Added configuration options to e-ink page flashes (#625)

* Recommit for e-ink pref changes

* Fixed state holder for flash interval

* Detekt

* Refactor suggested by Antsy

* inverted currentDisplayRefresh check for early exit

(cherry picked from commit 2f86f25d5b24c2054a604802dc65b8bc3a99c7c0)

# Conflicts:
#	app/src/main/java/eu/kanade/presentation/more/settings/screen/SettingsReaderScreen.kt
#	app/src/main/java/eu/kanade/presentation/reader/settings/GeneralSettingsPage.kt
#	app/src/main/java/eu/kanade/tachiyomi/ui/reader/setting/ReaderPreferences.kt

app/src/main/java/eu/kanade/presentation/reader/DisplayRefreshHost.kt

@@ -7,19 +7,42 @@ import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.Stable
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.graphics.Color
+import eu.kanade.tachiyomi.ui.reader.setting.ReaderPreferences
 import kotlinx.coroutines.delay
-import kotlin.time.Duration.Companion.seconds
+import tachiyomi.presentation.core.util.collectAsState
+import uy.kohesive.injekt.Injekt
+import uy.kohesive.injekt.api.get
+import kotlin.time.Duration.Companion.milliseconds
 
 @Stable
 class DisplayRefreshHost {
 
     internal var currentDisplayRefresh by mutableStateOf(false)
+    private val readerPreferences = Injekt.get<ReaderPreferences>()
+
+    internal val flashMillis = readerPreferences.flashDurationMillis()
+    internal val flashMode = readerPreferences.flashColor()
+
+    internal val flashIntervalPref = readerPreferences.flashPageInterval()
+
+    // Internal State for Flash
+    private var flashInterval = flashIntervalPref.get()
+    private var timesCalled = 0
 
     fun flash() {
-        currentDisplayRefresh = true
+        if (timesCalled % flashInterval == 0) {
+            currentDisplayRefresh = true
+        }
+        timesCalled += 1
+    }
+
+    fun setInterval(interval: Int) {
+        flashInterval = interval
+        timesCalled = 0
     }
 }
 
@@ -29,18 +52,39 @@ fun DisplayRefreshHost(
     modifier: Modifier = Modifier,
 ) {
     val currentDisplayRefresh = hostState.currentDisplayRefresh
+    val refreshDuration by hostState.flashMillis.collectAsState()
+    val flashMode by hostState.flashMode.collectAsState()
+    val flashInterval by hostState.flashIntervalPref.collectAsState()
+
+    var currentColor by remember { mutableStateOf<Color?>(null) }
+
     LaunchedEffect(currentDisplayRefresh) {
-        if (currentDisplayRefresh) {
-            delay(1.5.seconds)
-            hostState.currentDisplayRefresh = false
+        if (!currentDisplayRefresh) {
+            currentColor = null
+            return@LaunchedEffect
         }
+
+        val refreshDurationHalf = refreshDuration.milliseconds / 2
+        currentColor = if (flashMode == ReaderPreferences.FlashColor.BLACK) {
+            Color.Black
+        } else {
+            Color.White
+        }
+        delay(refreshDurationHalf)
+        if (flashMode == ReaderPreferences.FlashColor.WHITE_BLACK) {
+            currentColor = Color.Black
+        }
+        delay(refreshDurationHalf)
+        hostState.currentDisplayRefresh = false
+    }
+
+    LaunchedEffect(flashInterval) {
+        hostState.setInterval(flashInterval)
     }
 
     Canvas(
         modifier = modifier.fillMaxSize(),
     ) {
-        if (currentDisplayRefresh) {
-            drawRect(Color.Black)
-        }
+        currentColor?.let { drawRect(it) }
     }
 }