using Flurl.Http;
using Newtonsoft.Json.Linq;

namespace InnovEnergy.App.Backend.Services;

/// <summary>
/// Fetches and caches the list of Swiss electricity network providers (Netzbetreiber)
/// from the ELCOM/LINDAS SPARQL endpoint. Refreshes every 24 hours.
/// </summary>
public static class NetworkProviderService
{
    private static IReadOnlyList<string> _providers = Array.Empty<string>();
    private static Timer? _refreshTimer;

    private const string SparqlEndpoint = "https://ld.admin.ch/query";

    private const string SparqlQuery = @"
PREFIX schema: <http://schema.org/>
SELECT DISTINCT ?name
FROM <https://lindas.admin.ch/elcom/electricityprice>
WHERE {
  ?operator a schema:Organization ;
            schema:name ?name .
}
ORDER BY ?name";

    public static void Initialize()
    {
        // Fire-and-forget initial load
        Task.Run(RefreshAsync);

        // Refresh every 24 hours
        _refreshTimer = new Timer(
            _ => Task.Run(RefreshAsync),
            null,
            TimeSpan.FromHours(24),
            TimeSpan.FromHours(24)
        );

        Console.WriteLine("[NetworkProviderService] initialised.");
    }

    public static IReadOnlyList<string> GetProviders() => _providers;

    private static async Task RefreshAsync()
    {
        try
        {
            var response = await SparqlEndpoint
                .WithHeader("Accept", "application/sparql-results+json")
                .PostUrlEncodedAsync(new { query = SparqlQuery });

            var json = await response.GetStringAsync();
            var parsed = JObject.Parse(json);

            var names = parsed["results"]?["bindings"]?
                .Select(b => b["name"]?["value"]?.ToString())
                .Where(n => !string.IsNullOrWhiteSpace(n))
                .Distinct()
                .OrderBy(n => n)
                .ToList();

            if (names is { Count: > 0 })
            {
                _providers = names!;
                Console.WriteLine($"[NetworkProviderService] Loaded {names.Count} providers from ELCOM.");
            }
            else
            {
                Console.Error.WriteLine("[NetworkProviderService] SPARQL query returned no results.");
            }
        }
        catch (Exception ex)
        {
            Console.Error.WriteLine($"[NetworkProviderService] Failed to fetch providers: {ex.Message}");
        }
    }
}