add streaming file downloading feature

tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/bot/Ktor/KtorRequestsExecutor.kt

@@ -42,6 +42,14 @@ inline fun telegramBot(
     crossinline builder: KtorRequestsExecutorBuilder.() -> Unit = {}
 ): TelegramBot = telegramBot(TelegramAPIUrlsKeeper(token, apiUrl), builder)
 
+@RiskFeature
+fun createTelegramBotDefaultKtorCallRequestsFactories() = listOf(
+    SimpleRequestCallFactory(),
+    MultipartRequestCallFactory(),
+    DownloadFileRequestCallFactory,
+    DownloadFileChannelRequestCallFactory
+)
+
 class KtorRequestsExecutor(
     telegramAPIUrlsKeeper: TelegramAPIUrlsKeeper,
     client: HttpClient = HttpClient(),
@@ -52,7 +60,7 @@ class KtorRequestsExecutor(
 ) : BaseRequestsExecutor(telegramAPIUrlsKeeper) {
     private val callsFactories: List<KtorCallFactory> = callsFactories.run {
         if (!excludeDefaultFactories) {
-            this + listOf(SimpleRequestCallFactory(), MultipartRequestCallFactory(), DownloadFileRequestCallFactory)
+            this + createTelegramBotDefaultKtorCallRequestsFactories()
         } else {
             this
         }

tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/bot/Ktor/base/DownloadFileChannelRequestCallFactory.kt

@@ -0,0 +1,38 @@
+package dev.inmo.tgbotapi.bot.Ktor.base
+
+import dev.inmo.tgbotapi.bot.Ktor.KtorCallFactory
+import dev.inmo.tgbotapi.requests.DownloadFileStream
+import dev.inmo.tgbotapi.requests.abstracts.Request
+import dev.inmo.tgbotapi.utils.InputStreamAllocator
+import dev.inmo.tgbotapi.utils.TelegramAPIUrlsKeeper
+import io.ktor.client.HttpClient
+import io.ktor.client.call.receive
+import io.ktor.client.request.get
+import io.ktor.client.statement.HttpStatement
+import io.ktor.utils.io.*
+import kotlinx.coroutines.*
+import kotlinx.serialization.json.Json
+import kotlin.coroutines.coroutineContext
+
+object DownloadFileChannelRequestCallFactory : KtorCallFactory {
+    override suspend fun <T : Any> makeCall(
+        client: HttpClient,
+        urlsKeeper: TelegramAPIUrlsKeeper,
+        request: Request<T>,
+        jsonFormatter: Json
+    ): T? = (request as? DownloadFileStream) ?.let {
+        val fullUrl = urlsKeeper.createFileLinkUrl(it.filePath)
+
+        return InputStreamAllocator {
+            val scope = CoroutineScope(coroutineContext)
+            val outChannel = ByteChannel()
+            scope.launch {
+                client.get<HttpStatement>(fullUrl).execute { httpResponse ->
+                    val channel: ByteReadChannel = httpResponse.receive()
+                    channel.copyTo(outChannel)
+                }
+            }
+            outChannel
+        } as T
+    }
+}

tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/bot/Ktor/base/DownloadFileRequestCallFactory.kt

@@ -16,7 +16,7 @@ object DownloadFileRequestCallFactory : KtorCallFactory {
         request: Request<T>,
         jsonFormatter: Json
     ): T? = (request as? DownloadFile) ?.let {
-        val fullUrl = "${urlsKeeper.fileBaseUrl}/${it.filePath}"
+        val fullUrl = urlsKeeper.createFileLinkUrl(it.filePath)
 
         return safely {
             @Suppress("UNCHECKED_CAST")

tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/requests/DownloadFileStream.kt

@@ -0,0 +1,15 @@
+package dev.inmo.tgbotapi.requests
+
+import dev.inmo.tgbotapi.requests.abstracts.Request
+import dev.inmo.tgbotapi.utils.InputStreamAllocator
+import dev.inmo.tgbotapi.utils.InputStreamAllocatorSerializer
+import kotlinx.serialization.DeserializationStrategy
+
+class DownloadFileStream(
+    val filePath: String
+) : Request<InputStreamAllocator> {
+    override fun method(): String = filePath
+    override val resultDeserializer: DeserializationStrategy<InputStreamAllocator>
+        get() = InputStreamAllocatorSerializer
+
+}

tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/utils/InputStreamAllocator.kt

@@ -0,0 +1,31 @@
+package dev.inmo.tgbotapi.utils
+
+import dev.inmo.micro_utils.common.ByteArrayAllocatorSerializer
+import io.ktor.util.toByteArray
+import io.ktor.utils.io.ByteReadChannel
+import kotlinx.coroutines.*
+import kotlinx.serialization.KSerializer
+import kotlinx.serialization.descriptors.SerialDescriptor
+import kotlinx.serialization.encoding.Decoder
+import kotlinx.serialization.encoding.Encoder
+
+fun interface InputStreamAllocator {
+    suspend operator fun invoke(): ByteReadChannel
+}
+
+object InputStreamAllocatorSerializer : KSerializer<InputStreamAllocator> {
+    override val descriptor: SerialDescriptor = ByteArrayAllocatorSerializer.descriptor
+
+    override fun serialize(encoder: Encoder, value: InputStreamAllocator) {
+        TODO("Not yet implemented")
+//        ByteArrayAllocatorSerializer.serialize(
+//            encoder
+//        ) {
+//        }
+    }
+
+    override fun deserialize(decoder: Decoder): InputStreamAllocator {
+        val byteArrayAllocator = ByteArrayAllocatorSerializer.deserialize(decoder)
+        return InputStreamAllocator { ByteReadChannel(byteArrayAllocator()) }
+    }
+}

tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/utils/TelegramAPIUrlsKeeper.kt

@@ -26,4 +26,6 @@ class TelegramAPIUrlsKeeper(
         commonAPIUrl = "$correctedHost/bot$token"
         fileBaseUrl = "$correctedHost/file/bot$token"
     }
+
+    fun createFileLinkUrl(filePath: String) = "${fileBaseUrl}/$filePath"
 }