"""
全局请求速率限制器

默认按“所有爬虫进程共享一个桶”来限流，避免 `bash start.sh`
同时启动多个进程时，每个进程各自 5 次/秒，叠加后把代理冲爆。
"""
from contextlib import contextmanager
import json
import os
import tempfile
import time
import threading
from pathlib import Path
from uuid import uuid4

import fcntl
from request.proxy_config import is_proxy_enabled


class RateLimiter:
    """
    基于文件锁的跨进程滑动窗口限流器。

    - 同一台机器上的多个 Python 进程会共享同一个状态文件
    - 同一个进程内的多个线程也会一起走这个限流器
    """

    def __init__(
        self,
        max_requests_per_second: int = 5,
        window_seconds: float = 1.0,
        state_file: str | None = None,
    ):
        self.max_requests = max(1, int(max_requests_per_second))
        self.max_concurrent = max(
            1,
            int(os.getenv("PROXY_MAX_CONCURRENT_REQUESTS", str(self.max_requests))),
        )
        self.window_seconds = max(0.1, float(window_seconds))
        self.lease_seconds = max(
            5.0,
            float(os.getenv("PROXY_REQUEST_LEASE_SECONDS", "120")),
        )
        default_state = os.path.join(
            tempfile.gettempdir(),
            "lawyers_proxy_rate_limiter.json",
        )
        self.state_file = Path(
            state_file or os.getenv("PROXY_RATE_LIMIT_FILE", default_state)
        )
        self.lock_file = self.state_file.with_suffix(self.state_file.suffix + ".lock")
        self._thread_lock = threading.RLock()
        self.state_file.parent.mkdir(parents=True, exist_ok=True)
        self.lock_file.parent.mkdir(parents=True, exist_ok=True)

    def _load_state(self) -> dict:
        if not self.state_file.exists():
            return {"timestamps": [], "leases": {}}
        try:
            raw = self.state_file.read_text(encoding="utf-8").strip()
            if not raw:
                return {"timestamps": [], "leases": {}}
            data = json.loads(raw)
            if isinstance(data, list):
                return {
                    "timestamps": [float(item) for item in data],
                    "leases": {},
                }
            if not isinstance(data, dict):
                return {"timestamps": [], "leases": {}}
            timestamps = data.get("timestamps", []) or []
            leases = data.get("leases", {}) or {}
            return {
                "timestamps": [float(item) for item in timestamps],
                "leases": {str(key): float(value) for key, value in leases.items()},
            }
        except Exception:
            return {"timestamps": [], "leases": {}}

    def _save_state(self, state: dict) -> None:
        payload = json.dumps(state, ensure_ascii=False)
        self.state_file.write_text(payload, encoding="utf-8")

    def _normalize_state(self, state: dict, now: float) -> dict:
        timestamps = [
            float(ts)
            for ts in (state.get("timestamps", []) or [])
            if now - float(ts) < self.window_seconds
        ]
        leases = {
            str(key): float(value)
            for key, value in (state.get("leases", {}) or {}).items()
            if now - float(value) < self.lease_seconds
        }
        return {"timestamps": timestamps, "leases": leases}

    def acquire(self) -> None:
        token = None
        while True:
            token = self.try_acquire_slot()
            if token:
                self.release(token)
                return
            time.sleep(0.05)

    def try_acquire_slot(self) -> str | None:
        while True:
            wait_time = 0.0
            with self._thread_lock:
                with open(self.lock_file, "a+", encoding="utf-8") as lock_fp:
                    fcntl.flock(lock_fp.fileno(), fcntl.LOCK_EX)
                    now = time.time()
                    state = self._normalize_state(self._load_state(), now)
                    timestamps = state["timestamps"]
                    leases = state["leases"]

                    if len(timestamps) < self.max_requests and len(leases) < self.max_concurrent:
                        token = uuid4().hex
                        timestamps.append(now)
                        leases[token] = now
                        self._save_state(state)
                        fcntl.flock(lock_fp.fileno(), fcntl.LOCK_UN)
                        return token

                    wait_candidates = []
                    if len(timestamps) >= self.max_requests and timestamps:
                        wait_candidates.append(self.window_seconds - (now - timestamps[0]))
                    if len(leases) >= self.max_concurrent:
                        wait_candidates.append(0.05)
                    wait_time = max(0.05, min([item for item in wait_candidates if item > 0] or [0.05]))
                    fcntl.flock(lock_fp.fileno(), fcntl.LOCK_UN)

            time.sleep(wait_time)

    def release(self, token: str | None) -> None:
        if not token:
            return
        with self._thread_lock:
            with open(self.lock_file, "a+", encoding="utf-8") as lock_fp:
                fcntl.flock(lock_fp.fileno(), fcntl.LOCK_EX)
                now = time.time()
                state = self._normalize_state(self._load_state(), now)
                leases = state["leases"]
                if token in leases:
                    leases.pop(token, None)
                    self._save_state(state)
                else:
                    self._save_state(state)
                fcntl.flock(lock_fp.fileno(), fcntl.LOCK_UN)

    def can_make_request(self) -> bool:
        with self._thread_lock:
            with open(self.lock_file, "a+", encoding="utf-8") as lock_fp:
                fcntl.flock(lock_fp.fileno(), fcntl.LOCK_EX)
                now = time.time()
                state = self._normalize_state(self._load_state(), now)
                self._save_state(state)
                allowed = (
                    len(state["timestamps"]) < self.max_requests
                    and len(state["leases"]) < self.max_concurrent
                )
                fcntl.flock(lock_fp.fileno(), fcntl.LOCK_UN)
                return allowed


global_rate_limiter = RateLimiter(
    max_requests_per_second=int(os.getenv("PROXY_MAX_REQUESTS_PER_SECOND", "5"))
)


def _should_limit_proxy_requests() -> bool:
    """
    仅在当前进程实际启用代理时启用全局代理限流。
    """
    try:
        return is_proxy_enabled()
    except Exception:
        return True


def wait_for_request():
    """等待直到可以发起请求。"""
    if not _should_limit_proxy_requests():
        return
    global_rate_limiter.acquire()


def can_request_now() -> bool:
    """检查是否可以立即发起请求。"""
    if not _should_limit_proxy_requests():
        return True
    return global_rate_limiter.can_make_request()


@contextmanager
def request_slot():
    """
    申请一个跨进程共享的请求槽位，请求结束后自动释放。

    这样既能限制“每秒启动多少请求”，也能限制“同时在飞多少请求”。
    """
    if not _should_limit_proxy_requests():
        yield
        return

    token = global_rate_limiter.try_acquire_slot()
    try:
        yield
    finally:
        global_rate_limiter.release(token)