simplex buy warning popup

lib/pages/buy_view/buy_quote_preview.dart

@@ -1,6 +1,7 @@
 import 'package:flutter/material.dart';
 import 'package:flutter_svg/svg.dart';
 import 'package:stackwallet/models/buy/response_objects/quote.dart';
+import 'package:stackwallet/pages/buy_view/sub_widgets/buy_warning_popup.dart';
 import 'package:stackwallet/utilities/assets.dart';
 import 'package:stackwallet/utilities/text_styles.dart';
 import 'package:stackwallet/utilities/theme/stack_colors.dart';
@@ -28,8 +29,13 @@ class BuyQuotePreviewView extends StatefulWidget {
 class _BuyQuotePreviewViewState extends State<BuyQuotePreviewView> {
   final isDesktop = Util.isDesktop;
 
-  Future<void> _buy() async {
+  Future<void> _buyWarning() async {
-    // do buy/redirect to simplex page
+    await showDialog<void>(
+      context: context,
+      builder: (context) => BuyWarningPopup(
+        ticker: widget.quote.crypto.ticker.toUpperCase(),
+      ),
+    );
   }
 
   @override
@@ -177,7 +183,10 @@ class _BuyQuotePreviewViewState extends State<BuyQuotePreviewView> {
                 ),
                 SizedBox(
                   width: 64,
-                  child: SvgPicture.asset(Assets.buy.simplexLogo),
+                  height: 32,
+                  child: SvgPicture.asset(
+                    Assets.buy.simplexLogo,
+                  ),
                 ),
               ],
             ),
@@ -188,7 +197,7 @@ class _BuyQuotePreviewViewState extends State<BuyQuotePreviewView> {
           const Spacer(),
           PrimaryButton(
             label: "Buy",
-            onPressed: _buy,
+            onPressed: _buyWarning,
           )
         ],
       ),

lib/pages/buy_view/sub_widgets/buy_warning_popup.dart

@@ -0,0 +1,42 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_svg/svg.dart';
+import 'package:stackwallet/utilities/assets.dart';
+import 'package:stackwallet/widgets/desktop/primary_button.dart';
+import 'package:stackwallet/widgets/desktop/secondary_button.dart';
+import 'package:stackwallet/widgets/stack_dialog.dart';
+
+class BuyWarningPopup extends StatelessWidget {
+  const BuyWarningPopup({
+    Key? key,
+    required this.ticker,
+  }) : super(key: key);
+
+  final String ticker;
+
+  @override
+  Widget build(BuildContext context) {
+    return StackDialog(
+      title: "Buy $ticker",
+      message: "This purchase is provided and fulfilled by Simplex by nuvei "
+          "(a third party). You will be taken to their website. Please follow "
+          "their instructions.",
+      leftButton: SecondaryButton(
+        label: "Cancel",
+        onPressed: Navigator.of(context).pop,
+      ),
+      rightButton: PrimaryButton(
+        label: "Continue",
+        onPressed: () async {
+          // todo open simplex page in external browser
+        },
+      ),
+      icon: SizedBox(
+        width: 64,
+        height: 32,
+        child: SvgPicture.asset(
+          Assets.buy.simplexLogo,
+        ),
+      ),
+    );
+  }
+}