using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.Json;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Routing;
using Microsoft.Extensions.DependencyInjection;
using PolyTrader.Core.Configuration;
using PolyTrader.Web.Configuration;
using PolyTraderSharp.Models;
using PolyTraderSharp.Services;

namespace PolyTrader.Web.Endpoints
{
    /// <summary>
    /// Server-Einstellungen ohne Geheimnisse (#561). Was angezeigt und geändert werden darf, legt
    /// <see cref="ServerSettingsCatalog"/> fest.
    /// </summary>
    public static class ServerSettingsEndpoints
    {
        public sealed record UpdateServerSettingsRequest(Dictionary<string, JsonElement>? Values);

        public static IEndpointRouteBuilder MapServerSettingsEndpoints(this IEndpointRouteBuilder routes)
        {
            var group = routes.MapGroup("/api/settings/server");

            group.MapGet("/", (IServiceProvider sp) =>
            {
                var file = sp.GetService<ServerSettingsFile>();
                if (file == null)
                    return Results.Problem("Die Einstellungsdatei ist nicht verfügbar.", statusCode: StatusCodes.Status503ServiceUnavailable);

                try
                {
                    return Results.Ok(Describe(file.Read()));
                }
                catch (Exception ex)
                {
                    return Results.Problem(ex.Message, statusCode: StatusCodes.Status500InternalServerError);
                }
            });

            // Alles oder nichts: Erst werden alle Werte geprüft, dann wird in einem Zug geschrieben. Ein
            // halb übernommener Satz Einstellungen wäre schwerer zu verstehen als ein abgelehnter.
            group.MapPost("/", (UpdateServerSettingsRequest? req, IServiceProvider sp, TerminalLogger logger) =>
            {
                if (req?.Values == null || req.Values.Count == 0)
                    return Results.BadRequest(new { error = "Keine Werte übergeben: {\"values\": {\"Feld\": Wert}}." });

                var parsed = new List<(SettingDescriptor Field, object Value)>();
                var errors = new List<string>();

                foreach (var (key, raw) in req.Values)
                {
                    if (ServerSettingsCatalog.DesktopOnly.TryGetValue(key, out var reason))
                    {
                        logger.Warning($"🌐 WebUI: Änderung an {key} abgelehnt – nur im Desktop ({reason}).");
                        return Results.Json(new { error = $"{key} lässt sich nur im Desktop ändern ({reason}). Es wurde nichts geändert." },
                            statusCode: StatusCodes.Status403Forbidden);
                    }

                    var field = ServerSettingsCatalog.Find(key);
                    if (field == null || !field.Editable)
                    {
                        errors.Add($"{key}: im WebUI nicht vorhanden");
                        continue;
                    }

                    var (value, error) = field.Parse!(raw);
                    if (error != null) errors.Add($"{field.Label}: {error}");
                    else parsed.Add((field, value!));
                }

                if (errors.Count > 0)
                    return Results.BadRequest(new { error = "Nichts gespeichert. " + string.Join(" · ", errors), errors });

                var file = sp.GetService<ServerSettingsFile>();
                ServerSettings? written = null;
                var failed = PersistenceGuard.Write(file != null,
                    () => written = file!.Update(s => { foreach (var (f, v) in parsed) f.Assign!(s, v); }),
                    logger, "Server-Einstellungen");
                if (failed != null) return failed;

                // Den laufenden Stand nachziehen. Das Singleton lesen WSS-Client, Alchemy-Listener und der
                // VPN-Check des Watchdogs; VPN- und Watchdog-Dienst halten eigene, aus der Datei geladene Kopien.
                var live = sp.GetService<ServerSettings>();
                if (live != null)
                    foreach (var (f, v) in parsed) f.Assign!(live, v);
                sp.GetService<MullvadVpnService>()?.ReloadSettings();
                sp.GetService<WatchdogHeartbeatService>()?.ReloadSettings();

                logger.Info("🌐 WebUI: Server-Einstellungen geändert – " +
                            string.Join(", ", parsed.Select(p => $"{p.Field.Key}={p.Value}")));

                return Results.Ok(new
                {
                    success = true,
                    changed = parsed.Select(p => new { key = p.Field.Key, label = p.Field.Label, requiresRestart = p.Field.RequiresRestart }).ToList(),
                    restartRequired = parsed.Any(p => p.Field.RequiresRestart),
                    settings = Describe(written!)
                });
            });

            return routes;
        }

        internal static object Describe(ServerSettings s) => new
        {
            managedIn = "desktop",
            sections = ServerSettingsCatalog.Fields
                .GroupBy(f => f.Category)
                .Select(g => new
                {
                    title = g.Key,
                    fields = g.Select(f => new
                    {
                        key = f.Key,
                        label = f.Label,
                        description = f.Description,
                        kind = f.Kind.ToString().ToLowerInvariant(),
                        value = f.Get(s),
                        options = f.Options,
                        min = f.Min,
                        max = f.Max,
                        editable = f.Editable,
                        requiresRestart = f.RequiresRestart
                    }).ToList()
                }).ToList(),
            secrets = ServerSettingsCatalog.SecretStatus(s).Select(x => new { label = x.Label, status = x.Status }).ToList()
        };
    }
}