using AvParser.Core.Proxies;
using AvParser.Core.Settings;
using AvParser.Infrastructure.Logging;
using AvParser.Infrastructure.Storage;
using AvParser.UI.Localization;
using AvParser.UI.Responsive;
using AvParser.UI.Services;
using ReactiveUI;
using ReactiveUI.Primitives;
using ReactiveUI.Primitives.Concurrency;
using ReactiveUI.SourceGenerators;
using Serilog.Core;

namespace AvParser.UI.ViewModels;

/// <summary>Theme, logging level and where the app keeps its files.</summary>
public partial class SettingsViewModel : PageViewModel
{
    private readonly ISettingsService _settings;
    private readonly IThemeService _theme;
    private readonly LoggingLevelSwitch _levelSwitch;
    private readonly IProxyPool _proxyPool;
    private readonly ILocalizationService _localization;

    /// <summary>Selected theme. Applied immediately, not on an OK button.</summary>
    [Reactive]
    public partial LocalizedOption<AppTheme> SelectedTheme { get; set; }

    /// <summary>Selected UI language. Applied immediately.</summary>
    [Reactive]
    public partial LocalizedOption<AppLanguage> SelectedLanguage { get; set; }

    /// <summary>Selected Serilog level name. Takes effect immediately.</summary>
    [Reactive]
    public partial string SelectedLogLevel { get; set; }

    /// <summary>How the pool picks the next proxy.</summary>
    [Reactive]
    public partial LocalizedOption<ProxyRotation> SelectedRotation { get; set; }

    /// <summary>When proxy liveness is verified.</summary>
    [Reactive]
    public partial LocalizedOption<ProxyHealthCheck> SelectedHealthCheck { get; set; }

    /// <summary>Whether the remote proxy feed is consulted.</summary>
    [Reactive]
    public partial bool UseProxyFeed { get; set; }

    /// <summary>URL fetched to decide whether a proxy works.</summary>
    [Reactive]
    public partial string ProxyProbeUrl { get; set; }

    /// <summary>Per-proxy probe timeout, in seconds.</summary>
    [Reactive]
    public partial int ProxyProbeTimeoutSeconds { get; set; }

    /// <summary>How many probes run at once during a sweep.</summary>
    [Reactive]
    public partial int ProxyProbeConcurrency { get; set; }

    /// <summary>How many working proxies the startup warm-up aims for.</summary>
    [Reactive]
    public partial int ProxyMinimumLive { get; set; }

    /// <summary>Whether network parsers may run with no proxy available.</summary>
    [Reactive]
    public partial bool AllowDirectConnection { get; set; }

    /// <summary>Creates the page.</summary>
    public SettingsViewModel(
        ISettingsService settings,
        IThemeService theme,
        IAppPaths paths,
        LoggingLevelSwitch levelSwitch,
        IProxyPool proxyPool,
        ILocalizationService localization,
        ISequencer? mainThread = null
    )
    {
        _settings = settings ?? throw new ArgumentNullException(nameof(settings));
        _theme = theme ?? throw new ArgumentNullException(nameof(theme));
        _levelSwitch = levelSwitch ?? throw new ArgumentNullException(nameof(levelSwitch));
        _proxyPool = proxyPool ?? throw new ArgumentNullException(nameof(proxyPool));
        _localization = localization ?? throw new ArgumentNullException(nameof(localization));
        ArgumentNullException.ThrowIfNull(paths);

        var scheduler = mainThread ?? RxSchedulers.MainThreadScheduler;

        SettingsFile = paths.SettingsFile;
        LogDirectory = paths.LogDirectory;

        SelectedTheme = Option(Themes, theme.Current);
        SelectedLanguage = Option(Languages, localization.Current);
        SelectedLogLevel = settings.Current.MinimumLogLevel;

        var current = settings.Current;
        SelectedRotation = Option(Rotations, current.ProxyRotation);
        SelectedHealthCheck = Option(HealthChecks, current.ProxyHealthCheck);
        UseProxyFeed = current.ProxyUseFeed;
        ProxyProbeUrl = current.ProxyProbeUrl;
        ProxyProbeTimeoutSeconds = current.ProxyProbeTimeoutSeconds;
        ProxyProbeConcurrency = current.ProxyProbeConcurrency;
        ProxyMinimumLive = current.ProxyMinimumLive;
        AllowDirectConnection = current.AllowDirectConnection;

        this.WhenAnyValue(x => x.SelectedTheme).ObserveOn(scheduler).Subscribe(option => _theme.Apply(option.Value));

        this.WhenAnyValue(x => x.SelectedLanguage)
            .ObserveOn(scheduler)
            .Subscribe(option => _localization.Apply(option.Value));

        this.WhenAnyValue(x => x.SelectedLogLevel)
            .Where(static level => !string.IsNullOrEmpty(level))
            .DistinctUntilChanged()
            .Subscribe(ApplyLogLevel);

        // Keep the picker honest when the theme is flipped from the title-bar button.
        theme.Changes.ObserveOn(scheduler).Subscribe(value => SelectedTheme = Option(Themes, value));

        // Every proxy knob funnels through one handler: they all end up rebuilding the same
        // ProxyOptions, and applying them one at a time would reconfigure the pool six times.
        this.WhenAnyValue(
                x => x.SelectedRotation,
                x => x.SelectedHealthCheck,
                x => x.UseProxyFeed,
                x => x.ProxyProbeUrl,
                x => x.ProxyProbeTimeoutSeconds,
                x => x.ProxyProbeConcurrency,
                x => x.ProxyMinimumLive,
                x => x.AllowDirectConnection,
                (_, _, _, _, _, _, _, _) => RxVoid.Default
            )
            .Throttle(TimeSpan.FromMilliseconds(200), scheduler)
            .ObserveOn(scheduler)
            .Subscribe(_ => ApplyProxySettings());

        this.WhenAnyValue(x => x.SelectedRotation)
            .Subscribe(_ => this.RaisePropertyChanged(nameof(RotationDescription)));

        this.WhenAnyValue(x => x.SelectedHealthCheck)
            .Subscribe(_ => this.RaisePropertyChanged(nameof(HealthCheckDescription)));
    }

    /// <inheritdoc />
    public override string TitleKey => "Page.Settings";

    /// <inheritdoc />
    public override string IconKey => "IconSettings";

    /// <summary>Theme options offered by the picker.</summary>
    public IReadOnlyList<LocalizedOption<AppTheme>> Themes { get; } = LocalizedOption<AppTheme>.ForAll();

    /// <summary>Language options offered by the picker.</summary>
    public IReadOnlyList<LocalizedOption<AppLanguage>> Languages { get; } = LocalizedOption<AppLanguage>.ForAll();

    /// <summary>Serilog level names, most to least verbose.</summary>
    public IReadOnlyList<string> LogLevels => AppLogging.AvailableLevels;

    /// <summary>Rotation strategies offered by the picker.</summary>
    public IReadOnlyList<LocalizedOption<ProxyRotation>> Rotations { get; } = LocalizedOption<ProxyRotation>.ForAll();

    /// <summary>Liveness policies offered by the picker.</summary>
    public IReadOnlyList<LocalizedOption<ProxyHealthCheck>> HealthChecks { get; } =
        LocalizedOption<ProxyHealthCheck>.ForAll();

    /// <summary>Explains the selected rotation in one line.</summary>
    public string RotationDescription => Localizer.Instance[$"Settings.Rotation.{SelectedRotation.Value}"];

    /// <summary>Explains the selected health-check policy in one line.</summary>
    public string HealthCheckDescription => Localizer.Instance[$"Settings.HealthCheck.{SelectedHealthCheck.Value}"];

    /// <summary>Describes the compact breakpoint band.</summary>
    public string CompactHint => Localizer.Instance.Format("Settings.Breakpoint.CompactHint", MediumBreakpoint);

    /// <summary>Describes the medium breakpoint band.</summary>
    public string MediumHint =>
        Localizer.Instance.Format("Settings.Breakpoint.MediumHint", MediumBreakpoint, ExpandedBreakpoint);

    /// <summary>Describes the expanded breakpoint band.</summary>
    public string ExpandedHint => Localizer.Instance.Format("Settings.Breakpoint.ExpandedHint", ExpandedBreakpoint);

    /// <summary>Full path of the settings file.</summary>
    public string SettingsFile { get; }

    /// <summary>Directory holding rolling log files.</summary>
    public string LogDirectory { get; }

    /// <summary>Width in pixels at which the shell switches from compact to the icon rail.</summary>
    public double MediumBreakpoint => ResponsiveLayout.MediumMinWidth;

    /// <summary>Width in pixels at which the shell switches to the full sidebar.</summary>
    public double ExpandedBreakpoint => ResponsiveLayout.ExpandedMinWidth;

    /// <inheritdoc />
    protected override void OnLanguageChanged()
    {
        base.OnLanguageChanged();

        foreach (
            var name in new[]
            {
                nameof(RotationDescription),
                nameof(HealthCheckDescription),
                nameof(CompactHint),
                nameof(MediumHint),
                nameof(ExpandedHint),
            }
        )
        {
            this.RaisePropertyChanged(name);
        }
    }

    private static LocalizedOption<TValue> Option<TValue>(IReadOnlyList<LocalizedOption<TValue>> options, TValue value)
        where TValue : struct, Enum => options.First(option => option.Value.Equals(value));

    private void ApplyLogLevel(string level)
    {
        _levelSwitch.MinimumLevel = AppLogging.ParseLevel(level);
        _settings.Update(current => current with { MinimumLogLevel = level });
    }

    private void ApplyProxySettings()
    {
        AppSettings? applied = null;

        _settings.Update(current =>
        {
            applied = current with
            {
                ProxyRotation = SelectedRotation.Value,
                ProxyHealthCheck = SelectedHealthCheck.Value,
                ProxyUseFeed = UseProxyFeed,
                ProxyProbeUrl = ProxyProbeUrl,
                ProxyProbeTimeoutSeconds = ProxyProbeTimeoutSeconds,
                ProxyProbeConcurrency = ProxyProbeConcurrency,
                ProxyMinimumLive = ProxyMinimumLive,
                AllowDirectConnection = AllowDirectConnection,
            };

            return applied;
        });

        // Update() short-circuits a no-op change, so fall back to the stored value: the pool must
        // still be configured on the very first pass, when nothing has changed yet.
        _proxyPool.Configure((applied ?? _settings.Current).ToProxyOptions());
    }
}