"""Optional Redis wake-up channel; database remains authoritative job queue.

Redis outages degrade to timed polling and never lose durable jobs.  A bounded
list prevents idle systems accumulating unbounded notification entries.
"""
import os,socket,ssl,time
from urllib.parse import urlparse,unquote

URL=os.getenv('SITEFORGE_REDIS_URL','')

def _command(sock,*args):
    payload=b'*'+str(len(args)).encode()+b'\r\n'
    for arg in args:
        val=str(arg).encode()
        payload+=b'$'+str(len(val)).encode()+b'\r\n'+val+b'\r\n'
    sock.sendall(payload)
    buf=sock.makefile('rb')
    line=buf.readline()
    if not line:raise OSError('Redis disconnected')
    if line[:1]==b'-':raise OSError(line[1:].decode(errors='replace'))
    if line[:1] in (b':',b'+'):return line[1:].strip()
    if line[:1]==b'$':
        size=int(line[1:].strip())
        return buf.read(size+2) if size>=0 else None
    if line[:1]==b'*':
        count=int(line[1:].strip())
        for _ in range(max(count,0)):
            n=int(buf.readline()[1:].strip());buf.read(n+2)
        return count
    raise OSError('Unexpected Redis response')

def _socket():
    u=urlparse(URL)
    if u.scheme not in ('redis','rediss'):raise ValueError('Redis URL requires redis/rediss')
    s=socket.create_connection((u.hostname,u.port or 6379),timeout=3)
    s.settimeout(4)
    if u.scheme=='rediss':s=ssl.create_default_context().wrap_socket(s,server_hostname=u.hostname)
    if u.password:_command(s,'AUTH',unquote(u.password))
    if u.path and u.path not in ('','/','/0'):_command(s,'SELECT',int(u.path.strip('/')))
    return s

def notify():
    if not URL:return False
    try:
        with _socket() as s:
            _command(s,'LPUSH','siteforge:build:wakeup',1)
            _command(s,'LTRIM','siteforge:build:wakeup',0,1023)
        return True
    except (OSError,ValueError,TypeError):return False

def wait(fallback=1.5):
    if not URL:
        time.sleep(fallback);return
    try:
        with _socket() as s:_command(s,'BRPOP','siteforge:build:wakeup',1)
    except (OSError,ValueError,TypeError):time.sleep(fallback)