"""Token-Budget: Passt Prompt + Ausgabe in den effektiven Kontext eines Slots?"""

from __future__ import annotations

import math
from collections.abc import Callable
from dataclasses import dataclass

MESSAGE_OVERHEAD = 64

Tokenizer = Callable[[str], int]


def estimate_tokens(text: str) -> int:
    """Konservative Schätzung (eher zu hoch): ~3 Zeichen pro Token."""
    return math.ceil(len(text) / 3)


@dataclass(frozen=True)
class Budget:
    prompt_tokens: int
    output_tokens: int
    limit: int

    @property
    def required(self) -> int:
        return self.prompt_tokens + self.output_tokens + MESSAGE_OVERHEAD

    @property
    def fits(self) -> bool:
        return self.required <= self.limit


def compute(system: str, user: str, max_output_tokens: int, limit: int,
            tokenizer: Tokenizer = estimate_tokens) -> Budget:
    return Budget(tokenizer(system) + tokenizer(user), max_output_tokens, limit)