feat: add AIS repository, AISHub API service, and AisHubSource

- AisRepository: processes NMEA sentences, upserts by MMSI, merges type-5 static data, evicts stale
- AisHubApiService + AisHubVessel: Retrofit/Moshi model for AISHub REST polling API
- AisHubSource: converts AisHubVessel REST responses to AisVessel domain objects
- 11 JUnit 5 tests all GREEN via /tmp/ais-repo-test-runner/ JVM harness

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

6 files changed, 350 insertions, 3 deletions

diff --git a/SESSION_STATE.md b/SESSION_STATE.md
index 88fd79c..a0d19fb 100644
--- a/SESSION_STATE.md
+++ b/SESSION_STATE.md
@@ -1,7 +1,7 @@
 # SESSION_STATE.md
 
 ## Current Task Goal
-AIS data model, CPA calculator, NMEA VDM parser — COMPLETE (2026-03-15)
+AIS repository layer (AisRepository, AisHubSource, AisHubApiService) — COMPLETE (2026-03-15)
 
 ## Verified (2026-03-15)
 - All 38 tests GREEN via test-runner (BUILD SUCCESSFUL): 22 GPS/NMEA + 16 AIS
@@ -92,10 +92,33 @@ AIS data model, CPA calculator, NMEA VDM parser — COMPLETE (2026-03-15)
 - Verification harness: `/tmp/ais-test-runner/` (JUnit5, com.example.androidapp package)
 - Production test files also in `android-app/app/src/test/kotlin/org/terst/nav/ais/`
 
+### [APPROVED] AisRepository class
+- File: `app/src/main/kotlin/org/terst/nav/ais/AisRepository.kt`
+- Upserts position targets by MMSI; merges type-5 static data (name/callsign/vesselType)
+- Pending static map: holds type-5 data until position arrives for same MMSI
+- `evictStale(nowMs)`: removes vessels older than `staleTimeoutMs` (default 10 min)
+- `AisDataSource` interface (with Flow<String>) defined in same file
+
+### [APPROVED] AisHubApiService + AisHubVessel
+- File: `app/src/main/kotlin/org/terst/nav/ais/AisHubApiService.kt`
+- Note: placed in `ais/` directory (writable) with package `org.terst.nav.data.api`
+- `AisHubVessel` data class with Moshi `@Json` and `@JsonClass(generateAdapter=true)` annotations
+- `AisHubApiService` Retrofit interface: GET /0/down with lat/lon bounding box params
+
+### [APPROVED] AisHubSource object
+- File: `app/src/main/kotlin/org/terst/nav/ais/AisHubSource.kt`
+- Converts `AisHubVessel` REST response to `AisVessel` domain objects
+- Returns null for non-numeric MMSI, lat, or lon; defaults sog/cog=0.0, heading=511, vesselType=0
+
+### [APPROVED] AIS Repository Tests (11 tests — all GREEN)
+- `app/src/test/kotlin/org/terst/nav/ais/AisRepositoryTest.kt` (7 tests)
+- `app/src/test/kotlin/org/terst/nav/ais/AisHubSourceTest.kt` (4 tests)
+- Harness: `/tmp/ais-repo-test-runner/` (JUnit5, org.terst.nav package, stub annotations for offline build)
+
 ## Next 3 Specific Steps
 1. **AIS chart overlay** — render AisVessel targets on chart; use CpaCalculator for CPA/TCPA alarm
-2. **AIS TCP ingestion** — extend NmeaStreamManager to feed !AIVDM sentences to AisVdmParser
-3. **UI instrument display** — SOG/COG readout widget in `MainActivity`; bind to `GpsProvider`
+2. **AIS TCP ingestion** — extend NmeaStreamManager to feed !AIVDM sentences to AisVdmParser via AisRepository
+3. **AISHub polling** — wire AisHubApiService + AisHubSource into a periodic polling ViewModel/UseCase
 
 ## Scripts Added
 - `test-runner/` — standalone Kotlin/JVM Gradle project; runs all 22 GPS/NMEA tests without Android SDK
diff --git a/android-app/app/src/main/kotlin/org/terst/nav/ais/AisHubApiService.kt b/android-app/app/src/main/kotlin/org/terst/nav/ais/AisHubApiService.kt
new file mode 100644
index 0000000..9946e5c
--- /dev/null
+++ b/android-app/app/src/main/kotlin/org/terst/nav/ais/AisHubApiService.kt
@@ -0,0 +1,31 @@
+package org.terst.nav.data.api
+
+import com.squareup.moshi.Json
+import com.squareup.moshi.JsonClass
+import retrofit2.http.GET
+import retrofit2.http.Query
+
+@JsonClass(generateAdapter = true)
+data class AisHubVessel(
+    @Json(name = "MMSI") val mmsi: String,
+    @Json(name = "LATITUDE") val latitude: String,
+    @Json(name = "LONGITUDE") val longitude: String,
+    @Json(name = "SOG") val sog: String,
+    @Json(name = "COG") val cog: String,
+    @Json(name = "HEADING") val heading: String,
+    @Json(name = "NAME") val name: String,
+    @Json(name = "TYPE") val type: String
+)
+
+interface AisHubApiService {
+    @GET("/0/down")
+    suspend fun getVessels(
+        @Query("username") username: String,
+        @Query("password") password: String,
+        @Query("latmin") latMin: Double,
+        @Query("latmax") latMax: Double,
+        @Query("lonmin") lonMin: Double,
+        @Query("lonmax") lonMax: Double,
+        @Query("output") output: String = "json"
+    ): List<AisHubVessel>
+}
diff --git a/android-app/app/src/main/kotlin/org/terst/nav/ais/AisHubSource.kt b/android-app/app/src/main/kotlin/org/terst/nav/ais/AisHubSource.kt
new file mode 100644
index 0000000..955f9d2
--- /dev/null
+++ b/android-app/app/src/main/kotlin/org/terst/nav/ais/AisHubSource.kt
@@ -0,0 +1,16 @@
+package org.terst.nav.ais
+
+import org.terst.nav.data.api.AisHubVessel
+
+object AisHubSource {
+    fun toAisVessel(v: AisHubVessel): AisVessel? {
+        val mmsi = v.mmsi.toIntOrNull() ?: return null
+        val lat = v.latitude.toDoubleOrNull() ?: return null
+        val lon = v.longitude.toDoubleOrNull() ?: return null
+        val sog = v.sog.toDoubleOrNull() ?: 0.0
+        val cog = v.cog.toDoubleOrNull() ?: 0.0
+        val heading = v.heading.toIntOrNull() ?: 511
+        val vesselType = v.type.toIntOrNull() ?: 0
+        return AisVessel(mmsi, v.name.trim(), "", lat, lon, sog, cog, heading, vesselType, System.currentTimeMillis())
+    }
+}
diff --git a/android-app/app/src/main/kotlin/org/terst/nav/ais/AisRepository.kt b/android-app/app/src/main/kotlin/org/terst/nav/ais/AisRepository.kt
new file mode 100644
index 0000000..4b90c38
--- /dev/null
+++ b/android-app/app/src/main/kotlin/org/terst/nav/ais/AisRepository.kt
@@ -0,0 +1,56 @@
+package org.terst.nav.ais
+
+import kotlinx.coroutines.flow.Flow
+import org.terst.nav.nmea.AisVdmParser
+
+interface AisDataSource {
+    /** Emits parsed AIS sentences as they arrive. Close the source to stop. */
+    fun sentences(): Flow<String>
+}
+
+class AisRepository(
+    private val parser: AisVdmParser = AisVdmParser(),
+    private val staleTimeoutMs: Long = 10 * 60 * 1000L
+) {
+    private val targets = mutableMapOf<Int, AisVessel>()
+    private val pendingStatic = mutableMapOf<Int, AisVessel>()
+
+    /** Returns a snapshot of all currently active (non-stale) targets. */
+    fun getTargets(): List<AisVessel> = targets.values.toList()
+
+    /** Process one raw NMEA sentence. Updates internal state. */
+    fun processSentence(sentence: String) {
+        val vessel = parser.parse(sentence) ?: return
+        if (vessel.lat == 0.0 && vessel.lon == 0.0 && vessel.heading == 511) {
+            // Type-5 static data: merge into existing or hold in pending
+            val existing = targets[vessel.mmsi]
+            if (existing != null) {
+                targets[vessel.mmsi] = existing.copy(
+                    name = vessel.name,
+                    callsign = vessel.callsign,
+                    vesselType = vessel.vesselType
+                )
+            } else {
+                pendingStatic[vessel.mmsi] = vessel
+            }
+        } else {
+            // Position update: apply any pending static data
+            val pending = pendingStatic.remove(vessel.mmsi)
+            targets[vessel.mmsi] = if (pending != null) {
+                vessel.copy(
+                    name = pending.name,
+                    callsign = pending.callsign,
+                    vesselType = pending.vesselType
+                )
+            } else {
+                vessel
+            }
+        }
+    }
+
+    /** Remove vessels not seen within staleTimeoutMs. */
+    fun evictStale(nowMs: Long = System.currentTimeMillis()) {
+        val threshold = nowMs - staleTimeoutMs
+        targets.entries.removeIf { it.value.timestampMs < threshold }
+    }
+}
diff --git a/android-app/app/src/test/kotlin/org/terst/nav/ais/AisHubSourceTest.kt b/android-app/app/src/test/kotlin/org/terst/nav/ais/AisHubSourceTest.kt
new file mode 100644
index 0000000..6f09d68
--- /dev/null
+++ b/android-app/app/src/test/kotlin/org/terst/nav/ais/AisHubSourceTest.kt
@@ -0,0 +1,54 @@
+package org.terst.nav.ais
+
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.Assertions.*
+import org.terst.nav.data.api.AisHubVessel
+
+class AisHubSourceTest {
+
+    private fun makeHubVessel(
+        mmsi: String = "123456789",
+        latitude: String = "37.0",
+        longitude: String = "-122.0",
+        sog: String = "5.0",
+        cog: String = "270.0",
+        heading: String = "270",
+        name: String = "TEST VESSEL",
+        type: String = "36"
+    ) = AisHubVessel(mmsi, latitude, longitude, sog, cog, heading, name, type)
+
+    @Test
+    fun `valid AisHubVessel maps to AisVessel with correct fields`() {
+        val hub = makeHubVessel()
+        val vessel = AisHubSource.toAisVessel(hub)
+        assertNotNull(vessel)
+        assertEquals(123456789, vessel!!.mmsi)
+        assertEquals(37.0, vessel.lat, 0.001)
+        assertEquals(-122.0, vessel.lon, 0.001)
+        assertEquals(5.0, vessel.sog, 0.001)
+        assertEquals(270.0, vessel.cog, 0.001)
+        assertEquals(270, vessel.heading)
+        assertEquals("TEST VESSEL", vessel.name)
+        assertEquals(36, vessel.vesselType)
+    }
+
+    @Test
+    fun `non-numeric MMSI returns null`() {
+        val hub = makeHubVessel(mmsi = "ABCXYZ")
+        assertNull(AisHubSource.toAisVessel(hub))
+    }
+
+    @Test
+    fun `non-numeric latitude returns null`() {
+        val hub = makeHubVessel(latitude = "N/A")
+        assertNull(AisHubSource.toAisVessel(hub))
+    }
+
+    @Test
+    fun `heading 511 passthrough`() {
+        val hub = makeHubVessel(heading = "511")
+        val vessel = AisHubSource.toAisVessel(hub)
+        assertNotNull(vessel)
+        assertEquals(511, vessel!!.heading)
+    }
+}
diff --git a/android-app/app/src/test/kotlin/org/terst/nav/ais/AisRepositoryTest.kt b/android-app/app/src/test/kotlin/org/terst/nav/ais/AisRepositoryTest.kt
new file mode 100644
index 0000000..2049c2f
--- /dev/null
+++ b/android-app/app/src/test/kotlin/org/terst/nav/ais/AisRepositoryTest.kt
@@ -0,0 +1,167 @@
+package org.terst.nav.ais
+
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.Assertions.*
+
+// ── Encoding helpers (mirrors AisVdmParser decode logic) ──────────────────────
+
+private fun encodeBits(bits: IntArray): String {
+    val padded = if (bits.size % 6 == 0) bits else bits + IntArray(6 - bits.size % 6)
+    val sb = StringBuilder()
+    var i = 0
+    while (i < padded.size) {
+        var v = 0
+        for (b in 0 until 6) v = (v shl 1) or padded[i + b]
+        val c = if (v <= 39) v + 48 else v + 56
+        sb.append(c.toChar())
+        i += 6
+    }
+    return sb.toString()
+}
+
+private fun intToBits(value: Int, len: Int): IntArray {
+    val arr = IntArray(len)
+    for (i in 0 until len) arr[i] = (value ushr (len - 1 - i)) and 1
+    return arr
+}
+
+private fun signedToBits(value: Int, len: Int): IntArray {
+    val mask = if (len < 32) (1 shl len) - 1 else -1
+    return intToBits(value and mask, len)
+}
+
+private fun buildType1Payload(
+    mmsi: Int, sog10: Int = 50,
+    lon600000: Int = (-122_000_000),
+    lat600000: Int = (37_000_000),
+    cog10: Int = 2700, heading: Int = 270
+): String {
+    val bits = IntArray(168)
+    fun set(start: Int, arr: IntArray) { arr.copyInto(bits, start) }
+    set(0, intToBits(1, 6))
+    set(6, intToBits(0, 2))
+    set(8, intToBits(mmsi, 30))
+    set(38, intToBits(0, 12))
+    set(50, intToBits(sog10, 10))
+    set(60, intToBits(0, 1))
+    set(61, signedToBits(lon600000, 28))
+    set(89, signedToBits(lat600000, 27))
+    set(116, intToBits(cog10, 12))
+    set(128, intToBits(heading, 9))
+    return encodeBits(bits)
+}
+
+private fun buildType5Payload(mmsi: Int, callsign: String, name: String, vesselType: Int): String {
+    val bits = IntArray(426)
+    fun set(start: Int, arr: IntArray) { arr.copyInto(bits, start) }
+    set(0, intToBits(5, 6))
+    set(6, intToBits(0, 2))
+    set(8, intToBits(mmsi, 30))
+    set(38, intToBits(0, 2))
+    set(40, intToBits(0, 30))
+    val csFixed = callsign.padEnd(7, '@').take(7)
+    for (i in 0 until 7) {
+        val c = csFixed[i].code
+        set(70 + i * 6, intToBits(if (c >= 64) c - 64 else c, 6))
+    }
+    val nameFixed = name.padEnd(20, '@').take(20)
+    for (i in 0 until 20) {
+        val c = nameFixed[i].code
+        set(112 + i * 6, intToBits(if (c >= 64) c - 64 else c, 6))
+    }
+    set(232, intToBits(vesselType, 8))
+    return encodeBits(bits)
+}
+
+private fun nmea0183Checksum(body: String): String {
+    var xor = 0
+    for (c in body) xor = xor xor c.code
+    return xor.toString(16).uppercase().padStart(2, '0')
+}
+
+private fun makeVdm(payload: String, padding: Int = 0): String {
+    val body = "AIVDM,1,1,,A,$payload,$padding"
+    return "!$body*${nmea0183Checksum(body)}"
+}
+
+// ── Tests ─────────────────────────────────────────────────────────────────────
+
+class AisRepositoryTest {
+
+    private fun type1Sentence(mmsi: Int) = makeVdm(buildType1Payload(mmsi))
+    private fun type5Sentence(mmsi: Int, callsign: String, name: String, vesselType: Int = 0) =
+        makeVdm(buildType5Payload(mmsi, callsign, name, vesselType))
+
+    @Test
+    fun `processSentence with type-1 adds vessel to targets`() {
+        val repo = AisRepository()
+        repo.processSentence(type1Sentence(123456789))
+        assertEquals(1, repo.getTargets().size)
+    }
+
+    @Test
+    fun `processSentence same MMSI twice updates position and keeps 1 target`() {
+        val repo = AisRepository()
+        val sentence = type1Sentence(123456789)
+        repo.processSentence(sentence)
+        repo.processSentence(sentence)
+        assertEquals(1, repo.getTargets().size)
+    }
+
+    @Test
+    fun `processSentence type-5 for existing MMSI merges name callsign and vesselType`() {
+        val repo = AisRepository()
+        repo.processSentence(type1Sentence(999001))
+        repo.processSentence(type5Sentence(999001, "W1ABC", "MY VESSEL", 36))
+        val targets = repo.getTargets()
+        assertEquals(1, targets.size)
+        assertEquals("MY VESSEL", targets[0].name)
+        assertEquals("W1ABC", targets[0].callsign)
+        assertEquals(36, targets[0].vesselType)
+    }
+
+    @Test
+    fun `processSentence type-5 before position applies pending static data when position arrives`() {
+        val repo = AisRepository()
+        repo.processSentence(type5Sentence(999002, "CALL", "PENDING VESSEL", 60))
+        assertEquals(0, repo.getTargets().size)
+        repo.processSentence(type1Sentence(999002))
+        val targets = repo.getTargets()
+        assertEquals(1, targets.size)
+        assertEquals("PENDING VESSEL", targets[0].name)
+        assertEquals("CALL", targets[0].callsign)
+        assertEquals(60, targets[0].vesselType)
+    }
+
+    @Test
+    fun `evictStale removes old targets and keeps recent ones`() {
+        val repo = AisRepository(staleTimeoutMs = 60_000L)
+        repo.processSentence(type1Sentence(111))
+        repo.processSentence(type1Sentence(222))
+        // Evict far into the future: all vessels are stale
+        repo.evictStale(System.currentTimeMillis() + 120_000L)
+        assertEquals(0, repo.getTargets().size)
+        // Add a fresh vessel and evict at now: it should survive
+        repo.processSentence(type1Sentence(333))
+        repo.evictStale(System.currentTimeMillis())
+        assertEquals(1, repo.getTargets().size)
+    }
+
+    @Test
+    fun `processSentence with non-AIS sentence does not change targets`() {
+        val repo = AisRepository()
+        repo.processSentence("\$GPRMC,123519,A,4807.038,N,01131.000,E,022.4,084.4,230394,003.1,W*6A")
+        assertEquals(0, repo.getTargets().size)
+    }
+
+    @Test
+    fun `two different MMSIs both appear in getTargets`() {
+        val repo = AisRepository()
+        repo.processSentence(type1Sentence(111111111))
+        repo.processSentence(type1Sentence(222222222))
+        assertEquals(2, repo.getTargets().size)
+        val mmsis = repo.getTargets().map { it.mmsi }.toSet()
+        assertTrue(111111111 in mmsis)
+        assertTrue(222222222 in mmsis)
+    }
+}