content: /*
   * Copyright (C) 2022 The Android Open Source Project
   *
   * 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 com.anod.appwatcher.utils.color;
  
  import static androidx.annotation.RestrictTo.Scope.LIBRARY_GROUP;
  
  import androidx.annotation.RestrictTo;
  
  /**
   * A class that solves the HCT equation.
   *
   * @hide
   */
  @RestrictTo(LIBRARY_GROUP)
  public class HctSolver {
    private HctSolver() {}
  
    static final double[][] SCALED_DISCOUNT_FROM_LINRGB =
        new double[][] {
          new double[] {
            0.001200833568784504, 0.002389694492170889, 0.0002795742885861124,
          },
          new double[] {
            0.0005891086651375999, 0.0029785502573438758, 0.0003270666104008398,
          },
          new double[] {
            0.00010146692491640572, 0.0005364214359186694, 0.0032979401770712076,
          },
        };
  
    static final double[][] LINRGB_FROM_SCALED_DISCOUNT =
        new double[][] {
          new double[] {
            1373.2198709594231, -1100.4251190754821, -7.278681089101213,
          },
          new double[] {
            -271.815969077903, 559.6580465940733, -32.46047482791194,
          },
          new double[] {
            1.9622899599665666, -57.173814538844006, 308.7233197812385,
          },
        };
  
    static final double[] Y_FROM_LINRGB = new double[] {0.2126, 0.7152, 0.0722};
  
    static final double[] CRITICAL_PLANES =
        new double[] {
          0.015176349177441876,
          0.045529047532325624,
          0.07588174588720938,
          0.10623444424209313,
          0.13658714259697685,
          0.16693984095186062,
          0.19729253930674434,
          0.2276452376616281,
          0.2579979360165119,
          0.28835063437139563,
          0.3188300904430532,
          0.350925934958123,
          0.3848314933096426,
          0.42057480301049466,
          0.458183274052838,
          0.4976837250274023,
          0.5391024159806381,
          0.5824650784040898,
          0.6277969426914107,
          0.6751227633498623,
          0.7244668422128921,
          0.775853049866786,
          0.829304845476233,
          0.8848452951698498,
          0.942497089126609,
          1.0022825574869039,
          1.0642236851973577,
          1.1283421258858297,
          1.1946592148522128,
          1.2631959812511864,
          1.3339731595349034,
          1.407011200216447,
          1.4823302800086415,
          1.5599503113873272,
          1.6398909516233677,
          1.7221716113234105,
          1.8068114625156377,
          1.8938294463134073,
          1.9832442801866852,
          2.075074464868551,
          2.1693382909216234,
          2.2660538449872063,
          2.36523901573795,
          2.4669114995532007,
          2.5710888059345764,
          2.6777882626779785,
          2.7870270208169257,
          2.898822059350997,
          3.0131901897720907,
          3.1301480604002863,
          3.2497121605402226,
          3.3718988244681087,
          3.4967242352587946,
          3.624204428461639,
          3.754355295633311,
          3.887192587735158,
          4.022731918402185,
          4.160988767090289,
          4.301978482107941,
          4.445716283538092,
          4.592217266055746,
          4.741496401646282,
          4.893568542229298,
          5.048448422192488,
          5.20615066083972,
          5.3666897647573375,
          5.5300801301023865,
          5.696336044816294,
          5.865471690767354,
          6.037501145825082,
          6.212438385869475,
          6.390297286737924,
          6.571091626112461,
          6.7548350853498045,
          6.941541251256611,
          7.131223617812143,
          7.323895587840543,
          7.5195704746346665,
          7.7182615035334345,
          7.919981813454504,
          8.124744458384042,
          8.332562408825165,
          8.543448553206703,
          8.757415699253682,
          8.974476575321063,
          9.194643831691977,
          9.417930041841839,
          9.644347703669503,
          9.873909240696694,
          10.106627003236781,
          10.342513269534024,
          10.58158024687427,
          10.8238400726681,
          11.069304815507364,
          11.317986476196008,
          11.569896988756009,
          11.825048221409341,
          12.083451977536606,
          12.345119996613247,
          12.610063955123938,
          12.878295467455942,
          13.149826086772048,
          13.42466730586372,
          13.702830557985108,
          13.984327217668513,
          14.269168601521828,
          14.55736596900856,
          14.848930523210871,
          15.143873411576273,
          15.44220572664832,
          15.743938506781891,
          16.04908273684337,
          16.35764934889634,
          16.66964922287304,
          16.985093187232053,
          17.30399201960269,
          17.62635644741625,
          17.95219714852476,
          18.281524751807332,
          18.614349837764564,
          18.95068293910138,
          19.290534541298456,
          19.633915083172692,
          19.98083495742689,
          20.331304511189067,
          20.685334046541502,
          21.042933821039977,
          21.404114048223256,
          21.76888489811322,
          22.137256497705877,
          22.50923893145328,
          22.884842241736916,
          23.264076429332462,
          23.6469514538663,
          24.033477234264016,
          24.42366364919083,
          24.817520537484558,
          25.21505769858089,
          25.61628489293138,
          26.021211842414342,
          26.429848230738664,
          26.842203703840827,
          27.258287870275353,
          27.678110301598522,
          28.10168053274597,
          28.529008062403893,
          28.96010235337422,
          29.39497283293396,
          29.83362889318845,
          30.276079891419332,
          30.722335150426627,
          31.172403958865512,
          31.62629557157785,
          32.08401920991837,
          32.54558406207592,
          33.010999283389665,
          33.4802739966603,
          33.953417292456834,
          34.430438229418264,
          34.911345834551085,
          35.39614910352207,
          35.88485700094671,
          36.37747846067349,
          36.87402238606382,
          37.37449765026789,
          37.87891309649659,
          38.38727753828926,
          38.89959975977785,
          39.41588851594697,
          39.93615253289054,
          40.460400508064545,
          40.98864111053629,
          41.520882981230194,
          42.05713473317016,
          42.597404951718396,
          43.141702194811224,
          43.6900349931913,
          44.24241185063697,
          44.798841244188324,
          45.35933162437017,
          45.92389141541209,
          46.49252901546552,
          47.065252796817916,
          47.64207110610409,
          48.22299226451468,
          48.808024568002054,
          49.3971762874833,
          49.9904556690408,
          50.587870934119984,
          51.189430279724725,
          51.79514187861014,
          52.40501387947288,
          53.0190544071392,
          53.637271562750364,
          54.259673423945976,
          54.88626804504493,
          55.517063457223934,
          56.15206766869424,
          56.79128866487574,
          57.43473440856916,
          58.08241284012621,
          58.734331877617365,
          59.39049941699807,
          60.05092333227251,
          60.715611475655585,
          61.38457167773311,
          62.057811747619894,
          62.7353394731159,
          63.417162620860914,
          64.10328893648692,
          64.79372614476921,
          65.48848194977529,
          66.18756403501224,
          66.89098006357258,
          67.59873767827808,
          68.31084450182222,
          69.02730813691093,
          69.74813616640164,
          70.47333615344107,
          71.20291564160104,
          71.93688215501312,
          72.67524319850172,
          73.41800625771542,
          74.16517879925733,
          74.9167682708136,
          75.67278210128072,
          76.43322770089146,
          77.1981124613393,
          77.96744375590167,
          78.74122893956174,
          79.51947534912904,
          80.30219030335869,
          81.08938110306934,
          81.88105503125999,
          82.67721935322541,
          83.4778813166706,
          84.28304815182372,
          85.09272707154808,
          85.90692527145302,
          86.72564993000343,
          87.54890820862819,
          88.3767072518277,
          89.2090541872801,
          90.04595612594655,
          90.88742016217518,
          91.73345337380438,
          92.58406282226491,
          93.43925555268066,
          94.29903859396902,
          95.16341895893969,
          96.03240364439274,
          96.9059996312159,
          97.78421388448044,
          98.6670533535366,
          99.55452497210776,
        };
  
    /**
     * Sanitizes a small enough angle in radians.
     *
     * @param angle An angle in radians; must not deviate too much from 0.
     * @return A coterminal angle between 0 and 2pi.
     */
    static double sanitizeRadians(double angle) {
      return (angle + Math.PI * 8) % (Math.PI * 2);
    }
  
    /**
     * Delinearizes an RGB component, returning a floating-point number.
     *
     * @param rgbComponent 0.0 <= rgb_component <= 100.0, represents linear R/G/B channel
     * @return 0.0 <= output <= 255.0, color channel converted to regular RGB space
     */
    static double trueDelinearized(double rgbComponent) {
      double normalized = rgbComponent / 100.0;
      double delinearized = 0.0;
      if (normalized <= 0.0031308) {
        delinearized = normalized * 12.92;
      } else {
        delinearized = 1.055 * Math.pow(normalized, 1.0 / 2.4) - 0.055;
      }
      return delinearized * 255.0;
    }
  
    static double chromaticAdaptation(double component) {
      double af = Math.pow(Math.abs(component), 0.42);
      return MathUtils.signum(component) * 400.0 * af / (af + 27.13);
    }
  
    /**
     * Returns the hue of a linear RGB color in CAM16.
     *
     * @param linrgb The linear RGB coordinates of a color.
     * @return The hue of the color in CAM16, in radians.
     */
    static double hueOf(double[] linrgb) {
      double[] scaledDiscount = MathUtils.matrixMultiply(linrgb, SCALED_DISCOUNT_FROM_LINRGB);
      double rA = chromaticAdaptation(scaledDiscount[0]);
      double gA = chromaticAdaptation(scaledDiscount[1]);
      double bA = chromaticAdaptation(scaledDiscount[2]);
      // redness-greenness
      double a = (11.0 * rA + -12.0 * gA + bA) / 11.0;
      // yellowness-blueness
      double b = (rA + gA - 2.0 * bA) / 9.0;
      return Math.atan2(b, a);
    }
  
    static boolean areInCyclicOrder(double a, double b, double c) {
      double deltaAB = sanitizeRadians(b - a);
      double deltaAC = sanitizeRadians(c - a);
      return deltaAB < deltaAC;
    }
  
    /**
     * Solves the lerp equation.
     *
     * @param source The starting number.
     * @param mid The number in the middle.
     * @param target The ending number.
     * @return A number t such that lerp(source, target, t) = mid.
     */
    static double intercept(double source, double mid, double target) {
      return (mid - source) / (target - source);
    }
  
    static double[] lerpPoint(double[] source, double t, double[] target) {
      return new double[] {
        source[0] + (target[0] - source[0]) * t,
        source[1] + (target[1] - source[1]) * t,
        source[2] + (target[2] - source[2]) * t,
      };
    }
  
    /**
     * Intersects a segment with a plane.
     *
     * @param source The coordinates of point A.
     * @param coordinate The R-, G-, or B-coordinate of the plane.
     * @param target The coordinates of point B.
     * @param axis The axis the plane is perpendicular with. (0: R, 1: G, 2: B)
     * @return The intersection point of the segment AB with the plane R=coordinate, G=coordinate, or
     *     B=coordinate
     */
    static double[] setCoordinate(double[] source, double coordinate, double[] target, int axis) {
      double t = intercept(source[axis], coordinate, target[axis]);
      return lerpPoint(source, t, target);
    }
  
    static boolean isBounded(double x) {
      return 0.0 <= x && x <= 100.0;
    }
  
    /**
     * Returns the nth possible vertex of the polygonal intersection.
     *
     * @param y The Y value of the plane.
     * @param n The zero-based index of the point. 0 <= n <= 11.
     * @return The nth possible vertex of the polygonal intersection of the y plane and the RGB cube,
     *     in linear RGB coordinates, if it exists. If this possible vertex lies outside of the cube,
     *     [-1.0, -1.0, -1.0] is returned.
     */
    static double[] nthVertex(double y, int n) {
      double kR = Y_FROM_LINRGB[0];
      double kG = Y_FROM_LINRGB[1];
      double kB = Y_FROM_LINRGB[2];
      double coordA = n % 4 <= 1 ? 0.0 : 100.0;
      double coordB = n % 2 == 0 ? 0.0 : 100.0;
      if (n < 4) {
        double g = coordA;
        double b = coordB;
        double r = (y - g * kG - b * kB) / kR;
        if (isBounded(r)) {
          return new double[] {r, g, b};
        } else {
          return new double[] {-1.0, -1.0, -1.0};
        }
      } else if (n < 8) {
        double b = coordA;
        double r = coordB;
        double g = (y - r * kR - b * kB) / kG;
        if (isBounded(g)) {
          return new double[] {r, g, b};
        } else {
          return new double[] {-1.0, -1.0, -1.0};
        }
      } else {
        double r = coordA;
        double g = coordB;
        double b = (y - r * kR - g * kG) / kB;
        if (isBounded(b)) {
          return new double[] {r, g, b};
        } else {
          return new double[] {-1.0, -1.0, -1.0};
        }
      }
    }
  
    /**
     * Finds the segment containing the desired color.
     *
     * @param y The Y value of the color.
     * @param targetHue The hue of the color.
     * @return A list of two sets of linear RGB coordinates, each corresponding to an endpoint of the
     *     segment containing the desired color.
     */
    static double[][] bisectToSegment(double y, double targetHue) {
      double[] left = new double[] {-1.0, -1.0, -1.0};
      double[] right = left;
      double leftHue = 0.0;
      double rightHue = 0.0;
      boolean initialized = false;
      boolean uncut = true;
      for (int n = 0; n < 12; n++) {
        double[] mid = nthVertex(y, n);
        if (mid[0] < 0) {
          continue;
        }
        double midHue = hueOf(mid);
        if (!initialized) {
          left = mid;
          right = mid;
          leftHue = midHue;
          rightHue = midHue;
          initialized = true;
          continue;
        }
        if (uncut || areInCyclicOrder(leftHue, midHue, rightHue)) {
          uncut = false;
          if (areInCyclicOrder(leftHue, targetHue, midHue)) {
            right = mid;
            rightHue = midHue;
          } else {
            left = mid;
            leftHue = midHue;
          }
        }
      }
      return new double[][] {left, right};
    }
  
    static double[] midpoint(double[] a, double[] b) {
      return new double[] {
        (a[0] + b[0]) / 2, (a[1] + b[1]) / 2, (a[2] + b[2]) / 2,
      };
    }
  
    static int criticalPlaneBelow(double x) {
      return (int) Math.floor(x - 0.5);
    }
  
    static int criticalPlaneAbove(double x) {
      return (int) Math.ceil(x - 0.5);
    }
  
    /**
     * Finds a color with the given Y and hue on the boundary of the cube.
     *
     * @param y The Y value of the color.
     * @param targetHue The hue of the color.
     * @return The desired color, in linear RGB coordinates.
     */
    static double[] bisectToLimit(double y, double targetHue) {
      double[][] segment = bisectToSegment(y, targetHue);
      double[] left = segment[0];
      double leftHue = hueOf(left);
      double[] right = segment[1];
      for (int axis = 0; axis < 3; axis++) {
        if (left[axis] != right[axis]) {
          int lPlane = -1;
          int rPlane = 255;
          if (left[axis] < right[axis]) {
            lPlane = criticalPlaneBelow(trueDelinearized(left[axis]));
            rPlane = criticalPlaneAbove(trueDelinearized(right[axis]));
          } else {
            lPlane = criticalPlaneAbove(trueDelinearized(left[axis]));
            rPlane = criticalPlaneBelow(trueDelinearized(right[axis]));
          }
          for (int i = 0; i < 8; i++) {
            if (Math.abs(rPlane - lPlane) <= 1) {
              break;
            } else {
              int mPlane = (int) Math.floor((lPlane + rPlane) / 2.0);
              double midPlaneCoordinate = CRITICAL_PLANES[mPlane];
              double[] mid = setCoordinate(left, midPlaneCoordinate, right, axis);
              double midHue = hueOf(mid);
              if (areInCyclicOrder(leftHue, targetHue, midHue)) {
                right = mid;
                rPlane = mPlane;
              } else {
                left = mid;
                leftHue = midHue;
                lPlane = mPlane;
              }
            }
          }
        }
      }
      return midpoint(left, right);
    }
  
    static double inverseChromaticAdaptation(double adapted) {
      double adaptedAbs = Math.abs(adapted);
      double base = Math.max(0, 27.13 * adaptedAbs / (400.0 - adaptedAbs));
      return MathUtils.signum(adapted) * Math.pow(base, 1.0 / 0.42);
    }
  
    /**
     * Finds a color with the given hue, chroma, and Y.
     *
     * @param hueRadians The desired hue in radians.
     * @param chroma The desired chroma.
     * @param y The desired Y.
     * @return The desired color as a hexadecimal integer, if found; 0 otherwise.
     */
    static int findResultByJ(double hueRadians, double chroma, double y) {
      // Initial estimate of j.
      double j = Math.sqrt(y) * 11.0;
      // ===========================================================
      // Operations inlined from Cam16 to avoid repeated calculation
      // ===========================================================
      ViewingConditions viewingConditions = ViewingConditions.DEFAULT;
      double tInnerCoeff = 1 / Math.pow(1.64 - Math.pow(0.29, viewingConditions.getN()), 0.73);
      double eHue = 0.25 * (Math.cos(hueRadians + 2.0) + 3.8);
      double p1 = eHue * (50000.0 / 13.0) * viewingConditions.getNc() * viewingConditions.getNcb();
      double hSin = Math.sin(hueRadians);
      double hCos = Math.cos(hueRadians);
      for (int iterationRound = 0; iterationRound < 5; iterationRound++) {
        // ===========================================================
        // Operations inlined from Cam16 to avoid repeated calculation
        // ===========================================================
        double jNormalized = j / 100.0;
        double alpha = chroma == 0.0 || j == 0.0 ? 0.0 : chroma / Math.sqrt(jNormalized);
        double t = Math.pow(alpha * tInnerCoeff, 1.0 / 0.9);
        double ac =
            viewingConditions.getAw()
                * Math.pow(jNormalized, 1.0 / viewingConditions.getC() / viewingConditions.getZ());
        double p2 = ac / viewingConditions.getNbb();
        double gamma = 23.0 * (p2 + 0.305) * t / (23.0 * p1 + 11 * t * hCos + 108.0 * t * hSin);
        double a = gamma * hCos;
        double b = gamma * hSin;
        double rA = (460.0 * p2 + 451.0 * a + 288.0 * b) / 1403.0;
        double gA = (460.0 * p2 - 891.0 * a - 261.0 * b) / 1403.0;
        double bA = (460.0 * p2 - 220.0 * a - 6300.0 * b) / 1403.0;
        double rCScaled = inverseChromaticAdaptation(rA);
        double gCScaled = inverseChromaticAdaptation(gA);
        double bCScaled = inverseChromaticAdaptation(bA);
        double[] linrgb =
            MathUtils.matrixMultiply(
                new double[] {rCScaled, gCScaled, bCScaled}, LINRGB_FROM_SCALED_DISCOUNT);
        // ===========================================================
        // Operations inlined from Cam16 to avoid repeated calculation
        // ===========================================================
        if (linrgb[0] < 0 || linrgb[1] < 0 || linrgb[2] < 0) {
          return 0;
        }
        double kR = Y_FROM_LINRGB[0];
        double kG = Y_FROM_LINRGB[1];
        double kB = Y_FROM_LINRGB[2];
        double fnj = kR * linrgb[0] + kG * linrgb[1] + kB * linrgb[2];
        if (fnj <= 0) {
          return 0;
        }
        if (iterationRound == 4 || Math.abs(fnj - y) < 0.002) {
          if (linrgb[0] > 100.01 || linrgb[1] > 100.01 || linrgb[2] > 100.01) {
            return 0;
          }
          return ColorUtils.argbFromLinrgb(linrgb);
        }
        // Iterates with Newton method,
        // Using 2 * fn(j) / j as the approximation of fn'(j)
        j = j - (fnj - y) * j / (2 * fnj);
      }
      return 0;
    }
  
    /**
     * Finds an sRGB color with the given hue, chroma, and L*, if possible.
     *
     * @param hueDegrees The desired hue, in degrees.
     * @param chroma The desired chroma.
     * @param lstar The desired L*.
     * @return A hexadecimal representing the sRGB color. The color has sufficiently close hue,
     *     chroma, and L* to the desired values, if possible; otherwise, the hue and L* will be
     *     sufficiently close, and chroma will be maximized.
     */
    public static int solveToInt(double hueDegrees, double chroma, double lstar) {
      if (chroma < 0.0001 || lstar < 0.0001 || lstar > 99.9999) {
        return ColorUtils.argbFromLstar(lstar);
      }
      hueDegrees = MathUtils.sanitizeDegreesDouble(hueDegrees);
      double hueRadians = hueDegrees / 180 * Math.PI;
      double y = ColorUtils.yFromLstar(lstar);
      int exactAnswer = findResultByJ(hueRadians, chroma, y);
      if (exactAnswer != 0) {
        return exactAnswer;
      }
      double[] linrgb = bisectToLimit(y, hueRadians);
      return ColorUtils.argbFromLinrgb(linrgb);
    }
  
    /**
     * Finds an sRGB color with the given hue, chroma, and L*, if possible.
     *
     * @param hueDegrees The desired hue, in degrees.
     * @param chroma The desired chroma.
     * @param lstar The desired L*.
     * @return An CAM16 object representing the sRGB color. The color has sufficiently close hue,
     *     chroma, and L* to the desired values, if possible; otherwise, the hue and L* will be
     *     sufficiently close, and chroma will be maximized.
     */
    public static Cam16 solveToCam(double hueDegrees, double chroma, double lstar) {
      return Cam16.fromInt(solveToInt(hueDegrees, chroma, lstar));
    }
  }