JS: fix Instant.fromEpochSeconds on extreme values

Author: dkhalanskyjb

core/jsMain/src/Instant.kt

@@ -81,9 +81,11 @@ public actual class Instant internal constructor(internal val value: jtInstant)
         }
 
         actual fun fromEpochSeconds(epochSeconds: Long, nanosecondAdjustment: Long): Instant = try {
-            Instant(jtInstant.ofEpochSecond(epochSeconds, nanosecondAdjustment))
+            val secs = safeAdd(epochSeconds, floorDiv(nanosecondAdjustment, NANOS_PER_ONE.toLong()))
+            val nos = floorMod(nanosecondAdjustment, NANOS_PER_ONE.toLong()).toInt()
+            Instant(jtInstant.ofEpochSecond(secs, nos))
         } catch (e: Throwable) {
-            if (!e.isJodaDateTimeException()) throw e
+            if (!e.isJodaDateTimeException() && e !is ArithmeticException) throw e
             if (epochSeconds > 0) MAX else MIN
         }
 

core/jsMain/src/mathJs.kt

@@ -58,3 +58,35 @@ internal actual fun safeMultiply(a: Int, b: Int): Int {
     if (result > Int.MAX_VALUE || result < Int.MIN_VALUE) throw ArithmeticException("Multiplication overflows Int range: $a * $b.")
     return result.toInt()
 }
+
+/**
+ * Returns the floor division.
+ * <p>
+ * This returns {@code 0} for {@code floorDiv(0, 4)}.<br />
+ * This returns {@code -1} for {@code floorDiv(-1, 4)}.<br />
+ * This returns {@code -1} for {@code floorDiv(-2, 4)}.<br />
+ * This returns {@code -1} for {@code floorDiv(-3, 4)}.<br />
+ * This returns {@code -1} for {@code floorDiv(-4, 4)}.<br />
+ * This returns {@code -2} for {@code floorDiv(-5, 4)}.<br />
+ *
+ * @param a  the dividend
+ * @param b  the divisor
+ * @return the floor division
+ */
+internal fun floorDiv(a: Long, b: Long): Long = if (a >= 0) a / b else (a + 1) / b - 1
+
+/**
+ * Returns the floor modulus.
+ *
+ *
+ * This returns `0` for `floorMod(0, 4)`.<br></br>
+ * This returns `1` for `floorMod(-1, 4)`.<br></br>
+ * This returns `2` for `floorMod(-2, 4)`.<br></br>
+ * This returns `3` for `floorMod(-3, 4)`.<br></br>
+ * This returns `0` for `floorMod(-4, 4)`.<br></br>
+ *
+ * @param a  the dividend
+ * @param b  the divisor
+ * @return the floor modulus (positive)
+ */
+internal fun floorMod(a: Long, b: Long): Long = (a % b + b) % b