basics/stfx/ui/web-ui.h

#pragma once

#include "../storage/cbor-walker.h"
#include "../storage/stfx-storage.h"
#include "../param-info.h"

#include <string>
#include <vector>
#include <functional>
#include <atomic>
#include <memory>
#include <iostream> // we log to stderr if our queue gets full

namespace stfx { namespace web {

struct ParamContext {
	union {
		void *pointer;
		size_t index;
	};
	
	ParamContext() : index(0) {}
};

struct WebStateWriter : public storage::STFXStorageWriter<WebStateWriter> {
	using Super = storage::STFXStorageWriter<WebStateWriter>;

	using Super::Super;

	// There should never be a version mismatch, ignore this
	int version(int v) {return v;}

	// Include extra info
	bool extra() {
		return true;
	}
	template<class V>
	void extra(const char *key, V v) {
		(*this)(key, v);
	}
};

struct WebStateReader : public storage::STFXStorageReader<WebStateReader> {
	using Super = storage::STFXStorageReader<WebStateReader>;

	using Super::Super;
	
	// There should never be a version mismatch, ignore this
	int version(int v) {return v;}

	// We're interested in an extended set of values being sent back
	bool extra() {
		return true;
	}
	// But anything read-only gets skipped
	template<class V>
	void extra(const char *key, V v) {}

	void invalidate(const char *invalidatedKey) {
		// TODO: right now this is hacked together, by the params re-sending themselves whenever they would otherwise invalidate.
		// Instead, this would let us reply with only the keys which changed
	}
};

template<class S>
constexpr bool storageIsWeb() {return false;}
template<>
constexpr bool storageIsWeb<WebStateWriter>() {return true;}
template<>
constexpr bool storageIsWeb<WebStateReader>() {return true;}

/* Given an STFX template which (when insantiated) has inheritance like:

	EffectSTFX : Effect
	
This produces a template with inheritance like:

	WebSTFX : EffectSTFX : WebBase : Effect

The WebBase template replaces the ParamRange/ParamStepped classes, so that the UI can be updated when they change.  The outer WebSTFX class adds methods for forwarding messages between the effect and its webview.
*/

template<template<class, class...> class EffectSTFX, class SubClass>
struct WebUIHelper {

	template<class Effect>
	class WebBase : public Effect {
		using SuperRange = typename Effect::ParamRange;
		using SuperStepped = typename Effect::ParamStepped;
		
	protected:
		struct WebParamScanner : public storage::STFXStorageScanner<WebParamScanner>{
			SubClass *effect;
			std::vector<std::string> scope;
			
			WebParamScanner(SubClass *effect) : effect(effect) {}
			
			// Extra methods we add for STFX storage
			void info(const char *, const char *) {}
			int version(int v) {
				return v;
			}
			template<class PR>
			RangeParamInfo & range(const char *key, PR &param) {
				param.effect = effect;
				param.scope = scope;
				param.scope.emplace_back(key);
				param.info = std::unique_ptr<RangeParamInfo>{
					new RangeParamInfo(param)
				};
				return *param.info;
			}
			template<class PS>
			SteppedParamInfo & stepped(const char *key, PS &param) {
				param.effect = effect;
				param.scope = scope;
				param.scope.emplace_back(key);
				param.info = std::unique_ptr<SteppedParamInfo>{
					new SteppedParamInfo(param)
				};
				return *param.info;
			}
			template<class V>
			bool changed(const char *key, V &v) {
				(*this)(key, v);
				return false;
			}
			void invalidate(const char *) {}
		};

	public:
		using Effect::Effect;

		std::string webPage = "html/generic.html";
		int webWidth = 640, webHeight = 480;

		struct ParamRange : public SuperRange {
			using SuperRange::SuperRange;
			
			ParamContext context;
			
			ParamRange & operator=(double v) {
				bool changed = (v != *this);
				SuperRange::operator=(v);
				if (changed) sendUpdateMessage();
				return *this;
			}

			template<class Storage>
			void state(Storage &storage) {
				double prevV = *this;
				bool prevGesture = gesture;
				SuperRange::state(storage);
				
				constexpr bool isWeb = storageIsWeb<Storage>();
				if (isWeb) { // a bunch of extra state
					storage.extra("$type", "ParamRange");
					storage.extra("name", info->name);
					storage.extra("defaultValue", info->defaultValue);
					std::string text, units;
					info->toString((double)*this, text, units);
					storage.extra("text", text);
					storage.extra("textUnits", units);
					storage("gesture", gesture);

					double unit = info->toUnit(*this);
					if (storage.changed("rangeUnit", unit)) {
						SuperRange::operator=(info->fromUnit(unit));
						storage.invalidate("value");
					}
				}

				if (prevV != *this) {
					storage.invalidate("rangeUnit");
					storage.invalidate("text");
					storage.invalidate("textUnits");
					if (isWeb) {
						if (effect->paramListenerRange) {
							effect->paramListenerRange(context, *this);
						}
						sendUpdateMessage(); // TODO: shouldn't be necessary once we have `.invalidate()` working
					} else {
						sendUpdateMessage();
					}
				}
				if (gesture != prevGesture) {
					if (isWeb && effect->paramListenerGesture) {
						effect->paramListenerGesture(context, gesture);
					}
				}
			}

		private:
			friend struct WebParamScanner;
			SubClass *effect = nullptr;
			std::vector<std::string> scope;
			std::unique_ptr<RangeParamInfo> info;
			bool gesture = false;

			void sendUpdateMessage() {
				if (auto *m = effect->getEmptyMessage()) {
					signalsmith::cbor::CborWriter cbor{m->bytes};
					for (auto &key : scope) {
						cbor.openMap(1);
						cbor.addUtf8(key);
					}
					WebStateWriter storage{cbor};
					state(storage);
					m->markReady();
				}
			}
		};

		struct ParamStepped : public SuperStepped {
			using SuperStepped::SuperStepped;

			ParamContext context;

			ParamStepped & operator=(int v) {
				bool changed = (v != *this);
				SuperStepped::operator=(v);
				if (changed) sendUpdateMessage();
				return *this;
			}

			template<class Storage>
			void state(Storage &storage) {
				int prevV = *this;
				SuperStepped::state(storage);

				constexpr bool isWeb = storageIsWeb<Storage>();
				if (isWeb) {
					storage.extra("$type", "ParamStepped");
					storage.extra("low", info->low);
					storage.extra("high", info->high);
					storage.extra("name", info->name);
					std::string text = info->toString((int)*this);
					storage.extra("text", text);
				}

				if (prevV != *this) {
					storage.invalidate("text");
					if (isWeb) {
						if (effect->paramListenerStepped) {
							effect->paramListenerStepped(context, *this);
						}
						sendUpdateMessage(); // TODO: shouldn't be necessary once we have `.invalidate()` working
					} else {
						sendUpdateMessage();
					}
				}
			}

		private:
			friend struct WebParamScanner;
			SubClass *effect = nullptr;
			std::vector<std::string> scope;
			std::unique_ptr<SteppedParamInfo> info;

			void sendUpdateMessage() {
				if (auto *m = effect->getEmptyMessage()) {
					signalsmith::cbor::CborWriter cbor{m->bytes};
					for (auto &key : scope) {
						cbor.openMap(1);
						cbor.addUtf8(key);
					}
					WebStateWriter storage{cbor};
					state(storage);
					m->markReady();
				}
			}
		};
		
		template<class Storage>
		void meterState(Storage &storage) {}
	};
	
	template<class Effect, class... ExtraArgs>
	struct WebSTFX : public EffectSTFX<WebBase<Effect>, ExtraArgs...> {
		using Super = EffectSTFX<WebBase<Effect>, ExtraArgs...>;
	};
};

// Use this instead of a plain LibraryEffect
template<typename Sample, template<class, class...> class EffectSTFX, class... ExtraArgs>
struct WebUILibraryEffect : public LibraryEffect<Sample, WebUIHelper<EffectSTFX, WebUILibraryEffect<Sample, EffectSTFX, ExtraArgs...>>::template WebSTFX, ExtraArgs...> {
	using Super = LibraryEffect<Sample, WebUIHelper<EffectSTFX, WebUILibraryEffect<Sample, EffectSTFX, ExtraArgs...>>::template WebSTFX, ExtraArgs...>;

	template<class... Args>
	WebUILibraryEffect(Args... args) : Super(args...) {
		typename Super::WebParamScanner scanner{this};
		this->state(scanner);
	};

	// These are called when the parameter is changed from the web UI
	std::function<void(ParamContext, double)> paramListenerRange;
	std::function<void(ParamContext, bool)> paramListenerGesture;
	std::function<void(ParamContext, int)> paramListenerStepped;
	
	// This state includes all the parameters
	void saveState(std::vector<unsigned char> &bytes) {
		stfx::storage::STFXStorageWriter<> storage(bytes);
		this->state(storage);
	}
	void loadState(const std::vector<unsigned char> &bytes) {
		stfx::storage::STFXStorageReader<> storage(bytes);
		this->state(storage);
		requestEntireState();
	}

	struct WebMessage {
		std::vector<unsigned char> bytes;
		
		WebMessage() {
			bytes.reserve(256);
		}
		
		void sent() {
			readyToSend.clear();
		}

	private:
		friend class WebUILibraryEffect;
		friend struct Super::ParamRange;
		friend struct Super::ParamStepped;
		std::atomic_flag readyToSend = ATOMIC_FLAG_INIT;

		void markReady() {
			readyToSend.test_and_set();
		}
	};

	bool hasPendingWebMessage() const {
		auto &message = queue[readIndex];
		return message.readyToSend.test();
	}
	
	// Poll on the main thread (and directly after any `.webReceive()`), calling `.sent()` after you've sent it, repeat until you get `nullptr`
	WebMessage * getPendingWebMessage() {
		auto &message = queue[readIndex];
		if (!message.readyToSend.test()) return nullptr;
		if (++readIndex == queue.size()) readIndex = 0;

		if (resetQueue.test()) {
			// Clear ("send") every message aside from this one
			for (auto &m : queue) {
				if (&m == &message) continue;
				m.sent();
			}
			// Ready to start sending messages again, starting from the next index
			writeIndex.store(readIndex);
			resetQueue.clear();
			// any messages (state updates) sent after this won't assume a *newer* state than what we serialise below

			// Replace this one's message with the complete plugin state
			WebStateWriter storage(message.bytes);
			this->state(storage);
		}
		return &message;
	}

	// Call when the webview posts any message back
	void webReceive(const void *message, size_t size) {
		auto *bytes = (const unsigned char *)message;
		signalsmith::cbor::TaggedCborWalker cbor(bytes, bytes + size);
		
		if (cbor.isUtf8()) {
			if (cbor.utf8View() == "ready") {
				requestEntireState();
				return;
			}
		} else if (cbor.isArray()) {
			size_t length = cbor.length();
			cbor = cbor.enter();
			if (cbor.utf8View() == "meters" && length == 3) {
				double interval = ++cbor;
				double duration = ++cbor;
				metersInterval.store(interval*this->config.sampleRate);
				metersDuration.store(duration*this->config.sampleRate);
			}
		} else if (cbor.isMap()) {
			// Apply it as a merge
			WebStateReader reader(cbor);
			this->state(reader);
		}
	}

	void webClosed() {
		// stops new messages from being queued up until the reset message is sent
		requestEntireState();
	}

	// Replace `.process()` to add meter messages if they exist
	template<class Buffers>
	void process(Buffers &&buffers, int blockLength) {
		process(buffers, buffers, blockLength);
	}

	template<class Inputs, class Outputs>
	void process(Inputs &&inputs, Outputs &&outputs, int blockLength) {
		Super::process(inputs, outputs, blockLength);

		if (this->hasMeters()) {
			auto *m = getEmptyMessage();
			if (m) {
				signalsmith::cbor::CborWriter cbor{m->bytes};
				WebStateWriter storage{cbor};
				this->meterState(storage);
				m->markReady();
			}
			this->wantsMeters(false);
		}

		if (metersDuration.load() > 0) {
			metersDuration -= blockLength;
			samplesSinceMeters += blockLength;
			if (samplesSinceMeters > metersInterval.load()) {
				this->wantsMeters();
				samplesSinceMeters = 0;
			}
		}
	}
	
private:
	friend struct Super::ParamRange;
	friend struct Super::ParamStepped;
	
	std::atomic<int> metersInterval = 0, metersDuration = 0;
	int samplesSinceMeters = 0; // only used from `.process()`
	
	std::vector<WebMessage> queue = std::vector<WebMessage>(64); // power of 2 so that overflow doesn't mess with the modulo
	size_t readIndex = 0;
	std::atomic_flag resetQueue = ATOMIC_FLAG_INIT;

	// Atomic because multiple threads might write
	std::atomic<size_t> writeIndex = 0;
	WebMessage * getEmptyMessage() {
		if (resetQueue.test()) return nullptr;
		auto reservedIndex = writeIndex.fetch_add(1);
		auto &message = queue[reservedIndex%queue.size()];
		if (message.readyToSend.test()) {
			std::cerr << "Web message queue full - sending entire state instead\n";
			// When our queue is full, we drop the entire thing and re-send the entire state
			resetQueue.test_and_set();
			return nullptr;
		}
		message.bytes.resize(0);
		return &message;
	}

	void requestEntireState() {
		if (auto *m = getEmptyMessage()) {
			resetQueue.test_and_set();
			m->markReady();
		} // if this fails, then the queue is full and we're doing a reset anyway
	}};

}} // namespace