import json

class ChunkData:
    def __init__(self):
        self.current = {}
        self.original = {}
        self.filename = None

    def load(self, filename):
        try:
            with open(filename, 'r') as f:
                self.current = json.load(f)
            self.filename = filename
            self.original = json.loads(json.dumps(self.current))  # Deep copy
        except Exception as e:
            raise RuntimeError(f"Failed to load chunk file: {e}")

    def save(self, filename=None):
        fname = filename if filename else self.filename
        if not fname:
            raise ValueError("No filename specified for saving chunk.")
        try:
            with open(fname, 'w') as f:
                json.dump(self.current, f, indent=2)
            self.original = json.loads(json.dumps(self.current))  # Deep copy
            self.filename = fname
        except Exception as e:
            raise RuntimeError(f"Failed to save chunk file: {e}")

    def new(self):
        self.current = {}
        self.original = {}
        self.filename = None

    def isDirty(self):
        return json.dumps(self.current, sort_keys=True) != json.dumps(self.original, sort_keys=True)