package de.aikiit.game.kaiser;
   
   import lombok.Getter;
   import org.assertj.core.util.VisibleForTesting;
   
   import java.math.BigDecimal;
   import java.math.RoundingMode;
   import java.security.SecureRandom;
   import java.util.Random;
  
  import static org.apache.commons.lang3.compare.ComparableUtils.is;
  
  /**
   * This class encapsulates the game's logics and operations on its attributes.
   * As the game is based on rounds {@link #startNewRound()} starts a new round and performs calculations based on the player's actions.
   * <br />
   * In each round there is a chance for famine-induced loss,
   * which is handled in {@link #processFamine()} based on an underlying random probability factor.
   * <br />
   * Apart from these automated things the player can:
   * <ul>
   *     <li>{@link #buyLand(Long)} buy new land</li>
   *     <li>{@link #sellLand(Long)} sell existing land</li>
   *     <li>{@link #cultivate(Long)} cultivate land in order to achieve new yields</li>
   *     <li>{@link #feedToPopulation(Long)} give food to your population</li>
   * </ul>
   * After user interactions the round is finished in {@link #finishRoundAfterActions()}.
   */
  @Getter
  public class KaiserEngine {
      /**
       * e - External damage, e.g. loss due to rats.
       */
      private BigDecimal externalDamage = BigDecimal.ZERO; // e
      private BigDecimal deathToll; // d
      private BigDecimal increase; // i in original-  birthRate?
      private Integer zYear; // why z in original?
      private BigDecimal population = BigDecimal.ZERO; // h in original
      private BigDecimal area = BigDecimal.ZERO;
      private BigDecimal yield = BigDecimal.ZERO;
      private BigDecimal supplies = BigDecimal.ZERO;
      private BigDecimal humans = BigDecimal.ZERO;
      private BigDecimal deathTollSum; // d1 in original
      private BigDecimal percentDeathToll; // p1 in original
      private BigDecimal q = BigDecimal.ONE; // q - disaster/famineQuotient
      private BigDecimal cost = BigDecimal.ZERO;
  
      private static final Random RANDOM = new SecureRandom();
  
      /**
       * Default constructor to start a game with the given default settings.
       */
      public KaiserEngine() {
          this.population = BigDecimal.valueOf(95L);
          this.zYear = 0;
          this.yield = BigDecimal.valueOf(3L);
          this.supplies = BigDecimal.valueOf(2800L);
          this.humans = BigDecimal.valueOf(3000L);
          this.area = this.humans.divide(this.yield, RoundingMode.HALF_UP);
          this.increase = BigDecimal.valueOf(5L);
          this.deathToll = BigDecimal.ZERO;
          this.percentDeathToll = BigDecimal.ZERO;
          this.deathTollSum = BigDecimal.ZERO;
          this.externalDamage = this.humans.subtract(this.supplies);
      }
  
      /**
       * Starts a new round in performs initial calculations before user actions are taken into account.
       */
      public void startNewRound() {
          this.area = this.humans.divide(this.yield, 0, RoundingMode.HALF_UP);
          this.externalDamage = this.humans.subtract(this.supplies);
          this.zYear++;
          this.population = this.population.add(this.increase);
  
          processFamine();
          this.cost = getRandomNumberUntil(10);
          this.yield = cost.add(BigDecimal.valueOf(17L));
      }
  
      /**
       * Helper method to retrieve a new random number without any comma (scale=0).
       *
       * @param threshold number is greater than 0 and at most threshold.
       * @return a new random number.
       */
      BigDecimal getRandomNumberUntil(int threshold) {
          return BigDecimal.valueOf(RANDOM.nextInt(threshold + 1) + 1).setScale(0, RoundingMode.HALF_EVEN);
      }
  
      /**
       * Evaluate internally, if a famine is happening in the current round.
       * If so this method performs all necessary calculations/reductions within the currently running game.
       */
      public void processFamine() {
          if (is(q).lessThan(BigDecimal.ZERO)) {
              this.population = this.population.divide(BigDecimal.valueOf(2L), 0, RoundingMode.HALF_UP);
              System.out.println(KaiserEnginePrinter.ORANGE);
              System.out.println("Eine fürchterliche Seuche hat die halbe Stadt dahingerafft!");
             System.out.println(KaiserEnginePrinter.ANSI_RESET);
         }
         refreshFamineQuotient();
     }
 
     /**
      * Explicitly trigger the recalculation of the given internal famine calculation factor.
      */
     void refreshFamineQuotient() {
         this.q = getRandomNumberUntil(10).divide(BigDecimal.TEN, 0, RoundingMode.HALF_UP).subtract(new BigDecimal("0.3"));
 
     }
 
     /**
      * Allow setting the area value for testing purposes.
      * @param q q value.
      */
     @VisibleForTesting
     void setQ(BigDecimal q) {
         this.q = q;
     }
 
     /**
      * Allow setting the supplies value for testing purposes.
      * @param supplies current supplies.
      */
     @VisibleForTesting
     void setSupplies(BigDecimal supplies) {
         this.supplies = supplies;
     }
 
     /**
      * Allow setting the area value for testing purposes.
      * @param area current area.
      */
     @VisibleForTesting
     void setArea(BigDecimal area) {
         this.area = area;
     }
 
     /**
      * Calculates the available area per person in the current game.
      *
      * @return area per capita, called <b>L</b> in original. Land ownership?
      */
     public BigDecimal getAreaPerCapita() {
         return area.divide(population, 0, RoundingMode.HALF_UP);
     }
 
     /**
      * Performs an act of buying land (new land is acquired by reducing the supplies according to the current land price).
      * You cannot buy more than you can afford.
      *
      * @param buy how many hectares you want to buy. Negative input is ignored.
      * @return the given number of hectares. {@code 0} means that the player does not want to buy anything, which will trigger the possibility to sell land.
      */
     public long buyLand(Long buy) {
         if (buy < 0) {
             System.out.println(KaiserEnginePrinter.ANSI_PURPLE + "Ignoriere negative Eingaben - Du willst mich wohl verkackeiern." + KaiserEnginePrinter.ANSI_RESET);
         }
 
         if (buy > 0) {
             if (is(this.yield.multiply(BigDecimal.valueOf(buy))).lessThanOrEqualTo(this.supplies)) {
                 this.area = this.area.add(BigDecimal.valueOf(buy));
                 this.supplies = this.supplies.subtract(this.yield.multiply(BigDecimal.valueOf(buy)));
                 this.cost = BigDecimal.ZERO; // price is recalculated per round
             } else {
                 throw new IllegalArgumentException("Not Enough Supplies");
             }
         }
         return buy;
     }
 
     /**
      * Performs an act of selling land (resulting in an increase of supplies as the land is sold to the current land price).
      * You cannot sell more than you have.
      *
      * @param sell how many hectares you want to sell. Negative input is ignored.
      */
     public void sellLand(Long sell) {
         if (sell < 0) {
             System.out.println(KaiserEnginePrinter.ANSI_PURPLE + "Ignoriere negative Eingaben - Du willst mich wohl verkackeiern." + KaiserEnginePrinter.ANSI_RESET);
             return;
         }
 
         if (is(BigDecimal.valueOf(sell)).lessThan(this.area)) {
             this.area = this.area.subtract(BigDecimal.valueOf(sell));
             this.supplies = this.supplies.add(this.yield.multiply(BigDecimal.valueOf(sell)));
             this.cost = BigDecimal.ZERO; // price is recalculated per round
         } else {
             throw new IllegalArgumentException("Not Enough Land");
         }
     }
 
     /**
      * Performs an act of using supplies to feed your population.
      * You cannot give more than you have.
      *
      * @param feed how many dzt you want to feed
      */
     public void feedToPopulation(Long feed) {
         if (feed < 0) {
             System.out.println(KaiserEnginePrinter.ANSI_PURPLE + "Ignoriere negative Eingaben - Du willst mich wohl verkackeiern." + KaiserEnginePrinter.ANSI_RESET);
             return;
         }
 
         if (feed != 0) {
             if (is(BigDecimal.valueOf(feed)).lessThanOrEqualTo(this.supplies)) {
                 this.supplies = this.supplies.subtract(BigDecimal.valueOf(feed));
                 this.cost = BigDecimal.ONE; // price is recalculated per round
             } else {
                 throw new IllegalArgumentException("Not Enough in Stock");
             }
         }
     }
 
     /**
      * Performs an act of using your area and people to cultivate, plant crops for the upcoming season/next round.
      * You cannot give more than you have.
      *
      * @param cultivate how many hectares you want to use for agricultural purposes. Negative input is ignored. An input of {@code 0} will trigger a recalculation of the current land price.
      */
     public void cultivate(Long cultivate) {
         if (cultivate == 0) {
             calculateNewPrice();
             return;
         }
 
         if (cultivate < 0) {
             System.out.println(KaiserEnginePrinter.ANSI_PURPLE + "Ignoriere negative Eingaben - Du willst mich wohl verkackeiern." + KaiserEnginePrinter.ANSI_RESET);
             return;
         }
 
         if (is(this.area).lessThan(BigDecimal.valueOf(cultivate))) {
             throw new IllegalArgumentException("You cannot cultivate more area than you have.");
         }
 
         BigDecimal halfCultivate = BigDecimal.valueOf(cultivate).divide(BigDecimal.valueOf(2L), 0, RoundingMode.HALF_UP);
         if (is(this.supplies).lessThan(halfCultivate)) {
             throw new IllegalArgumentException("You cannot cultivate more than you have.");
         }
 
         if (is(BigDecimal.valueOf(cultivate)).greaterThan(getPopulation().multiply(BigDecimal.TEN))) {
             throw new IllegalArgumentException("Not enough workers available.");
         }
 
         // perform seeding
         this.supplies = this.supplies.subtract(halfCultivate);
         calculateNewPrice();
 
         // yields after cultivation and population increase
         this.yield = this.cost;
         this.humans = this.yield.multiply(BigDecimal.valueOf(cultivate));
 
         // cultivation kills rats ;)
         this.externalDamage = BigDecimal.ZERO;
         calculateNewPrice();
 
         // but add some external damage in some cases in a naiive manner
         // original condition stated: if int(c/2) <> c/2
         if (this.cost.divide(BigDecimal.valueOf(2L), 0, RoundingMode.DOWN).intValue() == this.cost.divide(BigDecimal.valueOf(2L), 0, RoundingMode.UP).intValue()) {
             this.externalDamage = this.supplies.divide(this.cost, 0, RoundingMode.HALF_UP);
         }
         this.supplies = this.supplies.subtract(this.externalDamage).add(this.humans);
         calculateNewPrice();
     }
 
     /**
      * Change price for next round.
      */
     @VisibleForTesting
     void calculateNewPrice() {
         this.cost = getRandomNumberUntil(5);
     }
 
     /**
      * Perform "round"-final calculations such as
      * <ul>
      * <li>number of people that died</li>
      * <li>adapt overall (internal) death statistics</li>
      * <li>refresh internal famine quotient</li>
      * </ul>
      */
     public void finishRoundAfterActions() {
         BigDecimal factor = BigDecimal.valueOf(20L).multiply(this.area).add(this.supplies);
         this.increase = cost.multiply(factor).divide(this.population, 0, RoundingMode.HALF_UP).divide(BigDecimal.valueOf(100).add(BigDecimal.ONE), 0, RoundingMode.HALF_UP);
 
         this.cost = this.q.divide(BigDecimal.valueOf(20L), 0, RoundingMode.HALF_UP);
         refreshFamineQuotient();
 
         if (is(this.population).lessThan(this.cost)) {
             this.deathToll = BigDecimal.ZERO;
             return; // start new round without any deaths
         }
 
         // calculate deaths
         this.deathToll = this.population.subtract(this.cost);
         if (is(this.deathToll).greaterThan(this.population.multiply(BigDecimal.valueOf(0.45)))) {
             System.out.println(KaiserEnginePrinter.ANSI_YELLOW);
             System.out.println("Sie haben " + this.deathToll + " Menschen in nur einem Jahr verhungern lassen!");
             System.out.println("Auf Grund dieser extremen Misswirtschaft, werden Sie nicht nur aus Amt und Würden gejagt,");
             System.out.println("sondern auch zum Versager des Jahres erklärt.");
             System.out.println(KaiserEnginePrinter.ANSI_RESET);
             return; // TODO stop the game here!
         }
 
         // calc death statistics
         // p1 = ((z-1)*p1+D*100/p)/z
         BigDecimal tempQuotient = this.percentDeathToll.multiply(BigDecimal.valueOf(this.zYear - 1)).add(this.deathToll.multiply(BigDecimal.valueOf(100)).divide(this.population, 0, RoundingMode.HALF_UP));
         this.percentDeathToll = tempQuotient.divide(BigDecimal.valueOf(this.zYear), 0, RoundingMode.HALF_UP);
 
         this.population = this.cost; // TODO why? shouldn't this somehow be added up?
         this.deathTollSum = this.deathTollSum.add(this.deathToll);
     }
 }