adding some helpers related to week days handling

commons/src/main/kotlin/com/simplemobiletools/commons/extensions/Context.kt

@@ -353,3 +353,17 @@ fun Context.isPackageInstalled(pkgName: String): Boolean {
         false
     }
 }
+
+// format day bits to strings like "Mon, Tue, Wed"
+fun Context.getSelectedDaysString(bitMask: Int): String {
+    val dayBits = arrayListOf(MONDAY_BIT, TUESDAY_BIT, WEDNESDAY_BIT, THURSDAY_BIT, FRIDAY_BIT, SATURDAY_BIT, SUNDAY_BIT)
+
+    val weekDays = resources.getStringArray(R.array.week_days)
+    var days = ""
+    dayBits.forEachIndexed { index, bit ->
+        if (bitMask and bit != 0) {
+            days += "${weekDays[index].substringTo(3)}, "
+        }
+    }
+    return days.trim().trimEnd(',')
+}

commons/src/main/kotlin/com/simplemobiletools/commons/extensions/String.kt

@@ -217,6 +217,14 @@ fun String.getPublicUri(context: Context) = context.getDocumentFile(this)?.uri ?
 
 fun String.getOTGPublicPath(context: Context) = "${context.baseConfig.OTGBasePath}%3A${substring(OTG_PATH.length).replace("/", "%2F")}"
 
+fun String.substringTo(cnt: Int): String {
+    return if (isEmpty()) {
+        ""
+    } else {
+        substring(0, Math.min(length, cnt))
+    }
+}
+
 fun String.getMimeType(): String {
     val typesMap = HashMap<String, String>().apply {
         put("323", "text/h323")

commons/src/main/kotlin/com/simplemobiletools/commons/helpers/Constants.kt

@@ -121,6 +121,17 @@ const val CONFLICT_SKIP = 1
 const val CONFLICT_OVERWRITE = 2
 const val CONFLICT_MERGE = 3
 
+const val MONDAY_BIT = 1
+const val TUESDAY_BIT = 2
+const val WEDNESDAY_BIT = 4
+const val THURSDAY_BIT = 8
+const val FRIDAY_BIT = 16
+const val SATURDAY_BIT = 32
+const val SUNDAY_BIT = 64
+const val EVERY_DAY_BIT = MONDAY_BIT or TUESDAY_BIT or WEDNESDAY_BIT or THURSDAY_BIT or FRIDAY_BIT or SATURDAY_BIT or SUNDAY_BIT
+const val WEEK_DAYS_BIT = MONDAY_BIT or TUESDAY_BIT or WEDNESDAY_BIT or THURSDAY_BIT or FRIDAY_BIT
+const val WEEKENDS_BIT = SATURDAY_BIT or SUNDAY_BIT
+
 fun getDateFormats() = arrayListOf(
         "yyyy-MM-dd",
         "yyyyMMdd",