using System;

namespace AcDream.Core.Rendering;

/// <summary>
/// Runtime-tunable knobs for the retail-faithful chase camera. Mirrors
/// the <see cref="AcDream.Core.Physics.PhysicsDiagnostics"/> pattern:
/// static fields seeded from env vars at process start, runtime-settable
/// via property setters that the DebugPanel writes to.
///
/// <para>
/// Spec: <c>docs/superpowers/specs/2026-05-18-retail-chase-camera-design.md</c>.
/// </para>
/// </summary>
public static class CameraDiagnostics
{
    /// <summary>
    /// Master toggle. When true (default, after visual ship 2026-05-18)
    /// the retail-faithful <c>AcDream.App.Rendering.RetailChaseCamera</c>
    /// is the active chase camera; when false, the legacy
    /// <c>AcDream.App.Rendering.ChaseCamera</c> rigid-follow camera is.
    /// Initial state from <c>ACDREAM_RETAIL_CHASE</c> — default-on if
    /// unset, off only when explicitly set to <c>"0"</c>. The legacy
    /// camera stays available via the DebugPanel toggle pending the
    /// follow-up deletion commit.
    /// </summary>
    public static bool UseRetailChaseCamera { get; set; } =
        Environment.GetEnvironmentVariable("ACDREAM_RETAIL_CHASE") != "0";

    /// <summary>
    /// When true (default), the camera basis follows the player's
    /// 5-frame averaged velocity vector — tilts with the terrain on
    /// hills. When false, the basis is built from a flat (yaw, 0) vector
    /// and the camera stays horizontal even on slopes. Initial state
    /// from <c>ACDREAM_CAMERA_ALIGN_SLOPE</c>; default-on if unset.
    /// </summary>
    public static bool AlignToSlope { get; set; } =
        Environment.GetEnvironmentVariable("ACDREAM_CAMERA_ALIGN_SLOPE") != "0";

    /// <summary>
    /// When true (default), the chase camera sweeps a 0.3 m collision
    /// sphere from the head-pivot to the desired eye and stops it at the
    /// first wall (retail <c>SmartBox::update_viewer</c> spring arm), so
    /// the eye never sits behind/inside geometry. Initial state from
    /// <c>ACDREAM_CAMERA_COLLIDE</c>; default-on if unset, off only when
    /// explicitly set to <c>"0"</c>.
    /// </summary>
    public static bool CollideCamera { get; set; } =
        Environment.GetEnvironmentVariable("ACDREAM_CAMERA_COLLIDE") != "0";

    /// <summary>
    /// Per-frame translation damping rate. Retail default 0.45. Higher
    /// (→ 1.0) snaps faster; lower (→ 0.0) lags more. Formula per frame:
    /// <c>alpha = clamp(TranslationStiffness * dt * 10, 0, 1)</c>.
    /// </summary>
    public static float TranslationStiffness { get; set; } = 0.45f;

    /// <summary>
    /// Per-frame rotation damping rate. Independent of translation —
    /// can be tuned higher so the camera swings to look at you faster
    /// than it physically catches up. Retail default 0.45.
    /// </summary>
    public static float RotationStiffness { get; set; } = 0.45f;

    /// <summary>
    /// Mouse-delta low-pass window (seconds). Mouse deltas spaced
    /// closer than this are averaged with the previous delta before
    /// being fed to pitch/yaw adjustments. Smooths out jitter on
    /// high-DPI mice. Retail default 0.25.
    /// </summary>
    public static float MouseLowPassWindowSec { get; set; } = 0.25f;

    /// <summary>
    /// Per-second rate that held-key offset adjustments
    /// (CameraZoomIn/Out, CameraRaise/Lower) integrate into the
    /// camera's Distance / Pitch. Retail default 40.0.
    /// </summary>
    public static float CameraAdjustmentSpeed { get; set; } = 40.0f;
}