import re
from random import SystemRandom

_rng = SystemRandom()

_NOTATION_RE = re.compile(r"^\s*(\d*)d(\d+)\s*(?:([+-])\s*(\d+))?\s*$", re.IGNORECASE)

TOOL_SCHEMA = {
    "name": "roll_dice",
    "description": (
        "Roll dice using standard D&D notation (e.g. '1d20+5', '2d6', 'd8-1'). "
        "Always use this tool for any dice roll that affects the game — never invent or guess a result yourself."
    ),
    "parameters": {
        "type": "object",
        "properties": {
            "notation": {
                "type": "string",
                "description": "Dice notation, e.g. '1d20+5'",
            },
            "reason": {
                "type": "string",
                "description": "Short reason for the roll, e.g. 'Geschicklichkeitsrettung, Schwierigkeit 13'",
            },
        },
        "required": ["notation"],
    },
}


def roll(notation: str) -> dict:
    match = _NOTATION_RE.match(notation)
    if not match:
        raise ValueError(f"Invalid dice notation: {notation!r}")

    count_str, sides_str, sign, modifier_str = match.groups()
    count = int(count_str) if count_str else 1
    sides = int(sides_str)

    if not (1 <= count <= 100) or not (2 <= sides <= 1000):
        raise ValueError(f"Dice notation out of allowed range: {notation!r}")

    modifier = int(modifier_str) if modifier_str else 0
    if sign == "-":
        modifier = -modifier

    rolls = [_rng.randint(1, sides) for _ in range(count)]
    total = sum(rolls) + modifier

    return {"notation": notation, "rolls": rolls, "modifier": modifier, "total": total}