using System.Net.Http.Headers;
using Microsoft.Extensions.Logging;

namespace MeterVault.Infrastructure.Ingestion;

/// <summary>Outcome of a Home Assistant connectivity test.</summary>
public sealed record HaTestResult(bool Ok, string Message, double? SampleValue = null);

/// <summary>
/// Verifies a Home Assistant connection from the admin UI: checks the base URL + resolved token
/// against <c>GET /api/</c>, and optionally reads one entity's state. Confirms the app can actually
/// read HA before a source is relied upon (SDD §6.2). Token is resolved by reference (env var).
/// </summary>
public sealed class HaConnectionTester(IHttpClientFactory httpClientFactory, ILogger<HaConnectionTester> logger)
{
    private readonly IHttpClientFactory _httpClientFactory = httpClientFactory;
    private readonly ILogger<HaConnectionTester> _logger = logger;

    public async Task<HaTestResult> TestAsync(
        string? baseUrl, string? tokenEnv, string? entityId, CancellationToken cancellationToken = default)
    {
        if (string.IsNullOrWhiteSpace(baseUrl))
        {
            return new HaTestResult(false, "Base URL is required.");
        }

        if (string.IsNullOrWhiteSpace(tokenEnv))
        {
            return new HaTestResult(false, "Token env-var name is required (the token is resolved from it at runtime).");
        }

        var token = Environment.GetEnvironmentVariable(tokenEnv);
        if (string.IsNullOrWhiteSpace(token))
        {
            return new HaTestResult(false, $"Environment variable '{tokenEnv}' is not set on the server.");
        }

        var client = _httpClientFactory.CreateClient();
        client.Timeout = TimeSpan.FromSeconds(10);

        try
        {
            using var request = new HttpRequestMessage(HttpMethod.Get, $"{baseUrl.TrimEnd('/')}/api/");
            request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", token);
            using var response = await client.SendAsync(request, cancellationToken).ConfigureAwait(false);
            if (!response.IsSuccessStatusCode)
            {
                return new HaTestResult(false, $"HA returned {(int)response.StatusCode} {response.ReasonPhrase}.");
            }

            if (string.IsNullOrWhiteSpace(entityId))
            {
                return new HaTestResult(true, "Connected — Home Assistant API reachable and token accepted.");
            }

            var state = await new HaStateClient(client).GetStateAsync(baseUrl, token, entityId, null, cancellationToken).ConfigureAwait(false);
            return state is { } value
                ? new HaTestResult(true, $"Connected — {entityId} = {value.Value}.", value.Value)
                : new HaTestResult(false, $"Connected, but '{entityId}' has no numeric state (unavailable/unknown or non-numeric).");
        }
        catch (Exception ex)
        {
            _logger.LogWarning(ex, "Home Assistant connection test failed for {BaseUrl}", baseUrl);
            return new HaTestResult(false, $"Connection failed: {ex.Message}");
        }
    }
}