ui: bring back donation button

For Google Play Store builds, we'll display an alert box. This was
inspired by the discussion around StreetComplete; hopefully we'll have a
similar okay outcome.

Link: https://github.com/streetcomplete/streetcomplete/issues/3768
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

ui/build.gradle

@@ -48,6 +48,9 @@ android {
         }
     }
     buildTypes {
+        all {
+            buildConfigField('boolean', 'IS_GOOGLE_PLAY', (findProperty('build.google_play') == 'true').toString())
+        }
         release {
             if (keystorePropertiesFile.exists()) signingConfig signingConfigs.release
             minifyEnabled true

ui/src/main/java/com/wireguard/android/preference/DonatePreference.kt

@@ -0,0 +1,38 @@
+/*
+ * Copyright © 2017-2023 WireGuard LLC. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package com.wireguard.android.preference
+
+import android.app.AlertDialog
+import android.content.ActivityNotFoundException
+import android.content.Context
+import android.content.Intent
+import android.net.Uri
+import android.util.AttributeSet
+import androidx.preference.Preference
+import com.wireguard.android.BuildConfig
+import com.wireguard.android.R
+
+class DonatePreference(context: Context, attrs: AttributeSet?) : Preference(context, attrs) {
+    override fun getSummary() = context.getString(R.string.donate_summary)
+
+    override fun getTitle() = context.getString(R.string.donate_title)
+
+    override fun onClick() {
+        if (BuildConfig.IS_GOOGLE_PLAY) {
+            AlertDialog.Builder(context)
+                .setTitle(R.string.donate_title)
+                .setMessage(R.string.donate_google_play_disappointment)
+                .show()
+            return
+        }
+        val intent = Intent(Intent.ACTION_VIEW)
+        intent.data = Uri.parse("https://www.wireguard.com/donations/")
+        try {
+            context.startActivity(intent)
+        } catch (ignored: ActivityNotFoundException) {
+        }
+    }
+}

ui/src/main/res/values/strings.xml

@@ -108,6 +108,9 @@
     <string name="tv_select_a_storage_drive">Select a storage drive</string>
     <string name="tv_no_file_picker">Please install a file management utility to browse files</string>
     <string name="tv_add_tunnel_get_started">Add a tunnel to get started</string>
+    <string name="donate_title">♥ Donate to the WireGuard Project</string>
+    <string name="donate_summary">Every contribution helps</string>
+    <string name="donate_google_play_disappointment">Thank you for supporting the WireGuard Project!\n\nUnfortunately, due to Google\'s policies, we\'re not allowed to link to the part of the project webpage where you can make a donation. Hopefully you can figure this out!\n\nThanks again for your contribution.</string>
     <string name="disable_config_export_title">Disable config exporting</string>
     <string name="disable_config_export_description">Disabling config exporting makes private keys less accessible</string>
     <string name="dns_servers">DNS servers</string>

ui/src/main/res/xml/preferences.xml

@@ -40,4 +40,6 @@
         android:summaryOff="@string/allow_remote_control_intents_summary_off"
         android:summaryOn="@string/allow_remote_control_intents_summary_on"
         android:title="@string/allow_remote_control_intents_title" />
+    <com.wireguard.android.preference.DonatePreference
+        android:singleLineTitle="false" />
 </androidx.preference.PreferenceScreen>