Implement and test realtime timestamp functions

Author: tom-andersen

firebase-firestore/src/main/java/com/google/firebase/firestore/model/Values.kt

@@ -750,11 +750,32 @@ internal object Values {
 
   @JvmStatic
   fun timestamp(seconds: Long, nanos: Int): Timestamp {
+    validateRange(seconds, nanos)
+
     // Firestore backend truncates precision down to microseconds. To ensure offline mode works
     // the same with regards to truncation, perform the truncation immediately without waiting for
     // the backend to do that.
     val truncatedNanoseconds: Int = nanos / 1000 * 1000
-
     return Timestamp.newBuilder().setSeconds(seconds).setNanos(truncatedNanoseconds).build()
   }
+
+  /**
+   * Ensures that the date and time are within what we consider valid ranges.
+   *
+   * More specifically, the nanoseconds need to be less than 1 billion- otherwise it would trip over
+   * into seconds, and need to be greater than zero.
+   *
+   * The seconds need to be after the date `1/1/1` and before the date `1/1/10000`.
+   *
+   * @throws IllegalArgumentException if the date and time are considered invalid
+   */
+  private fun validateRange(seconds: Long, nanoseconds: Int) {
+    require(nanoseconds in 0 until 1_000_000_000) {
+      "Timestamp nanoseconds out of range: $nanoseconds"
+    }
+
+    require(seconds in -62_135_596_800 until 253_402_300_800) {
+      "Timestamp seconds out of range: $seconds"
+    }
+  }
 }

firebase-firestore/src/main/java/com/google/firebase/firestore/pipeline/EvaluateResult.kt

@@ -26,8 +26,11 @@ internal sealed class EvaluateResult(val value: Value?) {
     fun timestamp(timestamp: Timestamp): EvaluateResult =
       EvaluateResultValue(encodeValue(timestamp))
     fun timestamp(seconds: Long, nanos: Int): EvaluateResult =
-      if (seconds !in -62_135_596_800 until 253_402_300_800) EvaluateResultError
-      else timestamp(Values.timestamp(seconds, nanos))
+      try {
+        timestamp(Values.timestamp(seconds, nanos))
+      } catch (e: IllegalArgumentException) {
+        EvaluateResultError
+      }
   }
 }
 

firebase-firestore/src/main/java/com/google/firebase/firestore/pipeline/evaluation.kt

@@ -568,14 +568,14 @@ internal val evaluateTimestampToUnixSeconds = unaryFunction { t: Timestamp ->
 internal val evaluateUnixMicrosToTimestamp = unaryFunction { micros: Long ->
   EvaluateResult.timestamp(
     Math.floorDiv(micros, L_MICROS_PER_SECOND),
-    Math.floorMod(micros, I_MICROS_PER_SECOND)
+    Math.floorMod(micros, I_MICROS_PER_SECOND) * 1000
   )
 }
 
 internal val evaluateUnixMillisToTimestamp = unaryFunction { millis: Long ->
   EvaluateResult.timestamp(
     Math.floorDiv(millis, L_MILLIS_PER_SECOND),
-    Math.floorMod(millis, I_MILLIS_PER_SECOND)
+    Math.floorMod(millis, I_MILLIS_PER_SECOND) * 1000_000
   )
 }