Share RRULE part tokenising

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

@@ -60,13 +60,7 @@ fun parseSimpleRecurrence(
     rrule: String,
     zone: TimeZone = TimeZone.currentSystemDefault(),
 ): SimpleRecurrence? {
-    val parts = rrule.removePrefix("RRULE:").split(';')
-        .filter { it.isNotBlank() }
-        .associate { token ->
-            val eq = token.indexOf('=')
-            if (eq <= 0) return null
-            token.substring(0, eq).uppercase() to token.substring(eq + 1)
-        }
+    val parts = rruleParts(rrule).associate { part -> (part.key ?: return null) to part.value }
     if (parts.keys.any { it !in setOf("FREQ", "INTERVAL", "UNTIL", "COUNT", "WKST", "BYDAY") }) {
         return null
     }
@@ -134,6 +128,20 @@ fun SimpleRecurrence.toRRule(zone: TimeZone = TimeZone.currentSystemDefault()):
     }
 }
 
+/** One `;`-separated part of an RRULE as written; [key] is null when it has no `KEY=`. */
+internal class RrulePart(val raw: String) {
+    private val eq = raw.indexOf('=')
+    val key: String? = if (eq > 0) raw.substring(0, eq).uppercase() else null
+    val value: String = if (eq > 0) raw.substring(eq + 1) else ""
+}
+
+/**
+ * [rule]'s non-blank parts, after an optional leading "RRULE:". What to do
+ * with a malformed one (reject, repair or skip) is the caller's call.
+ */
+internal fun rruleParts(rule: String): List<RrulePart> =
+    rule.removePrefix("RRULE:").split(';').filter { it.isNotBlank() }.map(::RrulePart)
+
 internal val RRULE_DAY_CODES: Map<DayOfWeek, String> = mapOf(
     DayOfWeek.MONDAY to "MO",
     DayOfWeek.TUESDAY to "TU",

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

@@ -19,30 +19,30 @@ import kotlinx.datetime.LocalDate
 fun realignRecurrence(rrule: String, oldStart: LocalDate, newStart: LocalDate): String? {
     if (oldStart == newStart) return rrule
     val prefix = if (rrule.startsWith("RRULE:")) "RRULE:" else ""
-    val parts = rrule.removePrefix("RRULE:").split(';').filter { it.isNotBlank() }
+    val parts = rruleParts(rrule)
     if (parts.isEmpty()) return null
+    var freq = false
     var weekly = false
+    var byDay = false
     val rebuilt = parts.map { part ->
-        val eq = part.indexOf('=')
-        if (eq <= 0) return null
-        val key = part.substring(0, eq).uppercase()
-        val value = part.substring(eq + 1).trim()
-        when (key) {
+        val value = part.value.trim()
+        when (part.key) {
             "FREQ" -> {
+                freq = true
                 weekly = value.equals("WEEKLY", ignoreCase = true)
-                part
+                part.raw
             }
             "BYDAY" -> {
+                byDay = true
                 val old = RRULE_DAY_CODES[oldStart.dayOfWeek] ?: return null
                 if (!value.equals(old, ignoreCase = true)) return null
                 "BYDAY=${RRULE_DAY_CODES.getValue(newStart.dayOfWeek)}"
             }
-            "INTERVAL", "COUNT", "UNTIL", "WKST" -> part
+            "INTERVAL", "COUNT", "UNTIL", "WKST" -> part.raw
             else -> return null
         }
     }
     // BYDAY is only simple on a weekly rule, matching parseSimpleRecurrence.
-    if (!weekly && parts.any { it.substringBefore('=').trim().uppercase() == "BYDAY" }) return null
-    if (parts.none { it.substringBefore('=').trim().uppercase() == "FREQ" }) return null
+    if (!freq || (byDay && !weekly)) return null
     return prefix + rebuilt.joinToString(";")
 }

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

@@ -1,5 +1,7 @@
 package de.jeanlucmakiola.calendula.domain.ics
 
+import de.jeanlucmakiola.calendula.domain.rruleParts
+
 private val VALID_FREQ = setOf(
     "SECONDLY", "MINUTELY", "HOURLY", "DAILY", "WEEKLY", "MONTHLY", "YEARLY",
 )
@@ -79,13 +81,12 @@ fun sanitizeRrule(raw: String?): SanitizedRrule {
         return kept.takeIf { it.isNotEmpty() }?.joinToString(",")
     }
 
-    for (part in rule.split(';')) {
-        // A stray separator ("FREQ=DAILY;") normalises away; nothing was lost.
-        // A part that carries text but no '=' ("FREQ=WEEKLY;BYDAY") is a part
-        // being dropped, so it falls through and marks the rule repaired.
-        if (part.isBlank()) continue
-        val key = part.substringBefore('=', "").trim().uppercase()
-        val value = if ('=' in part) part.substringAfter('=').trim() else ""
+    // A stray separator ("FREQ=DAILY;") normalises away; nothing was lost.
+    // A part that carries text but no '=' ("FREQ=WEEKLY;BYDAY") is a part
+    // being dropped, so it falls through and marks the rule repaired.
+    for (part in rruleParts(raw.orEmpty().trim())) {
+        val key = part.key?.trim().orEmpty()
+        val value = part.value.trim()
         val kept = when {
             key.isEmpty() || value.isEmpty() -> null
             key == "FREQ" ->

app/src/main/java/de/jeanlucmakiola/calendula/ui/common/RecurrenceText.kt

@@ -10,6 +10,7 @@ import androidx.compose.ui.text.font.FontStyle
 import de.jeanlucmakiola.calendula.R
 import de.jeanlucmakiola.calendula.domain.SimpleRecurrence
 import de.jeanlucmakiola.calendula.domain.occurrencesSpanYears
+import de.jeanlucmakiola.calendula.domain.rruleParts
 import de.jeanlucmakiola.calendula.domain.ics.parseBasicDate
 import de.jeanlucmakiola.calendula.domain.upcomingOccurrences
 import de.jeanlucmakiola.floret.locale.localizedDateFormatter
@@ -33,10 +34,7 @@ import java.util.Locale
  */
 @Composable
 fun recurrenceText(rrule: String, locale: Locale): AnnotatedString {
-    val parts = rrule.removePrefix("RRULE:").split(';').mapNotNull { token ->
-        val eq = token.indexOf('=')
-        if (eq <= 0) null else token.substring(0, eq).uppercase() to token.substring(eq + 1)
-    }.toMap()
+    val parts = rruleParts(rrule).mapNotNull { part -> part.key?.let { it to part.value } }.toMap()
 
     val freq = parts["FREQ"]?.uppercase()
     val interval = parts["INTERVAL"]?.toIntOrNull() ?: 1