Improve page loading progress displaying

app/src/main/java/org/koitharu/kotatsu/utils/ext/IO.kt

@@ -4,7 +4,10 @@ import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.Job
 import kotlinx.coroutines.currentCoroutineContext
 import kotlinx.coroutines.ensureActive
+import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.withContext
+import okhttp3.ResponseBody
+import org.koitharu.kotatsu.utils.progress.ProgressResponseBody
 import java.io.InputStream
 import java.io.OutputStream
 
@@ -25,3 +28,7 @@ suspend fun InputStream.copyToSuspending(
 	}
 	bytesCopied
 }
+
+fun ResponseBody.withProgress(progressState: MutableStateFlow<Float>): ResponseBody {
+	return ProgressResponseBody(this, progressState)
+}

app/src/main/java/org/koitharu/kotatsu/utils/progress/ProgressResponseBody.kt

@@ -0,0 +1,51 @@
+package org.koitharu.kotatsu.utils.progress
+
+import kotlinx.coroutines.flow.MutableStateFlow
+import okhttp3.MediaType
+import okhttp3.ResponseBody
+import okio.Buffer
+import okio.BufferedSource
+import okio.ForwardingSource
+import okio.Source
+import okio.buffer
+
+class ProgressResponseBody(
+	private val delegate: ResponseBody,
+	private val progressState: MutableStateFlow<Float>,
+) : ResponseBody() {
+
+	private var bufferedSource: BufferedSource? = null
+
+	override fun close() {
+		super.close()
+		delegate.close()
+	}
+
+	override fun contentLength(): Long = delegate.contentLength()
+
+	override fun contentType(): MediaType? = delegate.contentType()
+
+	override fun source(): BufferedSource {
+		return bufferedSource ?: ProgressSource(delegate.source(), contentLength(), progressState).buffer().also {
+			bufferedSource = it
+		}
+	}
+
+	private class ProgressSource(
+		delegate: Source,
+		private val contentLength: Long,
+		private val progressState: MutableStateFlow<Float>,
+	) : ForwardingSource(delegate) {
+
+		private var totalBytesRead = 0L
+
+		override fun read(sink: Buffer, byteCount: Long): Long {
+			val bytesRead = super.read(sink, byteCount)
+			if (contentLength > 0) {
+				totalBytesRead += if (bytesRead != -1L) bytesRead else 0
+				progressState.value = (totalBytesRead.toDouble() / contentLength.toDouble()).toFloat()
+			}
+			return bytesRead
+		}
+	}
+}