Replace gRPC Backend (#10)

**Rationale:**

Having two separate servers and communication methods resulted in additional maintenance & the need to convert often between backend & frontend data types.
By moving the backend communication off of gRPC and to just use websockets it both gives more control & allows for simplification of the implementation.

#8

**Changes:**

- Replaces gRPC backend.
  - New implementation automatically handles reconnect logic
- Implements an api layer
- Migrates examples to the api layer
- Implements a proc macro to make command handling easier
- Implements unit tests for the api layer (90+% coverage)
- Implements integration tests for the proc macro (90+% coverage)

Reviewed-on: #10
Co-authored-by: Sergey Savelyev <sergeysav.nn@gmail.com>
Co-committed-by: Sergey Savelyev <sergeysav.nn@gmail.com>

api-core/src/command.rs

@@ -0,0 +1,47 @@
+use crate::data_type::DataType;
+use crate::data_value::DataValue;
+use chrono::{DateTime, Utc};
+use serde::{Deserialize, Serialize};
+use std::collections::HashMap;
+use thiserror::Error;
+
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub struct CommandParameterDefinition {
+    pub name: String,
+    pub data_type: DataType,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub struct CommandDefinition {
+    pub name: String,
+    pub parameters: Vec<CommandParameterDefinition>,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub struct CommandHeader {
+    pub timestamp: DateTime<Utc>,
+}
+
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+pub struct Command {
+    #[serde(flatten)]
+    pub header: CommandHeader,
+    pub parameters: HashMap<String, DataValue>,
+}
+
+#[derive(Debug, PartialEq, Eq, Error)]
+pub enum IntoCommandDefinitionError {
+    #[error("Parameter Missing: {0}")]
+    ParameterMissing(String),
+    #[error("Mismatched Type for {parameter}. {expected:?} expected")]
+    MismatchedType {
+        parameter: String,
+        expected: DataType,
+    },
+}
+
+pub trait IntoCommandDefinition: Sized {
+    fn create(name: String) -> CommandDefinition;
+
+    fn parse(command: Command) -> Result<Self, IntoCommandDefinitionError>;
+}

api-core/src/data_type.rs

@@ -0,0 +1,26 @@
+use crate::data_value::DataValue;
+use derive_more::Display;
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize, Display)]
+pub enum DataType {
+    Float32,
+    Float64,
+    Boolean,
+}
+
+pub trait ToDataType: Into<DataValue> {
+    const DATA_TYPE: DataType;
+}
+
+macro_rules! impl_to_data_type {
+    ( $ty:ty, $value:expr ) => {
+        impl ToDataType for $ty {
+            const DATA_TYPE: DataType = $value;
+        }
+    };
+}
+
+impl_to_data_type!(f32, DataType::Float32);
+impl_to_data_type!(f64, DataType::Float64);
+impl_to_data_type!(bool, DataType::Boolean);

api-core/src/data_value.rs

@@ -0,0 +1,20 @@
+use crate::data_type::DataType;
+use derive_more::{From, TryInto};
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Clone, Copy, PartialEq, Serialize, Deserialize, From, TryInto)]
+pub enum DataValue {
+    Float32(f32),
+    Float64(f64),
+    Boolean(bool),
+}
+
+impl DataValue {
+    pub fn to_data_type(self) -> DataType {
+        match self {
+            DataValue::Float32(_) => DataType::Float32,
+            DataValue::Float64(_) => DataType::Float64,
+            DataValue::Boolean(_) => DataType::Boolean,
+        }
+    }
+}

api-core/src/lib.rs

@@ -0,0 +1,3 @@
+pub mod command;
+pub mod data_type;
+pub mod data_value;