        return;
+                      }
+
+                      if (sub == this.sub) {
+                        // no new subunit selected
+                        return;
+                      }
+
+                      convertSubunit(sub);
+                      setState(() {
+                        this.sub = sub;
+                      });
+                    },
+                  ))
+            ]
+          : [],
+
+      // value input field
+      Padding(
+        padding: const EdgeInsets.all(8),
+        child: TextField(
+          controller: controller,
+          keyboardType: unit.recommendedType,
+          decoration: InputDecoration(
+            labelText: AppLocalizations.of(context)!.inputUnitValueLabel,
+            border: const OutlineInputBorder(),
+          ),
+          onChanged: (value) {
+            final String intermediate =
+                (sub != null) ? sub!.convertFrom(value) : value;
+
+            if (widget.onValueChange != null) {
+              widget.onValueChange!(intermediate);
+            }
+          },
+        ),
+      ),
+    ]);
+  }
+
+  void convertSubunit(SubUnit? newest) {
+    final String old2intermediate =
+        (sub != null) ? sub!.convertFrom(value) : value;
+    final String intermediate2new = (newest != null)
+        ? newest.convertTo(old2intermediate)
+        : old2intermediate;
+
+    setState(() {
+      value = intermediate2new;
+    });
+  }
+
+  String get value {
+    return controller.text;
+  }
+
+  set value(String txt) {
+    controller.text = txt;
+  }
+}

lib/l10n/app_en.arb

@@ -352,8 +352,46 @@
   "productNameNone": "None",
   "selectCategoryLabel": "Category",
   "selectCategoryHint": "Select a category",
+  "selectCategoryHelp": "Categories determine your shopping list order",
   "selectLinkedProductLabel": "Linked Product",
-  "selectLinkedProductHint": "Link a product to your item",
+  "selectLinkedProductHint": "Select a linked Product",
+  "selectLinkedProductHelp": "Link a product to your item, to provide more information",
   "selectParentProductLabel": "Parent Product",
-  "selectParentProductHint": "Nest products by choosing a parent product"
+  "selectParentProductHint": "Select a parent Product",
+  "selectParentProductHelp": "Nest products by choosing a parent product",
+
+  "unitText": "Plain text",
+  "unitAmount": "Amount",
+  "unitMass": "Mass",
+  "unitVolume": "Volume",
+  "unitLength": "Length",
+  "unitArea": "Area",
+
+  "inputUnitValueLabel": "Value",
+  "selectUnitTypeLabel": "Unit Type",
+  "selectUnitLabel": "Unit",
+
+  "inputProductNameLabel":"Name",
+  "inputProductNameHint":"Product name",
+  "inputProductNameHelp":"Give the product a name",
+  "inputProductDescriptionLabel":"Description",
+  "inputProductDescriptionHint":"Product Description",
+  "inputProductDescriptionHelp":"Give a brief description of this product",
+  "inputProductEANLabel":"EAN",
+  "inputProductEANHint":"Product EAN",
+  "inputProductEANHelp":"Easily identify products in the shelf by looking at their ean",
+
+  "newItemShort": "Add",
+  "newItemLong": "Add new Shopping list entry",
+  "newProductShort": "New",
+  "newProductLong": "Create a new product",
+
+  "errorProductNameShouldNotBeEmpty": "Product name shouldn't be empty",
+
+  "viewParentProductTitle": "View parent Product",
+  "viewParentProductSubtitle": "This product is the child of a different product, have a look at it",
+  "viewProductChildrenTitle": "View children",
+  "viewProductChildrenSubtitle": "If other products specify this product as their parent, they are listed here",
+  "editProductTitle": "Edit Product",
+  "editProductSubtitle": "Change product metadata"
 }

lib/main.dart

@@ -5,6 +5,8 @@ import 'package:outbag_app/backend/themes.dart';
 import 'package:outbag_app/backend/user.dart';
 import 'package:outbag_app/backend/request.dart';
 import 'package:outbag_app/screens/room/categories/edit.dart';
+import 'package:outbag_app/screens/room/products/edit.dart';
+import 'package:outbag_app/screens/room/products/view.dart';
 
 import 'package:outbag_app/tools/fetch_wrapper.dart';
 
@@ -254,11 +256,34 @@ class _OutbagAppState extends State {
                             state.params['id'] ?? '')),
                         GoRoute(
                           name: 'edit-category',
-                          path: 'edit-category/:cid',
+                          path: 'edit-category/:category',
                           builder: (context, state)=>EditCategoryPage(
                             state.params['server'] ?? '',
                             state.params['id'] ?? '',
-                            id: int.tryParse(state.params['cid'] ?? ''))),
+                            id: int.tryParse(state.params['category'] ?? ''))),
+                        GoRoute(
+                          name: 'new-product',
+                          path: 'new-product',
+                          builder: (context, state)=>EditProductPage(
+                            server: state.params['server'] ?? '',
+                            room: state.params['id'] ?? '',)),
+                        GoRoute(
+                          name: 'view-product',
+                          path: 'p/:product',
+                          builder: (context, state)=>ViewProductPage(
+                            server: state.params['server'] ?? '',
+                            room: state.params['id'] ?? '',
+                            product: int.tryParse(state.params['product'] ?? '') ?? 0),
+                          routes: [
+                            GoRoute(
+                              name: 'edit-product',
+                              path: 'edit',
+                              builder: (context, state)=>EditProductPage(
+                                server: state.params['server'] ?? '',
+                                room: state.params['id'] ?? '',
+                                product: int.tryParse(state.params['product'] ?? ''))),
+                          ]
+                        ),
                     ])
                 ]),
             ]),

lib/screens/room/pages/list.dart

@@ -4,6 +4,7 @@ import 'package:outbag_app/backend/permissions.dart';
 import 'package:outbag_app/backend/request.dart';
 import 'package:outbag_app/backend/room.dart';
 import 'package:outbag_app/backend/user.dart';
+import 'package:outbag_app/components/category_chip.dart';
 import 'package:outbag_app/components/category_picker.dart';
 import 'package:outbag_app/components/labeled_divider.dart';
 import 'package:outbag_app/components/product_picker.dart';
@@ -292,8 +293,8 @@ class _ShoppingListPageState extends State<ShoppingListPage> {
           0))
       ? FloatingActionButton.extended(
         icon: const Icon(Icons.add),
-        label: Text(AppLocalizations.of(context)!.newCategoryShort),
+        label: Text(AppLocalizations.of(context)!.newItemShort),
-        tooltip: AppLocalizations.of(context)!.newCategoryLong,
+        tooltip: AppLocalizations.of(context)!.newItemLong,
         onPressed: () {
           // show new category popup
           context.pushNamed('new-item', params: {
@@ -351,10 +352,7 @@ class ShoppingListItem extends StatelessWidget {
         enabled: !inCart,
         title: Text(name),
         subtitle: Text(description),
-        trailing: ActionChip(
+        trailing: CategoryChip(category: category,),
-          avatar: Icon(Icons.square_rounded, color: category.color),
-          label: Text(category.name),
-        ),
         onTap: () {
           if (onTap != null) {
             onTap!();
@@ -398,8 +396,8 @@ class ShoppingListItemInfo extends StatelessWidget {
                     selected: item.category,
                     enabled: false),
                   ProductPicker(
-                    label:
+                    label:AppLocalizations.of(context)!.selectLinkedProductLabel,
-                    AppLocalizations.of(context)!.selectLinkedProductLabel,
+                    help:AppLocalizations.of(context)!.selectLinkedProductHelp,
                     products: products,
                     selected: item.link,
                     enabled: false)

lib/screens/room/pages/products.dart

@@ -85,8 +85,8 @@ class _RoomProductsPageState extends State<RoomProductsPage> {
           0))
       ? FloatingActionButton.extended(
         icon: const Icon(Icons.add),
-        label: Text(AppLocalizations.of(context)!.newCategoryShort),
+        label: Text(AppLocalizations.of(context)!.newProductShort),
-        tooltip: AppLocalizations.of(context)!.newCategoryLong,
+        tooltip: AppLocalizations.of(context)!.newProductLong,
         onPressed: () {
           // show new category popup
           context.pushNamed('new-product', params: {

lib/screens/room/products/edit.dart

@@ -0,0 +1,287 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_gen/gen_l10n/app_localizations.dart';
+import 'package:go_router/go_router.dart';
+import 'package:outbag_app/backend/request.dart';
+import 'package:outbag_app/backend/room.dart';
+import 'package:outbag_app/backend/user.dart';
+import 'package:outbag_app/components/category_picker.dart';
+import 'package:outbag_app/components/product_picker.dart';
+import 'package:outbag_app/components/value_unit_input.dart';
+import 'package:outbag_app/tools/fetch_wrapper.dart';
+import 'package:outbag_app/tools/snackbar.dart';
+import 'package:provider/provider.dart';
+
+class EditProductPage extends StatefulWidget {
+  final int? product;
+  final String server;
+  final String room;
+  const EditProductPage(
+      {required this.server, required this.room, this.product, super.key});
+
+  @override
+  State<StatefulWidget> createState() => _EditProductPageState();
+}
+
+class _EditProductPageState extends State<EditProductPage> {
+  // input controllers
+  final _ctrName = TextEditingController();
+  final _ctrDescription = TextEditingController();
+  final _ctrEAN = TextEditingController();
+  int? _ctrCategory;
+  int _ctrUnit = 0;
+  String _ctrValue = '';
+  int? _ctrParent;
+
+  // data cache
+  List<RoomCategory> categories = [];
+  List<RoomProduct> products = [];
+
+  void fetchCategories() {
+    final user = context.read<User>();
+
+    // TODO: load cached categories first
+
+    doNetworkRequest(ScaffoldMessenger.of(context),
+        req: () => postWithCreadentials(
+            credentials: user,
+            target: user.server,
+            path: 'getCategories',
+            body: {'room': widget.room, 'server': widget.server}),
+        onOK: (body) async {
+          final resp = body['data']
+              .map<RoomCategory>((raw) => RoomCategory.fromJSON(raw))
+              .toList();
+
+          setState(() {
+            categories = resp;
+          });
+        });
+  }
+
+  void fetchProducts() {
+    final user = context.read<User>();
+
+    // TODO: load cached products first
+
+    doNetworkRequest(ScaffoldMessenger.of(context),
+        req: () => postWithCreadentials(
+            credentials: user,
+            target: user.server,
+            path: 'getProducts',
+            body: {'room': widget.room, 'server': widget.server}),
+        onOK: (body) async {
+          final resp = body['data']
+              .map<RoomProduct>((raw) => RoomProduct.fromJSON(raw))
+              .toList();
+
+          if (widget.product != null) {
+            for (RoomProduct prod in resp) {
+              // load product info
+              // for current product
+              if (prod.id == widget.product) {
+                setState(() {
+                  _ctrName.text = prod.name;
+                  _ctrDescription.text = prod.description;
+                  _ctrEAN.text = prod.ean ?? '';
+                  _ctrUnit = prod.defaultUnit;
+                  _ctrValue = prod.defaultValue;
+                  _ctrParent = prod.parent;
+                  _ctrCategory = prod.category;
+                });
+              }
+            }
+          }
+
+          setState(() {
+            products = resp;
+          });
+        });
+  }
+
+  @override
+  void initState() {
+    super.initState();
+
+    WidgetsBinding.instance.addPostFrameCallback((_) {
+      fetchCategories();
+      fetchProducts();
+    });
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(
+        title: Text((widget.product == null)
+            ? AppLocalizations.of(context)!.createProduct
+            : AppLocalizations.of(context)!.editProduct),
+      ),
+      body: SingleChildScrollView(
+          child: Center(
+              child: Padding(
+                  padding: const EdgeInsets.all(14),
+                  child: ConstrainedBox(
+                      constraints: const BoxConstraints(maxWidth: 400),
+                      child: Column(
+                        mainAxisAlignment: MainAxisAlignment.center,
+                        crossAxisAlignment: CrossAxisAlignment.center,
+                        children: [
+                          Padding(
+                            padding: const EdgeInsets.all(8),
+                            child: TextField(
+                              controller: _ctrName,
+                              keyboardType: TextInputType.name,
+                              decoration: InputDecoration(
+                                prefixIcon: const Icon(Icons.badge),
+                                labelText: AppLocalizations.of(context)!
+                                    .inputProductNameLabel,
+                                hintText: AppLocalizations.of(context)!
+                                    .inputProductNameHint,
+                                helperText: AppLocalizations.of(context)!
+                                    .inputProductNameHelp,
+                                border: const OutlineInputBorder(),
+                              ),
+                            ),
+                          ),
+                          Padding(
+                            padding: const EdgeInsets.all(8),
+                            child: TextField(
+                              controller: _ctrDescription,
+                              keyboardType: TextInputType.text,
+                              decoration: InputDecoration(
+                                labelText: AppLocalizations.of(context)!
+                                    .inputProductDescriptionLabel,
+                                hintText: AppLocalizations.of(context)!
+                                    .inputProductDescriptionHint,
+                                helperText: AppLocalizations.of(context)!
+                                    .inputProductDescriptionHelp,
+                                prefixIcon: const Icon(Icons.dns),
+                                border: const OutlineInputBorder(),
+                              ),
+                            ),
+                          ),
+                          Padding(
+                            padding: const EdgeInsets.all(8),
+                            child: TextField(
+                              controller: _ctrEAN,
+                              keyboardType: TextInputType.phone,
+                              decoration: InputDecoration(
+                                labelText: AppLocalizations.of(context)!
+                                    .inputProductEANLabel,
+                                hintText: AppLocalizations.of(context)!
+                                    .inputProductEANHint,
+                                helperText: AppLocalizations.of(context)!
+                                    .inputProductEANHelp,
+                                prefixIcon: const Icon(Icons.qr_code_rounded),
+                                border: const OutlineInputBorder(),
+                              ),
+                            ),
+                          ),
+                          DynamicValueUnitInput(
+                            initialUnit: _ctrUnit,
+                            initialValue: _ctrValue,
+                            onUnitChange: (unit) {
+                              setState(() {
+                                _ctrUnit = unit;
+                              });
+                            },
+                            onValueChange: (value) {
+                              setState(() {
+                                _ctrValue = value;
+                              });
+                            },
+                          ),
+                          CategoryPicker(
+                            label: AppLocalizations.of(context)!
+                                .selectCategoryLabel,
+                            hint: AppLocalizations.of(context)!
+                                .selectCategoryHint,
+                            categories: categories,
+                            selected: _ctrCategory,
+                            onSelect: (cid) {
+                              setState(() {
+                                _ctrCategory = cid;
+                              });
+                            },
+                          ),
+                          ProductPicker(
+                            label: AppLocalizations.of(context)!
+                                .selectParentProductLabel,
+                            hint: AppLocalizations.of(context)!
+                                .selectParentProductHint,
+                            products: products,
+                            selected: _ctrParent,
+                            onSelect: (pid) {
+                              setState(() {
+                                _ctrParent = pid;
+                              });
+                            },
+                          )
+                        ],
+                      ))))),
+      floatingActionButton: FloatingActionButton.extended(
+          onPressed: () async {
+            final scaffMgr = ScaffoldMessenger.of(context);
+            final router = GoRouter.of(context);
+            final trans = AppLocalizations.of(context);
+            final nav = Navigator.of(context);
+
+            if (_ctrName.text.isEmpty) {
+              showSimpleSnackbar(scaffMgr,
+                  text: trans!.errorProductNameShouldNotBeEmpty,
+                  action: trans.ok);
+              return;
+            }
+
+            final user = context.read<User>();
+
+            if (widget.product == null) {
+              doNetworkRequest(scaffMgr,
+                  req: () => postWithCreadentials(
+                          credentials: user,
+                          target: user.server,
+                          path: 'addProduct',
+                          body: {
+                            'room': widget.room,
+                            'server': widget.server,
+                            'title': _ctrName.text,
+                            'description': _ctrDescription.text,
+                            'listCatID': _ctrCategory,
+                            'defUnit': _ctrUnit,
+                            'defValue': _ctrValue,
+                            'ean': _ctrEAN.text,
+                            'parent': _ctrParent
+                          }),
+                  onOK: (_) async {
+                    nav.pop();
+                  });
+            } else {
+              doNetworkRequest(scaffMgr,
+                  req: () => postWithCreadentials(
+                          credentials: user,
+                          target: user.server,
+                          path: 'changeProduct',
+                          body: {
+                            'listProdID': widget.product,
+                            'room': widget.room,
+                            'server': widget.server,
+                            'title': _ctrName.text,
+                            'description': _ctrDescription.text,
+                            'listCatID': _ctrCategory,
+                            'defUnit': _ctrUnit,
+                            'defValue': _ctrValue,
+                            'ean': _ctrEAN.text,
+                            'parent': _ctrParent
+                          }),
+                  onOK: (_) async {
+                    nav.pop();
+                  });
+            }
+          },
+          label: Text(widget.product != null
+              ? AppLocalizations.of(context)!.editProductShort
+              : AppLocalizations.of(context)!.createProductShort),
+          icon: Icon(widget.product != null ? Icons.edit : Icons.add)),
+    );
+  }
+}

lib/screens/room/products/view.dart

@@ -0,0 +1,215 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_gen/gen_l10n/app_localizations.dart';
+import 'package:go_router/go_router.dart';
+import 'package:outbag_app/backend/permissions.dart';
+import 'package:outbag_app/backend/request.dart';
+import 'package:outbag_app/backend/room.dart';
+import 'package:outbag_app/backend/user.dart';
+import 'package:outbag_app/components/category_chip.dart';
+import 'package:outbag_app/components/product_picker.dart';
+import 'package:outbag_app/tools/fetch_wrapper.dart';
+import 'package:provider/provider.dart';
+
+class ViewProductPage extends StatefulWidget {
+  final int product;
+  final String server;
+  final String room;
+  const ViewProductPage(
+    {required this.server,
+      required this.room,
+      required this.product,
+      super.key});
+
+  @override
+  State<StatefulWidget> createState() => _ViewProductPageState();
+}
+
+class _ViewProductPageState extends State<ViewProductPage> {
+  RoomProduct? product;
+  // data cache
+  List<RoomProduct> products = [];
+  Map<int?, RoomCategory> categories = {};
+
+  RoomInfo? info;
+
+  void fetchInfo() async {
+    final sm = ScaffoldMessenger.of(context);
+    final user = context.read<User>();
+
+    doNetworkRequest(
+      sm,
+      req: () => postWithCreadentials(
+        path: 'getRoomInfo',
+        credentials: user,
+        target: user.server,
+        body: {'room': widget.room, 'server': widget.server}),
+      onOK: (body) async {
+        final info = RoomInfo.fromJSON(body['data']);
+        setState(() {
+            this.info = info;
+        });
+        return true;
+      },
+    );
+  }
+
+  void fetchCategories() {
+    final user = context.read<User>();
+
+    // TODO: load cached categories first
+
+    doNetworkRequest(ScaffoldMessenger.of(context),
+      req: () => postWithCreadentials(
+        credentials: user,
+        target: user.server,
+        path: 'getCategories',
+        body: {'room': widget.room, 'server': widget.server}),
+      onOK: (body) async {
+        final resp = body['data']
+        .map<RoomCategory>((raw) => RoomCategory.fromJSON(raw))
+        .toList();
+
+        Map<int?, RoomCategory> map = {};
+
+        for (RoomCategory cat in resp) {
+          map[cat.id] = cat;
+        }
+        setState(() {
+            categories = map;
+        });
+    });
+  }
+
+  void fetchProducts() {
+    final user = context.read<User>();
+
+    // TODO: load cached products first
+
+    doNetworkRequest(ScaffoldMessenger.of(context),
+      req: () => postWithCreadentials(
+        credentials: user,
+        target: user.server,
+        path: 'getProducts',
+        body: {'room': widget.room, 'server': widget.server}),
+      onOK: (body) async {
+        final resp = body['data']
+        .map<RoomProduct>((raw) => RoomProduct.fromJSON(raw))
+        .toList();
+
+        for (RoomProduct prod in resp) {
+          // load product info
+          // for current product
+          if (prod.id == widget.product) {
+            setState(() {
+                product = prod;
+            });
+          }
+        }
+        setState(() {
+            products = resp;
+        });
+    });
+  }
+
+  @override
+  void initState() {
+    super.initState();
+
+    WidgetsBinding.instance.addPostFrameCallback((_) {
+        fetchCategories();
+        fetchProducts();
+        fetchInfo();
+    });
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final textTheme = Theme.of(context).textTheme;
+
+    return Scaffold(
+      appBar: AppBar(
+        title: Text(product?.name ?? ''),
+      ),
+      body: SingleChildScrollView(
+        child: Column(children: [
+            // display product into
+            Center(
+              child: Padding(
+                padding: const EdgeInsets.all(14),
+                child: Column(
+                  mainAxisAlignment: MainAxisAlignment.center,
+                  crossAxisAlignment: CrossAxisAlignment.center,
+                  children: [
+                    Text(product?.name ?? '', style: textTheme.headlineLarge),
+                    Text(product?.description ?? '',
+                      style: textTheme.titleMedium),
+                    Text(product?.ean ?? ''),
+                    CategoryChip(category: categories[product?.category]),
+                    ProductPicker(
+                      label: AppLocalizations.of(context)!
+                      .selectParentProductLabel,
+                      products: products,
+                      selected: product?.parent,
+                      enabled: false)
+                  ],
+            ))),
+
+            // show actions (if allowed / available
+            // edit product button
+            ...(info != null &&
+              (info!.isAdmin ||
+                info!.isOwner ||
+                (info!.permissions & RoomPermission.editRoomContent != 0)))
+            ? [
+              ListTile(
+                title: Text(AppLocalizations.of(context)!.editProductTitle),
+                subtitle:
+                Text(AppLocalizations.of(context)!.editProductSubtitle),
+                onTap: () {
+                  context.pushNamed('edit-product', params: {
+                      'server': widget.server,
+                      'id': widget.room,
+                      'product': widget.product.toString()
+                  });
+                },
+                trailing: const Icon(Icons.chevron_right),
+              ),
+            ]
+            : [],
+            // show parent?
+            ...(product?.parent != null)
+            ? [
+              ListTile(
+                title: Text(
+                  AppLocalizations.of(context)!.viewParentProductTitle),
+                subtitle: Text(
+                  AppLocalizations.of(context)!.viewParentProductSubtitle),
+                onTap: () {
+                  context.pushNamed('view-product', params: {
+                      'server': widget.server,
+                      'id': widget.room,
+                      'product': product!.parent.toString()
+                  });
+                },
+                trailing: const Icon(Icons.chevron_right),
+              ),
+            ]
+            : [],
+            // show/manage children
+            ListTile(
+              title: Text(AppLocalizations.of(context)!.viewProductChildrenTitle),
+              subtitle:
+              Text(AppLocalizations.of(context)!.viewProductChildrenSubtitle),
+              onTap: () {
+                context.pushNamed('view-product-children', params: {
+                    'server': widget.server,
+                    'id': widget.room,
+                    'product': widget.product.toString()
+                });
+              },
+              trailing: const Icon(Icons.chevron_right),
+            ),
+      ])),
+    );
+  }
+}