From b808aa4971ae02c0ce6b74b74238be75b6cf9737 Mon Sep 17 00:00:00 2001
From: Andrew Camilleri <evilkukka@gmail.com>
Date: Tue, 18 Jun 2019 18:31:20 +0200
Subject: [PATCH 1/2] allow language parameter in pay button endpoint

---
 BTCPayServer/Controllers/PublicController.cs          | 11 ++++++++++-
 .../Models/StoreViewModels/PayButtonViewModel.cs      |  1 +
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/BTCPayServer/Controllers/PublicController.cs b/BTCPayServer/Controllers/PublicController.cs
index 9faef2565..975e29e18 100644
--- a/BTCPayServer/Controllers/PublicController.cs
+++ b/BTCPayServer/Controllers/PublicController.cs
@@ -3,6 +3,7 @@ using System.Collections.Generic;
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
+using System.Web;
 using BTCPayServer.Filters;
 using BTCPayServer.Models;
 using BTCPayServer.Models.StoreViewModels;
@@ -58,7 +59,15 @@ namespace BTCPayServer.Controllers
                 RedirectURL = model.BrowserRedirect,
                 FullNotifications = true
             }, store, HttpContext.Request.GetAbsoluteRoot(), cancellationToken: cancellationToken);
-            return Redirect(invoice.Data.Url);
+            if (string.IsNullOrEmpty(model.Language))
+            {
+                return Redirect(invoice.Data.Url);
+            }
+            var uriBuilder = new UriBuilder(invoice.Data.Url);
+            var paramValues = HttpUtility.ParseQueryString(uriBuilder.Query);
+            paramValues.Add("lang", model.Language);
+            uriBuilder.Query = paramValues.ToString();
+            return Redirect(uriBuilder.Uri.AbsoluteUri);
         }
     }
 }
diff --git a/BTCPayServer/Models/StoreViewModels/PayButtonViewModel.cs b/BTCPayServer/Models/StoreViewModels/PayButtonViewModel.cs
index dc5c1ea23..122d476d8 100644
--- a/BTCPayServer/Models/StoreViewModels/PayButtonViewModel.cs
+++ b/BTCPayServer/Models/StoreViewModels/PayButtonViewModel.cs
@@ -30,6 +30,7 @@ namespace BTCPayServer.Models.StoreViewModels
         public string NotifyEmail { get; set; }
 
         public string StoreId { get; set; }
+        public string Language { get; set; }
 
         // Data that influences Pay Button UI, but not invoice creation
         public string UrlRoot { get; set; }

From 11670d0c0f5c021b6640245e276a80eff31315ef Mon Sep 17 00:00:00 2001
From: Kukks <evilkukka@gmail.com>
Date: Tue, 25 Jun 2019 21:01:37 +0200
Subject: [PATCH 2/2] make checkout param more generic and add it to pay button
 generator

---
 BTCPayServer/Controllers/PublicController.cs  |  6 ++++--
 .../StoreViewModels/PayButtonViewModel.cs     |  2 +-
 BTCPayServer/Views/Stores/PayButton.cshtml    | 20 ++++++++++++++++++-
 BTCPayServer/wwwroot/paybutton/paybutton.js   |  5 ++++-
 4 files changed, 28 insertions(+), 5 deletions(-)

diff --git a/BTCPayServer/Controllers/PublicController.cs b/BTCPayServer/Controllers/PublicController.cs
index 975e29e18..2d458f5f5 100644
--- a/BTCPayServer/Controllers/PublicController.cs
+++ b/BTCPayServer/Controllers/PublicController.cs
@@ -59,13 +59,15 @@ namespace BTCPayServer.Controllers
                 RedirectURL = model.BrowserRedirect,
                 FullNotifications = true
             }, store, HttpContext.Request.GetAbsoluteRoot(), cancellationToken: cancellationToken);
-            if (string.IsNullOrEmpty(model.Language))
+            if (string.IsNullOrEmpty(model.CheckoutQueryString))
             {
                 return Redirect(invoice.Data.Url);
             }
+
+            var additionalParamValues = HttpUtility.ParseQueryString(model.CheckoutQueryString);
             var uriBuilder = new UriBuilder(invoice.Data.Url);
             var paramValues = HttpUtility.ParseQueryString(uriBuilder.Query);
-            paramValues.Add("lang", model.Language);
+            paramValues.Add(additionalParamValues);
             uriBuilder.Query = paramValues.ToString();
             return Redirect(uriBuilder.Uri.AbsoluteUri);
         }
diff --git a/BTCPayServer/Models/StoreViewModels/PayButtonViewModel.cs b/BTCPayServer/Models/StoreViewModels/PayButtonViewModel.cs
index 122d476d8..126969d75 100644
--- a/BTCPayServer/Models/StoreViewModels/PayButtonViewModel.cs
+++ b/BTCPayServer/Models/StoreViewModels/PayButtonViewModel.cs
@@ -30,7 +30,7 @@ namespace BTCPayServer.Models.StoreViewModels
         public string NotifyEmail { get; set; }
 
         public string StoreId { get; set; }
-        public string Language { get; set; }
+        public string CheckoutQueryString { get; set; }
 
         // Data that influences Pay Button UI, but not invoice creation
         public string UrlRoot { get; set; }
diff --git a/BTCPayServer/Views/Stores/PayButton.cshtml b/BTCPayServer/Views/Stores/PayButton.cshtml
index 87c4a9b50..067c732d9 100644
--- a/BTCPayServer/Views/Stores/PayButton.cshtml
+++ b/BTCPayServer/Views/Stores/PayButton.cshtml
@@ -1,4 +1,4 @@
-@model PayButtonViewModel
+@model PayButtonViewModel
 @{
     Layout = "../Shared/_NavLayout.cshtml";
     ViewData.SetActivePageAndTitle(StoreNavPages.PayButton);
@@ -140,6 +140,24 @@
             Finally <i>Browser Redirect</i> defines where BtcPayServer will redirect customer after puchase is completed.
         </div>
     </div>
+     <h3>Advanced</h3>
+        <br />
+        <div class="row">
+            <div class="col-lg-7">
+                <div class="form-group">
+                    <label>Checkout Additional Query String</label>
+                    <input name="checkoutQueryString" type="text" class="form-control" placeholder="(optional)"
+                           v-model="srvModel.checkoutQueryString" v-on:change="inputChanges"
+                           :class="{'is-invalid': errors.has('checkoutQueryString') }">
+                    <small class="text-danger">{{ errors.first('checkoutQueryString') }}</small>
+                </div>
+            </div>
+            <div class="col-lg-5">
+                <br />
+                This parameter allows you to specify additional query string paramters that should be appended to the checkout page once the invoice is created. For example, <kbd>lang=da-DK</kbd> would load the checkout page in Danishby default.
+                
+            </div>
+        </div>
     <hr />
     <h3>Generated code</h3>
     <div class="row" v-show="!errors.any()">
diff --git a/BTCPayServer/wwwroot/paybutton/paybutton.js b/BTCPayServer/wwwroot/paybutton/paybutton.js
index eda819f62..ccdd0176d 100644
--- a/BTCPayServer/wwwroot/paybutton/paybutton.js
+++ b/BTCPayServer/wwwroot/paybutton/paybutton.js
@@ -26,7 +26,7 @@ function esc(input) {
 }
 
 Vue.use(VeeValidate);
-const dictionary = {
+var dictionary = {
     en: {
         attributes: {
             price: 'Price', checkoutDesc: 'Checkout Description', orderId: 'Order Id',
@@ -96,6 +96,9 @@ function inputChanges(event, buttonSize) {
     }
     if (srvModel.notifyEmail) {
         html += addinput("notifyEmail", srvModel.notifyEmail);
+    }   
+    if (srvModel.checkoutQueryString) {
+        html += addinput("checkoutQueryString", srvModel.checkoutQueryString);
     }
 
     html += '\n    <input type="image" src="' + esc(srvModel.payButtonImageUrl) + '" name="submit" style="width:' + width +