Generate types and methods for subscriptions.

Subscription calls differ from query and procedure calls in that they
are actually subscriptions to a websocket, not a standard HTTP call. For
this reason, they actually respond with a `Flow<*>`, not just one value.

Part of the actual CBOR implementation in kotlinx-serialization is
adapted here to support byte arrays as byte strings for parameterized
types, like List<ByteArray>.

Kotlin/kotlinx.serialization#2383

api-gen-runtime-internal/build.gradle.kts

@@ -16,13 +16,16 @@ kotlin {
     val commonMain by getting {
       dependencies {
         api(libs.kotlinx.coroutines)
-        api(libs.kotlinx.serialization.json)
+        api(libs.kotlinx.serialization.core)
         api(libs.ktor.core)
 
         api(project(":api-gen-runtime"))
 
+        implementation(libs.kotlinx.serialization.cbor)
+        implementation(libs.kotlinx.serialization.json)
         implementation(libs.ktor.contentnegotiation)
         implementation(libs.ktor.serialization.json)
+        implementation(libs.ktor.websockets)
 
         implementation(kotlin("reflect"))
       }

api-gen-runtime-internal/src/commonMain/kotlin/sh/christian/ozone/api/cbor/ByteArrayInput.kt

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2017-2021 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
+ *
+ * Copied until https://github.com/Kotlin/kotlinx.serialization/pull/2383 is merged and productionized.
+ */
+package sh.christian.ozone.api.cbor
+
+internal class ByteArrayInput(private var array: ByteArray) {
+  private var position: Int = 0
+  val availableBytes: Int get() = array.size - position
+
+  fun read(): Int {
+    return if (position < array.size) array[position++].toInt() and 0xFF else -1
+  }
+
+  fun read(b: ByteArray, offset: Int, length: Int): Int {
+    // avoid int overflow
+    if (offset < 0 || offset > b.size || length < 0
+      || length > b.size - offset
+    ) {
+      throw IndexOutOfBoundsException()
+    }
+    // Are there any bytes available?
+    if (this.position >= array.size) {
+      return -1
+    }
+    if (length == 0) {
+      return 0
+    }
+
+    val copied = if (this.array.size - position < length) this.array.size - position else length
+    array.copyInto(destination = b, destinationOffset = offset, startIndex = position, endIndex = position + copied)
+    position += copied
+    return copied
+  }
+
+  fun skip(length: Int) {
+    position += length
+  }
+}

api-gen-runtime-internal/src/commonMain/kotlin/sh/christian/ozone/api/cbor/ByteArrayOutput.kt

@@ -0,0 +1,52 @@
+/*
+ * Copyright 2017-2021 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
+ *
+ * Copied until https://github.com/Kotlin/kotlinx.serialization/pull/2383 is merged and productionized.
+ */
+package sh.christian.ozone.api.cbor
+
+internal class ByteArrayOutput {
+  private var array: ByteArray = ByteArray(32)
+  private var position: Int = 0
+
+  private fun ensureCapacity(elementsToAppend: Int) {
+    if (position + elementsToAppend <= array.size) {
+      return
+    }
+    val newArray = ByteArray((position + elementsToAppend).takeHighestOneBit() shl 1)
+    array.copyInto(newArray)
+    array = newArray
+  }
+
+  fun toByteArray(): ByteArray {
+    val newArray = ByteArray(position)
+    array.copyInto(newArray, startIndex = 0, endIndex = this.position)
+    return newArray
+  }
+
+  fun write(buffer: ByteArray, offset: Int = 0, count: Int = buffer.size) {
+    // avoid int overflow
+    if (offset < 0 || offset > buffer.size || count < 0
+      || count > buffer.size - offset
+    ) {
+      throw IndexOutOfBoundsException()
+    }
+    if (count == 0) {
+      return
+    }
+
+    ensureCapacity(count)
+    buffer.copyInto(
+      destination = array,
+      destinationOffset = this.position,
+      startIndex = offset,
+      endIndex = offset + count
+    )
+    this.position += count
+  }
+
+  fun write(byteValue: Int) {
+    ensureCapacity(1)
+    array[position++] = byteValue.toByte()
+  }
+}

api-gen-runtime-internal/src/commonMain/kotlin/sh/christian/ozone/api/cbor/CborDecodingException.kt

@@ -0,0 +1,21 @@
+/*
+ * Copyright 2017-2021 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
+ *
+ * Copied until https://github.com/Kotlin/kotlinx.serialization/pull/2383 is merged and productionized.
+ */
+package sh.christian.ozone.api.cbor
+
+import kotlinx.serialization.SerializationException
+
+internal class CborDecodingException(message: String) : SerializationException(message)
+
+internal fun CborDecodingException(expected: String, foundByte: Int) =
+  CborDecodingException("Expected $expected, but found ${printByte(foundByte)}")
+
+internal fun printByte(b: Int): String {
+  val hexCode = "0123456789ABCDEF"
+  return buildString {
+    append(hexCode[b shr 4 and 0xF])
+    append(hexCode[b and 0xF])
+  }
+}