"""
速率限制检测器 - 解析429响应头，区分并发限制和RPM限制
"""

from datetime import datetime, timezone

from src.core.logger import logger


class RateLimitType:
    """速率限制类型"""

    CONCURRENT = "concurrent"  # 并发限制
    RPM = "rpm"  # 每分钟请求数限制
    DAILY = "daily"  # 每日限制
    MONTHLY = "monthly"  # 每月限制
    UNKNOWN = "unknown"  # 未知类型


class RateLimitInfo:
    """速率限制信息"""

    def __init__(
        self,
        limit_type: str,
        retry_after: int | None = None,
        limit_value: int | None = None,
        remaining: int | None = None,
        reset_at: datetime | None = None,
        current_usage: int | None = None,
        raw_headers: dict[str, str] | None = None,
    ):
        self.limit_type = limit_type
        self.retry_after = retry_after  # 需要等待的秒数
        self.limit_value = limit_value  # 限制值
        self.remaining = remaining  # 剩余配额
        self.reset_at = reset_at  # 重置时间
        self.current_usage = current_usage  # 当前使用量
        self.raw_headers = raw_headers or {}

    def __repr__(self) -> str:
        return (
            f"RateLimitInfo(type={self.limit_type}, "
            f"retry_after={self.retry_after}, "
            f"limit={self.limit_value}, "
            f"remaining={self.remaining})"
        )


class RateLimitDetector:
    """
    速率限制检测器

    支持的提供商：
    - Anthropic Claude API
    - OpenAI API
    - 通用 HTTP 标准头
    """

    @staticmethod
    def detect_from_headers(
        headers: dict[str, str],
        provider_name: str = "unknown",
        current_usage: int | None = None,
    ) -> RateLimitInfo:
        """
        从响应头中检测速率限制类型

        Args:
            headers: 429响应的HTTP头
            provider_name: 提供商名称（用于选择解析策略）
            current_usage: 当前使用量（RPM 计数，用于启发式判断是否为并发限制）

        Returns:
            RateLimitInfo对象
        """
        # 标准化header key (转小写)
        headers_lower = {k.lower(): v for k, v in headers.items()}

        # 根据提供商选择解析策略
        if "anthropic" in provider_name.lower() or "claude" in provider_name.lower():
            return RateLimitDetector._parse_anthropic_headers(headers_lower, current_usage)
        elif "openai" in provider_name.lower():
            return RateLimitDetector._parse_openai_headers(headers_lower, current_usage)
        else:
            return RateLimitDetector._parse_generic_headers(headers_lower, current_usage)

    @staticmethod
    def _parse_anthropic_headers(
        headers: dict[str, str],
        current_usage: int | None = None,
    ) -> RateLimitInfo:
        """
        解析 Anthropic Claude API 的速率限制头

        常见头部：
        - anthropic-ratelimit-requests-limit: 50
        - anthropic-ratelimit-requests-remaining: 0
        - anthropic-ratelimit-requests-reset: 2024-01-01T00:00:00Z
        - anthropic-ratelimit-tokens-limit: 100000
        - anthropic-ratelimit-tokens-remaining: 50000
        - retry-after: 60
        """
        retry_after = RateLimitDetector._parse_retry_after(headers)

        # 获取请求限制信息
        requests_limit = RateLimitDetector._parse_int(
            headers.get("anthropic-ratelimit-requests-limit")
        )
        requests_remaining = RateLimitDetector._parse_int(
            headers.get("anthropic-ratelimit-requests-remaining")
        )
        requests_reset = RateLimitDetector._parse_datetime(
            headers.get("anthropic-ratelimit-requests-reset")
        )

        # 判断限制类型
        # 1. 明确的 RPM 限制：请求数剩余为 0
        if requests_remaining is not None and requests_remaining == 0:
            return RateLimitInfo(
                limit_type=RateLimitType.RPM,
                retry_after=retry_after,
                limit_value=requests_limit,
                remaining=requests_remaining,
                reset_at=requests_reset,
                raw_headers=headers,
            )

        # 2. 并发限制判断（多条件策略）
        # 注意：current_usage 是 RPM 计数（当前分钟请求数），不是真正的并发数
        #
        # 判断条件（满足任一即可）：
        # A. 强判断：remaining > 0 且 retry_after <= 30（Provider 明确告知还有配额但需要等待）
        # B. 弱判断：只有 retry_after <= 5 且缺少 remaining 头（短等待时间是并发限制的典型特征）
        #
        # 选择保守的 retry_after 阈值：
        # - 强判断用 30 秒（有 remaining 头时）
        # - 弱判断用 5 秒（无 remaining 头时，更保守）
        is_likely_concurrent = False
        concurrent_reason = ""

        # 条件 A：remaining > 0 且 retry_after <= 30
        if (
            requests_remaining is not None
            and requests_remaining > 0
            and retry_after is not None
            and retry_after <= 30
        ):
            is_likely_concurrent = True
            concurrent_reason = (
                f"remaining={requests_remaining} > 0, retry_after={retry_after}s <= 30s"
            )

        # 条件 B：无 remaining 头但 retry_after 很短（<= 5 秒）
        elif requests_remaining is None and retry_after is not None and retry_after <= 5:
            is_likely_concurrent = True
            concurrent_reason = f"no remaining header, retry_after={retry_after}s <= 5s"

        if is_likely_concurrent:
            logger.info(f"检测到并发限制: {concurrent_reason}")
            return RateLimitInfo(
                limit_type=RateLimitType.CONCURRENT,
                retry_after=retry_after,
                current_usage=current_usage,
                raw_headers=headers,
            )

        # 3. 默认视为 RPM 限制（更保守的处理）
        # 无法明确区分时，视为 RPM 限制让系统降低 RPM
        # 这比误判为并发限制（不降 RPM）更安全
        if retry_after is not None or requests_limit is not None:
            logger.info(
                f"无法明确区分限制类型，保守视为 RPM 限制: "
                f"remaining={requests_remaining}, retry_after={retry_after}"
            )
            return RateLimitInfo(
                limit_type=RateLimitType.RPM,
                retry_after=retry_after,
                limit_value=requests_limit,
                remaining=requests_remaining,
                reset_at=requests_reset,
                current_usage=current_usage,
                raw_headers=headers,
            )

        # 4. 完全没有信息，标记为未知
        return RateLimitInfo(
            limit_type=RateLimitType.UNKNOWN,
            retry_after=retry_after,
            raw_headers=headers,
        )

    @staticmethod
    def _parse_openai_headers(
        headers: dict[str, str],
        current_usage: int | None = None,
    ) -> RateLimitInfo:
        """
        解析 OpenAI API 的速率限制头

        常见头部：
        - x-ratelimit-limit-requests: 3500
        - x-ratelimit-remaining-requests: 0
        - x-ratelimit-reset-requests: 2024-01-01T00:00:00Z
        - x-ratelimit-limit-tokens: 90000
        - x-ratelimit-remaining-tokens: 50000
        - retry-after: 60
        """
        retry_after = RateLimitDetector._parse_retry_after(headers)

        # 获取请求限制信息
        requests_limit = RateLimitDetector._parse_int(headers.get("x-ratelimit-limit-requests"))
        requests_remaining = RateLimitDetector._parse_int(
            headers.get("x-ratelimit-remaining-requests")
        )
        requests_reset = RateLimitDetector._parse_datetime(
            headers.get("x-ratelimit-reset-requests")
        )

        # 判断限制类型
        # 1. 明确的 RPM 限制
        if requests_remaining is not None and requests_remaining == 0:
            return RateLimitInfo(
                limit_type=RateLimitType.RPM,
                retry_after=retry_after,
                limit_value=requests_limit,
                remaining=requests_remaining,
                reset_at=requests_reset,
                raw_headers=headers,
            )

        # 2. 并发限制判断（多条件策略）
        # 判断条件（满足任一即可）：
        # A. 强判断：remaining > 0 且 retry_after <= 30
        # B. 弱判断：只有 retry_after <= 5 且缺少 remaining 头
        is_likely_concurrent = False
        concurrent_reason = ""

        if (
            requests_remaining is not None
            and requests_remaining > 0
            and retry_after is not None
            and retry_after <= 30
        ):
            is_likely_concurrent = True
            concurrent_reason = (
                f"remaining={requests_remaining} > 0, retry_after={retry_after}s <= 30s"
            )
        elif requests_remaining is None and retry_after is not None and retry_after <= 5:
            is_likely_concurrent = True
            concurrent_reason = f"no remaining header, retry_after={retry_after}s <= 5s"

        if is_likely_concurrent:
            logger.info(f"检测到并发限制: {concurrent_reason}")
            return RateLimitInfo(
                limit_type=RateLimitType.CONCURRENT,
                retry_after=retry_after,
                current_usage=current_usage,
                raw_headers=headers,
            )

        # 3. 默认视为 RPM 限制（更保守的处理）
        if retry_after is not None or requests_limit is not None:
            logger.info(
                f"无法明确区分限制类型，保守视为 RPM 限制: "
                f"remaining={requests_remaining}, retry_after={retry_after}"
            )
            return RateLimitInfo(
                limit_type=RateLimitType.RPM,
                retry_after=retry_after,
                limit_value=requests_limit,
                remaining=requests_remaining,
                reset_at=requests_reset,
                current_usage=current_usage,
                raw_headers=headers,
            )

        # 4. 完全没有信息，标记为未知
        return RateLimitInfo(
            limit_type=RateLimitType.UNKNOWN,
            retry_after=retry_after,
            raw_headers=headers,
        )

    @staticmethod
    def _parse_generic_headers(
        headers: dict[str, str],
        current_usage: int | None = None,
    ) -> RateLimitInfo:
        """
        解析通用的速率限制头

        标准头部：
        - retry-after: 60
        - x-ratelimit-limit: 100
        - x-ratelimit-remaining: 0
        - x-ratelimit-reset: 1609459200
        """
        retry_after = RateLimitDetector._parse_retry_after(headers)

        limit_value = RateLimitDetector._parse_int(headers.get("x-ratelimit-limit"))
        remaining = RateLimitDetector._parse_int(headers.get("x-ratelimit-remaining"))

        # 1. 明确的 RPM 限制
        if remaining is not None and remaining == 0:
            return RateLimitInfo(
                limit_type=RateLimitType.RPM,
                retry_after=retry_after,
                limit_value=limit_value,
                remaining=remaining,
                raw_headers=headers,
            )

        # 2. 并发限制判断（多条件策略）
        # 判断条件（满足任一即可）：
        # A. 强判断：remaining > 0 且 retry_after <= 30
        # B. 弱判断：只有 retry_after <= 5 且缺少 remaining 头
        is_likely_concurrent = False
        concurrent_reason = ""

        if (
            remaining is not None
            and remaining > 0
            and retry_after is not None
            and retry_after <= 30
        ):
            is_likely_concurrent = True
            concurrent_reason = f"remaining={remaining} > 0, retry_after={retry_after}s <= 30s"
        elif remaining is None and retry_after is not None and retry_after <= 5:
            is_likely_concurrent = True
            concurrent_reason = f"no remaining header, retry_after={retry_after}s <= 5s"

        if is_likely_concurrent:
            logger.info(f"检测到并发限制: {concurrent_reason}")
            return RateLimitInfo(
                limit_type=RateLimitType.CONCURRENT,
                retry_after=retry_after,
                current_usage=current_usage,
                raw_headers=headers,
            )

        # 3. 默认视为 RPM 限制（更保守的处理）
        if retry_after is not None or limit_value is not None:
            logger.info(
                f"无法明确区分限制类型，保守视为 RPM 限制: "
                f"remaining={remaining}, retry_after={retry_after}"
            )
            return RateLimitInfo(
                limit_type=RateLimitType.RPM,
                retry_after=retry_after,
                limit_value=limit_value,
                remaining=remaining,
                current_usage=current_usage,
                raw_headers=headers,
            )

        # 4. 完全没有信息，标记为未知
        return RateLimitInfo(
            limit_type=RateLimitType.UNKNOWN,
            retry_after=retry_after,
            raw_headers=headers,
        )

    @staticmethod
    def _parse_retry_after(headers: dict[str, str]) -> int | None:
        """解析 Retry-After 头"""
        retry_after_str = headers.get("retry-after")
        if not retry_after_str:
            return None

        try:
            # 尝试解析为整数（秒数）
            return int(retry_after_str)
        except ValueError:
            # 尝试解析为HTTP日期格式
            try:
                retry_date = datetime.strptime(retry_after_str, "%a, %d %b %Y %H:%M:%S %Z")
                delta = retry_date - datetime.now(timezone.utc)
                return max(int(delta.total_seconds()), 0)
            except Exception:
                return None

    @staticmethod
    def _parse_int(value: str | None) -> int | None:
        """安全解析整数"""
        if not value:
            return None
        try:
            return int(value)
        except (ValueError, TypeError):
            return None

    @staticmethod
    def _parse_datetime(value: str | None) -> datetime | None:
        """安全解析ISO 8601日期时间"""
        if not value:
            return None
        try:
            # 尝试解析 ISO 8601 格式
            if value.endswith("Z"):
                value = value[:-1] + "+00:00"
            return datetime.fromisoformat(value)
        except (ValueError, TypeError):
            return None


# 便捷函数
def detect_rate_limit_type(
    headers: dict[str, str],
    provider_name: str = "unknown",
    current_usage: int | None = None,
) -> RateLimitInfo:
    """
    检测速率限制类型（便捷函数）

    Args:
        headers: 429响应头
        provider_name: 提供商名称
        current_usage: 当前使用量（RPM 计数）

    Returns:
        RateLimitInfo对象
    """
    return RateLimitDetector.detect_from_headers(headers, provider_name, current_usage)