using System;

using UnityEngine;

namespace Framework.Support {

  /// <summary>Helper methods for interpolating</summary>
  public static class InterpolationHelper {

    /// <summary>Interpolates a typical camera fade</summary>
    /// <param name="t">Running interpolation time</param>
    /// <param name="totalTime">Total time of the faqde</param>
    /// <param name="fadeInTime">Duration of the fade in</param>
    /// <param name="fadeOutTime">Duration of the fade out</param>
    /// <returns>The interpolated fade level</returns>
    public static float InterpolateFade(
      float t, float totalTime, float fadeInTime, float fadeOutTime
    ) {
      if(fadeInTime <= 0.0f) {

        // Neither fade-in or fade-out are present. Always return 1.0
        if(fadeOutTime <= 0.0f) {
          return 1.0f;
        }

        // Only fade-out is present. Everything before fade-out is 1.0,
        // everything after it is 0.0
        float remainingTime = totalTime - t;
        if(remainingTime < fadeOutTime) {
          return Math.Max(0.0f, remainingTime / fadeOutTime);
        } else {
          return 1.0f;
        }

      } else if(fadeOutTime <= 0.0f) {

        // Only fade-in is present. Everything before fade-in is 0.0,
        // everything after it is 1.0
        if(t < fadeInTime) {
          return Math.Max(0.0f, t / fadeInTime);
        } else {
          return 1.0f;
        }

      } else {

        // TODO: Do both fade-in and fade-out and calculate where max levels meet
        //   So there's no skip when the length is shorter than the fade time
        return 0.5f;

      }
    }

  }

} // namespace Framework.Support