using System.Net;
using System.Text;
using LibreHardwareMonitor.Hardware;

var port = Environment.GetEnvironmentVariable("PORT");
if (!int.TryParse(port, out var httpPort))
{
	httpPort = 9646; // default port
}

var listener = new HttpListener();
listener.Prefixes.Add($"http://*:{httpPort}/");
listener.Start();

var computer = new Computer
{
	IsCpuEnabled = true,
	IsGpuEnabled = true,
	IsMemoryEnabled = true,
	IsMotherboardEnabled = true,
	IsControllerEnabled = true,
	IsNetworkEnabled = true,
	IsStorageEnabled = true
};

computer.Open();

Console.WriteLine($"LibreHardwareMonitorExporter listening on http://localhost:{httpPort}/metrics");

while (true)
{
	var context = await listener.GetContextAsync();
	if (context.Request.HttpMethod != "GET")
	{
		context.Response.StatusCode = 405;
		context.Response.Close();
		continue;
	}

	if (context.Request.Url?.AbsolutePath != "/metrics")
	{
		context.Response.StatusCode = 404;
		context.Response.Close();
		continue;
	}

	var body = new StringBuilder();
	AppendMetrics(body, computer);
	var bytes = Encoding.UTF8.GetBytes(body.ToString());
	context.Response.StatusCode = 200;
	context.Response.ContentType = "text/plain; version=0.0.4";
	context.Response.ContentEncoding = Encoding.UTF8;
	context.Response.ContentLength64 = bytes.Length;
	await context.Response.OutputStream.WriteAsync(bytes, 0, bytes.Length);
	context.Response.Close();
}

static void AppendMetrics(StringBuilder output, Computer computer)
{
	var updateVisitor = new UpdateVisitor();
	computer.Accept(updateVisitor);

	// Basic example metrics for temperature, load, clock, power, fan
	foreach (var hardware in computer.Hardware)
	{
		EmitHardwareMetrics(output, hardware);
		foreach (var sub in hardware.SubHardware)
		{
			EmitHardwareMetrics(output, sub);
		}
	}
}

static void EmitHardwareMetrics(StringBuilder output, IHardware hardware)
{
	var hardwareLabel = SanitizeLabel(hardware.Name);
	foreach (var sensor in hardware.Sensors)
	{
		if (sensor.Value is null) continue;
		var sensorLabel = SanitizeLabel(sensor.Name);
		var value = sensor.Value.Value;
		var metricName = sensor.SensorType switch
		{
			SensorType.Temperature => "lhm_temperature_celsius",
			SensorType.Load => "lhm_load_percent",
			SensorType.Clock => "lhm_clock_mhz",
			SensorType.Power => "lhm_power_watts",
			SensorType.Fan => "lhm_fan_rpm",
			SensorType.Voltage => "lhm_voltage_volts",
			SensorType.Data => "lhm_data",
			SensorType.Level => "lhm_level",
			SensorType.Throughput => "lhm_throughput_bytes_per_sec",
			SensorType.Factor => "lhm_factor",
			SensorType.Flow => "lhm_flow_lph",
			SensorType.Control => "lhm_control_percent",
			_ => null
		};

		if (metricName == null) continue;
		output.Append(metricName);
		output.Append("{");
		output.Append($"hardware=\"{hardwareLabel}\",sensor=\"{sensorLabel}\",type=\"{sensor.SensorType}\"");
		output.Append("} ");
		output.AppendLine(value.ToString(System.Globalization.CultureInfo.InvariantCulture));
	}
}

static string SanitizeLabel(string raw)
{
	var sb = new StringBuilder(raw.Length);
	foreach (var ch in raw)
	{
		if ((ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z') || (ch >= '0' && ch <= '9') || ch == '_' || ch == ':' || ch == '.')
		{
			sb.Append(ch);
		}
		else
		{
			sb.Append('_');
		}
	}
	return sb.ToString();
}

sealed class UpdateVisitor : IVisitor
{
	public void VisitComputer(IComputer computer)
	{
		computer.Traverse(this);
	}

	public void VisitHardware(IHardware hardware)
	{
		hardware.Update();
		foreach (var sub in hardware.SubHardware)
		{
			sub.Accept(this);
		}
	}

	public void VisitSensor(ISensor sensor) { }
	public void VisitParameter(IParameter parameter) { }
}