#!/usr/bin/env python3
"""Multi-room chat met Server-Sent Events. Stdlib only, single file, 3.6+.

Run:
    python3 sse-chat.py --port 8082

Open http://127.0.0.1:8082/ in twee browsers en chat. Geen JS-deps:
alleen EventSource + fetch.

Spec (dit bestand is de spec):

    Endpoint                         Method  Statusen    Beschrijving
    /api/rooms                       GET     200         Kamers + aantallen
    /api/rooms                       POST    201/400     Kamer aanmaken {"room"}
    /api/rooms/{room}/messages       GET     200/404     History (?since=&limit=)
    /api/rooms/{room}/messages       POST    201/400/404 Bericht {"nick","text"}
    /events?room={room}              GET     200/404     SSE-stream (id/event/retry)
    /                                GET     200         Embedded UI
    /healthz                         GET     200         {"ok":true,...}

    SSE-events: "message" (JSON-bericht), "hello" (laatste id bij connect).
    Reconnect: Last-Event-ID-header of ?since= wordt gerespecteerd, gemiste
    berichten worden nagezonden. Heartbeat: ": ping" elke 15 s.

    Kamernamen: ^[a-z0-9-]{1,32}$. Standaardkamers: lobby, random, tech.

Caps: MAX_ROOMS 50, MAX_HISTORY 200/room, MAX_NICK 32, MAX_TEXT 2000,
MAX_BODY 8 KiB, HEARTBEAT 15 s.
"""

import argparse
import json
import re
import socketserver
import threading
import time
from collections import deque
from http.server import BaseHTTPRequestHandler, HTTPServer
from urllib.parse import parse_qs, urlparse

try:
    from queue import Queue, Empty
except ImportError:  # Python 2 fallback, nooit gebruikt maar goedkoop
    from Queue import Queue, Empty

ROOM_RE = re.compile(r"^[a-z0-9-]{1,32}$")


class ChatError(Exception):
    def __init__(self, status, message):
        super(ChatError, self).__init__(message)
        self.status = status
        self.message = message


class ChatStore(object):
    """Kamers, history en SSE-abonnees. Alles achter een RLock."""

    MAX_ROOMS = 50
    MAX_HISTORY = 200
    MAX_SUBSCRIBERS = 500
    DEFAULT_ROOMS = ("lobby", "random", "tech")

    def __init__(self):
        self._lock = threading.RLock()
        self._rooms = {}
        self._subs = {}
        for room in self.DEFAULT_ROOMS:
            self._rooms[room] = {"messages": deque(maxlen=self.MAX_HISTORY),
                                 "next_id": 1}

    @staticmethod
    def _now():
        return time.strftime("%Y-%m-%dT%H:%M:%SZ", time.gmtime())

    def rooms(self):
        with self._lock:
            return [{"room": name, "messages": len(info["messages"])}
                    for name, info in sorted(self._rooms.items())]

    def create_room(self, room):
        if not isinstance(room, str) or not ROOM_RE.match(room):
            raise ChatError(400, "bad room (want [a-z0-9-]{1,32})")
        with self._lock:
            if room in self._rooms:
                raise ChatError(409, "room exists")
            if len(self._rooms) >= self.MAX_ROOMS:
                raise ChatError(507, "too many rooms")
            self._rooms[room] = {"messages": deque(maxlen=self.MAX_HISTORY),
                                 "next_id": 1}
            return {"room": room, "messages": 0}

    def _require(self, room):
        if room not in self._rooms:
            raise ChatError(404, "no such room")
        return self._rooms[room]

    def history(self, room, since=0, limit=100):
        with self._lock:
            info = self._require(room)
            items = [m for m in info["messages"] if m["id"] > since]
            return items[-limit:]

    def post(self, room, nick, text):
        if not isinstance(nick, str) or not 1 <= len(nick.strip()) <= 32:
            raise ChatError(400, "nick must be 1..32 chars")
        if not isinstance(text, str) or not 1 <= len(text.strip()) <= 2000:
            raise ChatError(400, "text must be 1..2000 chars")
        with self._lock:
            info = self._require(room)
            msg = {"id": info["next_id"], "room": room,
                   "nick": nick.strip()[:32], "text": text.strip()[:2000],
                   "ts": self._now()}
            info["next_id"] += 1
            info["messages"].append(msg)
            subs = list(self._subs.get(room, []))
        for queue in subs:
            try:
                queue.put_nowait(msg)
            except Exception:
                pass
        return msg

    def subscribe(self, room):
        with self._lock:
            self._require(room)
            total = sum(len(v) for v in self._subs.values())
            if total >= self.MAX_SUBSCRIBERS:
                raise ChatError(503, "too many subscribers")
            queue = Queue(maxsize=200)
            self._subs.setdefault(room, []).append(queue)
            return queue

    def unsubscribe(self, room, queue):
        with self._lock:
            subs = self._subs.get(room, [])
            if queue in subs:
                subs.remove(queue)


class ChatHandler(BaseHTTPRequestHandler):
    server_version = "TaiChat/1.0"
    protocol_version = "HTTP/1.1"
    MAX_BODY = 8 * 1024
    HEARTBEAT = 15

    def log_message(self, fmt, *args):
        pass

    def _send(self, code, body=b"", ctype="text/plain; charset=utf-8"):
        if isinstance(body, str):
            body = body.encode("utf-8")
        self.send_response(code)
        self.send_header("Content-Type", ctype)
        self.send_header("Content-Length", str(len(body)))
        self.end_headers()
        if self.command != "HEAD" and body:
            self.wfile.write(body)

    def _json(self, code, obj):
        self._send(code, json.dumps(obj), "application/json")

    def _read_json(self):
        try:
            length = int(self.headers.get("Content-Length", "0") or "0")
        except ValueError:
            raise ChatError(400, "bad Content-Length")
        if length < 0 or length > self.MAX_BODY:
            raise ChatError(413, "body too large")
        raw = self.rfile.read(length) if length else b""
        try:
            data = json.loads((raw or b"{}").decode("utf-8"))
        except (UnicodeDecodeError, ValueError):
            raise ChatError(400, "body is not valid JSON")
        if not isinstance(data, dict):
            raise ChatError(400, "body must be a JSON object")
        return data

    def _events(self, room, since):
        store = self.server.chat  # type: ChatStore
        try:
            queue = store.subscribe(room)
        except ChatError as exc:
            self._json(exc.status, {"error": exc.message})
            return
        self.send_response(200)
        self.send_header("Content-Type", "text/event-stream")
        self.send_header("Cache-Control", "no-cache")
        self.send_header("Connection", "keep-alive")
        self.send_header("X-Accel-Buffering", "no")
        self.end_headers()
        try:
            self._sse("hello", {"room": room, "since": since})
            for msg in store.history(room, since=since, limit=200):
                self._sse("message", msg, msg["id"])
            while True:
                try:
                    msg = queue.get(timeout=self.HEARTBEAT)
                except Empty:
                    self.wfile.write(b": ping\n\n")
                    self.wfile.flush()
                    continue
                if msg["id"] <= since:
                    continue
                since = msg["id"]
                self._sse("message", msg, msg["id"])
        except (BrokenPipeError, ConnectionResetError, OSError):
            pass
        finally:
            store.unsubscribe(room, queue)

    def _sse(self, event, obj, msg_id=None):
        lines = ["event: %s" % event]
        if msg_id is not None:
            lines.append("id: %d" % msg_id)
        lines.append("retry: 3000")
        for chunk in json.dumps(obj).split("\n"):
            lines.append("data: %s" % chunk)
        self.wfile.write(("\n".join(lines) + "\n\n").encode("utf-8"))
        self.wfile.flush()

    def _handle(self):
        store = self.server.chat  # type: ChatStore
        parsed = urlparse(self.path)
        parts = [p for p in parsed.path.split("/") if p]
        method = self.command
        if not parts:
            if method != "GET":
                raise ChatError(405, "method not allowed")
            self._send(200, CHAT_HTML, "text/html; charset=utf-8")
            return
        if parts == ["healthz"]:
            rooms = store.rooms()
            self._json(200, {"ok": True, "rooms": len(rooms),
                             "messages": sum(r["messages"] for r in rooms)})
            return
        if parts == ["events"] and method == "GET":
            qs = parse_qs(parsed.query)
            room = qs.get("room", ["lobby"])[0]
            since = qs.get("since", ["0"])[0]
            last_id = self.headers.get("Last-Event-ID", "").strip()
            if last_id.isdigit():
                since = last_id
            try:
                since = max(0, int(since))
            except ValueError:
                raise ChatError(400, "bad since")
            self._events(room, since)
            return
        if parts[0] != "api" or len(parts) < 2 or parts[1] != "rooms":
            raise ChatError(404, "unknown endpoint")
        if len(parts) == 2:
            if method == "GET":
                self._json(200, {"rooms": store.rooms()})
            elif method == "POST":
                data = self._read_json()
                self._json(201, store.create_room(data.get("room", "")))
            else:
                raise ChatError(405, "method not allowed")
            return
        room = parts[2]
        if len(parts) == 4 and parts[3] == "messages":
            if method == "GET":
                qs = parse_qs(parsed.query)
                try:
                    since = max(0, int(qs.get("since", ["0"])[0]))
                    limit = min(max(int(qs.get("limit", ["100"])[0]), 1), 200)
                except ValueError:
                    raise ChatError(400, "bad since/limit")
                self._json(200, {"room": room, "messages": store.history(
                    room, since=since, limit=limit)})
            elif method == "POST":
                data = self._read_json()
                self._json(201, store.post(room, data.get("nick", ""),
                                           data.get("text", "")))
            else:
                raise ChatError(405, "method not allowed")
            return
        raise ChatError(404, "unknown endpoint")

    def _dispatch(self):
        try:
            self._handle()
        except ChatError as exc:
            self._json(exc.status, {"error": exc.message})
        except BrokenPipeError:
            pass

    do_GET = _dispatch
    do_HEAD = _dispatch
    do_POST = _dispatch


CHAT_HTML = """<!DOCTYPE html>
<html lang="nl"><head><meta charset="utf-8">
<meta name="viewport" content="width=device-width,initial-scale=1">
<title>Chat</title>
<style>
*{box-sizing:border-box}
body{font-family:system-ui,-apple-system,"Segoe UI",sans-serif;margin:0;
color:#1a1a1a;display:flex;height:100vh}
aside{width:12em;flex-shrink:0;border-right:1px solid #ddd;padding:1em;
overflow-y:auto}
aside h2{font-size:.85em;text-transform:uppercase;letter-spacing:.04em;
color:#666;margin:0 0 .6em}
aside ul{list-style:none;margin:0;padding:0}
aside li button{width:100%;text-align:left;padding:.5em .6em;border:none;
background:none;font-size:1em;border-radius:6px;cursor:pointer}
aside li button[aria-current=true]{background:#1a1a1a;color:#fff}
aside form{display:flex;gap:.4em;margin-top:.8em}
aside form input{flex:1;min-width:0;padding:.4em;font-size:.9em;
border:1px solid #ddd;border-radius:6px}
main{flex:1;display:flex;flex-direction:column;min-width:0}
header{padding:.7em 1em;border-bottom:1px solid #ddd;display:flex;
align-items:center;gap:.6em}
header h1{font-size:1.1em;margin:0}
header .status{font-size:.8em;color:#666;margin-left:auto}
.roomselect{display:none;padding:.6em 1em;border-bottom:1px solid #ddd}
.roomselect select{width:100%;padding:.5em;font-size:1em}
#log{flex:1;overflow-y:auto;padding:1em;margin:0;list-style:none}
#log li{margin-bottom:.55em;overflow-wrap:break-word}
#log .nick{font-weight:700}
#log .ts{color:#888;font-size:.8em;margin-left:.5em}
#log .sys{color:#666;font-style:italic}
form.send{display:flex;gap:.5em;padding:.8em;border-top:1px solid #ddd}
form.send input{padding:.6em;font-size:1em;border:1px solid #ddd;
border-radius:6px}
form.send #nick{width:7em;flex-shrink:0}
form.send #text{flex:1;min-width:0}
@media(max-width:40em){
  aside{display:none}
  .roomselect{display:block}
  form.send #nick{width:5em}
}
</style></head><body>
<aside><h2>Kamers</h2><ul id="rooms"></ul>
<form id="newroom"><input id="roomname" maxlength="32" placeholder="nieuwe-kamer"
pattern="[a-z0-9-]{1,32}"><button type="submit">+</button></form></aside>
<main>
<header><h1 id="title">#lobby</h1><span class="status" id="status">verbinden...</span></header>
<div class="roomselect"><select id="roompick" aria-label="Kamer"></select></div>
<ul id="log"></ul>
<form class="send" id="send"><input id="nick" maxlength="32" placeholder="naam"
autocomplete="off"><input id="text" maxlength="2000" placeholder="bericht..."
autocomplete="off"><button type="submit">Stuur</button></form>
</main>
<script>
"use strict";
var room="lobby",es=null,lastId=0;
function esc(s){return s.replace(/[&<>"]/g,function(c){
return {"&":"&amp;","<":"&lt;",">":"&gt;",'"':"&quot;"}[c];});}
function addMsg(m){
lastId=Math.max(lastId,m.id);
var li=document.createElement("li");
var d=new Date(m.ts.replace("Z","+00:00"));
var t=("0"+d.getHours()).slice(-2)+":"+("0"+d.getMinutes()).slice(-2);
li.innerHTML='<span class="nick">'+esc(m.nick)+"</span> "+
esc(m.text)+'<span class="ts">'+t+"</span>";
var log=document.getElementById("log");
log.appendChild(li);log.scrollTop=log.scrollHeight;}
function sys(t){var li=document.createElement("li");
li.innerHTML='<span class="sys">'+esc(t)+"</span>";
var log=document.getElementById("log");
log.appendChild(li);log.scrollTop=log.scrollHeight;}
function connect(){
if(es)es.close();
document.getElementById("log").innerHTML="";lastId=0;
document.getElementById("status").textContent="verbinden...";
es=new EventSource("events?room="+encodeURIComponent(room));
es.addEventListener("hello",function(){
document.getElementById("status").textContent="live";});
es.addEventListener("message",function(e){addMsg(JSON.parse(e.data));});
es.onerror=function(){
document.getElementById("status").textContent="opnieuw verbinden...";};}
function loadRooms(){
fetch("api/rooms").then(function(r){return r.json();}).then(function(d){
var ul=document.getElementById("rooms");ul.innerHTML="";
var pick=document.getElementById("roompick");pick.innerHTML="";
d.rooms.forEach(function(r){
var li=document.createElement("li");
var b=document.createElement("button");b.textContent="#"+r.room;
b.setAttribute("aria-current",r.room===room?"true":"false");
b.addEventListener("click",function(){setRoom(r.room);});
li.appendChild(b);ul.appendChild(li);
var o=document.createElement("option");o.value=r.room;
o.textContent="#"+r.room+" ("+r.messages+")";
if(r.room===room)o.selected=true;pick.appendChild(o);});});}
function setRoom(r){room=r;
document.getElementById("title").textContent="#"+r;connect();loadRooms();}
document.getElementById("roompick").addEventListener("change",function(e){
setRoom(e.target.value);});
document.getElementById("newroom").addEventListener("submit",function(e){
e.preventDefault();var i=document.getElementById("roomname");
if(!i.value)return;
fetch("api/rooms",{method:"POST",headers:{"Content-Type":"application/json"},
body:JSON.stringify({room:i.value})}).then(function(r){
if(r.ok){i.value="";loadRooms();}else{r.json().then(function(d){
alert(d.error);});}});});
document.getElementById("send").addEventListener("submit",function(e){
e.preventDefault();
var n=document.getElementById("nick"),t=document.getElementById("text");
if(!n.value.trim()||!t.value.trim())return;
fetch("api/rooms/"+encodeURIComponent(room)+"/messages",{method:"POST",
headers:{"Content-Type":"application/json"},
body:JSON.stringify({nick:n.value,text:t.value})}).then(function(r){
if(r.ok){t.value="";}else{r.json().then(function(d){sys(d.error);});}});});
loadRooms();connect();
setInterval(loadRooms,30000);
</script></body></html>
"""


class ChatServer(socketserver.ThreadingMixIn, HTTPServer):
    daemon_threads = True
    allow_reuse_address = True


def main(argv=None):
    parser = argparse.ArgumentParser(
        description="Multi-room SSE chat (stdlib only).")
    parser.add_argument("--host", default="127.0.0.1")
    parser.add_argument("--port", type=int, default=8082)
    args = parser.parse_args(argv)
    server = ChatServer((args.host, args.port), ChatHandler)
    server.chat = ChatStore()
    print("chat: http://%s:%d/" % (args.host, args.port))
    try:
        server.serve_forever()
    except KeyboardInterrupt:
        pass


if __name__ == "__main__":
    main()