fix(dashpay): improve timeskew handling for CoinJoin

wallet/res/values/strings-extra.xml

@@ -697,4 +697,6 @@
     <string name="masternode_key_not_used">Not used</string>
     <string name="masternode_key_revoked">Revoked</string>
     <string name="masternode_key_private_public_base64">Private / Public Keys (base64)</string>
+    <string name="timeskew_ahead">ahead</string>
+    <string name="timeskew_behind">behind</string>
 </resources>

wallet/res/values/strings.xml

@@ -43,7 +43,7 @@
     <string name="wallet_low_storage_dialog_button_apps">Manage apps</string>
     <string name="wallet_timeskew_dialog_title">Check date &amp; time settings</string>
     <string name="wallet_timeskew_dialog_msg">Your device time is off by %d minutes. You probably cannot send or receive Dash due to this problem.\n\nYou should check and if necessary correct your date, time and timezone settings.</string>
-    <string name="wallet_coinjoin_timeskew_dialog_msg">Your device time is off by %d seconds. You cannot use CoinJoin due to this problem.\n\nThe time settings on your device needs to be changed to “Set time automatically” to use CoinJoin.</string>
+    <string name="wallet_coinjoin_timeskew_dialog_msg">Your device time is %s by %d seconds. You cannot use CoinJoin due to this problem.\n\nThe time settings on your device needs to be changed to “Set time automatically” to use CoinJoin.</string>
     <string name="settings_coinjoin_timeskew_dialog_msg">Your device time is off by more than 2 seconds. You cannot use CoinJoin due to this problem.\n\nThe time settings on your device needs to be changed to “Set time automatically” before using CoinJoin.</string>
     <string name="send_coins_activity_title">Send Dash</string>
     <string name="send_coins_fragment_request_payment_request_progress">Fetching signature from %s…</string>

wallet/src/de/schildbach/wallet/service/CoinJoinService.kt

@@ -116,10 +116,19 @@ class CoinJoinMixingService @Inject constructor(
         const val DEFAULT_SESSIONS = 4
         const val DEFAULT_DENOMINATIONS_GOAL = 50
         const val DEFAULT_DENOMINATIONS_HARDCAP = 300
-        const val MAX_ALLOWED_TIMESKEW = 4000L // 4 seconds
+        const val MAX_ALLOWED_AHEAD_TIMESKEW = 5000L // 5 seconds
+        const val MAX_ALLOWED_BEHIND_TIMESKEW = 20000L // 20 seconds
 
         // these are not for production
-        val FAST_MIXING_DENOMINATIONS_REMOVE = listOf<Denomination>() // Denomination.THOUSANDTH)
+        val FAST_MIXING_DENOMINATIONS_REMOVE = listOf<Denomination>() // Denomination.THOUSANDTH
+
+        fun isInsideTimeSkewBounds(timeSkew: Long): Boolean {
+            return if (timeSkew > 0) {
+                timeSkew < MAX_ALLOWED_AHEAD_TIMESKEW
+            } else {
+                (-timeSkew) < MAX_ALLOWED_BEHIND_TIMESKEW
+            }
+        }
     }
 
     private val coinJoinManager: CoinJoinManager?
@@ -148,7 +157,7 @@ class CoinJoinMixingService @Inject constructor(
     private var networkStatus: NetworkStatus = NetworkStatus.UNKNOWN
     private var isSynced = false
     private var hasAnonymizableBalance: Boolean = false
-    private var timeSkew: Long = Long.MIN_VALUE
+    private var timeSkew: Long = 0L
 
     // https://stackoverflow.com/questions/55421710/how-to-suspend-kotlin-coroutine-until-notified
     private val updateMutex = Mutex(locked = false)
@@ -292,7 +301,7 @@ class CoinJoinMixingService @Inject constructor(
             this.mode = mode
             this.timeSkew = timeSkew
 
-            if (mode == CoinJoinMode.NONE || timeSkew > MAX_ALLOWED_TIMESKEW) {
+            if (mode == CoinJoinMode.NONE || !isInsideTimeSkewBounds(timeSkew)) {
                 updateMixingState(MixingStatus.NOT_STARTED)
             } else {
                 configureMixing()

wallet/src/de/schildbach/wallet/ui/main/MainViewModel.kt

@@ -97,17 +97,15 @@ import org.dash.wallet.common.services.analytics.AnalyticsTimer
 import org.dash.wallet.common.transactions.TransactionUtils.isEntirelySelf
 import org.dash.wallet.common.transactions.TransactionWrapper
 import org.dash.wallet.common.transactions.TransactionWrapperComparator
-import org.dash.wallet.common.util.Constants.HTTP_CLIENT
-import org.dash.wallet.common.util.head
 import org.dash.wallet.common.util.toBigDecimal
 import org.dash.wallet.integrations.crowdnode.transactions.FullCrowdNodeSignUpTxSet
 import org.slf4j.LoggerFactory
+import java.lang.Math.abs
 import java.text.DecimalFormat
 import java.util.Currency
 import java.util.Locale
 import javax.inject.Inject
 import kotlin.collections.set
-import kotlin.math.abs
 
 @OptIn(ExperimentalCoroutinesApi::class, FlowPreview::class)
 @HiltViewModel
@@ -138,7 +136,9 @@ class MainViewModel @Inject constructor(
         private const val THROTTLE_DURATION = 500L
         private const val DIRECTION_KEY = "tx_direction"
         private const val TIME_SKEW_TOLERANCE = 3600000 // seconds (1 hour)
-        private const val TIME_SKEW_TOLERANCE_COINJOIN = 4000 // seconds
+        private const val TIME_SKEW_AHEAD_TOLERANCE_COINJOIN = 5000 // 5 seconds
+        private const val TIME_SKEW_BEHIND_TOLERANCE_COINJOIN = 20000 // 20 seconds
+
         private val log = LoggerFactory.getLogger(MainViewModel::class.java)
     }
 
@@ -392,10 +392,11 @@ class MainViewModel @Inject constructor(
             val maxAllowedTimeSkew = if (coinJoinConfig.getMode() == CoinJoinMode.NONE) {
                 TIME_SKEW_TOLERANCE
             } else {
-                TIME_SKEW_TOLERANCE_COINJOIN
+                if (timeSkew > 0) TIME_SKEW_AHEAD_TOLERANCE_COINJOIN else TIME_SKEW_BEHIND_TOLERANCE_COINJOIN
             }
             coinJoinService.updateTimeSkew(timeSkew)
-            return Pair(timeSkew > maxAllowedTimeSkew, timeSkew)
+            log.info("timeskew: {} ms", timeSkew)
+            return Pair(kotlin.math.abs(timeSkew) > maxAllowedTimeSkew, timeSkew)
         } catch (ex: Exception) {
             // Ignore errors
             Pair(false, 0)

wallet/src/de/schildbach/wallet/ui/main/WalletActivityExt.kt

@@ -45,6 +45,7 @@ import org.dash.wallet.common.services.analytics.AnalyticsConstants
 import org.dash.wallet.common.ui.dialogs.AdaptiveDialog
 import org.dash.wallet.common.ui.dialogs.AdaptiveDialog.Companion.create
 import org.dash.wallet.common.util.openCustomTab
+import kotlin.math.abs
 
 object WalletActivityExt {
     private const val STORAGE_TOLERANCE = 500 // MB
@@ -101,7 +102,7 @@ object WalletActivityExt {
             if (isTimeSkewed && (!timeSkewDialogShown || coinJoinOn)) {
                 timeSkewDialogShown = true
                 // add 1 to round up so 2.2 seconds appears as 3
-                showTimeSkewAlertDialog(1 + timeSkew / 1000, coinJoinOn)
+                showTimeSkewAlertDialog((if (timeSkew > 0) 1 else -1) + timeSkew / 1000L, coinJoinOn)
             }
         }
     }
@@ -179,7 +180,8 @@ object WalletActivityExt {
             R.drawable.ic_warning,
             getString(R.string.wallet_timeskew_dialog_title),
             if (coinJoin) {
-                getString(R.string.wallet_coinjoin_timeskew_dialog_msg, diffSeconds)
+                val position = getString(if (diffSeconds > 0) R.string.timeskew_ahead else R.string.timeskew_behind)
+                getString(R.string.wallet_coinjoin_timeskew_dialog_msg, position, abs(diffSeconds))
             } else {
                 getString(R.string.wallet_timeskew_dialog_msg, diffSeconds / 1000)
             },

wallet/src/de/schildbach/wallet/util/TimeUtils.kt

@@ -54,5 +54,5 @@ suspend fun getTimeSkew(): Long {
         requireNotNull(networkTime)
     }
     val systemTimeMillis = System.currentTimeMillis()
-    return abs(systemTimeMillis - networkTime)
+    return systemTimeMillis - networkTime
 }