/*
 * DynamicColor
 *
 * Copyright 2015-present Yannick Loriot.
 * http://yannickloriot.com
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 *
 */

#if os(iOS) || os(tvOS) || os(watchOS)
  import UIKit
#elseif os(OSX)
  import AppKit
#endif

/**
 Object representing a gradient object. It allows you to manipulate colors inside different gradients and color spaces.
 */
final public class DynamicGradient {
  let colors: [DynamicColor]

  /**
   Initializes and creates a gradient from a color array.

   - Parameter colors: An array of colors.
   */
  public init(colors: [DynamicColor]) {
    self.colors = colors
  }

  /**
   Returns the color palette of `amount` elements by grabbing equidistant colors.

   - Parameter amount: An amount of colors to return. 2 by default.
   - Parameter colorspace: The color space used to mix the colors. By default it uses the RBG color space.
   - Returns: An array of DynamicColor objects with equi-distant space in the gradient.
   */
  public func colorPalette(amount: UInt = 2, inColorSpace colorspace: DynamicColorSpace = .rgb) -> [DynamicColor] {
    guard amount > 0 && colors.count > 0 else {
      return []
    }

    guard colors.count > 1 else {
      return (0 ..< amount).map { _ in colors[0] }
    }

    let increment = 1.0 / CGFloat(amount - 1)

    return (0 ..< amount).map { pickColorAt(scale: CGFloat($0) * increment, inColorSpace: colorspace) }
  }

  /**
   Picks up and returns the color at the given scale by interpolating the colors.

   For example, given this color array `[red, green, blue]` and a scale of `0.25` you will get a kaki color.

   - Parameter scale: A float value between 0.0 and 1.0.
   - Parameter colorspace: The color space used to mix the colors. By default it uses the RBG color space.
   - Returns: A DynamicColor object corresponding to the color at the given scale.
   */
  public func pickColorAt(scale: CGFloat, inColorSpace colorspace: DynamicColorSpace = .rgb) -> DynamicColor {
    guard colors.count > 1 else {
      return colors.first ?? .black
    }

    let clippedScale = clip(scale, 0.0, 1.0)
    let positions    = (0 ..< colors.count).map { CGFloat($0) / CGFloat(colors.count - 1) }

    var color: DynamicColor = .black

    for (index, position) in positions.enumerated() {
      guard clippedScale <= position else { continue }

      guard clippedScale != 0.0 && clippedScale != 1.0 else {
        return colors[index]
      }

      let previousPosition = positions[index - 1]
      let weight           = (clippedScale - previousPosition) / (position - previousPosition)

      color = colors[index - 1].mixed(withColor: colors[index], weight: weight, inColorSpace: colorspace)

      break
    }

    return color
  }
}