ui: mute theme-aware peer colors for contrast

Extract PeerColorStyle so each palette owns saturation/value, keeping
hues stable while dark mode stays bright-but-muted and light mode avoids
neon labels. New themes only need to supply their own style.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/src/main/java/com/bitchat/android/ui/theme/BitchatPalette.kt

@@ -41,10 +41,11 @@ data class BitchatPalette(
     val accentPurple: Color,
 
     // MARK: - Deterministic peer colors
-    /** Chroma applied after deriving a peer's stable hue. */
-    val peerColorSaturation: Float,
-    /** Brightness applied after deriving a peer's stable hue. */
-    val peerColorValue: Float,
+    /**
+     * Saturation/value applied after deriving a peer's stable hue. Swap this when adding a
+     * new theme — see [PeerColorStyle] for contrast guidelines.
+     */
+    val peerColors: PeerColorStyle,
 )
 
 val DarkBitchatPalette = BitchatPalette(
@@ -56,8 +57,7 @@ val DarkBitchatPalette = BitchatPalette(
     textTertiary = Color(0xFF6B776B),
     accentOrange = Color(0xFFFF9F0A),
     accentPurple = Color(0xFFBF5AF2),
-    peerColorSaturation = 1f,
-    peerColorValue = 1f,
+    peerColors = PeerColorStyle.Dark,
 )
 
 val LightBitchatPalette = BitchatPalette(
@@ -69,8 +69,7 @@ val LightBitchatPalette = BitchatPalette(
     textTertiary = Color(0xFF757F75),
     accentOrange = Color(0xFFFF9500),
     accentPurple = Color(0xFFAF52DE),
-    peerColorSaturation = 0.85f,
-    peerColorValue = 0.45f,
+    peerColors = PeerColorStyle.Light,
 )
 
 val LocalBitchatPalette = staticCompositionLocalOf { DarkBitchatPalette }

app/src/main/java/com/bitchat/android/ui/theme/PeerColors.kt

@@ -1,9 +1,36 @@
 package com.bitchat.android.ui.theme
 
+import androidx.compose.runtime.Immutable
 import androidx.compose.ui.graphics.Color
 import com.bitchat.android.ui.PeerIdentity
 import kotlin.math.abs
 
+/**
+ * Theme-specific chroma applied after a peer's stable hue is derived.
+ *
+ * Hue stays identity-stable across themes (and byte-identical to iOS). Only saturation
+ * and value change so peer labels remain readable on each background.
+ *
+ * Guidelines when adding a future theme:
+ * - Dim / dark backgrounds: keep [value] high so colors are not lost against the surface;
+ *   prefer muted [saturation] over neon.
+ * - Light backgrounds: keep [value] moderate-low so colors are not blinding; avoid
+ *   near-full saturation.
+ */
+@Immutable
+data class PeerColorStyle(
+    val saturation: Float,
+    val value: Float,
+) {
+    companion object {
+        /** Soft pastels that stay bright enough on near-black chat surfaces. */
+        val Dark = PeerColorStyle(saturation = 0.55f, value = 0.82f)
+
+        /** Deeper, less saturated tones that stay readable on near-white surfaces. */
+        val Light = PeerColorStyle(saturation = 0.70f, value = 0.42f)
+    }
+}
+
 /**
  * The single identity-to-color boundary used by chat, people sheets, and mentions.
  *
@@ -22,9 +49,10 @@ fun colorForPeer(identity: PeerIdentity, palette: BitchatPalette): Color {
         hue = (hue + 0.12) % 1.0
     }
 
+    val style = palette.peerColors
     return Color.hsv(
         hue = (hue * 360).toFloat(),
-        saturation = palette.peerColorSaturation,
-        value = palette.peerColorValue
+        saturation = style.saturation,
+        value = style.value
     )
 }

app/src/test/java/com/bitchat/android/ui/ChatUIUtilsTest.kt

@@ -14,6 +14,7 @@ import com.bitchat.android.ui.theme.LightBitchatColorScheme
 import com.bitchat.android.ui.theme.LightBitchatPalette
 import com.bitchat.android.ui.theme.MessageBodyTextStyle
 import com.bitchat.android.ui.theme.MessageSenderTextStyle
+import com.bitchat.android.ui.theme.PeerColorStyle
 import com.bitchat.android.ui.theme.colorForPeer
 import java.text.SimpleDateFormat
 import java.util.Date
@@ -444,8 +445,8 @@ class ChatUIUtilsTest {
 
     @Test
     fun `peer color hue is stable across light and dark, only chroma differs`() {
-        // Hue derivation must stay byte-identical to iOS; only saturation/value are tuned for
-        // the redesigned neutral message body.
+        // Hue derivation must stay byte-identical to iOS; only saturation/value are tuned per
+        // theme so dark mode stays muted-but-bright and light mode stays deep-but-readable.
         val identity = PeerIdentity.mesh("abc")
         val dark = colorForPeer(identity, DarkBitchatPalette)
         val light = colorForPeer(identity, LightBitchatPalette)
@@ -456,10 +457,16 @@ class ChatUIUtilsTest {
         rgbToHsv(light.red, light.green, light.blue, lightHsv)
 
         assertEquals(darkHsv[0].toDouble(), lightHsv[0].toDouble(), 1.0)
-        assertEquals(1.0, darkHsv[1].toDouble(), 0.01)
-        assertEquals(1.0, darkHsv[2].toDouble(), 0.01)
-        assertEquals(0.85, lightHsv[1].toDouble(), 0.01)
-        assertEquals(0.45, lightHsv[2].toDouble(), 0.01)
+        assertEquals(PeerColorStyle.Dark.saturation.toDouble(), darkHsv[1].toDouble(), 0.01)
+        assertEquals(PeerColorStyle.Dark.value.toDouble(), darkHsv[2].toDouble(), 0.01)
+        assertEquals(PeerColorStyle.Light.saturation.toDouble(), lightHsv[1].toDouble(), 0.01)
+        assertEquals(PeerColorStyle.Light.value.toDouble(), lightHsv[2].toDouble(), 0.01)
+        // Dark theme: muted chroma, never dark (readable on near-black).
+        assertTrue(darkHsv[1] < 0.75f)
+        assertTrue(darkHsv[2] >= 0.75f)
+        // Light theme: avoid neon / near-white peer labels.
+        assertTrue(lightHsv[1] < 0.85f)
+        assertTrue(lightHsv[2] <= 0.55f)
     }
 
     @Test
@@ -485,7 +492,7 @@ class ChatUIUtilsTest {
         assertEquals(Color(0xFFF5F5F5), DarkBitchatColorScheme.onSurface)
         assertTrue(LightBitchatColorScheme.onSurface != DarkBitchatColorScheme.onSurface)
         assertTrue(
-            LightBitchatPalette.peerColorValue != DarkBitchatPalette.peerColorValue
+            LightBitchatPalette.peerColors != DarkBitchatPalette.peerColors
         )
     }