add support of ranges in strings

src/commonTest/kotlin/com/insanusmokrassar/krontab/utils/StringParseTest.kt

@@ -1,12 +1,12 @@
 package com.insanusmokrassar.krontab.utils
 
 import com.insanusmokrassar.krontab.buildSchedule
-import com.insanusmokrassar.krontab.builder.buildSchedule
-import com.insanusmokrassar.krontab.createSimpleScheduler
 import com.soywiz.klock.DateTime
 import kotlinx.coroutines.*
 import kotlinx.coroutines.flow.collect
 import kotlinx.coroutines.flow.takeWhile
+import kotlin.math.max
+import kotlin.math.min
 import kotlin.test.Test
 import kotlin.test.assertEquals
 
@@ -60,4 +60,23 @@ class StringParseTest {
             }
         }
     }
+    @Test
+    fun testThatFlowIsCorrectlyWorkEverySeveralSecondsRangeBuiltOnString() {
+        val rangesEnds = listOf(0 to 5, 30 to 35)
+        val kronScheduler = buildSchedule("${rangesEnds.joinToString(",") { "${it.first}-${it.second}" }} * * * *")
+
+        val flow = kronScheduler.asFlow()
+
+        runTest {
+            val ranges = rangesEnds.map { it.first .. it.second }.flatten().toMutableList()
+            val expectedCollects = rangesEnds.sumBy { it.second - it.first + 1 }
+            var collected = 0
+
+            flow.takeWhile { ranges.isNotEmpty() }.collect {
+                ranges.remove(it.seconds)
+                collected++
+            }
+            assertEquals(expectedCollects, collected)
+        }
+    }
 }