/*
 * Copyright 2023 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package dynamiccolor

import utils.MathUtils

/**
 * A class containing a value that changes with the contrast level.
 *
 * Usually represents the contrast requirements for a dynamic color on its background. The four
 * values correspond to values for contrast levels -1.0, 0.0, 0.5, and 1.0, respectively.
 *
 * @property low Value for contrast level -1.0
 * @property normal Value for contrast level 0.0
 * @property medium Value for contrast level 0.5
 * @property high Value for contrast level 1.0
 */
class ContrastCurve(val low: Double, val normal: Double, val medium: Double, val high: Double) {
  /**
   * Returns the value at a given contrast level.
   *
   * @param contrastLevel The contrast level. 0.0 is the default (normal); -1.0 is the lowest; 1.0
   *   is the highest.
   * @return The value. For contrast ratios, a number between 1.0 and 21.0.
   */
  fun get(contrastLevel: Double): Double {
    return when {
      contrastLevel <= -1.0 -> low
      contrastLevel < 0.0 -> MathUtils.lerp(low, normal, contrastLevel + 1.0)
      contrastLevel < 0.5 -> MathUtils.lerp(normal, medium, contrastLevel / 0.5)
      contrastLevel < 1.0 -> MathUtils.lerp(medium, high, (contrastLevel - 0.5) / 0.5)
      else -> high
    }
  }
}
