package suicideChess;

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Random;

import suicideChess.Move.NotAValidMoveException;
import suicideChess.Square.NotAValidSquare;

/**
 * This class is used to play the first few moves of a game
 * 
 * @author Jean-Baptiste Hétier
 * @version $LastChangedRevision$, $LastChangedDate$
 * 
 */
public class OpeningBook {
    
    @SuppressWarnings("serial")
    public static class NoOpeningMovesLeft extends Exception {
        NoOpeningMovesLeft(String s) { super(s); };
    }
    
    //This array will hold all book variants.
    private static ArrayList<String[]> book; //each arrayList is an array of one possible opening moves (index 0 is the first move).
    static void load() { openingBookLoad("openbook"); reset();} //initialise with file 'problems' if found in current directory
    
    /**
     * This function is used to load an openingbook file
     * @param file
     */
    public static void openingBookLoad(String file) {
        //declared here only to make visible to finally clause
        BufferedReader problemReader = null;
        book = new ArrayList<String[]>();
        try {
            problemReader = new BufferedReader(new FileReader(file));
            String line = null; //not declared within while loop
            while ((line = problemReader.readLine()) != null) {
                if (!line.startsWith("#")) { //ignore lines starting with # (comments)
                    book.add(line.split("\\s")); //each space defines a new move
                }
            }
        }
        catch (FileNotFoundException e) {
            System.out.println("File '"+file+"' not found. Opening book won't be available.");
        }
        catch (IOException e){
            System.out.println("Error reading file '"+file+"'.");
        }
        finally {
            try {
                if (problemReader!= null) {
                    problemReader.close();
                }
            }
            catch (IOException ex) {
                ex.printStackTrace();
            }
        }
        System.out.println(book.size()+" opening variants loaded.");
    }
        
    //  this variable is the currentBook
    private static boolean[] validMoves;
    
    /**
     * This function should be called everytime a game is reset
     */
    public static void reset() {
        validMoves = new boolean[book.size()];
        for (int i=0; i<validMoves.length; i++)
            validMoves[i]=true; //all moves are valid
        nbOfMovesThatHaveBeenPlayed = 0;
    }
    
    //used to access the correct index in the list of moves
    private static int nbOfMovesThatHaveBeenPlayed = 0;
    
    
    /**
     * everytime a move is played by the opposite player, the computer should be notified
     * using this function. He will update the list of moves that can be played
     */
    public static void played(Move move) {
        for (int i=0; i<validMoves.length; i++) {
            if(validMoves[i] && (book.get(i).length>nbOfMovesThatHaveBeenPlayed)) {
                if (!(book.get(i)[nbOfMovesThatHaveBeenPlayed].equals(move.toString()))) {
                    validMoves[i]=false; //this branch is not valid anymore
                }
            }
        }
        nbOfMovesThatHaveBeenPlayed++;
    }
    
    /**
     * Returns a move from the book if available, given a bitboard.
     * @param bitboard
     * @return
     * @throws NotAValidMoveException
     * @throws NotAValidSquare
     * @throws NoOpeningMovesLeft
     */
    public static Move getMove(Board bitboard) throws NotAValidMoveException, NotAValidSquare, NoOpeningMovesLeft {
        ArrayList<Move> possibleMoves = new ArrayList<Move>();
        for (int i=0; i<validMoves.length; i++) {
            if(validMoves[i] && (book.get(i).length>nbOfMovesThatHaveBeenPlayed)) {
                possibleMoves.add(new Move(book.get(i)[nbOfMovesThatHaveBeenPlayed],bitboard));
                if (SuicideChess.postThinkingOutput()) {
                    String formatVariation = "";
                    for(int j=nbOfMovesThatHaveBeenPlayed; j<book.get(i).length; j++) {
                        formatVariation += book.get(i)[j]+" ";
                    }
                    System.out.println(" "+1+"\t"+0+"\t"+0+"\t"+validMoves.length+"\t"+formatVariation+" [Book Move]");
                }
            }
        }
        //select one of the possible moves randomly
        if(possibleMoves.size()==0) {
            throw new NoOpeningMovesLeft("No moves left in opening book.");
        }
        
        Random generator = new Random();
        Move chosenMove = possibleMoves.get(generator.nextInt(possibleMoves.size()));
        return chosenMove;
    }

}