import json
import traceback

def playlist(items: list[str]) -> str:
    return json.dumps({
        "type": "items",
        "data": items,
    })

def dl_progress(msg: str) -> str:
    return json.dumps({
        "type": "dl_progress",
        "data": msg,
    })

def dl_end(ret: int) -> str:
    return json.dumps({
        "type": "dl_end",
        "data": ret,
    })

def error(ex: Exception) -> str:
    traceback.print_tb(ex.__traceback__)
    return json.dumps({
        "type": "error",
        "data": {
            "type": ex.__class__.__qualname__,
            "message": str(ex),
        }
    })