Gamelib/src/main/java/uulm/teamname/marvelous/gamelibrary/ai/BoardAnalyzer.java

package uulm.teamname.marvelous.gamelibrary.ai;

import uulm.teamname.marvelous.gamelibrary.entities.EntityID;
import uulm.teamname.marvelous.gamelibrary.entities.EntityType;
import uulm.teamname.marvelous.gamelibrary.gamelogic.GameStateView;

import java.util.ArrayList;
import java.util.HashMap;

class BoardAnalyzer {
    private final Board origin;
    private final EntityType player;
    private final HashMap<Integer, Float> scoreCache = new HashMap<>();
    private final HashMap<Integer, ArrayList<Action>> actionCache = new HashMap<>();
    private Action bestAction = null;

    public BoardAnalyzer(GameStateView state, EntityID turn) {
        this.origin = Board.generate(state, turn);
        this.player = turn.type;
    }

    public Action analyze(GameStateView state) {
        Node tree = new Node(origin, new Action(ActionType.None));

        int maxDepth = 2;
        int depth = 0;
        long startTime = System.nanoTime();
        while(System.nanoTime() - startTime <= 1000 * 1000 * 1000) {
            expandTree(tree, state);
            depth++;
            if(depth > maxDepth) {
                break;
            }
        }

        alphaBetaMax(tree, Float.MIN_VALUE, Float.MAX_VALUE, true);

        if(bestAction != null) {
            return bestAction;
        }

        return new Action(ActionType.None);
    }

    private Float alphaBetaMax(Node root, Float a, Float b, boolean main) {
        if(!root.hasChildren()) {
            return calculateScore(root.board);
        }
        Float w = a;
        for(Node child: root.getChildren()) {
            Float v;
            if(child.board.turn.type == child.board.origin) {
                v = alphaBetaMax(child, a, w, false);
            }else {
                v = alphaBetaMin(child, w, b);
            }
            if(v > w) {
                w = v;
            }
            if(w >= b) {
                if(main) {
                    bestAction = child.action;
                }
                return w;
            }
            if(main) {
                bestAction = child.action;
            }
        }
        return w;
    }

    private Float alphaBetaMin(Node root, Float a, Float b) {
        if(!root.hasChildren()) {
            return calculateScore(root.board);
        }
        Float w = b;
        for(Node child: root.getChildren()) {
            Float v;
            if(child.board.turn.type == child.board.origin) {
                v = alphaBetaMax(child, a, w, false);
            }else {
                v = alphaBetaMin(child, w, b);
            }
            if(v < w) {
                w = v;
            }
            if(w <= a) {
                return w;
            }
        }
        return w;
    }

    private ArrayList<Node> getLeaves(Node root) {
        return getLeaves(root, new ArrayList<>());
    }

    private ArrayList<Node> getLeaves(Node root, ArrayList<Node> accumulator) {
        for(Node child: root.getChildren()) {
            if(child.hasChildren()) {
                getLeaves(child, accumulator);
            }else {
                accumulator.add(child);
            }
        }
        return accumulator;
    }

    private void expandTree(Node root, GameStateView state) {
        if(!root.hasChildren()) {
            expandNode(root, state);
            return;
        }
        for(Node child: root.getChildren()) {
            if(child.board.ended) {
                continue;
            }
            if(child.hasChildren()) {
                expandTree(child, state);
            }else {
                expandNode(child, state);
            }
        }
    }

    private void expandNode(Node origin, GameStateView state) {
        ArrayList<Action> actions = generateActions(origin.board, state);
        for(Action action: actions) {
            Board result = origin.board.applyAction(state, action);
            scoreCache.put(result.hashCode(), result.calculateScore());
            origin.addChild(result, action, result.calculateScore());
        }
    }

    private ArrayList<Action> generateActions(Board board, GameStateView state) {
        int hash = board.hashCode();
        if(actionCache.containsKey(hash)) {
            return actionCache.get(hash);
        }else {
            ArrayList<Action> result = board.generateActions(state);
            actionCache.put(hash, result);
            return result;
        }
    }

    private Float calculateScore(Board board) {
        int hash = board.hashCode();
        if(scoreCache.containsKey(hash)) {
            return scoreCache.get(hash);
        }else {
            Float result = board.calculateScore();
            scoreCache.put(hash, result);
            return result;
        }
    }
}