Add two-way databinding for lua, and flesh out the lua statusbar

9 files changed, 354 insertions, 11 deletions

diff --git a/src/lua/CMakeLists.txt b/src/lua/CMakeLists.txt
index a2dd8739..f179a881 100644
--- a/src/lua/CMakeLists.txt
+++ b/src/lua/CMakeLists.txt
@@ -3,7 +3,7 @@
 # SPDX-License-Identifier: GPL-3.0-only
 
 idf_component_register(
-  SRCS "lua_thread.cpp" "bridge.cpp"
+  SRCS "lua_thread.cpp" "bridge.cpp" "property.cpp"
   INCLUDE_DIRS "include"
   REQUIRES "drivers" "lvgl" "tinyfsm" "events" "system_fsm" "database" "esp_timer" "battery" "esp-idf-lua" "luavgl")
 target_compile_options(${COMPONENT_LIB} PRIVATE ${EXTRA_WARNINGS})
diff --git a/src/lua/bridge.cpp b/src/lua/bridge.cpp
index acc64c31..ba6f50b4 100644
--- a/src/lua/bridge.cpp
+++ b/src/lua/bridge.cpp
@@ -10,10 +10,12 @@
 #include <string>
 
 #include "esp_log.h"
-#include "event_queue.hpp"
-#include "lua.h"
+#include "lauxlib.h"
 #include "lua.hpp"
 #include "lvgl.h"
+
+#include "event_queue.hpp"
+#include "property.hpp"
 #include "service_locator.hpp"
 #include "ui_events.hpp"
 
@@ -53,9 +55,7 @@ static auto lua_legacy_ui(lua_State* state) -> int {
 }
 
 static auto get_indexes(lua_State* state) -> int {
-  lua_pushstring(state, kBridgeKey);
-  lua_gettable(state, LUA_REGISTRYINDEX);
-  Bridge* instance = reinterpret_cast<Bridge*>(lua_touserdata(state, -1));
+  Bridge* instance = Bridge::Get(state);
 
   lua_newtable(state);
 
@@ -80,8 +80,14 @@ static auto lua_database(lua_State* state) -> int {
   return 1;
 }
 
+auto Bridge::Get(lua_State* state) -> Bridge* {
+  lua_pushstring(state, kBridgeKey);
+  lua_gettable(state, LUA_REGISTRYINDEX);
+  return reinterpret_cast<Bridge*>(lua_touserdata(state, -1));
+}
+
 Bridge::Bridge(system_fsm::ServiceLocator& services, lua_State& s)
-    : services_(services), state_(s) {
+    : services_(services), state_(s), bindings_(s) {
   lua_pushstring(&s, kBridgeKey);
   lua_pushlightuserdata(&s, this);
   lua_settable(&s, LUA_REGISTRYINDEX);
@@ -93,4 +99,31 @@ Bridge::Bridge(system_fsm::ServiceLocator& services, lua_State& s)
   lua_pop(&s, 1);
 }
 
+static auto new_property_module(lua_State* state) -> int {
+  const char* name = luaL_checkstring(state, 1);
+  luaL_newmetatable(state, name);
+
+  lua_pushstring(state, "__index");
+  lua_pushvalue(state, -2);
+  lua_settable(state, -3);  // metatable.__index = metatable
+
+  return 1;
+}
+
+auto Bridge::AddPropertyModule(
+    const std::string& name,
+    std::vector<std::pair<std::string, std::shared_ptr<Property>>> props)
+    -> void {
+  // Create the module (or retrieve it if one with this name already exists)
+  luaL_requiref(&state_, name.c_str(), new_property_module, true);
+
+  for (const auto& prop : props) {
+    lua_pushstring(&state_, prop.first.c_str());
+    bindings_.Register(&state_, prop.second.get());
+    lua_settable(&state_, -3);  // metatable.propname = property
+  }
+
+  lua_pop(&state_, 1);  // pop the module off the stack
+}
+
 }  // namespace lua
diff --git a/src/lua/include/bridge.hpp b/src/lua/include/bridge.hpp
index 059d0604..26401d14 100644
--- a/src/lua/include/bridge.hpp
+++ b/src/lua/include/bridge.hpp
@@ -11,19 +11,28 @@
 
 #include "lua.hpp"
 #include "lvgl.h"
+#include "property.hpp"
 #include "service_locator.hpp"
 
 namespace lua {
 
 class Bridge {
  public:
+  static auto Get(lua_State* state) -> Bridge*;
+
   Bridge(system_fsm::ServiceLocator&, lua_State& s);
 
+  auto AddPropertyModule(
+      const std::string&,
+      std::vector<std::pair<std::string, std::shared_ptr<Property>>>) -> void;
+
   system_fsm::ServiceLocator& services() { return services_; }
+  PropertyBindings& bindings() { return bindings_; }
 
  private:
   system_fsm::ServiceLocator& services_;
   lua_State& state_;
+  PropertyBindings bindings_;
 };
 
 }  // namespace lua
diff --git a/src/lua/include/lua_thread.hpp b/src/lua/include/lua_thread.hpp
index 381b1bdb..939d0cda 100644
--- a/src/lua/include/lua_thread.hpp
+++ b/src/lua/include/lua_thread.hpp
@@ -27,6 +27,8 @@ class LuaThread {
 
   auto RunScript(const std::string& path) -> bool;
 
+  auto bridge() -> Bridge& { return *bridge_; }
+
  private:
   LuaThread(std::unique_ptr<Allocator>&, std::unique_ptr<Bridge>&, lua_State*);
 
diff --git a/src/lua/include/property.hpp b/src/lua/include/property.hpp
new file mode 100644
index 00000000..b6b4718f
--- /dev/null
+++ b/src/lua/include/property.hpp
@@ -0,0 +1,47 @@
+/*
+ * Copyright 2023 jacqueline <me@jacqueline.id.au>
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#pragma once
+
+#include <memory>
+#include <string>
+
+#include "lua.hpp"
+#include "lvgl.h"
+#include "service_locator.hpp"
+
+namespace lua {
+
+using LuaValue = std::variant<std::monostate, int, float, bool, std::string>;
+
+class Property {
+ public:
+  Property() : Property(std::monostate{}) {}
+  Property(const LuaValue&);
+  Property(const LuaValue&, std::function<bool(const LuaValue&)>);
+
+  auto IsTwoWay() -> bool { return cb_.has_value(); }
+
+  auto PushValue(lua_State& s) -> int;
+  auto PopValue(lua_State& s) -> bool;
+  auto Update(const LuaValue& new_val) -> void;
+
+  auto AddLuaBinding(lua_State*, int ref) -> void;
+
+ private:
+  LuaValue value_;
+  std::optional<std::function<bool(const LuaValue&)>> cb_;
+  std::vector<std::pair<lua_State*, int>> bindings_;
+};
+
+class PropertyBindings {
+ public:
+  PropertyBindings(lua_State&);
+
+  auto Register(lua_State*, Property*) -> void;
+};
+
+}  // namespace lua
diff --git a/src/lua/lua_thread.cpp b/src/lua/lua_thread.cpp
index cb7066a5..eb2f5107 100644
--- a/src/lua/lua_thread.cpp
+++ b/src/lua/lua_thread.cpp
@@ -5,11 +5,11 @@
  */
 
 #include "lua_thread.hpp"
+
 #include <memory>
 
 #include "esp_heap_caps.h"
 #include "esp_log.h"
-#include "lua.h"
 #include "lua.hpp"
 #include "luavgl.h"
 #include "service_locator.hpp"
diff --git a/src/lua/property.cpp b/src/lua/property.cpp
new file mode 100644
index 00000000..3130077b
--- /dev/null
+++ b/src/lua/property.cpp
@@ -0,0 +1,196 @@
+/*
+ * Copyright 2023 jacqueline <me@jacqueline.id.au>
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#include "property.hpp"
+
+#include <memory>
+#include <string>
+
+#include "lua.h"
+#include "lua.hpp"
+#include "lvgl.h"
+#include "service_locator.hpp"
+
+namespace lua {
+
+static const char kMetatableName[] = "property";
+static const char kBindingsTable[] = "bindings";
+
+static auto check_property(lua_State* state) -> Property* {
+  void* data = luaL_checkudata(state, 1, kMetatableName);
+  luaL_argcheck(state, data != NULL, 1, "`property` expected");
+  return *reinterpret_cast<Property**>(data);
+}
+
+static auto property_get(lua_State* state) -> int {
+  Property* p = check_property(state);
+  p->PushValue(*state);
+  return 1;
+}
+
+static auto property_set(lua_State* state) -> int {
+  Property* p = check_property(state);
+  luaL_argcheck(state, p->IsTwoWay(), 1, "property is read-only");
+  bool valid = p->PopValue(*state);
+  lua_pushboolean(state, valid);
+  return 1;
+}
+
+static auto property_bind(lua_State* state) -> int {
+  Property* p = check_property(state);
+  luaL_checktype(state, 2, LUA_TFUNCTION);
+
+  // Copy the function, as we need to invoke it then store our reference.
+  lua_pushvalue(state, 2);
+  // ...and another copy, since we return the original closure.
+  lua_pushvalue(state, 2);
+
+  // FIXME: This should ideally be lua_pcall, for safety.
+  p->PushValue(*state);
+  lua_call(state, 1, 0);  // Invoke the initial binding.
+
+  lua_pushstring(state, kBindingsTable);
+  lua_gettable(state, LUA_REGISTRYINDEX);  // REGISTRY[kBindingsTable]
+  lua_insert(state, -2);          // Move bindings to the bottom, with fn above.
+  int ref = luaL_ref(state, -2);  // bindings[ref] = fn
+
+  p->AddLuaBinding(state, ref);
+
+  // Pop the bindings table, leaving one of the copiesw of the callback fn at
+  // the top of the stack.
+  lua_pop(state, 1);
+
+  return 1;
+}
+
+static const struct luaL_Reg kPropertyBindingFuncs[] = {{"get", property_get},
+                                                        {"set", property_set},
+                                                        {"bind", property_bind},
+                                                        {NULL, NULL}};
+
+PropertyBindings::PropertyBindings(lua_State& s) {
+  // Create the metatable responsible for the Property API.
+  luaL_newmetatable(&s, kMetatableName);
+
+  lua_pushliteral(&s, "__index");
+  lua_pushvalue(&s, -2);
+  lua_settable(&s, -3);  // metatable.__index = metatable
+
+  // Add our binding funcs (get, set, bind) to the metatable.
+  luaL_setfuncs(&s, kPropertyBindingFuncs, 0);
+
+  // Create a weak table in the registry to hold live bindings.
+  lua_pushstring(&s, kBindingsTable);
+  lua_newtable(&s);  // bindings = {}
+
+  // Metatable for the weak table. Values are weak.
+  lua_newtable(&s);  // meta = {}
+  lua_pushliteral(&s, "__mode");
+  lua_pushliteral(&s, "v");
+  lua_settable(&s, -3);      // meta.__mode='v'
+  lua_setmetatable(&s, -2);  // setmetatable(bindings, meta)
+
+  lua_settable(&s, LUA_REGISTRYINDEX);  // REGISTRY[kBindingsTable] = bindings
+}
+
+auto PropertyBindings::Register(lua_State* s, Property* prop) -> void {
+  Property** data =
+      reinterpret_cast<Property**>(lua_newuserdata(s, sizeof(Property*)));
+  *data = prop;
+
+  luaL_setmetatable(s, kMetatableName);
+}
+
+template <class... Ts>
+inline constexpr bool always_false_v = false;
+
+Property::Property(const LuaValue& val) : value_(val), cb_() {}
+
+Property::Property(const LuaValue& val,
+                   std::function<bool(const LuaValue& val)> cb)
+    : value_(val), cb_(cb) {}
+
+auto Property::PushValue(lua_State& s) -> int {
+  std::visit(
+      [&](auto&& arg) {
+        using T = std::decay_t<decltype(arg)>;
+        if constexpr (std::is_same_v<T, std::monostate>) {
+          lua_pushnil(&s);
+        } else if constexpr (std::is_same_v<T, int>) {
+          lua_pushinteger(&s, arg);
+        } else if constexpr (std::is_same_v<T, float>) {
+          lua_pushnumber(&s, arg);
+        } else if constexpr (std::is_same_v<T, bool>) {
+          lua_pushboolean(&s, arg);
+        } else if constexpr (std::is_same_v<T, std::string>) {
+          lua_pushstring(&s, arg.c_str());
+        } else {
+          static_assert(always_false_v<T>, "PushValue missing type");
+        }
+      },
+      value_);
+  return 1;
+}
+
+auto Property::PopValue(lua_State& s) -> bool {
+  LuaValue new_val;
+  switch (lua_type(&s, 2)) {
+    case LUA_TNIL:
+      new_val = std::monostate{};
+      break;
+    case LUA_TNUMBER:
+      if (lua_isinteger(&s, 2)) {
+        new_val = lua_tointeger(&s, 2);
+      } else {
+        new_val = lua_tonumber(&s, 2);
+      }
+      break;
+    case LUA_TBOOLEAN:
+      new_val = lua_toboolean(&s, 2);
+      break;
+    case LUA_TSTRING:
+      new_val = lua_tostring(&s, 2);
+      break;
+    default:
+      return false;
+  }
+
+  if (cb_ && std::invoke(*cb_, new_val)) {
+    Update(new_val);
+    return true;
+  }
+  return false;
+}
+
+auto Property::Update(const LuaValue& v) -> void {
+  value_ = v;
+
+  for (int i = bindings_.size() - 1; i >= 0; i--) {
+    auto& b = bindings_[i];
+
+    lua_pushstring(b.first, kBindingsTable);
+    lua_gettable(b.first, LUA_REGISTRYINDEX);       // REGISTRY[kBindingsTable]
+    int type = lua_rawgeti(b.first, -1, b.second);  // push bindings[i]
+
+    // Has closure has been GCed?
+    if (type == LUA_TNIL) {
+      // Clean up after ourselves.
+      lua_pop(b.first, 1);
+      // Remove the binding.
+      bindings_.erase(bindings_.begin() + i);
+      continue;
+    }
+
+    PushValue(*b.first);      // push the argument
+    lua_call(b.first, 1, 0);  // invoke the closure
+  }
+}
+
+auto Property::AddLuaBinding(lua_State* state, int ref) -> void {
+  bindings_.push_back({state, ref});
+}
+
+}  // namespace lua
diff --git a/src/ui/include/ui_fsm.hpp b/src/ui/include/ui_fsm.hpp
index 7d1d62d6..39fae4b0 100644
--- a/src/ui/include/ui_fsm.hpp
+++ b/src/ui/include/ui_fsm.hpp
@@ -21,6 +21,7 @@
 #include "model_playback.hpp"
 #include "model_top_bar.hpp"
 #include "nvs.hpp"
+#include "property.hpp"
 #include "relative_wheel.hpp"
 #include "screen_playing.hpp"
 #include "screen_settings.hpp"
@@ -56,9 +57,9 @@ class UiState : public tinyfsm::Fsm<UiState> {
   /* Fallback event handler. Does nothing. */
   void react(const tinyfsm::Event& ev) {}
 
-  void react(const system_fsm::BatteryStateChanged&);
-  void react(const audio::PlaybackStarted&);
-  void react(const audio::PlaybackFinished&);
+  virtual void react(const system_fsm::BatteryStateChanged&);
+  virtual void react(const audio::PlaybackStarted&);
+  virtual void react(const audio::PlaybackFinished&);
   void react(const audio::PlaybackUpdate&);
   void react(const audio::QueueUpdate&);
 
@@ -127,7 +128,19 @@ class Lua : public UiState {
   void react(const internal::ShowNowPlaying&) override;
   void react(const internal::ShowSettingsPage&) override;
 
+  void react(const system_fsm::BatteryStateChanged&) override;
+  void react(const audio::PlaybackStarted&) override;
+  void react(const audio::PlaybackFinished&) override;
+
   using UiState::react;
+
+ private:
+  std::shared_ptr<lua::Property> battery_pct_;
+  std::shared_ptr<lua::Property> battery_mv_;
+  std::shared_ptr<lua::Property> battery_charging_;
+  std::shared_ptr<lua::Property> bluetooth_en_;
+  std::shared_ptr<lua::Property> playback_playing_;
+  std::shared_ptr<lua::Property> playback_track_;
 };
 
 class Onboarding : public UiState {
diff --git a/src/ui/ui_fsm.cpp b/src/ui/ui_fsm.cpp
index 748e08f9..9ecc9b7c 100644
--- a/src/ui/ui_fsm.cpp
+++ b/src/ui/ui_fsm.cpp
@@ -33,6 +33,7 @@
 #include "modal_progress.hpp"
 #include "model_playback.hpp"
 #include "nvs.hpp"
+#include "property.hpp"
 #include "relative_wheel.hpp"
 #include "screen.hpp"
 #include "screen_lua.hpp"
@@ -183,7 +184,36 @@ void Lua::entry() {
     sCurrentScreen.reset(new Screen());
     lv_group_set_default(sCurrentScreen->group());
 
+    auto bat =
+        sServices->battery().State().value_or(battery::Battery::BatteryState{});
+    battery_pct_ =
+        std::make_shared<lua::Property>(static_cast<int>(bat.percent));
+    battery_mv_ =
+        std::make_shared<lua::Property>(static_cast<int>(bat.millivolts));
+    battery_charging_ = std::make_shared<lua::Property>(bat.is_charging);
+
+    bluetooth_en_ = std::make_shared<lua::Property>(false);
+    playback_playing_ = std::make_shared<lua::Property>(false);
+    playback_track_ = std::make_shared<lua::Property>();
+
     sLua.reset(lua::LuaThread::Start(*sServices, sCurrentScreen->content()));
+    sLua->bridge().AddPropertyModule("power",
+                                     {
+                                         {"battery_pct", battery_pct_},
+                                         {"battery_millivolts", battery_mv_},
+                                         {"plugged_in", battery_charging_},
+                                     });
+    sLua->bridge().AddPropertyModule("bluetooth",
+                                     {
+                                         {"enabled", bluetooth_en_},
+                                         {"connected", bluetooth_en_},
+                                     });
+    sLua->bridge().AddPropertyModule("playback",
+                                     {
+                                         {"playing", playback_playing_},
+                                         {"track", playback_track_},
+                                     });
+
     sLua->RunScript("/lua/main.lua");
 
     lv_group_set_default(NULL);
@@ -216,6 +246,19 @@ void Lua::react(const internal::ShowSettingsPage& ev) {
   transit<Browse>();
 }
 
+void Lua::react(const system_fsm::BatteryStateChanged& ev) {
+  battery_pct_->Update(static_cast<int>(ev.new_state.percent));
+  battery_mv_->Update(static_cast<int>(ev.new_state.millivolts));
+}
+
+void Lua::react(const audio::PlaybackStarted&) {
+  playback_playing_->Update(true);
+}
+
+void Lua::react(const audio::PlaybackFinished&) {
+  playback_playing_->Update(false);
+}
+
 void Onboarding::entry() {
   progress_ = 0;
   has_formatted_ = false;