MeterVault/tests/Integration.Tests/Ingestion/HaWebSocketProtocolTests.cs

using System.Text.Json;
using MeterVault.Infrastructure.Ingestion;

namespace MeterVault.Integration.Tests.Ingestion;

/// <summary>
/// The pure Home Assistant WebSocket protocol helpers: URL derivation, the auth/subscribe frames,
/// and reading the entity id + numeric value out of a <c>state_changed</c> event (the transport is
/// exercised separately). No network — these are the parts that must be provably correct.
/// </summary>
public sealed class HaWebSocketProtocolTests
{
    [Theory]
    [InlineData("http://ha.local:8123", "ws", "ha.local", 8123)]
    [InlineData("http://ha.local:8123/", "ws", "ha.local", 8123)]
    [InlineData("https://ha.example.com", "wss", "ha.example.com", 443)]
    public void WebSocketUri_maps_scheme_and_appends_api_path(string baseUrl, string scheme, string host, int port)
    {
        var uri = HaWebSocketProtocol.WebSocketUri(baseUrl);

        Assert.Equal(scheme, uri.Scheme);
        Assert.Equal(host, uri.Host);
        Assert.Equal(port, uri.Port);
        Assert.Equal("/api/websocket", uri.AbsolutePath);
    }

    [Fact]
    public void AuthMessage_carries_type_and_token()
    {
        using var doc = JsonDocument.Parse(HaWebSocketProtocol.AuthMessage("secret-token"));

        Assert.Equal("auth", doc.RootElement.GetProperty("type").GetString());
        Assert.Equal("secret-token", doc.RootElement.GetProperty("access_token").GetString());
    }

    [Fact]
    public void SubscribeStateChanged_requests_state_changed_events()
    {
        using var doc = JsonDocument.Parse(HaWebSocketProtocol.SubscribeStateChanged(7));

        Assert.Equal(7, doc.RootElement.GetProperty("id").GetInt32());
        Assert.Equal("subscribe_events", doc.RootElement.GetProperty("type").GetString());
        Assert.Equal("state_changed", doc.RootElement.GetProperty("event_type").GetString());
    }

    [Theory]
    [InlineData("{\"type\":\"auth_required\",\"ha_version\":\"2024.6\"}", true, false, false)]
    [InlineData("{\"type\":\"auth_ok\"}", false, true, false)]
    [InlineData("{\"type\":\"auth_invalid\",\"message\":\"bad token\"}", false, false, true)]
    public void Auth_message_types_are_recognized(string json, bool required, bool ok, bool invalid)
    {
        using var doc = JsonDocument.Parse(json);
        var root = doc.RootElement;

        Assert.Equal(required, HaWebSocketProtocol.IsAuthRequired(root));
        Assert.Equal(ok, HaWebSocketProtocol.IsAuthOk(root));
        Assert.Equal(invalid, HaWebSocketProtocol.IsAuthInvalid(root));
    }

    [Fact]
    public void TryReadStateChanged_extracts_entity_and_numeric_state()
    {
        using var doc = JsonDocument.Parse(StateChangedEvent(state: "1234.5"));

        Assert.True(HaWebSocketProtocol.TryReadStateChanged(doc.RootElement, out var entityId, out var newState));
        Assert.Equal("sensor.house_power", entityId);

        var parsed = HaStateClient.ParseStateElement(newState, attribute: null);
        Assert.NotNull(parsed);
        Assert.Equal(1234.5, parsed!.Value.Value, 3);
        Assert.Equal(new DateTimeOffset(2024, 6, 15, 10, 0, 0, TimeSpan.Zero), parsed.Value.Time);
    }

    [Fact]
    public void TryReadStateChanged_reads_a_named_attribute()
    {
        using var doc = JsonDocument.Parse(StateChangedEvent(state: "on"));

        Assert.True(HaWebSocketProtocol.TryReadStateChanged(doc.RootElement, out _, out var newState));
        // state "on" is non-numeric, but the 'current' attribute is a number.
        Assert.Null(HaStateClient.ParseStateElement(newState, attribute: null));
        var byAttribute = HaStateClient.ParseStateElement(newState, attribute: "current");
        Assert.Equal(42, byAttribute!.Value.Value, 3);
    }

    [Fact]
    public void TryReadStateChanged_ignores_removed_entities_and_other_events()
    {
        using var removed = JsonDocument.Parse(
            "{\"type\":\"event\",\"event\":{\"event_type\":\"state_changed\",\"data\":{\"entity_id\":\"sensor.x\",\"new_state\":null}}}");
        Assert.False(HaWebSocketProtocol.TryReadStateChanged(removed.RootElement, out _, out _));

        using var other = JsonDocument.Parse(
            "{\"type\":\"event\",\"event\":{\"event_type\":\"call_service\",\"data\":{}}}");
        Assert.False(HaWebSocketProtocol.TryReadStateChanged(other.RootElement, out _, out _));

        using var result = JsonDocument.Parse("{\"id\":1,\"type\":\"result\",\"success\":true}");
        Assert.False(HaWebSocketProtocol.TryReadStateChanged(result.RootElement, out _, out _));
    }

    private static string StateChangedEvent(string state) => $$"""
        {
          "id": 1,
          "type": "event",
          "event": {
            "event_type": "state_changed",
            "data": {
              "entity_id": "sensor.house_power",
              "new_state": {
                "entity_id": "sensor.house_power",
                "state": "{{state}}",
                "attributes": { "unit_of_measurement": "W", "current": 42 },
                "last_updated": "2024-06-15T10:00:00+00:00"
              }
            }
          }
        }
        """;
}