Tidy IcsParser day arithmetic, index scans and wire lookups

app/src/main/java/de/jeanlucmakiola/calendula/domain/Recurrence.kt

@@ -65,13 +65,8 @@ fun parseSimpleRecurrence(
         return null
     }
 
-    val freq = when (parts["FREQ"]?.uppercase()) {
-        "DAILY" -> RecurrenceFreq.Daily
-        "WEEKLY" -> RecurrenceFreq.Weekly
-        "MONTHLY" -> RecurrenceFreq.Monthly
-        "YEARLY" -> RecurrenceFreq.Yearly
-        else -> return null
-    }
+    val freq = RecurrenceFreq.entries.firstOrNull { it.name.equals(parts["FREQ"], ignoreCase = true) }
+        ?: return null
     val interval = parts["INTERVAL"]?.let { it.toIntOrNull()?.takeIf { n -> n >= 1 } ?: return null } ?: 1
 
     // BYDAY is simple only as plain weekday picks on a weekly rule; ordinal

app/src/main/java/de/jeanlucmakiola/calendula/domain/ics/IcsParser.kt

@@ -9,10 +9,10 @@ import kotlinx.datetime.atStartOfDayIn
 import kotlinx.datetime.toInstant
 import kotlinx.datetime.toLocalDateTime
 import kotlin.math.ceil
+import kotlin.time.Duration.Companion.days
+import kotlin.time.Duration.Companion.milliseconds
 import kotlin.time.Instant
 
-/** Milliseconds in a calendar day; all-day times are UTC midnights, so this is exact. */
-private const val DAY_MILLIS = 86_400_000L
 private const val MINUTES_PER_DAY = 1_440
 
 /**
@@ -316,13 +316,9 @@ class IcsParser(private val deviceZone: TimeZone = TimeZone.currentSystemDefault
         dtEnd: IcsDateTime?,
         duration: String?,
     ): Instant {
-        val explicit = dtEnd?.instant ?: duration?.let {
-            Instant.fromEpochMilliseconds(
-                start.instant.toEpochMilliseconds() + parseRfc2445DurationMillis(it),
-            )
-        }
+        val explicit = dtEnd?.instant ?: duration?.let { start.instant + parseRfc2445DurationMillis(it).milliseconds }
         if (!start.isAllDay) return explicit ?: start.instant
-        return explicit?.takeIf { it > start.instant } ?: start.instant.plusDays(1)
+        return explicit?.takeIf { it > start.instant } ?: (start.instant + 1.days)
     }
 
     /**
@@ -419,9 +415,6 @@ class IcsParser(private val deviceZone: TimeZone = TimeZone.currentSystemDefault
         fun IcsContentLine.isBegin(component: String) =
             name == "BEGIN" && value.trim().equals(component, true)
 
-        fun Instant.plusDays(days: Int): Instant =
-            Instant.fromEpochMilliseconds(toEpochMilliseconds() + days * DAY_MILLIS)
-
         /**
          * A single-valued `CATEGORIES`, which is what the Fossify family writes
          * for the source calendar's name. A multi-item list is a tag list and
@@ -440,42 +433,26 @@ class IcsParser(private val deviceZone: TimeZone = TimeZone.currentSystemDefault
                 .takeIf { it.isNotEmpty() && !it.equals("null", true) }
         }
 
-        /** Index of the matching `END:<component>` at/after [from], or list end. */
         /**
          * Where an unterminated component's body has to stop: the next top-level
          * `VEVENT` / `VTODO` in `[from, end)`, or [end] when there is none. A
          * nested `VALARM` is part of the body and is not a boundary.
          */
-        fun indexOfNextComponent(lines: List<String>, from: Int, end: Int): Int {
-            var i = from
-            while (i < end) {
+        fun indexOfNextComponent(lines: List<String>, from: Int, end: Int): Int =
+            (from until end).firstOrNull { i ->
                 val line = parseContentLine(lines[i])
-                if (line != null && (line.isBegin("VEVENT") || line.isBegin("VTODO"))) {
-                    return i
-                }
-                i++
-            }
-            return end
-        }
+                line != null && (line.isBegin("VEVENT") || line.isBegin("VTODO"))
+            } ?: end
 
-        fun indexOfEnd(lines: List<String>, from: Int, component: String): Int {
-            var i = from
-            while (i < lines.size) {
+        /** Index of the matching `END:<component>` at/after [from], or list end. */
+        fun indexOfEnd(lines: List<String>, from: Int, component: String): Int =
+            (from until lines.size).firstOrNull { i ->
                 val line = parseContentLine(lines[i])
-                if (line != null && line.name == "END" &&
-                    line.value.trim().equals(component, true)
-                ) {
-                    return i
-                }
-                i++
-            }
-            return lines.size
-        }
+                line != null && line.name == "END" && line.value.trim().equals(component, true)
+            } ?: lines.size
 
-        fun mapIcsStatus(value: String): EventStatus = when (value.trim().uppercase()) {
-            "TENTATIVE" -> EventStatus.Tentative
-            "CANCELLED" -> EventStatus.Cancelled
-            else -> EventStatus.Confirmed
-        }
+        fun mapIcsStatus(value: String): EventStatus =
+            EventStatus.entries.firstOrNull { it.name.equals(value.trim(), ignoreCase = true) }
+                ?: EventStatus.Confirmed
     }
 }