feat: mutual match screen target-grid chip (needle bearing + grid + distance); grid mode centering no longer swallowed when station position is not yet available

core/presentation/src/main/java/com/rtbishop/look4sat/core/presentation/GridTargetChip.kt

@@ -0,0 +1,146 @@
+package com.rtbishop.look4sat.core.presentation
+
+import androidx.compose.foundation.Canvas
+import androidx.compose.foundation.background
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.geometry.Offset
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.graphics.Path
+import androidx.compose.ui.graphics.drawscope.Stroke
+import androidx.compose.ui.graphics.drawscope.rotate
+import androidx.compose.ui.text.font.FontFamily
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.unit.dp
+import androidx.compose.ui.unit.sp
+import kotlin.math.atan2
+import kotlin.math.cos
+import kotlin.math.sin
+import kotlin.math.sqrt
+
+/**
+ * Format a Maidenhead locator for display. Per IARU convention and the user's
+ * preference: field letters (1-2) and square digits (3-4) uppercase, sub-square
+ * letters (5-6 of a 6/8-char locator) lowercase, e.g. "OL62" / "OL62kl".
+ */
+fun formatGridDisplay(grid: String): String? {
+    val g = grid.trim().uppercase()
+    if (g.length !in listOf(4, 6, 8) || g.any { !it.isLetterOrDigit() }) return null
+    if (g.length == 4) return g
+    if (g.length == 6) return g.take(4) + g.drop(4).lowercase()
+    return g.take(4) + g.drop(4).take(2).lowercase() + g.drop(6)
+}
+
+/**
+ * Top-bar chip for the mutual-match screen: navigation needle (rotated by the
+ * great-circle bearing to the target grid, 0 deg = north), grid locator and
+ * distance. Shows a dimmed placeholder when no target grid is entered.
+ */
+@Composable
+fun GridTargetChip(
+    grid: String?,
+    distanceKm: Double?,
+    bearingDeg: Double?,
+    modifier: Modifier = Modifier
+) {
+    val configured = grid != null && distanceKm != null && bearingDeg != null
+    val accent = MaterialTheme.colorScheme.tertiaryContainer
+    val placeholder = MaterialTheme.colorScheme.onSurfaceVariant
+    Row(
+        verticalAlignment = Alignment.CenterVertically,
+        horizontalArrangement = Arrangement.spacedBy(8.dp),
+        modifier = modifier
+            .height(36.dp)
+            .background(
+                color = MaterialTheme.colorScheme.surface.copy(alpha = if (configured) 0.9f else 0.45f),
+                shape = RoundedCornerShape(12.dp)
+            )
+            .padding(horizontal = 12.dp)
+    ) {
+        NavigationNeedle(
+            bearingDeg = bearingDeg ?: 0.0,
+            color = if (configured) accent else placeholder,
+            dimmed = !configured,
+            modifier = Modifier.size(22.dp)
+        )
+        Text(
+            text = grid?.let { formatGridDisplay(it) } ?: "----",
+            fontSize = 15.sp,
+            fontWeight = FontWeight.Bold,
+            fontFamily = FontFamily.Monospace,
+            color = if (configured) accent else placeholder,
+            letterSpacing = 1.sp
+        )
+        Text(
+            text = distanceKm?.let { "${"%,.0f".format(it)} km" } ?: "-- km",
+            fontSize = 14.sp,
+            color = if (configured) Color.White else placeholder,
+            modifier = Modifier
+                .background(
+                    color = if (configured) MaterialTheme.colorScheme.onSurfaceVariant else Color.Transparent,
+                    shape = RoundedCornerShape(8.dp)
+                )
+                .padding(horizontal = 8.dp, vertical = 2.dp)
+        )
+    }
+}
+
+/**
+ * Map-style navigation needle: slim triangular pointer whose tip points at
+ * [bearingDeg] (0 = north/up, clockwise positive).
+ */
+@Composable
+private fun NavigationNeedle(
+    bearingDeg: Double,
+    color: Color,
+    dimmed: Boolean,
+    modifier: Modifier = Modifier
+) {
+    Canvas(modifier = modifier) {
+        val cx = size.width / 2f
+        val cy = size.height / 2f
+        val r = size.minDimension / 2f
+        if (dimmed) {
+            drawCircle(color = color, radius = r * 0.92f, style = Stroke(width = 1.5f))
+        }
+        rotate(degrees = bearingDeg.toFloat(), pivot = Offset(cx, cy)) {
+            val path = Path().apply {
+                moveTo(cx, cy - r * 0.9f)          // tip (north before rotation)
+                lineTo(cx - r * 0.42f, cy + r * 0.55f)
+                lineTo(cx, cy + r * 0.28f)
+                lineTo(cx + r * 0.42f, cy + r * 0.55f)
+                close()
+            }
+            drawPath(path, color = color)
+        }
+    }
+}
+
+/** Great-circle distance in km between two positions. */
+fun greatCircleDistanceKm(lat1: Double, lon1: Double, lat2: Double, lon2: Double): Double {
+    val rad = Math.PI / 180.0
+    val dLat = (lat2 - lat1) * rad
+    val dLon = (lon2 - lon1) * rad
+    val a = sin(dLat / 2) * sin(dLat / 2) +
+        cos(lat1 * rad) * cos(lat2 * rad) * sin(dLon / 2) * sin(dLon / 2)
+    return 6371.0 * 2 * kotlin.math.atan2(kotlin.math.sqrt(a), kotlin.math.sqrt(1 - a))
+}
+
+/** Initial great-circle bearing in degrees (0 = north, clockwise). */
+fun greatCircleBearingDeg(lat1: Double, lon1: Double, lat2: Double, lon2: Double): Double {
+    val rad = Math.PI / 180.0
+    val dLon = (lon2 - lon1) * rad
+    val y = sin(dLon) * cos(lat2 * rad)
+    val x = cos(lat1 * rad) * sin(lat2 * rad) -
+        sin(lat1 * rad) * cos(lat2 * rad) * cos(dLon)
+    return (Math.atan2(y, x) / rad + 360.0) % 360.0
+}