From f906bab1a5f7490d7243e959fe202378e42c7ec5 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Sat, 13 Nov 2021 11:05:39 -0500
Subject: [PATCH] Provides feedback on interrupt flags, starts on state
 machine.

---
 Machines/Amiga/Audio.cpp   | 23 +++++++++++++++++++++++
 Machines/Amiga/Audio.hpp   |  8 +++++++-
 Machines/Amiga/Chipset.cpp |  1 +
 3 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/Machines/Amiga/Audio.cpp b/Machines/Amiga/Audio.cpp
index d64f5b2fb..3cb36159b 100644
--- a/Machines/Amiga/Audio.cpp
+++ b/Machines/Amiga/Audio.cpp
@@ -8,6 +8,8 @@
 
 #include "Audio.hpp"
 
+#include "Flags.hpp"
+
 #define LOG_PREFIX "[Audio] "
 #include "../../Outputs/Log.hpp"
 
@@ -61,10 +63,31 @@ void Audio::set_channel_enables(uint16_t enables) {
 void Audio::set_modulation_flags(uint16_t) {
 }
 
+void Audio::set_interrupt_requests(uint16_t requests) {
+	channels_[0].interrupt_pending = requests & uint16_t(InterruptFlag::AudioChannel0);
+	channels_[1].interrupt_pending = requests & uint16_t(InterruptFlag::AudioChannel1);
+	channels_[2].interrupt_pending = requests & uint16_t(InterruptFlag::AudioChannel2);
+	channels_[3].interrupt_pending = requests & uint16_t(InterruptFlag::AudioChannel3);
+}
+
 void Audio::run_for([[maybe_unused]] Cycles duration) {
 	// TODO:
 	//
 	// Check whether any channel's period counter is exhausted and, if
 	// so, attempt to consume another sample. If there are no more samples
 	// and length is 0, trigger an interrupt.
+
+	using State = Channel::State;
+	for(int c = 0; c < 4; c++) {
+		switch(channels_[c].state) {
+			case State::Disabled:
+				if(channels_[c].has_data && !channels_[c].dma_enabled && !channels_[c].interrupt_pending) {
+					channels_[c].state = Channel::State::PlayingHigh;
+					// TODO: [volcntrld, percntrld, pbufldl, AUDxID]
+				}
+			break;
+
+			default: break;
+		}
+	}
 }
diff --git a/Machines/Amiga/Audio.hpp b/Machines/Amiga/Audio.hpp
index e595cf2fb..867be81df 100644
--- a/Machines/Amiga/Audio.hpp
+++ b/Machines/Amiga/Audio.hpp
@@ -53,6 +53,9 @@ class Audio: public DMADevice<4> {
 		/// their neighbours.
 		void set_modulation_flags(uint16_t);
 
+		/// Sets which interrupt requests are currently active.
+		void set_interrupt_requests(uint16_t);
+
 	private:
 		struct Channel {
 			// The data latch plus a count of unused samples
@@ -74,6 +77,9 @@ class Audio: public DMADevice<4> {
 			// Indicates whether DMA is enabled for this channel.
 			bool dma_enabled = false;
 
+			// Records whether this audio interrupt is pending.
+			bool interrupt_pending = false;
+
 			// Replicates the Hardware Reference Manual state machine;
 			// comments indicate which of the documented states each
 			// label refers to.
@@ -83,7 +89,7 @@ class Audio: public DMADevice<4> {
 				WaitingForDMA,		// 101
 				PlayingHigh,		// 010
 				PlayingLow,			// 011
-			} state_;
+			} state = State::Disabled;
 		} channels_[4];
 };
 
diff --git a/Machines/Amiga/Chipset.cpp b/Machines/Amiga/Chipset.cpp
index 3dbf31217..8972d529e 100644
--- a/Machines/Amiga/Chipset.cpp
+++ b/Machines/Amiga/Chipset.cpp
@@ -750,6 +750,7 @@ void Chipset::perform(const CPU::MC68000::Microcycle &cycle) {
 		case Write(0x09c):		// INTREQ
 			ApplySetClear(interrupt_requests_, 0x7fff);
 			update_interrupts();
+			audio_->set_interrupt_requests(interrupt_requests_);
 		break;
 		case Read(0x01e):		// INTREQR
 			cycle.set_value16(interrupt_requests_);