data: add ColumnReader.toEventInstance() with defensive validation (§8)

app/src/main/java/de/jeanlucmakiola/calendula/data/calendar/InstanceMapper.kt

@@ -0,0 +1,41 @@
+package de.jeanlucmakiola.calendula.data.calendar
+
+import android.util.Log
+import de.jeanlucmakiola.calendula.domain.EventInstance
+
+private const val TAG = "InstanceMapper"
+
+internal fun ColumnReader.toEventInstance(): EventInstance? {
+    val begin = getLong(InstanceProjection.IDX_BEGIN)
+    val end = getLong(InstanceProjection.IDX_END)
+
+    if (begin < 0L) {
+        Log.w(TAG, "Dropping row with negative begin=$begin")
+        return null
+    }
+    if (end < begin) {
+        Log.w(TAG, "Dropping row with end=$end < begin=$begin")
+        return null
+    }
+
+    val rawTitle = getString(InstanceProjection.IDX_TITLE)
+    val title = if (rawTitle.isNullOrEmpty()) Fallbacks.UNTITLED_EVENT else rawTitle
+
+    val color = if (isNull(InstanceProjection.IDX_EVENT_COLOR)) {
+        getInt(InstanceProjection.IDX_CALENDAR_COLOR)
+    } else {
+        getInt(InstanceProjection.IDX_EVENT_COLOR)
+    }
+
+    return EventInstance(
+        instanceId = getLong(InstanceProjection.IDX_INSTANCE_ID),
+        eventId = getLong(InstanceProjection.IDX_EVENT_ID),
+        calendarId = getLong(InstanceProjection.IDX_CALENDAR_ID),
+        title = title,
+        start = begin.toKotlinInstantFromEpochMillis(),
+        end = end.toKotlinInstantFromEpochMillis(),
+        isAllDay = getInt(InstanceProjection.IDX_ALL_DAY) != 0,
+        color = color,
+        location = getString(InstanceProjection.IDX_LOCATION),
+    )
+}