"""Hub Server-Sent Events: um único fluxo /eventos substitui os pollings do painel."""
from collections import deque
import json
import threading
import time
from urllib.parse import parse_qs, urlsplit

PING = 15


class Eventos:
    def __init__(self, buffer=200):
        self.cond = threading.Condition()
        self.seq = 0
        self.buffer = deque(maxlen=buffer)
        self.fechado = False

    def publicar(self, tipo, dados):
        corpo = json.dumps(dados, ensure_ascii=False)
        with self.cond:
            self.seq += 1
            self.buffer.append((self.seq, tipo, corpo))
            self.cond.notify_all()
        return self.seq

    def desde(self, seq):
        with self.cond:
            return [e for e in self.buffer if e[0] > seq]

    def fechar(self):
        with self.cond:
            self.fechado = True
            self.cond.notify_all()

    def atender(self, h):
        url = urlsplit(h.path)
        try:
            ultimo = int(h.headers.get('Last-Event-ID') or parse_qs(url.query).get('desde', ['0'])[0])
        except ValueError:
            ultimo = 0
        with self.cond:
            # Cliente novo (ou que perdeu demais): começa do agora e lê /estado.
            if ultimo <= 0 or (self.buffer and ultimo < self.buffer[0][0] - 1) or ultimo > self.seq:
                ultimo = self.seq
        h.send_response(200)
        h.send_header('Content-Type', 'text/event-stream; charset=utf-8')
        h.send_header('Cache-Control', 'no-store')
        h.send_header('X-Accel-Buffering', 'no')
        h.end_headers()
        try:
            h.wfile.write(f'retry: 3000\nevent: pronto\nid: {ultimo}\ndata: {{"seq": {ultimo}}}\n\n'.encode())
            while True:
                limite = time.monotonic() + PING
                with self.cond:
                    while not self.fechado and (not self.buffer or self.buffer[-1][0] <= ultimo):
                        resta = limite - time.monotonic()
                        if resta <= 0:
                            break
                        self.cond.wait(resta)
                    if self.fechado:
                        return
                    novos = [e for e in self.buffer if e[0] > ultimo]
                if not novos:
                    h.wfile.write(b': ping\n\n')
                    continue
                for seq, tipo, corpo in novos:
                    h.wfile.write(f'id: {seq}\nevent: {tipo}\ndata: {corpo}\n\n'.encode())
                    ultimo = seq
        except (BrokenPipeError, ConnectionResetError, ConnectionAbortedError, OSError):
            return