[#289] Crash while typing characters to Zec amount text field.

- Filed issue to SDK project.
- Temporary workaround to prevent SDK from returning negative results and thus to avoid app crashing.
- SuppressWarnings - ReturnCount - ZecString.
- Added unit test for validation of implemented workaround.

sdk-ext-ui-lib/src/androidTest/java/cash/z/ecc/sdk/ext/ui/model/ZecStringTest.kt

@@ -3,12 +3,17 @@ package cash.z.ecc.sdk.ext.ui.model
 import android.content.Context
 import android.content.res.Configuration
 import androidx.test.core.app.ApplicationProvider
+import androidx.test.filters.SmallTest
+import cash.z.ecc.android.sdk.ext.Conversions
 import cash.z.ecc.sdk.model.Zatoshi
 import org.junit.Assert.assertEquals
 import org.junit.Ignore
 import org.junit.Test
+import java.math.BigDecimal
 import java.util.Locale
+import kotlin.test.assertNotNull
 import kotlin.test.assertNull
+import kotlin.test.assertTrue
 
 class ZecStringTest {
 
@@ -87,4 +92,18 @@ class ZecStringTest {
         assertNull(Zatoshi.fromZecString(context, "1,23,", EN_US_MONETARY_SEPARATORS))
         assertNull(Zatoshi.fromZecString(context, "1,234,", EN_US_MONETARY_SEPARATORS))
     }
+
+    // TODO [472]: https://github.com/zcash/zcash-android-wallet-sdk/issues/472
+    @Test
+    @SmallTest
+    fun overflow_number_test() {
+        assertNotNull(Zatoshi.fromZecString(context, "1", EN_US_MONETARY_SEPARATORS))
+        assertNotNull(Zatoshi.fromZecString(context, "1,000", EN_US_MONETARY_SEPARATORS))
+        assertNotNull(Zatoshi.fromZecString(context, "10,000,000,000", EN_US_MONETARY_SEPARATORS))
+        assertNull(Zatoshi.fromZecString(context, "100,000,000,000", EN_US_MONETARY_SEPARATORS))
+
+        val overflowCausingNumber = 100000000000L
+        assertTrue(BigDecimal(overflowCausingNumber).times(Conversions.ONE_ZEC_IN_ZATOSHI) > BigDecimal(Long.MAX_VALUE))
+        assertNull(Zatoshi.fromZecString(context, overflowCausingNumber.toString(), EN_US_MONETARY_SEPARATORS))
+    }
 }

sdk-ext-ui-lib/src/main/java/cash/z/ecc/sdk/ext/ui/model/ZecString.kt

@@ -1,6 +1,7 @@
 package cash.z.ecc.sdk.ext.ui.model
 
 import android.content.Context
+import cash.z.ecc.android.sdk.ext.Conversions
 import cash.z.ecc.android.sdk.ext.convertZatoshiToZecString
 import cash.z.ecc.android.sdk.ext.convertZecToZatoshi
 import cash.z.ecc.sdk.ext.ui.ZecStringExt
@@ -67,6 +68,7 @@ fun Zatoshi.toZecString() = value.convertZatoshiToZecString(DECIMALS, DECIMALS)
 /**
  * @return [zecString] parsed into Zatoshi or null if parsing failed.
  */
+@SuppressWarnings("ReturnCount")
 fun Zatoshi.Companion.fromZecString(
     context: Context,
     zecString: String,
@@ -97,5 +99,11 @@ fun Zatoshi.Companion.fromZecString(
         null
     }
 
+    // TODO [472]: https://github.com/zcash/zcash-android-wallet-sdk/issues/472
+    // temporary workaround to prevent SDK to returns us negative result
+    if (bigDecimal?.times(Conversions.ONE_ZEC_IN_ZATOSHI)?.compareTo(BigDecimal(Long.MAX_VALUE)) ?: 0 > 0) {
+        return null
+    }
+
     return Zatoshi(bigDecimal.convertZecToZatoshi())
 }