package sudoku.solver;

import sudoku.MultiDoku;
import sudoku.MutableCell;
import sudoku.constraint.IConstraint;

import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.Stack;

public class Solver {
    Stack<MutableCell> stack;

    public Solver() {
    }

    public MultiDoku solve(MultiDoku doku, List<IConstraint> constraints) throws Exception {
        if (!doku.isValid(constraints)) {
            throw new Exception("Invalid doku");
        }
        List<MutableCell> allMutableCells = doku.getMutableCells();
        List<MutableCell> remainingCellsToCheck = new ArrayList<>(allMutableCells);
        Random rand = new Random();
        while (!remainingCellsToCheck.isEmpty()) {
            int indexCurrentCell = rand.nextInt(remainingCellsToCheck.size());
            MutableCell currentCell = remainingCellsToCheck.get(indexCurrentCell);
            if (currentCell.getPossibleSymbols().isEmpty()){
                MutableCell modify = stack.pop();
                modify.removeSymbolFromPossibilities(modify.clearCurrentSymbol());
            } else {
                int symbol = currentCell.getPossibleSymbols().get(0);
                currentCell.setSymbolIndex(symbol);
                stack.push(currentCell);
                try {
                    doku.updateSymbolsPossibilities();
                } catch (Exception e) {
                    //TODO rollback
                }
                //TODO check constraints integrity in sudoku


            }




            remainingCellsToCheck.remove(indexCurrentCell);
        }
        return doku;
    }
}