xl-project/app/src/main/java/xl/model/XLModel.java

package xl.model;

import java.io.IOException;
import java.util.*;

import xl.expr.Environment;
import xl.expr.ExprParser;
import xl.util.XLException;

public class XLModel extends Observable implements Environment {
    private Map<String, Cell> map;
    private String status;
    private String currentAddress;

    // The observers that are registered to be notified
    private List<Observer> observers = new ArrayList<>();

    public XLModel() {
        status = "";
        currentAddress = "A1";
        map = new java.util.HashMap<String, Cell>();
    }

    public String getCurrentAddress() {
        return currentAddress;
    }

    public void setCurrentAddress(String currentAddress) {
        this.currentAddress = currentAddress;
    }

    public Optional<Cell> getCell(String address) {
        return Optional.ofNullable(map.get(address));
    }

    public boolean remove(String address) {
        // Save the existing cell at the specified address
        Cell oldCell = map.get(address);

        if (oldCell != null) {
            map.remove(address);

            // If the output is invalid, restore the old cell
            if (hasWrongOutputs()) {
                map.put(address, oldCell);
                status = "Cannot remove cell";
                return false;
            }
        }

        return true;
    }

    public void add(String address, String text) {
        try {
            createCell(address, text);
        } catch (XLException e) {
            status = "Error creating cell";
            return;
        }
        
        // Tell observers that the model has changed
        setChanged();
        notifyObservers();
    }

    public String getStatus() {
        return status;
    }

    public void clearStatus() {
        status = "";
    }

    public void clearCell() {
        if (remove(currentAddress)) {
            notifyObservers();
        }
    }

    public void clearAll() {
        map.clear();
        clearStatus();
        setChanged();
        notifyObservers();
    }

    public void load(String path) {
        try (XLBufferedReader reader = new XLBufferedReader(path)) {
            map.clear();
            reader.load(map);
            status = "";
        } catch (IOException e) {
            status = "Error loading file";
        }
        setChanged();
        notifyObservers();
    }

    public void save(String path) {
        try (XLPrintStream xlPrintStream = new XLPrintStream(path)) {
            xlPrintStream.save(map.entrySet());
        } catch (IOException e) {
            status = "Error saving file";
        }
    }

    public String getAddressValue(String address) {
        if (map.containsKey(address)) {
            Cell cell = map.get(address);
            if (cell instanceof CommentCell) {
                return cell.displayValue();
            }
            return Double.toString(cell.cellValue(this));
        }
        return "";
    }

    public String getAddressContent(String address) {
        if (map.containsKey(address)) {
            Cell cell = map.get(address);
            if (cell instanceof CommentCell) {
                return "#" + map.get(address).displayValue();
            }
            return map.get(address).displayValue();
        } else {
            return "";
        }
    }

    public boolean containsKey(String address) {
        return map.containsKey(address);
    }

    private void createCell(String address, String text) {
        if (text.length() > 0 && text.charAt(0) == '#') {
            map.put(address, new CommentCell(text.substring(1)));
        } else {
            ExprParser parser = new ExprParser();
            try {
                Cell newCell = new ExpressionCell(parser.build(text));
                Cell oldCell = map.get(address);
                BombCell bomb = new BombCell();
                map.put(address, bomb);
                if (hasCircularDependancy(newCell) || hasWrongOutputs()) {
                    if (oldCell != null) {
                        map.put(address, oldCell);
                    } else {
                        map.remove(address);
                    }
                }
            } catch (IOException e) {
                throw XLException.ERROR_CREATECELL;
            }
        }
    }

    private boolean hasCircularDependancy(Cell cell) {
        try {
            cell.cellValue(this);
            map.put(currentAddress, cell);
            status = "";
        } catch (XLException e) {
            status = e.getMessage();
            return true;
        } catch (NullPointerException e) {
            status = e.toString();
            return true;
        }
        return false;
    }

    private boolean hasWrongOutputs() {
        for (Map.Entry<String, Cell> entry : map.entrySet()) {
            try {
                entry.getValue().cellValue(this);
            } catch (Exception e) {
                status = "cannot update";
                return true;
            }
        }
        return false;
    }

    @Override
    public double value(String name) {
        // Check if the cell is referencing itself
        if (currentAddress.equals(name)) {
            throw XLException.ERROR_RECURSIVE;
        }
        // Check if the cell is empty
        if (map.containsKey(name)) {
            return map.get(name).cellValue(this);
        } else {
            throw XLException.ERROR_EMPTY_REF;
        }
    }

    public void addObserver(Observer o) {
        observers.add(o);
    }

    public void notifyObservers() {
        for (Observer o : observers) {
            o.update(this, null);
        }
    }
}