"""Cross-session rate limit guard for Nous Portal.

Writes rate limit state to a shared file so all sessions (CLI, gateway,
cron, auxiliary) can check whether Nous Portal is currently rate-limited
before making requests. Without it each 429 fans out into up to 9 calls per
turn (3 SDK retries x 3 Hermes retries), all counted against RPH.
"""

from __future__ import annotations

import contextlib
import json
import logging
import os
import tempfile
import time
from typing import Any, Mapping, Optional
from utils import atomic_replace
from agent.rate_limit_tracker import (
    _BUCKET_TAGS,
    _fmt_seconds,
    _safe_float,
    _safe_int,
    has_rate_limit_headers,
    lower_headers,
)

logger = logging.getLogger(__name__)

# Reset windows shorter than this are transient upstream jitter, not a quota
# exhaustion worth a cross-session breaker trip.
_MIN_RESET_FOR_BREAKER_SECONDS = 60.0

format_remaining = _fmt_seconds


def _state_path() -> str:
    """Return the path to the Nous rate limit state file."""
    try:
        from hermes_constants import get_hermes_home
        base = get_hermes_home()
    except ImportError:
        base = os.path.join(os.path.expanduser("~"), ".hermes")
    return os.path.join(base, "rate_limits", "nous.json")


def _parse_reset_seconds(headers: Optional[Mapping[str, str]]) -> Optional[float]:
    """Best reset estimate (seconds from now) from hourly, per-minute, then retry-after headers."""
    lowered = lower_headers(headers)
    for key in (
        "x-ratelimit-reset-requests-1h",
        "x-ratelimit-reset-requests",
        "retry-after",
    ):
        val = _safe_float(lowered.get(key), 0.0)
        if val > 0:
            return val
    return None


def record_nous_rate_limit(
    *,
    headers: Optional[Mapping[str, str]] = None,
    error_context: Optional[dict[str, Any]] = None,
    default_cooldown: float = 300.0,
) -> None:
    """Record that Nous Portal is rate-limited in the shared state file.

    Reset time comes from headers, then ``error_context["reset_at"]`` (body
    parsing), then ``default_cooldown``.
    """
    now = time.time()
    reset_at = None

    header_seconds = _parse_reset_seconds(headers)
    if header_seconds is not None:
        reset_at = now + header_seconds

    if reset_at is None and isinstance(error_context, dict):
        ctx_reset = error_context.get("reset_at")
        if isinstance(ctx_reset, (int, float)) and ctx_reset > now:
            reset_at = float(ctx_reset)

    if reset_at is None:
        reset_at = now + default_cooldown

    path = _state_path()
    try:
        state_dir = os.path.dirname(path)
        os.makedirs(state_dir, exist_ok=True)

        state = {
            "reset_at": reset_at,
            "recorded_at": now,
            "reset_seconds": reset_at - now,
        }

        fd, tmp_path = tempfile.mkstemp(dir=state_dir, suffix=".tmp")
        try:
            with os.fdopen(fd, "w", encoding="utf-8") as f:
                json.dump(state, f)
            atomic_replace(tmp_path, path)
        except Exception:
            with contextlib.suppress(OSError):
                os.unlink(tmp_path)
            raise

        logger.info(
            "Nous rate limit recorded: resets in %.0fs (at %.0f)",
            reset_at - now, reset_at,
        )
    except Exception as exc:
        logger.debug("Failed to write Nous rate limit state: %s", exc)


def nous_rate_limit_remaining() -> Optional[float]:
    """Seconds remaining until reset, or None if not rate-limited (expired state is removed)."""
    path = _state_path()
    try:
        with open(path, encoding="utf-8") as f:
            state = json.load(f)
        remaining = state.get("reset_at", 0) - time.time()
        if remaining > 0:
            return remaining
        with contextlib.suppress(OSError):
            os.unlink(path)
        return None
    except (FileNotFoundError, json.JSONDecodeError, KeyError, TypeError):
        return None


def clear_nous_rate_limit() -> None:
    """Clear the rate limit state (e.g., after a successful Nous request)."""
    try:
        os.unlink(_state_path())
    except FileNotFoundError:
        pass
    except OSError as exc:
        logger.debug("Failed to clear Nous rate limit state: %s", exc)


def _is_exhausted(remaining: Optional[int], reset: Optional[float]) -> bool:
    """remaining == 0 AND a reset window long enough to be a real quota exhaustion."""
    return (
        remaining is not None
        and remaining <= 0
        and reset is not None
        and reset >= _MIN_RESET_FOR_BREAKER_SECONDS
    )


def is_genuine_nous_rate_limit(
    *,
    headers: Optional[Mapping[str, str]] = None,
    last_known_state: Optional[Any] = None,
) -> bool:
    """Decide whether a 429 from Nous Portal is a real account rate limit.

    Nous multiplexes upstream providers behind one key, so a 429 may be one
    upstream model out of capacity (clears in seconds) rather than our quota;
    tripping the breaker on that would block every Nous model for minutes.
    Only an exhausted bucket (remaining == 0 with reset >= 60s) in the 429's
    own headers, or in the last-known-good ``RateLimitState``, is genuine.
    """
    if _has_exhausted_bucket(_parse_buckets_from_headers(headers)):
        return True
    return last_known_state is not None and _has_exhausted_bucket_in_object(last_known_state)


def _parse_buckets_from_headers(
    headers: Optional[Mapping[str, str]],
) -> dict[str, tuple[Optional[int], Optional[float]]]:
    """Extract (remaining, reset_seconds) per bucket from x-ratelimit-* headers ({} if none)."""
    lowered = lower_headers(headers)
    if not has_rate_limit_headers(lowered):
        return {}

    result: dict[str, tuple[Optional[int], Optional[float]]] = {}
    for _attr, tag in _BUCKET_TAGS:
        remaining = _safe_int(lowered.get(f"x-ratelimit-remaining-{tag}"), None)
        reset = _safe_float(lowered.get(f"x-ratelimit-reset-{tag}"), None)
        if remaining is not None or reset is not None:
            result[tag] = (remaining, reset)
    return result


def _has_exhausted_bucket(
    buckets: Mapping[str, tuple[Optional[int], Optional[float]]],
) -> bool:
    return any(_is_exhausted(remaining, reset) for remaining, reset in buckets.values())


def _has_exhausted_bucket_in_object(state: Any) -> bool:
    """Check a RateLimitState-like object (duck-typed; missing attrs are skipped)."""
    for attr, _tag in _BUCKET_TAGS:
        bucket = getattr(state, attr, None)
        if bucket is None or (getattr(bucket, "limit", 0) or 0) <= 0:
            continue
        remaining = getattr(bucket, "remaining", 0) or 0
        reset = getattr(bucket, "remaining_seconds_now", None)
        if reset is None:
            reset = getattr(bucket, "reset_seconds", 0.0) or 0.0
        if _is_exhausted(remaining, reset):
            return True
    return False