package spreadsheet;

import java.util.HashSet;
import java.util.Set;
import spreadsheet.api.CellLocation;
import spreadsheet.api.ExpressionUtils;
import spreadsheet.api.value.InvalidValue;
import spreadsheet.api.value.Value;
import spreadsheet.api.observer.Observer;

public class Cell implements Observer<Cell> {

	private CellLocation location;
	private Spreadsheet sheet;
	private String exp;
	private Value val;
	private Set<Observer<Cell>> depCells = new HashSet<Observer<Cell>>();

	public Cell (CellLocation location, Spreadsheet sheet) {
		this.location = location;
		this.sheet = sheet;
		this.exp = "";
		this.val = null;
	}

	public String getExpression() {
		return exp;
	}

	public void setExpression(String newExp) {
		removeObserver(this);
		this.exp = newExp;
		this.val = new InvalidValue(newExp);
		sheet.recomputeCells.add(this);
		Set<CellLocation> refCells = ExpressionUtils.getReferencedLocations(newExp);

		for (CellLocation refCell : refCells) {
			Cell newCell = sheet.map.get(refCell);
			depCells.add(newCell);
		}

	}

	public Value getValue() {
		return val;
	}

	public void setValue(Value newValue) {
		this.val = newValue;
	}

	@Override
	public void update(Cell changed) {
		setExpression(changed.getExpression());

		if (!sheet.recomputeCells.contains(this)) {
			this.val = new InvalidValue(this.exp);
		}

	}

	private void removeObserver(Observer<Cell> observer) {
		depCells.remove(observer);
	}

}