using UnityEngine;

/// <summary>
/// Limits the game's frame rate.
///
/// Sets <see cref="Application.targetFrameRate"/> and adjusts VSync
/// (<see cref="QualitySettings.vSyncCount"/>) accordingly. IMPORTANT: as long as
/// VSync is active, Unity ignores targetFrameRate - the limit then only takes
/// effect when VSync is off. This script therefore disables VSync automatically
/// as soon as an FPS limit is set (see <see cref="disableVSyncWhenLimiting"/>).
///
/// Changes apply live: in the editor via OnValidate (also in Play mode while
/// tweaking values in the Inspector).
///
/// Simply attach to any (ideally persistent) GameObject in the scene.
/// </summary>
[DisallowMultipleComponent]
public class FrameRateLimiter : MonoBehaviour
{
    [Header("Limit")]
    [Tooltip("ON = the frame rate is capped to 'Target FPS'. OFF = unlimited " +
             "(targetFrameRate = -1, platform default).")]
    public bool limitFrameRate = true;

    [Tooltip("Target frame rate in frames per second when the limit is active.")]
    [Range(1, 360)]
    public int targetFps = 60;

    [Header("VSync")]
    [Tooltip("When an FPS limit is set, disable VSync automatically. " +
             "Otherwise VSync would override targetFrameRate and the limit " +
             "would have no effect. Normally leave this ON.")]
    public bool disableVSyncWhenLimiting = true;

    [Tooltip("VSync count to use when NO limit is active " +
             "(0 = VSync off, 1 = every screen refresh, 2 = every second refresh).")]
    [Range(0, 2)]
    public int vSyncCountWhenUnlimited = 0;

    void OnEnable()
    {
        Apply();
    }

    void OnValidate()
    {
        // Live adjustment when changing values in the Inspector (also in Play mode).
        if (Application.isPlaying)
            Apply();
    }

    /// <summary>
    /// Applies the current limit (FPS + VSync) to the Unity settings.
    /// Can also be called externally.
    /// </summary>
    public void Apply()
    {
        if (limitFrameRate)
        {
            if (disableVSyncWhenLimiting)
                QualitySettings.vSyncCount = 0;

            Application.targetFrameRate = Mathf.Max(1, targetFps);
        }
        else
        {
            QualitySettings.vSyncCount = vSyncCountWhenUnlimited;
            Application.targetFrameRate = -1; // platform default / unlimited
        }
    }

    /// <summary>Enable/disable the limit (e.g. for UI buttons).</summary>
    public void SetLimitEnabled(bool enabled)
    {
        limitFrameRate = enabled;
        Apply();
    }

    /// <summary>Set the target FPS and enable the limit (e.g. for UI sliders).</summary>
    public void SetTargetFps(int fps)
    {
        targetFps = Mathf.Max(1, fps);
        limitFrameRate = true;
        Apply();
    }
}