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+# SmartMeter
+
+A .NET 10 server application that reads energy data from smart meters via the SML (Smart Message Language) protocol and publishes values over MQTT. It runs as a systemd daemon on Linux and connects to the meter through a serial optical coupler.
+
+## Project Structure
+
+```
+SmartMeter.sln
+source/
+  CreativeCoders.SmartMessageLanguage/      # SML framing, TLV parsing, CRC validation, OBIS value extraction
+  CreativeCoders.SmartMeter.Core/           # Serial port abstraction, reactive data pipeline, configuration
+  CreativeCoders.SmartMeter.DataProcessing/ # Value processing (power calculation, throttling) and MQTT publishing
+  CreativeCoders.SmartMeter.Server.Core/    # Daemon host builder, server lifecycle orchestration
+  CreativeCoders.SmartMeter.Server.Linux/   # Linux systemd daemon entry point
+  CreativeCoders.SmartMeter.Cli/            # CLI tool for diagnostics and manual data retrieval
+tests/
+  CreativeCoders.SmartMessageLanguage.Tests/
+  CreativeCoders.SmartMeter.Core.Tests/
+  CreativeCoders.SmartMeter.DataProcessing.Tests/
+  CreativeCoders.SmartMeter.Server.Core.Tests/
+build/                                      # Cake build project (CreativeCoders.CakeBuild)
+```
+
+## Tech Stack
+
+- **Runtime:** .NET 10 (`net10.0`), C# with nullable reference types and implicit usings
+- **Reactive Streams:** `System.Reactive` for the entire data pipeline
+- **MQTT:** `MQTTnet` for broker communication
+- **Serial I/O:** `System.IO.Ports` for optical coupler access
+- **Daemon:** `CreativeCoders.Daemon.Linux` for systemd integration
+- **Logging:** Serilog with console sink
+- **CLI:** Spectre.Console (`IAnsiConsole`)
+- **Build:** Cake via `CreativeCoders.CakeBuild`, scripts: `build.sh` / `build.ps1` / `build.cmd`
+- **Package Management:** Central version management via `Directory.Packages.props`
+
+## Testing Stack
+
+- **Framework:** xUnit
+- **Mocking:** FakeItEasy
+- **Assertions:** AwesomeAssertions
+- **Coverage:** coverlet.collector
+- **Time Testing:** `Microsoft.Extensions.TimeProvider.Testing` (FakeTimeProvider)
+
+## Data Flow
+
+```
+Serial Port (byte[])
+    |  ReactiveSerialPort
+    v
+SML Frame Detection
+    |  SmlMessageDetector (start/end escape sequences, CRC-16/X-25 validation)
+    v
+SML Parsing
+    |  SmlParser (TLV parsing, OBIS value extraction with decimal scaling)
+    v
+Reactive Data Pipeline
+    |  SmartMeterReactiveDataPipeline
+    |  Filters OBIS codes: 1-0:1.8.0 (purchased), 1-0:2.8.0 (sold)
+    |  Applies configurable energy offsets
+    v
+Value Processing
+    |  SmlValueProcessor
+    |  Calculates instantaneous power from energy differentials
+    |  Derives GridPowerBalance from current power values
+    |  Throttles unchanged values (30s minimum, 5m window)
+    v
+MQTT Publishing
+    |  MqttValuePublisher (background worker, auto-reconnect)
+    |  Topic: smartmeter/values/{ValueType}
+    |  Payload: JSON or plain decimal (GridPowerBalance uses plain)
+    v
+MQTT Broker
+```
+
+## Key Types
+
+| Type | File | Purpose |
+|------|------|---------|
+| `SmlMessageDetector` | `SmartMessageLanguage/Framing/SmlMessageDetector.cs` | Streaming SML frame boundary detection |
+| `SmlParser` | `SmartMessageLanguage/Parsing/SmlParser.cs` | TLV-based SML protocol parser |
+| `SmartMeterReactiveDataPipeline` | `SmartMeter.Core/SmlData/SmartMeterReactiveDataPipeline.cs` | OBIS code filtering and value conversion |
+| `SmlValueProcessor` | `SmartMeter.DataProcessing/SmlValueProcessor.cs` | Power calculation, throttling, balance derivation |
+| `MqttValuePublisher` | `SmartMeter.DataProcessing/MqttValuePublisher.cs` | MQTT client with queued publishing |
+| `SmartMeterServer` | `SmartMeter.Server.Core/SmartMeterServer.cs` | Daemon lifecycle (`IDaemonService`) |
+| `SmartMeterDaemonHostBuilder` | `SmartMeter.Server.Core/SmartMeterDaemonHostBuilder.cs` | Host configuration, DI, Serilog setup |
+
+## Published MQTT Values
+
+| SmartMeterValueType | Description | Format |
+|---------------------|-------------|--------|
+| `TotalPurchasedEnergy` | Cumulative energy purchased from grid | JSON |
+| `TotalSoldEnergy` | Cumulative energy sold to grid | JSON |
+| `CurrentPurchasingPower` | Current power drawn from grid | JSON |
+| `CurrentSellingPower` | Current power fed into grid | JSON |
+| `GridPowerBalance` | Net power balance (positive = purchasing, negative = selling) | Plain decimal |
+
+## Dependency Injection
+
+Services are registered in layers:
+
+1. `AddSml()` -- registers `ISmlParser`, `ISmlMessageDetector`
+2. `AddSmartMeterServer()` -- calls `AddSml()`, registers `IReactiveSerialPortFactory`, `ISmartMeterReactiveDataPipeline`, `ISmartMeterUnlocker`
+3. `SmartMeterDaemonHostBuilder.ConfigureServices()` -- registers `IMqttValuePublisher`, `ISmartMeterDataProducer`
+
+## Configuration
+
+The server reads `/etc/smartmeter.conf`. Key options:
+
+| Option | Default | Description |
+|--------|---------|-------------|
+| `PortName` | `/dev/ttyUSB0` | Serial port device path |
+| `Mqtt:Server` | -- | MQTT broker URI (required) |
+| `Mqtt:ClientName` | `SmartMeterClient` | MQTT client identifier |
+| `Mqtt:TopicTemplate` | `smartmeter/values/{0}` | Topic template (`{0}` = value type) |
+
+## Common Commands
+
+```bash
+# Build
+./build.sh
+# or
+dotnet build
+
+# Run tests
+dotnet test
+
+# Run specific test project
+dotnet test tests/CreativeCoders.SmartMeter.DataProcessing.Tests
+
+# Install on Linux
+./install-smartmeter.sh
+
+# Service management
+sudo systemctl status smartmeter-server
+sudo journalctl -u smartmeter-server -f
+```
+
+## CI/CD
+
+Workflows in `.github/workflows/`:
+
+| Workflow | Trigger | Purpose |
+|----------|---------|---------|
+| `main.yml` | Push to `main` | Build, test, publish NuGet, create GitHub release |
+| `pull-request.yml` | PR events | PR validation |
+| `integration.yml` | -- | Integration testing |
+| `release.yml` | -- | Release management |