from __future__ import annotations

import json
import re
from dataclasses import dataclass
from datetime import datetime, timedelta, timezone

from utils.helper import UpstreamHTTPError


@dataclass(frozen=True)
class UploadLimit:
    blocked_until: datetime
    reason: str


class UploadUnavailableError(RuntimeError):
    def __init__(self, blocked_until: datetime | None = None, *, attempts_exhausted: bool = False):
        message = (
            "多个账号上传受限，本次自动切换已达到上限，请稍后重试。"
            if attempts_exhausted else "当前没有可用于参考图上传的账号，请等待上传额度恢复或添加可用账号。"
        )
        if blocked_until:
            message += f" 已知上传限制最早预计恢复时间：{blocked_until.astimezone().strftime('%Y-%m-%d %H:%M:%S %Z')}。"
        super().__init__(message)


def parse_upload_limit(error: Exception, now: datetime | None = None) -> UploadLimit | None:
    """Recognize file quota failures only at the upstream upload allocation endpoint."""
    if not isinstance(error, UpstreamHTTPError) or error.status_code != 429 or error.context != "/backend-api/files":
        return None
    body = error.body
    if isinstance(body, str):
        try:
            body = json.loads(body)
        except (ValueError, TypeError):
            return None
    if not isinstance(body, dict):
        return None
    detail = body.get("detail") or body.get("error") or body
    if not isinstance(detail, dict):
        return None
    reason = str(detail.get("message") or "文件上传额度已用尽")
    codes = {str(detail.get(key) or "").lower() for key in ("code", "error_code", "type")}
    if not codes.intersection({"throttled", "file_upload_limit_exceeded", "upload_limit_exceeded"}) and not (
        "上传上限" in reason or "upload limit" in reason.lower()
    ):
        return None
    now = now or datetime.now(timezone.utc)
    for key in ("retry_at", "reset_at"):
        value = detail.get(key)
        if value:
            try:
                reset = datetime.fromisoformat(str(value).replace("Z", "+00:00"))
                if reset.tzinfo and reset > now:
                    return UploadLimit(reset, reason)
            except (ValueError, TypeError):
                pass
    if error.retry_after is not None and error.retry_after > 0:
        seconds = min(error.retry_after, 365 * 86400)
    else:
        units = {"小时": 3600, "分钟": 60, "秒": 1, "天": 86400,
                 "day": 86400, "hour": 3600, "minute": 60, "second": 1}
        matches = re.findall(r"(\d+(?:\.\d+)?)\s*(小时|分钟|秒|天|days?|hours?|minutes?|seconds?)", reason.lower())
        seconds = sum(float(number) * units[unit.rstrip("s")] for number, unit in matches)
        # Unknown reset time: temporary cooling, never a fabricated daily reset.
        seconds = min(seconds, 365 * 86400) if seconds > 0 else 15 * 60
    return UploadLimit(now + timedelta(seconds=max(1, seconds)), reason)