# Set the number of cells of the board here 9, 16, 25 etc
num_grid_cells = 16
piece_color = color(255, 175, 0)
background_color = color(235, 231, 178)
piece_shadow_dark = color(206, 141, 0)
piece_shadow_light = color(255, 214, 126)

def setup():
    global piece, piece_number, row_length, piece_side_length
    size(400, 400)  # Window size width and height must be egual
    background(200, 50, 0)
    row_length = int(sqrt(num_grid_cells))
    piece_side_length = width / row_length
    textSize(piece_side_length / 2.7)
    textAlign(CENTER)
    # Setting the x and y values for each cell on grid
    xy_val = []
    t = 0
    for i in range(0, num_grid_cells, row_length):
        for j in range(row_length):
            xy_val.append((j * piece_side_length,
                           t * piece_side_length))
        t += 1
    piece = []  # Puzzle piece objects
    placed = [False] * num_grid_cells  # to help placing the pieces randomly
    piece_number = 0
    # Placing pieces randomly in grid
    while (piece_number < num_grid_cells):
        p = int(random(0, num_grid_cells))
        # Once placed will be set to True to avoid adding again at this location
        if not placed[p]:
            # Creating the piece objects list
            piece.append(PuzzlePiece(piece_number, xy_val[p][0], xy_val[p][1]))
            placed[p] = True
            piece[piece_number].design()  # Draw newly create piece object
            piece_number += 1

def draw():
    # Search all piece object indexes and verify which one is mouse pressed
    for i in range(num_grid_cells):
        if (mousePressed and
                piece[i].x <= mouseX <= piece[i].x + piece_side_length and
                piece[i].y <= mouseY <= piece[i].y + piece_side_length and
                piece[i].piece_number != 15):
            if (pieceMove(piece[num_grid_cells - 1].x, piece[num_grid_cells - 1].y, piece[i].x, piece[i].y)):
                # Remember x and y value of final piece index (white piece)
                temp_x = int(piece[num_grid_cells - 1].x)
                temp_y = int(piece[num_grid_cells - 1].y)
                # Store clicked x and y value in final index of piece list
                piece[num_grid_cells - 1].set_pos(piece[i].x, piece[i].y)
                # Store temp x and y value (the last/previous final index
                # values) in current clicked piece
                piece[i].set_pos(temp_x, temp_y)
                # draw the final index piece index (only final piece index is
                # painted white)
                piece[num_grid_cells - 1].design()
                piece[i].design()  # Draw a numbered piece of current index

def pieceMove(final_index_piece_x, final_index_piece_y, current_index_x, current_index_y):
    # If both x's from clicked and white piece have same value meaning in same horizontal column
    # AND current clicked y value is equal to white piece y value - piece side lenght OR
    # current clicked y value + piece side lenght is egual to white piece y
    if (current_index_x == final_index_piece_x and (current_index_y == final_index_piece_y - piece_side_length or
                                                    (current_index_y == final_index_piece_y + piece_side_length))):
        return True
    # If both y's from clicked and white piece have same value meaning in same vertical column AND current clicked x value
    # is equal to white piece x value - piece side lenght OR current clicked x value + piece side lenght is
    # egual to white piece x
    elif (current_index_y == final_index_piece_y and (current_index_x == final_index_piece_x - piece_side_length or
                                                      (current_index_x == final_index_piece_x + piece_side_length))):
        return True
    else:
        return False

class PuzzlePiece:

    def __init__(self, pn, xp, yp):
        self.piece_number = pn
        self.x = xp
        self.y = yp

    def set_pos(self, xp, yp):
        self.x = xp
        self.y = yp

    def design(self):
        noStroke()
        fill(piece_color)
        if (self.piece_number == num_grid_cells - 1):
            fill(background_color)
        rect(self.x + 1, self.y + 1,
             piece_side_length - 1, piece_side_length - 1)
        if (self.piece_number != num_grid_cells - 1):
            fill(0)  # Black text shadow
            text(self.piece_number + 1, self.x + piece_side_length / 2 + 2,
                 self.y + piece_side_length / 2 + textAscent() / 2)
            fill(255)
            text(self.piece_number + 1, self.x + piece_side_length / 2,
                 self.y + piece_side_length / 2 + textAscent() / 2)
            stroke(piece_shadow_dark)
            line(self.x + piece_side_length - 1, self.y + 1, self.x +
                 piece_side_length - 1, self.y + piece_side_length - 1)  # Right side shadow
            line(self.x + 2, self.y + piece_side_length, self.x +
                 piece_side_length - 1, self.y + piece_side_length)  # Bottom side shadow
            stroke(piece_shadow_light)
            # Left bright
            line(self.x + 2, self.y - 1, self.x + 2,
                 self.y + piece_side_length)
            # Upper bright
            line(self.x + 2, self.y + 1, self.x +
                 piece_side_length - 1, self.y + 1)