Add MergedMidiAccess (bring it back from managed-midi).

ktmidi/src/commonMain/kotlin/dev/atsushieno/ktmidi/MergedMidiAccess.kt

@@ -0,0 +1,55 @@
+package dev.atsushieno.ktmidi
+
+
+class MergedMidiAccess(override val name: String, private val list: List<MidiAccess>) : MidiAccess() {
+    private class MidiPortDetailsWrapper(
+        val midiAccess: MidiAccess,
+        val source: MidiPortDetails
+    ) : MidiPortDetails {
+        override val id = "${midiAccess.name}_${source.id}"
+        override val manufacturer = source.manufacturer
+        override val name = source.name
+        override val version = source.version
+        override val midiTransportProtocol = source.midiTransportProtocol
+    }
+
+    private class MidiInputWrapper(
+        override val details: MidiPortDetailsWrapper,
+        private val impl: MidiInput
+    ) : MidiInput {
+        override fun setMessageReceivedListener(listener: OnMidiReceivedEventListener) =
+            impl.setMessageReceivedListener(listener)
+
+        override val connectionState: MidiPortConnectionState by impl::connectionState
+
+        override fun close() = impl.close()
+
+    }
+
+    private class MidiOutputWrapper(
+        override val details: MidiPortDetailsWrapper,
+        private val impl: MidiOutput
+    ): MidiOutput {
+        override fun send(mevent: ByteArray, offset: Int, length: Int, timestampInNanoseconds: Long) =
+            impl.send(mevent, offset, length, timestampInNanoseconds)
+
+        override val connectionState: MidiPortConnectionState by impl::connectionState
+
+        override fun close() = impl.close()
+    }
+
+    override val inputs: Iterable<MidiPortDetails>
+        get() = list.flatMap { access -> access.inputs.map { MidiPortDetailsWrapper(access, it) } }
+    override val outputs: Iterable<MidiPortDetails>
+        get() = list.flatMap { access -> access.outputs.map { MidiPortDetailsWrapper(access, it) } }
+
+    override suspend fun openInput(portId: String): MidiInput {
+        val details = inputs.first { it.id == portId } as MidiPortDetailsWrapper
+        return MidiInputWrapper(details, details.midiAccess.openInput(details.source.id))
+    }
+
+    override suspend fun openOutput(portId: String): MidiOutput {
+        val details = outputs.first { it.id == portId } as MidiPortDetailsWrapper
+        return MidiOutputWrapper(details, details.midiAccess.openOutput(details.source.id))
+    }
+}