feat(lotw): auto-sync grids on app start with separate toggle

Mirrors the ephemeris auto-update check: on every app start, if LoTW
credentials are configured, the new 'auto-sync LoTW grids' toggle is on,
at least one manual sync was done before, and today has not synced yet
(ARRL rate limit, ~once a day), pull confirmations since the last sync
and merge them. Same callsign -> incremental merge; callsign change ->
full replace. Manual dialog and automatic path share the orchestration
(mode resolution, gate, merge/persist) moved to core:domain
LoTWGridSync.kt; LoTWSyncMode moved to core:domain. 8 unit tests.

core/domain/src/main/java/com/rtbishop/look4sat/core/domain/model/Settings.kt

@@ -64,7 +64,10 @@ data class OtherSettings(
     val shouldSeeWhatsNew: Boolean,
     val sstvMode: String = "Auto",
     val lowElevation: Double = 15.0,
-    val highElevation: Double = 45.0
+    val highElevation: Double = 45.0,
+    /** Independent auto-sync toggle for LoTW confirmed grids (separate from the
+     *  ephemeris auto-update; only effective after at least one manual sync). */
+    val stateOfAutoLotwSync: Boolean = true
 )
 
 data class DataSourcesSettings(

core/domain/src/main/java/com/rtbishop/look4sat/core/domain/repository/LoTWGridSync.kt

@@ -0,0 +1,125 @@
+/*
+ * Look4Sat. Amateur radio satellite tracker and pass predictor.
+ * Copyright (C) 2019-2026 Arty Bishop and contributors.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+package com.rtbishop.look4sat.core.domain.repository
+
+import com.rtbishop.look4sat.core.domain.model.GridQso
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.withContext
+import java.text.SimpleDateFormat
+import java.util.Date
+import java.util.Locale
+import java.util.TimeZone
+
+/**
+ * Shared LoTW sync orchestration used by BOTH the manual sync (settings screen)
+ * and the automatic sync on app start (MainApplication), so the two paths can
+ * never drift apart:
+ *
+ * - [LoTWSyncMode.Incremental] pulls only the confirmations since the last sync
+ *   and MERGES them into the stored grids/QSOs (grids only grow; QSO detail is
+ *   deduped by call + QSO time).
+ * - [LoTWSyncMode.Full] pulls everything and REPLACES the stored data.
+ */
+
+/** UTC date ("yyyyMMdd") of the given instant — the LoTW sync cursor granularity. */
+fun lotwSyncToday(now: Long = System.currentTimeMillis()): String =
+    SimpleDateFormat("yyyyMMdd", Locale.US)
+        .apply { timeZone = TimeZone.getTimeZone("UTC") }
+        .format(Date(now))
+
+/**
+ * Resolves the effective sync mode for a given request:
+ * - an explicit [LoTWSyncMode.Full] request is always honored;
+ * - an [LoTWSyncMode.Incremental] request is honored only when the callsign
+ *   matches the last sync — a first sync, an unknown/empty record or a
+ *   callsign change falls back to [LoTWSyncMode.Full] so no stale grids from
+ *   another account linger.
+ * With [requested] == null (automatic sync) it picks incremental whenever
+ * possible and full otherwise.
+ */
+fun resolveLoTWSyncMode(
+    lastSyncCallsign: String,
+    callsign: String,
+    requested: LoTWSyncMode?
+): LoTWSyncMode {
+    if (requested == LoTWSyncMode.Full) return LoTWSyncMode.Full
+    val sameCall = lastSyncCallsign.isNotBlank() && lastSyncCallsign == callsign
+    return if (sameCall) LoTWSyncMode.Incremental else LoTWSyncMode.Full
+}
+
+/**
+ * Whether the automatic LoTW sync should run now — mirrors the ephemeris
+ * auto-update check: credentials configured, the LoTW auto-sync toggle on, at
+ * least one prior manual sync (the first sync stays manual/full), and not
+ * already synced today (ARRL limits report pulls, ~once a day per account).
+ */
+fun shouldAutoSyncLoTW(
+    isConfigured: Boolean,
+    autoLotwSyncEnabled: Boolean,
+    lastSyncDate: String,
+    today: String
+): Boolean = isConfigured && autoLotwSyncEnabled && lastSyncDate.isNotBlank() && lastSyncDate != today
+
+/**
+ * Applies a successful LoTW report to the stored grid data and advances the
+ * sync cursor so the next incremental pull asks LoTW for only the
+ * confirmations since today. Persistence runs on the IO dispatcher — building
+ * the per-grid QSO JSON and writing SharedPreferences blocks the calling
+ * thread, and for large accounts (multi-MB JSON) that froze the main thread
+ * after a manual sync ('bar done but app stuck').
+ *
+ * @return the resulting number of worked grids.
+ */
+suspend fun applyLoTWGridResult(
+    settingsRepo: ISettingsRepo,
+    result: LoTWResult.Success,
+    mode: LoTWSyncMode,
+    callsign: String,
+    now: Long = System.currentTimeMillis()
+): Int {
+    val existingGrids = settingsRepo.getWorkedGrids()
+    val existingQsos = settingsRepo.getWorkedGridQsos()
+    val existingRoamed = settingsRepo.getRoamedGrids()
+    val mergedGrids = if (mode == LoTWSyncMode.Incremental) existingGrids + result.grids else result.grids
+    val mergedQsos = if (mode == LoTWSyncMode.Incremental) mergeGridQsos(existingQsos, result.qsos) else result.qsos
+    val mergedRoamed = if (mode == LoTWSyncMode.Incremental) existingRoamed + result.roamedGrids else result.roamedGrids
+    settingsRepo.setLastLotwSyncDate(lotwSyncToday(now))
+    settingsRepo.setLastLotwSyncCallsign(callsign)
+    withContext(Dispatchers.IO) {
+        settingsRepo.setWorkedGrids(mergedGrids)
+        settingsRepo.setWorkedGridQsos(mergedQsos)
+        settingsRepo.setRoamedGrids(mergedRoamed)
+    }
+    return mergedGrids.size
+}
+
+/** Merge fresh QSO detail into existing per-grid lists, dedup by call + QSO time. */
+fun mergeGridQsos(
+    existing: Map<String, List<GridQso>>,
+    fresh: Map<String, List<GridQso>>
+): Map<String, List<GridQso>> {
+    val merged = existing.mapValues { (_, list) -> list.toMutableList() }.toMutableMap()
+    fresh.forEach { (grid, list) ->
+        val target = merged.getOrPut(grid) { mutableListOf() }
+        val known = target.mapTo(mutableSetOf()) { it.call to it.epochMs }
+        list.forEach { qso ->
+            if (known.add(qso.call to qso.epochMs)) target.add(qso)
+        }
+    }
+    return merged
+}

core/domain/src/main/java/com/rtbishop/look4sat/core/domain/repository/LoTWResult.kt

@@ -46,3 +46,6 @@ sealed class LoTWResult {
     /** Any other network-level failure (DNS, TLS, connection reset, HTTP 5xx). */
     data class NetworkError(val detail: String) : LoTWResult()
 }
+
+/** What a LoTW sync does: pull everything, or only new QSLs since the last sync. */
+enum class LoTWSyncMode { Full, Incremental }

core/domain/src/test/java/com/rtbishop/look4sat/core/domain/repository/LoTWGridSyncTest.kt

@@ -0,0 +1,261 @@
+/*
+ * Look4Sat. Amateur radio satellite tracker and pass predictor.
+ * Copyright (C) 2019-2026 Arty Bishop and contributors.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+package com.rtbishop.look4sat.core.domain.repository
+
+import com.rtbishop.look4sat.core.domain.model.DatabaseState
+import com.rtbishop.look4sat.core.domain.model.DataSourcesSettings
+import com.rtbishop.look4sat.core.domain.model.GridQso
+import com.rtbishop.look4sat.core.domain.model.LoTWSettings
+import com.rtbishop.look4sat.core.domain.model.OtherSettings
+import com.rtbishop.look4sat.core.domain.model.PassesSettings
+import com.rtbishop.look4sat.core.domain.model.RCSettings
+import com.rtbishop.look4sat.core.domain.model.RadioControlSettings
+import com.rtbishop.look4sat.core.domain.model.WavelogSettings
+import com.rtbishop.look4sat.core.domain.predict.GeoPos
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.runBlocking
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertTrue
+import org.junit.Test
+
+class LoTWGridSyncTest {
+
+    // 2026-09-16T00:00:00Z — fixed "now" for the cursor assertions.
+    private val now = 1_789_516_800_000L
+
+    // region resolveLoTWSyncMode
+
+    @Test
+    fun resolveModeHonorsExplicitFull() {
+        assertEquals(LoTWSyncMode.Full, resolveLoTWSyncMode("BA7OPF", "BA7OPF", LoTWSyncMode.Full))
+        assertEquals(LoTWSyncMode.Full, resolveLoTWSyncMode("", "BA7OPF", LoTWSyncMode.Full))
+    }
+
+    @Test
+    fun resolveModeAllowsIncrementalOnlyForSameCallsign() {
+        assertEquals(
+            LoTWSyncMode.Incremental,
+            resolveLoTWSyncMode("BA7OPF", "BA7OPF", LoTWSyncMode.Incremental)
+        )
+        assertEquals(
+            LoTWSyncMode.Full,
+            resolveLoTWSyncMode("BG7ABC", "BA7OPF", LoTWSyncMode.Incremental)
+        )
+        assertEquals(
+            LoTWSyncMode.Full,
+            resolveLoTWSyncMode("", "BA7OPF", LoTWSyncMode.Incremental)
+        )
+    }
+
+    @Test
+    fun resolveModeForAutoSyncPicksIncrementalWhenPossible() {
+        assertEquals(LoTWSyncMode.Incremental, resolveLoTWSyncMode("BA7OPF", "BA7OPF", null))
+        assertEquals(LoTWSyncMode.Full, resolveLoTWSyncMode("BG7ABC", "BA7OPF", null))
+        assertEquals(LoTWSyncMode.Full, resolveLoTWSyncMode("", "BA7OPF", null))
+    }
+
+    // endregion
+
+    // region shouldAutoSyncLoTW
+
+    @Test
+    fun autoSyncGateRequiresEverything() {
+        val today = "20260916"
+        // Not configured.
+        assertFalse(shouldAutoSyncLoTW(false, true, "20260915", today))
+        // Auto-update toggle off.
+        assertFalse(shouldAutoSyncLoTW(true, false, "20260915", today))
+        // Never synced manually — first sync stays manual/full.
+        assertFalse(shouldAutoSyncLoTW(true, true, "", today))
+        // Already synced today — ARRL rate-limit guard.
+        assertFalse(shouldAutoSyncLoTW(true, true, today, today))
+        // All gates open.
+        assertTrue(shouldAutoSyncLoTW(true, true, "20260915", today))
+    }
+
+    // endregion
+
+    // region mergeGridQsos
+
+    @Test
+    fun mergeGridQsosDedupsByCallAndTime() {
+        val existing = mapOf(
+            "OL62" to listOf(qso("BA7ABC", 1000L)),
+            "OL63" to listOf(qso("BA7DEF", 2000L))
+        )
+        val fresh = mapOf(
+            // Same grid, same QSO re-delivered by an overlapping since-date.
+            "OL62" to listOf(qso("BA7ABC", 1000L)),
+            // Same grid, brand-new QSO.
+            "OL62" to listOf(qso("BA7GHI", 3000L)),
+            // New grid entirely.
+            "PM95" to listOf(qso("BA7JKL", 4000L))
+        )
+        val merged = mergeGridQsos(existing, fresh)
+        assertEquals(setOf("OL62", "OL63", "PM95"), merged.keys)
+        assertEquals(2, merged["OL62"]?.size) // BA7ABC once, BA7GHI added
+        assertEquals(1, merged["OL63"]?.size)
+        assertEquals(1, merged["PM95"]?.size)
+    }
+
+    @Test
+    fun mergeGridQsosHandlesEmptySides() {
+        val fresh = mapOf("OL62" to listOf(qso("BA7ABC", 1000L)))
+        assertEquals(fresh, mergeGridQsos(emptyMap(), fresh))
+        // An empty incremental pull must leave the stored side untouched.
+        assertEquals(fresh, mergeGridQsos(fresh, emptyMap()))
+        assertEquals(emptyMap<String, List<GridQso>>(), mergeGridQsos(emptyMap(), emptyMap()))
+    }
+
+    // endregion
+
+    // region applyLoTWGridResult
+
+    @Test
+    fun applyIncrementalMergesAndAdvancesCursor() = runBlocking {
+        val repo = FakeSettingsRepo().apply {
+            setWorkedGrids(setOf("OL62"))
+            setWorkedGridQsos(mapOf("OL62" to listOf(qso("BA7ABC", 1000L))))
+            setRoamedGrids(setOf("OL62"))
+            setLastLotwSyncDate("20260915")
+            setLastLotwSyncCallsign("BA7OPF")
+        }
+        val result = LoTWResult.Success(
+            grids = setOf("OL62", "PM95"),
+            qsos = mapOf("OL62" to listOf(qso("BA7ABC", 1000L)), "PM95" to listOf(qso("BA7GHI", 2000L))),
+            roamedGrids = setOf("PM95")
+        )
+        val count = applyLoTWGridResult(repo, result, LoTWSyncMode.Incremental, "BA7OPF", now)
+
+        assertEquals(2, count)
+        assertEquals(setOf("OL62", "PM95"), repo.getWorkedGrids())
+        assertEquals(1, repo.getWorkedGridQsos()["OL62"]?.size) // deduped
+        assertEquals(setOf("OL62", "PM95"), repo.getRoamedGrids())
+        assertEquals("20260916", repo.getLastLotwSyncDate())
+        assertEquals("BA7OPF", repo.getLastLotwSyncCallsign())
+    }
+
+    @Test
+    fun applyFullReplacesEverythingAndAdvancesCursor() = runBlocking {
+        val repo = FakeSettingsRepo().apply {
+            setWorkedGrids(setOf("OL62", "STALE"))
+            setWorkedGridQsos(mapOf("STALE" to listOf(qso("BG7OLD", 1L))))
+            setRoamedGrids(setOf("STALE"))
+            setLastLotwSyncDate("20260910")
+            setLastLotwSyncCallsign("BG7OLD")
+        }
+        val result = LoTWResult.Success(
+            grids = setOf("PM95"),
+            qsos = mapOf("PM95" to listOf(qso("BA7GHI", 2000L))),
+            roamedGrids = setOf("PM95")
+        )
+        val count = applyLoTWGridResult(repo, result, LoTWSyncMode.Full, "BA7OPF", now)
+
+        assertEquals(1, count)
+        assertEquals(setOf("PM95"), repo.getWorkedGrids())
+        assertEquals(setOf("PM95"), repo.getWorkedGridQsos().keys)
+        assertEquals(setOf("PM95"), repo.getRoamedGrids())
+        assertEquals("20260916", repo.getLastLotwSyncDate())
+        assertEquals("BA7OPF", repo.getLastLotwSyncCallsign())
+    }
+
+    // endregion
+
+    private fun qso(call: String, epochMs: Long): GridQso =
+        GridQso(call, epochMs, "FO-29", "FM", "70CM", "2M")
+
+    /**
+     * Minimal ISettingsRepo fake backing only the LoTW sync surface; the rest
+     * throws (mirrors the FakeSettingsRepo pattern used in feature tests).
+     */
+    private class FakeSettingsRepo : ISettingsRepo {
+        override val stationPosition: StateFlow<GeoPos> = MutableStateFlow(GeoPos(23.13, 113.26))
+        override val appVersionName: String = "test"
+        override val selectedIds: StateFlow<List<Int>> = MutableStateFlow(emptyList())
+        override val selectedTypes: StateFlow<List<String>> = MutableStateFlow(emptyList())
+        override val passesSettings: StateFlow<PassesSettings> = MutableStateFlow(
+            PassesSettings(hoursAhead = 24, minElevation = 10.0, selectedModes = emptyList())
+        )
+        override val databaseState: StateFlow<DatabaseState> = MutableStateFlow(DatabaseState(0, 0, 0L))
+        override val rcSettings: StateFlow<RCSettings> = MutableStateFlow(
+            RCSettings(false, "", "", "", false, "", "", "", 0L, false, "", "", "", false, "", "")
+        )
+        override val otherSettings: StateFlow<OtherSettings> = MutableStateFlow(
+            OtherSettings(
+                stateOfAutoUpdate = true,
+                stateOfSensors = false,
+                stateOfSweep = false,
+                stateOfUtc = false,
+                stateOfLightTheme = false,
+                stateOfNightMode = false,
+                stateOfMapGrid = false,
+                shouldSeeWarning = false,
+                shouldSeeWhatsNew = false
+            )
+        )
+        override val dataSourcesSettings: StateFlow<DataSourcesSettings> = MutableStateFlow(
+            DataSourcesSettings(satelliteUrls = emptyList(), transceiversUrls = emptyList())
+        )
+        override val dataSourcesStatus: StateFlow<Map<String, Int>> = MutableStateFlow(emptyMap())
+        override val radioControlSettings: StateFlow<RadioControlSettings> = MutableStateFlow(
+            RadioControlSettings(false, RadioControlSettings.MODEL_YAESU_FT817, "", "", "", "", 9600)
+        )
+        override val wavelogSettings: StateFlow<WavelogSettings> = MutableStateFlow(WavelogSettings())
+        override val lotwSettings: StateFlow<LoTWSettings> = MutableStateFlow(LoTWSettings())
+
+        private var workedGrids: Set<String> = emptySet()
+        private var workedGridQsos: Map<String, List<GridQso>> = emptyMap()
+        private var roamedGrids: Set<String> = emptySet()
+        private var lastSyncDate: String = ""
+        private var lastSyncCallsign: String = ""
+
+        override fun getWorkedGrids(): Set<String> = workedGrids
+        override fun setWorkedGrids(grids: Set<String>) { workedGrids = grids }
+        override fun getWorkedGridQsos(): Map<String, List<GridQso>> = workedGridQsos
+        override fun setWorkedGridQsos(qsos: Map<String, List<GridQso>>) { workedGridQsos = qsos }
+        override fun getRoamedGrids(): Set<String> = roamedGrids
+        override fun setRoamedGrids(grids: Set<String>) { roamedGrids = grids }
+        override fun getLastLotwSyncDate(): String = lastSyncDate
+        override fun setLastLotwSyncDate(date: String) { lastSyncDate = date }
+        override fun getLastLotwSyncCallsign(): String = lastSyncCallsign
+        override fun setLastLotwSyncCallsign(callsign: String) { lastSyncCallsign = callsign }
+
+        override fun setSelectedIds(ids: List<Int>) = TODO()
+        override fun setSelectedTypes(types: List<String>) = TODO()
+        override fun setPassesSettings(settings: PassesSettings) = TODO()
+        override fun setStationPosition(latitude: Double, longitude: Double, altitude: Double): Boolean = TODO()
+        override fun setStationPosition(): Boolean = TODO()
+        override fun setStationPosition(locator: String): Boolean = TODO()
+        override fun getSatelliteTypesIds(types: List<String>): List<Int> = TODO()
+        override fun setSatelliteTypeIds(type: String, ids: List<Int>) = TODO()
+        override fun updateDatabaseState(state: DatabaseState) = TODO()
+        override fun updateRCSettings(settings: RCSettings) = TODO()
+        override fun updateOtherSettings(transform: (OtherSettings) -> OtherSettings) = TODO()
+        override fun updateDataSourcesSettings(settings: DataSourcesSettings) = TODO()
+        override fun updateDataSourcesStatus(status: Map<String, Int>) = TODO()
+        override fun updateRadioControlSettings(settings: RadioControlSettings) = TODO()
+        override fun getSatelliteOffset(catnum: Int): String = ""
+        override fun setSatelliteOffset(catnum: Int, offset: String) = TODO()
+        override fun getAmSatCallsign(): String = ""
+        override fun setAmSatCallsign(callsign: String) = TODO()
+        override fun updateWavelogSettings(settings: WavelogSettings) = TODO()
+        override fun updateLoTWSettings(settings: LoTWSettings) = TODO()
+    }
+}