using System.Collections.Generic;
using AcDream.UI.Abstractions.Settings;

namespace AcDream.UI.Abstractions.Panels.Settings;

/// <summary>
/// Particle visibility distance policy. Retail uses the GfxObj-authored
/// distance exactly; Extended is the acdream default requested for longer
/// distant-effect visibility, with the corresponding CPU cost.
/// </summary>
public enum ParticleRange
{
    Retail = 0,
    Extended = 1,
}

/// <summary>
/// Immutable, value-equal user overrides for one selected render pack. Keys
/// are stable setting IDs and compare case-insensitively; values remain the
/// declaration's invariant string representation until descriptor validation.
/// </summary>
public sealed class RenderPackSettingOverrides :
    IReadOnlyDictionary<string, string>,
    IEquatable<RenderPackSettingOverrides>
{
    private readonly SortedDictionary<string, string> _values;

    public static RenderPackSettingOverrides Empty { get; } = new([]);

    public RenderPackSettingOverrides(
        IEnumerable<KeyValuePair<string, string>> values)
    {
        ArgumentNullException.ThrowIfNull(values);
        _values = new SortedDictionary<string, string>(StringComparer.OrdinalIgnoreCase);
        foreach ((string key, string value) in values)
        {
            ArgumentNullException.ThrowIfNull(key);
            ArgumentNullException.ThrowIfNull(value);
            _values[key] = value;
        }
    }

    public int Count => _values.Count;

    public IEnumerable<string> Keys => _values.Keys;

    public IEnumerable<string> Values => _values.Values;

    public string this[string key] => _values[key];

    public bool ContainsKey(string key) => _values.ContainsKey(key);

    public bool TryGetValue(string key, out string value) =>
        _values.TryGetValue(key, out value!);

    public IEnumerator<KeyValuePair<string, string>> GetEnumerator() =>
        _values.GetEnumerator();

    System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() =>
        GetEnumerator();

    public RenderPackSettingOverrides Set(string settingId, string value)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(settingId);
        ArgumentNullException.ThrowIfNull(value);
        var next = new SortedDictionary<string, string>(
            _values,
            StringComparer.OrdinalIgnoreCase)
        {
            [settingId] = value,
        };
        return new RenderPackSettingOverrides(next);
    }

    public bool Equals(RenderPackSettingOverrides? other) =>
        other is not null
        && _values.Count == other._values.Count
        && _values.All(pair => other._values.TryGetValue(pair.Key, out string? value)
            && string.Equals(pair.Value, value, StringComparison.Ordinal));

    public override bool Equals(object? obj) =>
        obj is RenderPackSettingOverrides other && Equals(other);

    public override int GetHashCode()
    {
        var hash = new HashCode();
        foreach ((string key, string value) in _values)
        {
            hash.Add(key, StringComparer.OrdinalIgnoreCase);
            hash.Add(value, StringComparer.Ordinal);
        }
        return hash.ToHashCode();
    }
}

/// <summary>
/// Stable, user-authored selection of one optional render pack. Logical ids
/// are persisted instead of menu indexes so discovery order can never select a
/// different pack or preset after an install/update. The renderer normalizes a
/// missing, malformed, unavailable, or incompatible selection back to
/// <see cref="Retail"/> and retains the precise reason for diagnostics.
/// </summary>
public sealed record RenderPackSelectionSettings(
    string PackId,
    string? PackVersion,
    string PresetId)
{
    public const string RetailPackId = "retail";
    public const string RetailPresetId = "off";

    public static RenderPackSelectionSettings Retail { get; } = new(
        RetailPackId,
        PackVersion: null,
        RetailPresetId);

    /// <summary>
    /// User-authored values keyed by the selected pack's stable setting IDs.
    /// Empty by default so pre-render-pack settings files upgrade without a
    /// migration write.
    /// </summary>
    public RenderPackSettingOverrides SettingOverrides { get; init; } =
        RenderPackSettingOverrides.Empty;

    public bool IsRetail =>
        string.Equals(PackId, RetailPackId, StringComparison.OrdinalIgnoreCase);
}

/// <summary>
/// Display-related preferences persisted to <c>settings.json</c>.
/// Originally documented as "no retail equivalent for FOV / vsync etc" —
/// Campaign OP slice OP6's Config-tab research corrected that: retail's
/// <c>gmClient::InitUIPreferences @0x004035b0</c> DOES register
/// <c>Render_FieldOfView</c> (<c>ID_Graphics_FieldOfView</c>, range
/// [10,160]), <c>Display_SyncToRefresh</c>, <c>Display_Resolution</c>, and
/// <c>Render_ScreenBrightness</c> (<see cref="ScreenBrightness"/> below,
/// range [-1,1]) as genuine <c>UserPreferences.ini</c> rows — they simply
/// had no acdream UI surface until OP6's Config tab. Resolution/
/// Fullscreen are LIVE on save (<c>RuntimeSettingsTargets.
/// ApplyDisplayWindowState</c> resizes the window immediately); VSync/FOV/
/// Gamma apply at the next launch only (<c>RuntimeSettingsController.
/// ApplyStartup</c>), matching this record's pre-existing behaviour — OP6
/// did not change when these three take effect, only how they're reached.
///
/// <para>
/// Records are immutable; mutation goes through <c>with</c>-expressions —
/// e.g. <c>RuntimeSettingsController.SaveDisplay</c>'s callers, or the
/// OP9-retired <c>SettingsVM.SetDisplay</c>'s draft assignment before that.
/// </para>
/// </summary>
public sealed record DisplaySettings(
    string Resolution,
    bool Fullscreen,
    bool VSync,
    float FieldOfView,
    float Gamma,
    bool ShowFps,
    QualityPreset Quality,
    ParticleRange ParticleRange,
    // Campaign OP slice OP6: the Config tab's "Graphics Options" +
    // "Rendering Quality Options" rows with no acdream renderer consumer —
    // the world renderer is Vulkan + one aggregate QualityPreset, not
    // per-feature knobs (register row, OP6). Persisted faithfully; every
    // default below is retail's own byte-verified
    // gmClient::InitUIPreferences / gmConfigUI::InitOptions literal.
    //
    // OP6 rework (2026-08-11, review S2): Screen Brightness gets its OWN
    // field — the rejected slice reused Gamma (a pre-existing multiplier,
    // default 1.0, legacy Settings-panel range [0.5, 2.0]), a genuinely
    // different unit system from retail's own Render_ScreenBrightness
    // range [-1, 1] / default 0 (AttachPreference @0x004043df,
    // SetPreferenceRange @0x004043f3). Overloading Gamma pinned the Config
    // row at the WRONG default (a fresh Gamma=1.0 normalizes to the
    // slider's maximum, not center) and made Defaults write a value (0)
    // outside the legacy slider's own range. Gamma itself is untouched —
    // still the pre-existing multiplier the legacy Settings panel drives.
    float ScreenBrightness = 0f,
    bool AutomaticDegrades = false,
    float GraphicsPerformance = 0f,
    float DegradeDistance = 50f,
    int LandscapeTextureDetail = 2,
    int EnvironmentTextureDetail = 1,
    int TextureFiltering = 1,
    // UNRESOLVED (OP6, cite in register row): retail's own
    // SetDefaultValue(8) does not index its 6-entry SetEnumChoices array
    // (VeryLow..Extreme) — reproduced faithfully as an opaque int, not
    // guessed into a clamped index.
    int LandscapeDrawDistance = 8,
    bool BuildingDetailTextures = true,
    bool MultiPassAlpha = false)
{
    /// <summary>
    /// Opt-in graphics enhancement selection. This is deliberately separate
    /// from <see cref="Quality"/>, which remains the authoritative retail
    /// renderer/streaming quality preset. Keeping the default here means an
    /// upgraded settings file that predates shader packs deserializes to the
    /// exact retail path without a migration write.
    /// </summary>
    public RenderPackSelectionSettings RenderPack { get; init; } =
        RenderPackSelectionSettings.Retail;

    /// <summary>Values used on first launch / when settings.json is absent.
    /// Geometry defaults preserve the pre-L.0 runtime state: Resolution
    /// matches the WindowOptions startup size (1280×720). FieldOfView is
    /// retail's <c>m_fGameFOV</c> in degrees — registered default 90, range
    /// [10,160] (<c>gmClient::InitUIPreferences @0x004035b0</c>; #389
    /// corrected the pre-port 60, which encoded the old direct-vertical-FOV
    /// semantics this record no longer means). VSync defaults on so normal
    /// rendering is synchronized to the active monitor, while
    /// ShowFps matches retail's initially-hidden SmartBox FPS readout.</summary>
    public static DisplaySettings Default { get; } = new(
        Resolution:   "1280x720",
        Fullscreen:   false,
        VSync:        true,
        FieldOfView:  90f,
        Gamma:        1.0f,
        ShowFps:      false,
        Quality:      QualityPreset.High,
        ParticleRange: ParticleRange.Extended);

    /// <summary>
    /// FALLBACK resolution presets — used only when the monitor's real mode
    /// list is unavailable (fixture/conformance callers, headless mounts). In
    /// production the Config dropdown is populated from the display's actual
    /// modes, curated to modern formats (#391, user-directed 2026-08-13:
    /// "we should only support modern resolutions. Not any old format") —
    /// see <c>AcDream.App.Rendering.DisplayModeCatalog</c>, whose curation
    /// filter this fallback list also passes through. Retail's own list was
    /// the adapter's full mode enumeration including 4:3 legacy modes, with
    /// <c>800x600</c> as the authored Config-tab default
    /// (<c>gmConfigUI::InitOptions SetDefaultValue(0x03200258)</c>,
    /// <c>gmClient::Init @0x004047af</c>) — the curation and the desktop-mode
    /// default that replaces it are a deliberate deviation carried in the
    /// divergence register (see the #391 row).
    /// </summary>
    public static IReadOnlyList<string> AvailableResolutions { get; } = new[]
    {
        "1280x720",
        "1366x768",
        "1600x900",
        "1920x1080",
        "2560x1440",
        "3840x2160",
    };
}