init

4 files changed, 1112 insertions, 0 deletions

diff --git a/src/constants.rs b/src/constants.rs
new file mode 100644
index 0000000..a67b6fe
--- /dev/null
+++ b/src/constants.rs
@@ -0,0 +1,97 @@
+#![allow(unused)]
+
+pub const HA_DOMAIN_SENSOR: &str = "sensor";
+pub const HA_DOMAIN_BINARY_SENSOR: &str = "binary_sensor";
+pub const HA_DOMAIN_SWITCH: &str = "switch";
+pub const HA_DOMAIN_LIGHT: &str = "light";
+pub const HA_DOMAIN_BUTTON: &str = "button";
+pub const HA_DOMAIN_SELECT: &str = "select";
+
+pub const HA_DEVICE_CLASS_SENSOR_APPARENT_POWER: &str = "apparent_power";
+pub const HA_DEVICE_CLASS_SENSOR_AQI: &str = "aqi";
+pub const HA_DEVICE_CLASS_SENSOR_ATMOSPHERIC_PRESSURE: &str = "atmospheric_pressure";
+pub const HA_DEVICE_CLASS_SENSOR_BATTERY: &str = "battery";
+pub const HA_DEVICE_CLASS_SENSOR_CARBON_DIOXIDE: &str = "carbon_dioxide";
+pub const HA_DEVICE_CLASS_SENSOR_CARBON_MONOXIDE: &str = "carbon_monoxide";
+pub const HA_DEVICE_CLASS_SENSOR_CURRENT: &str = "current";
+pub const HA_DEVICE_CLASS_SENSOR_DATA_RATE: &str = "data_rate";
+pub const HA_DEVICE_CLASS_SENSOR_DATA_SIZE: &str = "data_size";
+pub const HA_DEVICE_CLASS_SENSOR_DATE: &str = "date";
+pub const HA_DEVICE_CLASS_SENSOR_DISTANCE: &str = "distance";
+pub const HA_DEVICE_CLASS_SENSOR_DURATION: &str = "duration";
+pub const HA_DEVICE_CLASS_SENSOR_ENERGY: &str = "energy";
+pub const HA_DEVICE_CLASS_SENSOR_ENERGY_STORAGE: &str = "energy_storage";
+pub const HA_DEVICE_CLASS_SENSOR_ENUM: &str = "enum";
+pub const HA_DEVICE_CLASS_SENSOR_FREQUENCY: &str = "frequency";
+pub const HA_DEVICE_CLASS_SENSOR_GAS: &str = "gas";
+pub const HA_DEVICE_CLASS_SENSOR_HUMIDITY: &str = "humidity";
+pub const HA_DEVICE_CLASS_SENSOR_ILLUMINANCE: &str = "illuminance";
+pub const HA_DEVICE_CLASS_SENSOR_IRRADIANCE: &str = "irradiance";
+pub const HA_DEVICE_CLASS_SENSOR_MOISTURE: &str = "moisture";
+pub const HA_DEVICE_CLASS_SENSOR_MONETARY: &str = "monetary";
+pub const HA_DEVICE_CLASS_SENSOR_NITROGEN_DIOXIDE: &str = "nitrogen_dioxide";
+pub const HA_DEVICE_CLASS_SENSOR_NITROGEN_MONOXIDE: &str = "nitrogen_monoxide";
+pub const HA_DEVICE_CLASS_SENSOR_NITROUS_OXIDE: &str = "nitrous_oxide";
+pub const HA_DEVICE_CLASS_SENSOR_OZONE: &str = "ozone";
+pub const HA_DEVICE_CLASS_SENSOR_PH: &str = "ph";
+pub const HA_DEVICE_CLASS_SENSOR_PM1: &str = "pm1";
+pub const HA_DEVICE_CLASS_SENSOR_PM25: &str = "pm25";
+pub const HA_DEVICE_CLASS_SENSOR_PM10: &str = "pm10";
+pub const HA_DEVICE_CLASS_SENSOR_POWER_FACTOR: &str = "power_factor";
+pub const HA_DEVICE_CLASS_SENSOR_POWER: &str = "power";
+pub const HA_DEVICE_CLASS_SENSOR_PRECIPITATION: &str = "precipitation";
+pub const HA_DEVICE_CLASS_SENSOR_PRECIPITATION_INTENSITY: &str = "precipitation_intensity";
+pub const HA_DEVICE_CLASS_SENSOR_PRESSURE: &str = "pressure";
+pub const HA_DEVICE_CLASS_SENSOR_REACTIVE_POWER: &str = "reactive_power";
+pub const HA_DEVICE_CLASS_SENSOR_SIGNAL_STRENGTH: &str = "signal_strength";
+pub const HA_DEVICE_CLASS_SENSOR_SOUND_PRESSURE: &str = "sound_pressure";
+pub const HA_DEVICE_CLASS_SENSOR_SPEED: &str = "speed";
+pub const HA_DEVICE_CLASS_SENSOR_SULPHUR_DIOXIDE: &str = "sulphur_dioxide";
+pub const HA_DEVICE_CLASS_SENSOR_TEMPERATURE: &str = "temperature";
+pub const HA_DEVICE_CLASS_SENSOR_TIMESTAMP: &str = "timestamp";
+pub const HA_DEVICE_CLASS_SENSOR_VOLATILE_ORGANIC_COMPOUNDS: &str = "volatile_organic_compounds";
+pub const HA_DEVICE_CLASS_SENSOR_VOLATILE_ORGANIC_COMPOUNDS_PARTS: &str =
+    "volatile_organic_compounds_parts";
+pub const HA_DEVICE_CLASS_SENSOR_VOLTAGE: &str = "voltage";
+pub const HA_DEVICE_CLASS_SENSOR_VOLUME: &str = "volume";
+pub const HA_DEVICE_CLASS_SENSOR_VOLUME_FLOW_RATE: &str = "volume_flow_rate";
+pub const HA_DEVICE_CLASS_SENSOR_VOLUME_STORAGE: &str = "volume_storage";
+pub const HA_DEVICE_CLASS_SENSOR_WATER: &str = "water";
+pub const HA_DEVICE_CLASS_SENSOR_WEIGHT: &str = "weight";
+pub const HA_DEVICE_CLASS_SENSOR_WIND_SPEED: &str = "wind_speed";
+
+pub const HA_DEVICE_CLASS_BINARY_SENSOR_BATTERY: &str = "battery";
+pub const HA_DEVICE_CLASS_BINARY_SENSOR_BATTERY_CHARGING: &str = "battery_charging";
+pub const HA_DEVICE_CLASS_BINARY_SENSOR_CARBON_MONOXIDE: &str = "carbon_monoxide";
+pub const HA_DEVICE_CLASS_BINARY_SENSOR_COLD: &str = "cold";
+pub const HA_DEVICE_CLASS_BINARY_SENSOR_CONNECTIVITY: &str = "connectivity";
+pub const HA_DEVICE_CLASS_BINARY_SENSOR_DOOR: &str = "door";
+pub const HA_DEVICE_CLASS_BINARY_SENSOR_GARAGE_DOOR: &str = "garage_door";
+pub const HA_DEVICE_CLASS_BINARY_SENSOR_GAS: &str = "gas";
+pub const HA_DEVICE_CLASS_BINARY_SENSOR_HEAT: &str = "heat";
+pub const HA_DEVICE_CLASS_BINARY_SENSOR_LIGHT: &str = "light";
+pub const HA_DEVICE_CLASS_BINARY_SENSOR_LOCK: &str = "lock";
+pub const HA_DEVICE_CLASS_BINARY_SENSOR_MOISTURE: &str = "moisture";
+pub const HA_DEVICE_CLASS_BINARY_SENSOR_MOTION: &str = "motion";
+pub const HA_DEVICE_CLASS_BINARY_SENSOR_MOVING: &str = "moving";
+pub const HA_DEVICE_CLASS_BINARY_SENSOR_OCCUPANCY: &str = "occupancy";
+pub const HA_DEVICE_CLASS_BINARY_SENSOR_OPENING: &str = "opening";
+pub const HA_DEVICE_CLASS_BINARY_SENSOR_PLUG: &str = "plug";
+pub const HA_DEVICE_CLASS_BINARY_SENSOR_POWER: &str = "power";
+pub const HA_DEVICE_CLASS_BINARY_SENSOR_PRESENCE: &str = "presence";
+pub const HA_DEVICE_CLASS_BINARY_SENSOR_PROBLEM: &str = "problem";
+pub const HA_DEVICE_CLASS_BINARY_SENSOR_RUNNING: &str = "running";
+pub const HA_DEVICE_CLASS_BINARY_SENSOR_SAFETY: &str = "safety";
+pub const HA_DEVICE_CLASS_BINARY_SENSOR_SMOKE: &str = "smoke";
+pub const HA_DEVICE_CLASS_BINARY_SENSOR_SOUND: &str = "sound";
+pub const HA_DEVICE_CLASS_BINARY_SENSOR_TAMPER: &str = "tamper";
+pub const HA_DEVICE_CLASS_BINARY_SENSOR_UPDATE: &str = "update";
+pub const HA_DEVICE_CLASS_BINARY_SENSOR_VIBRATION: &str = "vibration";
+pub const HA_DEVICE_CLASS_BINARY_SENSOR_WINDOW: &str = "window";
+
+pub const HA_DEVICE_CLASS_BUTTON_IDENTIFY: &str = "identify";
+pub const HA_DEVICE_CLASS_BUTTON_RESTART: &str = "restart";
+pub const HA_DEVICE_CLASS_BUTTON_UPDATE: &str = "update";
+
+pub const HA_DEVICE_CLASS_SWITCH_OUTLET: &str = "outlet";
+pub const HA_DEVICE_CLASS_SWITCH_SWITCH: &str = "switch";
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..5ecd5ea
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,967 @@
+#![no_std]
+
+use core::{
+    cell::RefCell,
+    net::SocketAddrV4,
+    sync::atomic::{AtomicBool, AtomicU32},
+    task::Waker,
+};
+
+use defmt::Format;
+use embassy_net::tcp::TcpSocket;
+use embassy_sync::waitqueue::AtomicWaker;
+use embassy_time::Timer;
+use heapless::{
+    Vec, VecView,
+    string::{String, StringView},
+};
+use serde::Serialize;
+
+mod constants;
+mod transport;
+mod unit;
+
+pub use constants::*;
+pub use transport::Transport;
+pub use unit::*;
+
+enum Unit {
+    Temperature(TemperatureUnit),
+}
+
+impl Unit {
+    fn as_str(&self) -> &'static str {
+        match self {
+            Unit::Temperature(unit) => unit.as_str(),
+        }
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum ComponentType {
+    Sensor,
+    BinarySensor,
+}
+
+impl core::fmt::Display for ComponentType {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        f.write_str(self.as_str())
+    }
+}
+
+impl ComponentType {
+    fn as_str(&self) -> &'static str {
+        match self {
+            ComponentType::Sensor => "sensor",
+            ComponentType::BinarySensor => "binary_sensor",
+        }
+    }
+}
+
+// TODO: see what classes need this and defaults
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum StateClass {
+    Measurement,
+    Total,
+    TotalIncreasing,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum DeviceClass {
+    Temperature {
+        unit: TemperatureUnit,
+    },
+    Humidity {
+        unit: HumidityUnit,
+    },
+
+    // binary sensors
+    Door,
+    Window,
+    Motion,
+    Occupancy,
+    Opening,
+    Plug,
+    Presence,
+    Problem,
+    Safety,
+    Smoke,
+    Sound,
+    Vibration,
+
+    Battery {
+        unit: BatteryUnit,
+    },
+    Illuminance {
+        unit: LightUnit,
+    },
+    Pressure {
+        unit: PressureUnit,
+    },
+    Generic {
+        device_class: Option<&'static str>,
+        unit: Option<&'static str>,
+    },
+    Energy {
+        unit: EnergyUnit,
+    },
+}
+
+impl DeviceClass {
+    fn tag(&self) -> &'static str {
+        match self {
+            DeviceClass::Temperature { .. } => "temperature",
+            DeviceClass::Humidity { .. } => "humidity",
+            _ => todo!(),
+        }
+    }
+
+    fn unit_of_measurement(&self) -> Option<Unit> {
+        // TODO: fix
+        Some(Unit::Temperature(TemperatureUnit::Celcius))
+    }
+
+    fn component_type(&self) -> ComponentType {
+        match self {
+            DeviceClass::Temperature { .. } => ComponentType::Sensor,
+            DeviceClass::Humidity { .. } => ComponentType::Sensor,
+            DeviceClass::Door => ComponentType::BinarySensor,
+            DeviceClass::Window => ComponentType::BinarySensor,
+            _ => todo!(),
+        }
+    }
+}
+
+pub trait Entity {
+    // TODO: possibly collapse all these functions into a single one that returns a struct
+    fn id(&self) -> &'static str;
+    fn name(&self) -> &'static str;
+    fn device_class(&self) -> DeviceClass;
+    fn register_waker(&self, waker: &Waker);
+    fn value(&self) -> Option<StateValue>;
+}
+
+// TODO: figure out proper atomic orderings
+
+struct StateContainer {
+    dirty: AtomicBool,
+    waker: AtomicWaker,
+    value: StateContainerValue,
+}
+
+impl StateContainer {
+    const fn new(value: StateContainerValue) -> Self {
+        Self {
+            dirty: AtomicBool::new(false),
+            waker: AtomicWaker::new(),
+            value,
+        }
+    }
+
+    pub const fn new_u32() -> Self {
+        Self::new(StateContainerValue::U32(AtomicU32::new(0)))
+    }
+
+    pub const fn new_f32() -> Self {
+        Self::new(StateContainerValue::F32(AtomicU32::new(0)))
+    }
+}
+
+enum StateContainerValue {
+    U32(AtomicU32),
+    F32(AtomicU32),
+}
+
+pub enum StateValue {
+    U32(u32),
+    F32(f32),
+}
+
+#[derive(Debug, Format, Clone, Copy, Serialize)]
+struct DeviceDiscovery<'a> {
+    identifiers: &'a [&'a str],
+    name: &'a str,
+    manufacturer: &'a str,
+    model: &'a str,
+}
+
+pub enum SensorKind {
+    Generic,
+    Temperature { unit: TemperatureUnit },
+    Humidity { unit: HumidityUnit },
+    // TODO: complete
+}
+
+impl SensorKind {
+    fn as_str(&self) -> &'static str {
+        match self {
+            SensorKind::Generic => "sensor",
+            SensorKind::Temperature { .. } => "temperature",
+            SensorKind::Humidity { .. } => "humidity",
+        }
+    }
+}
+
+impl core::fmt::Display for SensorKind {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        f.write_str(self.as_str())
+    }
+}
+
+enum BinarySensorKind {
+    Generic,
+    Motion,
+    Door,
+    Window,
+    Occupancy,
+    // TODO: complete
+}
+
+impl BinarySensorKind {
+    fn as_str(&self) -> &'static str {
+        match self {
+            BinarySensorKind::Generic => "binary_sensor",
+            BinarySensorKind::Motion => "motion",
+            BinarySensorKind::Door => "door",
+            BinarySensorKind::Window => "window",
+            BinarySensorKind::Occupancy => "occupancy",
+        }
+    }
+}
+
+impl core::fmt::Display for BinarySensorKind {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        f.write_str(self.as_str())
+    }
+}
+
+enum SwitchKind {
+    Generic,
+    Outlet,
+    Switch,
+}
+
+impl SwitchKind {
+    fn as_str(&self) -> &'static str {
+        match self {
+            SwitchKind::Generic => "switch",
+            SwitchKind::Outlet => "outlet",
+            SwitchKind::Switch => "switch",
+        }
+    }
+}
+
+impl core::fmt::Display for SwitchKind {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        f.write_str(self.as_str())
+    }
+}
+
+enum ButtonKind {
+    Generic,
+    Identify,
+    Restart,
+    Update,
+}
+
+impl ButtonKind {
+    fn as_str(&self) -> &'static str {
+        match self {
+            ButtonKind::Generic => "button",
+            ButtonKind::Identify => "identify",
+            ButtonKind::Restart => "restart",
+            ButtonKind::Update => "update",
+        }
+    }
+}
+
+impl core::fmt::Display for ButtonKind {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        f.write_str(self.as_str())
+    }
+}
+
+enum NumberKind {
+    Generic,
+    // TODO: alot of different ones
+    // https://www.home-assistant.io/integrations/number
+}
+
+impl NumberKind {
+    fn as_str(&self) -> &'static str {
+        match self {
+            NumberKind::Generic => "number",
+        }
+    }
+}
+
+impl core::fmt::Display for NumberKind {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        f.write_str(self.as_str())
+    }
+}
+
+// this is called the component type in the ha api
+pub enum EntityDomain {
+    Sensor(SensorKind),
+    BinarySensor(BinarySensorKind),
+    Switch(SwitchKind),
+    Light,
+    Button(ButtonKind),
+    Select,
+}
+
+impl core::fmt::Display for EntityDomain {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        f.write_str(self.as_str())
+    }
+}
+
+impl EntityDomain {
+    fn as_str(&self) -> &'static str {
+        match self {
+            EntityDomain::Sensor(_) => "sensor",
+            EntityDomain::BinarySensor(_) => "binary_sensor",
+            EntityDomain::Switch(_) => "switch",
+            EntityDomain::Light => "light",
+            EntityDomain::Button(_) => "button",
+            EntityDomain::Select => "select",
+        }
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+enum EntityCategory {
+    Config,
+    Diagnostic,
+}
+
+#[derive(Debug, Format, Serialize)]
+struct EntityDiscovery<'a> {
+    #[serde(rename = "unique_id")]
+    id: &'a str,
+
+    name: &'a str,
+
+    #[serde(skip_serializing_if = "Option::is_none")]
+    device_class: Option<&'a str>,
+
+    #[serde(skip_serializing_if = "Option::is_none")]
+    state_topic: Option<&'a str>,
+
+    #[serde(skip_serializing_if = "Option::is_none")]
+    command_topic: Option<&'a str>,
+
+    #[serde(skip_serializing_if = "Option::is_none")]
+    unit_of_measurement: Option<&'a str>,
+
+    #[serde(skip_serializing_if = "Option::is_none")]
+    schema: Option<&'a str>,
+
+    #[serde(skip_serializing_if = "Option::is_none")]
+    state_class: Option<&'a str>,
+
+    #[serde(skip_serializing_if = "Option::is_none")]
+    icon: Option<&'a str>,
+
+    device: &'a DeviceDiscovery<'a>,
+}
+
+struct DiscoveryTopicDisplay<'a> {
+    domain: &'a str,
+    device_id: &'a str,
+    entity_id: &'a str,
+}
+
+impl<'a> core::fmt::Display for DiscoveryTopicDisplay<'a> {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        write!(
+            f,
+            "homeassistant/{}/{}_{}/config",
+            self.domain, self.device_id, self.entity_id
+        )
+    }
+}
+
+struct StateTopicDisplay<'a> {
+    device_id: &'a str,
+    entity_id: &'a str,
+}
+
+impl<'a> core::fmt::Display for StateTopicDisplay<'a> {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        write!(f, "embassy-ha/{}/{}/state", self.device_id, self.entity_id)
+    }
+}
+
+struct CommandTopicDisplay<'a> {
+    device_id: &'a str,
+    entity_id: &'a str,
+}
+
+impl<'a> core::fmt::Display for CommandTopicDisplay<'a> {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        write!(
+            f,
+            "embassy-ha/{}/{}/command",
+            self.device_id, self.entity_id
+        )
+    }
+}
+
+pub struct DeviceConfig {
+    pub device_id: &'static str,
+    pub device_name: &'static str,
+    pub manufacturer: &'static str,
+    pub model: &'static str,
+}
+
+pub struct DeviceResources {
+    waker: AtomicWaker,
+    entities: [RefCell<Option<EntityData>>; Self::ENTITY_LIMIT],
+
+    mqtt_resources: embedded_mqtt::ClientResources,
+    publish_buffer: Vec<u8, 2048>,
+    subscribe_buffer: Vec<u8, 128>,
+    discovery_buffer: Vec<u8, 2048>,
+    discovery_topic_buffer: String<128>,
+    state_topic_buffer: String<128>,
+    command_topic_buffer: String<128>,
+}
+
+impl DeviceResources {
+    const RX_BUFFER_LEN: usize = 2048;
+    const TX_BUFFER_LEN: usize = 2048;
+    const ENTITY_LIMIT: usize = 16;
+}
+
+impl Default for DeviceResources {
+    fn default() -> Self {
+        Self {
+            waker: AtomicWaker::new(),
+            entities: [const { RefCell::new(None) }; Self::ENTITY_LIMIT],
+
+            mqtt_resources: Default::default(),
+            publish_buffer: Default::default(),
+            subscribe_buffer: Default::default(),
+            discovery_buffer: Default::default(),
+            discovery_topic_buffer: Default::default(),
+            state_topic_buffer: Default::default(),
+            command_topic_buffer: Default::default(),
+        }
+    }
+}
+
+pub struct TemperatureSensor<'a>(Entity2<'a>);
+
+impl<'a> TemperatureSensor<'a> {
+    pub fn publish(&mut self, temperature: f32) {
+        use core::fmt::Write;
+        self.0
+            .publish_with(|view| write!(view, "{}", temperature).unwrap());
+    }
+}
+
+pub struct Button<'a>(Entity2<'a>);
+
+impl<'a> Button<'a> {
+    pub async fn pressed(&mut self) {
+        self.0.wait_command().await;
+    }
+}
+
+pub struct EntityConfig {
+    pub id: &'static str,
+    pub name: &'static str,
+    pub domain: &'static str,
+    pub device_class: Option<&'static str>,
+    pub measurement_unit: Option<&'static str>,
+    pub icon: Option<&'static str>,
+    pub category: Option<&'static str>,
+    pub state_class: Option<&'static str>,
+    pub schema: Option<&'static str>,
+}
+
+struct EntityData {
+    config: EntityConfig,
+    publish_dirty: bool,
+    publish_value: heapless::Vec<u8, 64>,
+    command_dirty: bool,
+    command_value: heapless::Vec<u8, 64>,
+    command_wait_waker: Option<Waker>,
+}
+
+pub struct Entity2<'a> {
+    data: &'a RefCell<Option<EntityData>>,
+    waker: &'a AtomicWaker,
+}
+
+impl<'a> Entity2<'a> {
+    pub fn publish(&mut self, payload: &[u8]) {
+        self.publish_with(|view| view.extend_from_slice(payload).unwrap());
+    }
+
+    pub fn publish_with<F>(&mut self, f: F)
+    where
+        F: FnOnce(&mut VecView<u8>),
+    {
+        self.with_data(move |data| {
+            data.publish_value.clear();
+            f(data.publish_value.as_mut_view());
+            data.publish_dirty = true;
+        });
+        self.waker.wake();
+    }
+
+    pub async fn wait_command(&mut self) {
+        struct Fut<'a, 'b>(&'a mut Entity2<'b>);
+
+        impl<'a, 'b> core::future::Future for Fut<'a, 'b> {
+            type Output = ();
+
+            fn poll(
+                mut self: core::pin::Pin<&mut Self>,
+                cx: &mut core::task::Context<'_>,
+            ) -> core::task::Poll<Self::Output> {
+                let this = &mut self.as_mut().0;
+                this.with_data(|data| {
+                    let dirty = data.command_dirty;
+                    if dirty {
+                        data.command_dirty = false;
+                        data.command_wait_waker = None;
+                        core::task::Poll::Ready(())
+                    } else {
+                        // TODO: avoid clone if waker would wake
+                        data.command_wait_waker = Some(cx.waker().clone());
+                        core::task::Poll::Pending
+                    }
+                })
+            }
+        }
+
+        Fut(self).await
+    }
+
+    pub fn with_command<F, R>(&mut self, f: F) -> R
+    where
+        F: FnOnce(&[u8]) -> R,
+    {
+        self.with_data(|data| f(data.command_value.as_slice()))
+    }
+
+    fn with_data<F, R>(&self, f: F) -> R
+    where
+        F: FnOnce(&mut EntityData) -> R,
+    {
+        f(self.data.borrow_mut().as_mut().unwrap())
+    }
+}
+
+pub struct Device<'a> {
+    config: DeviceConfig,
+
+    // resources
+    waker: &'a AtomicWaker,
+    entities: &'a [RefCell<Option<EntityData>>],
+
+    mqtt_resources: &'a mut embedded_mqtt::ClientResources,
+    publish_buffer: &'a mut VecView<u8>,
+    subscribe_buffer: &'a mut VecView<u8>,
+    discovery_buffer: &'a mut VecView<u8>,
+    discovery_topic_buffer: &'a mut StringView,
+    state_topic_buffer: &'a mut StringView,
+    command_topic_buffer: &'a mut StringView,
+}
+
+impl<'a> Device<'a> {
+    pub fn new(resources: &'a mut DeviceResources, config: DeviceConfig) -> Self {
+        Self {
+            config,
+            waker: &resources.waker,
+            entities: &resources.entities,
+
+            mqtt_resources: &mut resources.mqtt_resources,
+            publish_buffer: &mut resources.publish_buffer,
+            subscribe_buffer: &mut resources.subscribe_buffer,
+            discovery_buffer: &mut resources.discovery_buffer,
+            discovery_topic_buffer: &mut resources.discovery_topic_buffer,
+            state_topic_buffer: &mut resources.state_topic_buffer,
+            command_topic_buffer: &mut resources.command_topic_buffer,
+        }
+    }
+
+    pub fn create_entity(&self, config: EntityConfig) -> Entity2<'a> {
+        let index = 'outer: {
+            for idx in 0..self.entities.len() {
+                if self.entities[idx].borrow().is_none() {
+                    break 'outer idx;
+                }
+            }
+            panic!("device entity limit reached");
+        };
+
+        let data = EntityData {
+            config,
+            publish_dirty: false,
+            publish_value: Default::default(),
+            command_dirty: false,
+            command_value: Default::default(),
+            command_wait_waker: None,
+        };
+        self.entities[index].replace(Some(data));
+
+        Entity2 {
+            data: &self.entities[index],
+            waker: self.waker,
+        }
+    }
+
+    pub fn create_temperature_sensor(
+        &self,
+        id: &'static str,
+        name: &'static str,
+        unit: TemperatureUnit,
+    ) -> TemperatureSensor<'a> {
+        let entity = self.create_entity(EntityConfig {
+            id,
+            name,
+            domain: HA_DOMAIN_SENSOR,
+            device_class: Some(HA_DEVICE_CLASS_SENSOR_TEMPERATURE),
+            measurement_unit: Some(unit.as_str()),
+            icon: None,
+            category: None,
+            state_class: None,
+            schema: None,
+        });
+        TemperatureSensor(entity)
+    }
+
+    pub fn create_button(&self, id: &'static str, name: &'static str) -> Button<'a> {
+        let entity = self.create_entity(EntityConfig {
+            id,
+            name,
+            domain: HA_DOMAIN_BUTTON,
+            device_class: None,
+            measurement_unit: None,
+            icon: None,
+            category: None,
+            state_class: None,
+            schema: None,
+        });
+        Button(entity)
+    }
+
+    pub async fn run<T: Transport>(&mut self, transport: &mut T) -> ! {
+        loop {
+            self.run_iteration(&mut *transport).await;
+            Timer::after_millis(5000).await;
+        }
+    }
+
+    async fn run_iteration<T: Transport>(&mut self, transport: T) {
+        let mut client = embedded_mqtt::Client::new(self.mqtt_resources, transport);
+        client.connect("embassy-ha-client-id").await.unwrap();
+
+        defmt::info!("sending discover messages");
+        let device_discovery = DeviceDiscovery {
+            identifiers: &[self.config.device_id],
+            name: self.config.device_name,
+            manufacturer: self.config.manufacturer,
+            model: self.config.model,
+        };
+
+        for entity in self.entities {
+            use core::fmt::Write;
+
+            self.publish_buffer.clear();
+            self.subscribe_buffer.clear();
+            self.discovery_buffer.clear();
+            self.discovery_topic_buffer.clear();
+            self.state_topic_buffer.clear();
+            self.command_topic_buffer.clear();
+
+            // borrow the entity and fill out the buffers to be sent
+            // this should be done inside a block so that we do not hold the RefMut across an
+            // await
+            {
+                let mut entity = entity.borrow_mut();
+                let entity = match entity.as_mut() {
+                    Some(entity) => entity,
+                    None => break,
+                };
+                let entity_config = &entity.config;
+
+                write!(
+                    self.discovery_topic_buffer,
+                    "{}",
+                    DiscoveryTopicDisplay {
+                        domain: entity_config.domain,
+                        device_id: self.config.device_id,
+                        entity_id: entity_config.id,
+                    }
+                )
+                .unwrap();
+
+                write!(
+                    self.state_topic_buffer,
+                    "{}",
+                    StateTopicDisplay {
+                        device_id: self.config.device_id,
+                        entity_id: entity_config.id
+                    }
+                )
+                .unwrap();
+
+                write!(
+                    self.command_topic_buffer,
+                    "{}",
+                    CommandTopicDisplay {
+                        device_id: self.config.device_id,
+                        entity_id: entity_config.id
+                    }
+                )
+                .unwrap();
+
+                let discovery = EntityDiscovery {
+                    id: entity_config.id,
+                    name: entity_config.name,
+                    device_class: entity_config.device_class,
+                    state_topic: Some(self.state_topic_buffer.as_str()),
+                    command_topic: Some(self.command_topic_buffer.as_str()),
+                    unit_of_measurement: entity_config.measurement_unit,
+                    schema: entity_config.schema,
+                    state_class: entity_config.state_class,
+                    icon: entity_config.icon,
+                    device: &device_discovery,
+                };
+                defmt::info!("discovery: {}", discovery);
+
+                self.discovery_buffer
+                    .resize(self.discovery_buffer.capacity(), 0)
+                    .unwrap();
+                let n = serde_json_core::to_slice(&discovery, &mut self.discovery_buffer).unwrap();
+                self.discovery_buffer.truncate(n);
+            }
+
+            defmt::info!(
+                "sending discovery to {}",
+                self.discovery_topic_buffer.as_str()
+            );
+            client
+                .publish(&self.discovery_topic_buffer, &self.discovery_buffer)
+                .await
+                .unwrap();
+            client.subscribe(&self.command_topic_buffer).await.unwrap();
+        }
+
+        loop {
+            use core::fmt::Write;
+
+            for entity in self.entities {
+                {
+                    let mut entity = entity.borrow_mut();
+                    let entity = match entity.as_mut() {
+                        Some(entity) => entity,
+                        None => break,
+                    };
+
+                    if !entity.publish_dirty {
+                        continue;
+                    }
+
+                    entity.publish_dirty = false;
+
+                    self.state_topic_buffer.clear();
+                    write!(
+                        self.state_topic_buffer,
+                        "{}",
+                        StateTopicDisplay {
+                            device_id: self.config.device_id,
+                            entity_id: entity.config.id
+                        }
+                    )
+                    .unwrap();
+
+                    self.publish_buffer.clear();
+                    self.publish_buffer
+                        .extend_from_slice(entity.publish_value.as_slice())
+                        .unwrap();
+                }
+
+                client
+                    .publish(&self.state_topic_buffer, self.publish_buffer)
+                    .await
+                    .unwrap();
+            }
+
+            let receive = client.receive();
+            let waker = wait_on_atomic_waker(self.waker);
+            match embassy_futures::select::select(receive, waker).await {
+                embassy_futures::select::Either::First(packet) => {
+                    let packet = packet.unwrap();
+                    let mut read_buffer = [0u8; 128];
+                    if let embedded_mqtt::Packet::Publish(publish) = packet {
+                        if publish.data_len > 128 {
+                            defmt::warn!("mqtt publish payload too large, ignoring message");
+                        } else {
+                            let b = &mut read_buffer[..publish.data_len];
+                            client.receive_data(b).await.unwrap();
+                            defmt::info!("receive value {}", str::from_utf8(b).unwrap());
+                            for entity in self.entities {
+                                let mut entity = entity.borrow_mut();
+                                if let Some(entity) = entity.as_mut() {
+                                    entity.command_dirty = true;
+                                    entity.command_value.clear();
+                                    entity.command_value.extend_from_slice(b"ON").unwrap();
+                                    if let Some(ref waker) = entity.command_wait_waker {
+                                        waker.wake_by_ref();
+                                    }
+                                }
+                            }
+                        }
+                    }
+                }
+                embassy_futures::select::Either::Second(_) => {}
+            }
+        }
+    }
+}
+
+async fn wait_on_atomic_waker(waker: &AtomicWaker) {
+    struct F<'a>(&'a AtomicWaker, bool);
+    impl<'a> core::future::Future for F<'a> {
+        type Output = ();
+
+        fn poll(
+            self: core::pin::Pin<&mut Self>,
+            cx: &mut core::task::Context<'_>,
+        ) -> core::task::Poll<Self::Output> {
+            if !self.1 {
+                self.0.register(cx.waker());
+                self.get_mut().1 = true;
+                core::task::Poll::Pending
+            } else {
+                core::task::Poll::Ready(())
+            }
+        }
+    }
+    F(waker, false).await
+}
+
+/*
+  Step-by-Step Process
+
+  1. What are you measuring/controlling?
+
+  Start with the physical thing:
+  - "I want to measure temperature"
+  - "I want to detect if a door is open"
+  - "I want to control a relay"
+  - "I want a button to restart the device"
+
+  2. Pick the component type based on behavior
+
+  Ask yourself:
+  - Is it read-only or controllable?
+  - Does it have numeric values or on/off states?
+
+  Decision tree:
+  Read-only measurement?
+  ├─ Numeric value (23.5, 65%, etc.)
+  │  └─ Component: sensor
+  └─ On/off state (open/closed, detected/not detected)
+     └─ Component: binary_sensor
+
+  Controllable?
+  ├─ On/off control
+  │  └─ Component: switch (or light for LEDs)
+  ├─ Adjustable number
+  │  └─ Component: number
+  ├─ Select from options
+  │  └─ Component: select
+  └─ Trigger action (no state)
+     └─ Component: button
+
+  3. Pick the device_class (if applicable)
+
+  Now look at the component type you chose:
+
+  For sensor - What kind of measurement?
+  - Temperature → device_class: "temperature"
+  - Humidity → device_class: "humidity"
+  - Pressure → device_class: "pressure"
+  - Custom metric → device_class: None
+
+  For binary_sensor - What kind of detection?
+  - Door → device_class: "door"
+  - Motion → device_class: "motion"
+  - Window → device_class: "window"
+  - Generic → device_class: None
+
+  For button - No device_class needed!
+
+  4. Pick units (if applicable)
+
+  Based on your device_class:
+  - Temperature → "°C" or "°F"
+  - Humidity → "%"
+  - Pressure → "hPa"
+
+  Examples
+
+  Example 1: DHT22 Temperature Reading
+
+  1. What? → Measure temperature
+  2. Component? → sensor (numeric, read-only)
+  3. Device class? → "temperature"
+  4. Unit? → "°C"
+
+  Result:
+  - Discovery: homeassistant/sensor/pico2w_temp/config
+  - JSON: device_class: "temperature", unit_of_measurement: "°C"
+
+  Example 2: Reed Switch on Door
+
+  1. What? → Detect door open/closed
+  2. Component? → binary_sensor (on/off state, read-only)
+  3. Device class? → "door"
+  4. Unit? → N/A
+
+  Result:
+  - Discovery: homeassistant/binary_sensor/pico2w_door/config
+  - JSON: device_class: "door"
+
+  Example 3: Relay Control
+
+  1. What? → Control a relay
+  2. Component? → switch (on/off, controllable)
+  3. Device class? → None (switches typically don't have device_class)
+  4. Unit? → N/A
+
+  Result:
+  - Discovery: homeassistant/switch/pico2w_relay/config
+  - JSON: No device_class needed
+
+  Example 4: Restart Button
+
+  1. What? → Trigger device restart
+  2. Component? → button (action trigger, no state)
+  3. Device class? → None (buttons don't have device_class)
+  4. Unit? → N/A
+
+  Result:
+  - Discovery: homeassistant/button/pico2w_restart/config
+  - JSON: No device_class, no state_topic
+
+  TL;DR Workflow
+
+  Physical thing
+      ↓
+  Component type (behavior: read-only numeric? binary? controllable?)
+      ↓
+  Device class (what specific type?)
+      ↓
+  Units (if numeric)
+
+  Does this mental model make sense now?
+*/
diff --git a/src/transport.rs b/src/transport.rs
new file mode 100644
index 0000000..5214b37
--- /dev/null
+++ b/src/transport.rs
@@ -0,0 +1,3 @@
+pub trait Transport: embedded_io_async::Read + embedded_io_async::Write {}
+
+impl<T> Transport for T where T: embedded_io_async::Read + embedded_io_async::Write {}
diff --git a/src/unit.rs b/src/unit.rs
new file mode 100644
index 0000000..4f3ca19
--- /dev/null
+++ b/src/unit.rs
@@ -0,0 +1,45 @@
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum TemperatureUnit {
+    Celcius,
+    Kelvin,
+    Fahrenheit,
+    Other(&'static str),
+}
+
+impl TemperatureUnit {
+    pub fn as_str(&self) -> &'static str {
+        // TODO: improve
+        match self {
+            TemperatureUnit::Celcius => "C",
+            TemperatureUnit::Kelvin => "k",
+            TemperatureUnit::Fahrenheit => "F",
+            TemperatureUnit::Other(other) => other,
+        }
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum HumidityUnit {
+    Percentage,
+    Other(&'static str),
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum BatteryUnit {
+    Percentage,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum LightUnit {
+    Lux,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum PressureUnit {
+    HectoPascal,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum EnergyUnit {
+    KiloWattHour,
+}