package org.terst.nav.gps

import org.junit.Assert.*
import org.junit.Before
import org.junit.Test

// ── Fake implementation (no Android dependencies) ────────────────────────────

class FakeGpsProvider : GpsProvider {
    var currentPosition: GpsPosition? = null
    private val listeners = mutableListOf<GpsListener>()
    var started = false

    override fun start() { started = true }
    override fun stop() { started = false }
    override val position: GpsPosition? get() = currentPosition
    override fun addListener(listener: GpsListener) { listeners.add(listener) }
    override fun removeListener(listener: GpsListener) { listeners.remove(listener) }

    fun simulatePosition(pos: GpsPosition) {
        currentPosition = pos
        listeners.forEach { it.onPositionUpdate(pos) }
    }

    fun simulateFixLost() { listeners.forEach { it.onFixLost() } }
}

// ── Test helpers ─────────────────────────────────────────────────────────────

private fun makePosition(lat: Double = 41.0, lon: Double = -71.0, sog: Double = 5.0) =
    GpsPosition(lat, lon, sog, cog = 180.0, timestampMs = 1_000L)

private class RecordingListener : GpsListener {
    val positions = mutableListOf<GpsPosition>()
    var fixLostCount = 0

    override fun onPositionUpdate(position: GpsPosition) { positions.add(position) }
    override fun onFixLost() { fixLostCount++ }
}

// ── Tests ─────────────────────────────────────────────────────────────────────

class GpsProviderTest {

    private lateinit var provider: FakeGpsProvider

    @Before
    fun setUp() {
        provider = FakeGpsProvider()
    }

    @Test
    fun `start sets started to true`() {
        provider.start()
        assertTrue(provider.started)
    }

    @Test
    fun `stop sets started to false`() {
        provider.start()
        provider.stop()
        assertFalse(provider.started)
    }

    @Test
    fun `listener receives position update`() {
        val listener = RecordingListener()
        provider.addListener(listener)
        val pos = makePosition()
        provider.simulatePosition(pos)
        assertEquals(1, listener.positions.size)
        assertEquals(pos, listener.positions[0])
    }

    @Test
    fun `listener notified of fix lost`() {
        val listener = RecordingListener()
        provider.addListener(listener)
        provider.simulateFixLost()
        assertEquals(1, listener.fixLostCount)
    }

    @Test
    fun `multiple listeners all receive position update`() {
        val l1 = RecordingListener()
        val l2 = RecordingListener()
        val l3 = RecordingListener()
        provider.addListener(l1)
        provider.addListener(l2)
        provider.addListener(l3)
        provider.simulatePosition(makePosition())
        assertEquals(1, l1.positions.size)
        assertEquals(1, l2.positions.size)
        assertEquals(1, l3.positions.size)
    }

    @Test
    fun `multiple listeners all notified of fix lost`() {
        val l1 = RecordingListener()
        val l2 = RecordingListener()
        provider.addListener(l1)
        provider.addListener(l2)
        provider.simulateFixLost()
        assertEquals(1, l1.fixLostCount)
        assertEquals(1, l2.fixLostCount)
    }

    @Test
    fun `removing listener stops notifications`() {
        val listener = RecordingListener()
        provider.addListener(listener)
        provider.removeListener(listener)
        provider.simulatePosition(makePosition())
        provider.simulateFixLost()
        assertEquals(0, listener.positions.size)
        assertEquals(0, listener.fixLostCount)
    }

    @Test
    fun `position property reflects last simulated position`() {
        assertNull(provider.position)
        val pos = makePosition(lat = 42.5, lon = -70.0)
        provider.simulatePosition(pos)
        assertEquals(pos, provider.position)
    }

    @Test
    fun `SOG conversion sanity check - 1 mps is approximately 1_94384 knots`() {
        // 1 m/s * 1.94384 = 1.94384 knots — validate constant used in DeviceGpsProvider
        val knots = 1.0 * 1.94384
        assertEquals(1.94384, knots, 0.00001)
    }
}