"""API 速率限制器实现。

提供基于固定时间窗口的速率限制，适合 Tushare 等按分钟计费的 API。
"""

import time
import threading
from typing import Optional
from dataclasses import dataclass


@dataclass
class RateLimiterStats:
    """速率限制器统计信息。"""

    total_requests: int = 0
    successful_requests: int = 0
    denied_requests: int = 0
    total_wait_time: float = 0.0
    current_window_requests: int = 0
    window_start_time: float = 0.0


class TokenBucketRateLimiter:
    """基于固定时间窗口的速率限制器。

    适合 Tushare 等按时间窗口（如每分钟）限制请求数的 API 场景。
    在窗口期内，请求数达到上限后将阻塞或等待下一个窗口。

    Attributes:
        capacity: 每个时间窗口内允许的最大请求数
        window_seconds: 时间窗口长度（秒）
    """

    def __init__(
        self,
        capacity: int = 100,
        refill_rate_per_second: float = 1.67,
        initial_tokens: Optional[int] = None,
    ) -> None:
        """初始化速率限制器。

        Args:
            capacity: 每个时间窗口内允许的最大请求数
            refill_rate_per_second: 保留参数（向后兼容），实际使用 window_seconds=60
            initial_tokens: 保留参数（向后兼容）
        """
        self.capacity = capacity
        # Tushare 通常按分钟限制，所以固定使用 60 秒窗口
        self.window_seconds = 60.0

        self._requests_in_window = 0
        self._window_start = time.monotonic()
        self._lock = threading.RLock()
        self._stats = RateLimiterStats()
        self._stats.window_start_time = self._window_start

    def _is_new_window(self) -> bool:
        """检查是否已进入新的时间窗口。"""
        current_time = time.monotonic()
        elapsed = current_time - self._window_start
        return elapsed >= self.window_seconds

    def _reset_window(self) -> None:
        """重置时间窗口。"""
        self._window_start = time.monotonic()
        self._requests_in_window = 0
        self._stats.window_start_time = self._window_start

    def acquire(self, timeout: float = float("inf")) -> tuple[bool, float]:
        """获取请求许可。

        如果在当前窗口内请求数已达上限，则等待到下一个窗口。

        Args:
            timeout: 最大等待时间（秒），默认无限等待

        Returns:
            (success, wait_time): 是否成功获取许可，以及等待时间
        """
        start_time = time.monotonic()

        with self._lock:
            # 检查是否需要进入新窗口
            if self._is_new_window():
                self._reset_window()

            # 如果当前窗口还有余量，直接通过
            if self._requests_in_window < self.capacity:
                self._requests_in_window += 1
                self._stats.total_requests += 1
                self._stats.successful_requests += 1
                self._stats.current_window_requests = self._requests_in_window
                return True, 0.0

            # 当前窗口已满，计算需要等待的时间
            current_time = time.monotonic()
            time_to_next_window = self.window_seconds - (
                current_time - self._window_start
            )

            if time_to_next_window <= 0:
                # 刚好进入新窗口
                self._reset_window()
                self._requests_in_window = 1
                self._stats.total_requests += 1
                self._stats.successful_requests += 1
                self._stats.current_window_requests = 1
                return True, 0.0

            # 检查是否能在超时时间内等待
            if timeout != float("inf") and time_to_next_window > timeout:
                self._stats.total_requests += 1
                self._stats.denied_requests += 1
                return False, timeout

        # 需要等待到下一个窗口
        if timeout != float("inf"):
            time_to_wait = min(time_to_next_window, timeout)
        else:
            time_to_wait = time_to_next_window

        time.sleep(time_to_wait)

        # 重新尝试获取许可
        with self._lock:
            # 再次检查窗口状态（可能其他线程已经重置了窗口）
            if self._is_new_window():
                self._reset_window()

            if self._requests_in_window < self.capacity:
                self._requests_in_window += 1
                wait_time = time.monotonic() - start_time
                self._stats.total_requests += 1
                self._stats.successful_requests += 1
                self._stats.total_wait_time += wait_time
                self._stats.current_window_requests = self._requests_in_window
                return True, wait_time
            else:
                # 在极端情况下，等待后仍然无法获取（其他线程抢先）
                wait_time = time.monotonic() - start_time
                self._stats.total_requests += 1
                self._stats.denied_requests += 1
                return False, wait_time

    def acquire_nonblocking(self) -> tuple[bool, float]:
        """尝试非阻塞地获取请求许可。

        Returns:
            (success, wait_time): 是否成功获取许可，以及需要等待的时间
        """
        with self._lock:
            # 检查是否需要进入新窗口
            if self._is_new_window():
                self._reset_window()

            # 如果当前窗口还有余量，直接通过
            if self._requests_in_window < self.capacity:
                self._requests_in_window += 1
                self._stats.total_requests += 1
                self._stats.successful_requests += 1
                self._stats.current_window_requests = self._requests_in_window
                return True, 0.0

            # 当前窗口已满，计算需要等待的时间
            current_time = time.monotonic()
            time_to_next_window = self.window_seconds - (
                current_time - self._window_start
            )

            self._stats.total_requests += 1
            self._stats.denied_requests += 1
            return False, max(0.0, time_to_next_window)

    def get_available_tokens(self) -> float:
        """获取当前窗口剩余可用请求数。

        Returns:
            当前窗口剩余可用请求数
        """
        with self._lock:
            if self._is_new_window():
                return float(self.capacity)
            return float(self.capacity - self._requests_in_window)

    def get_stats(self) -> RateLimiterStats:
        """获取速率限制器统计信息。

        Returns:
            RateLimiterStats 实例
        """
        with self._lock:
            self._stats.current_window_requests = self._requests_in_window
            return self._stats