"""The gates between a small model's mistake and your filesystem."""

from __future__ import annotations

import os
import re
from dataclasses import dataclass, field
from typing import Pattern

from tiny_computer_agent.actions import Action
from tiny_computer_agent.observe import Observation

DEFAULT_DENY_TEXT = (
    r"\bsudo\b",
    r"\brm\s+-rf\b",
    r"\bmkfs\b",
    r"\bdd\s+if=",
    r"\bchmod\s+777\b",
    r"\bgit\s+push\s+--force\b",
    r"password",
    r"api[_-]?key",
    r"\bseed\s+phrase\b",
)

DEFAULT_DENY_LABELS = (
    "terminal",
    "shell",
    "keychain",
    "password manager",
    "bank",
    "wallet",
    "credit card",
)

DEFAULT_DENY_KEYS = ("ctrl+alt+t", "ctrl+alt+delete", "ctrl+shift+escape")


class PolicyViolation(RuntimeError):
    """Raised when an action is refused. The loop stops; nothing is executed."""


@dataclass
class Policy:
    """Rules an action must pass before it is executed.

    dry_run            : when True (the default) the loop uses a DryRunExecutor
    step_budget        : hard cap on actions per episode
    deny_text_patterns : regexes a `type` action may not contain
    deny_labels        : substrings that block a click on a matching element
    deny_keys          : key chords that are never pressed
    kill_switch_path   : if this file exists, the episode aborts before the next
                         action — create it to stop a live run
    allow_grid_clicks  : numbered grid cells are *blind* clicks: they carry no
                         meaning, only coordinates. Allowed while planning (a dry
                         run touches nothing), refused with real input unless this
                         is set, because "click cell 47" is a guess about your
                         desktop, not a decision about it.
    """

    dry_run: bool = True
    step_budget: int = 20
    deny_text_patterns: tuple[str, ...] = DEFAULT_DENY_TEXT
    deny_labels: tuple[str, ...] = DEFAULT_DENY_LABELS
    deny_keys: tuple[str, ...] = DEFAULT_DENY_KEYS
    kill_switch_path: str | None = None
    allow_grid_clicks: bool = False
    _compiled: tuple[Pattern[str], ...] = field(default=(), init=False, repr=False)

    def __post_init__(self) -> None:
        self._compiled = tuple(re.compile(p, re.IGNORECASE) for p in self.deny_text_patterns)
        if self.step_budget < 1:
            raise ValueError("step_budget must be at least 1")

    def should_stop(self) -> bool:
        """True when the kill switch exists. Checked before every action."""
        return bool(self.kill_switch_path) and os.path.exists(self.kill_switch_path)

    def check(self, action: Action, observation: Observation | None = None) -> None:
        """Raise :class:`PolicyViolation` if the action is not allowed."""
        if action.kind == "type" and action.text:
            for pattern in self._compiled:
                if pattern.search(action.text):
                    raise PolicyViolation(
                        f"typing {pattern.pattern!r} is on the deny list"
                    )

        if action.kind == "key" and action.keys:
            chord = "+".join(k.strip().lower() for k in action.keys.split("+") if k.strip())
            if chord in {k.lower() for k in self.deny_keys}:
                raise PolicyViolation(f"key chord {action.keys!r} is on the deny list")

        if action.kind == "click" and action.label:
            element = observation.find(action.label) if observation is not None else None
            if not self.dry_run and not self.allow_grid_clicks:
                is_grid = (element is not None and element.kind == "grid") or (
                    element is None and action.label.strip().lower().startswith("cell ")
                )
                if is_grid:
                    raise PolicyViolation(
                        "clicking a numbered grid cell is a blind click; install an OCR "
                        "engine or pass --allow-grid if you really mean it"
                    )
            haystack = (element.label if element is not None else action.label).lower()
            for denied in self.deny_labels:
                if denied.lower() in haystack:
                    raise PolicyViolation(
                        f"clicking {action.label!r} is on the deny list ({denied!r})"
                    )