/*
 * Copyright (C) 2026 Mateusz Gruszczyński @linuxiarz.pl
 * Source-Available Code / Dual-Licensed.
 * 
 * Free for non-commercial and evaluation use under terms of BSL/GPLv3.
 * Commercial or production use requires a valid paid license.
 * See LICENSE file in repository root for details.
 */

import { logError, logInfo, logWarn } from "@rustpad/logger";

const DEFAULT_HEARTBEAT_INTERVAL_MS = 10000;
const DEFAULT_HEARTBEAT_TIMEOUT_MS = 30000;
const DEFAULT_MAX_RECONNECT_DELAY_MS = 12000;
const DEFAULT_LATENCY_SAMPLE_WINDOW = 20;

class RoomSocket {
  constructor(options) {
    Object.assign(this, options);
    this.socket = null;
    this.reconnectTimer = null;
    this.pingTimer = null;
    this.stopped = false;
    this.intentionalClose = false;
    this.reconnectAttempt = 0;
    this.pendingPings = new Map();
    this.heartbeatIntervalMs = DEFAULT_HEARTBEAT_INTERVAL_MS;
    this.heartbeatTimeoutMs = DEFAULT_HEARTBEAT_TIMEOUT_MS;
    this.maxReconnectDelayMs = DEFAULT_MAX_RECONNECT_DELAY_MS;
    this.latencySampleWindow = DEFAULT_LATENCY_SAMPLE_WINDOW;
    this.latencySamples = [];
    this.totalReconnects = 0;
    this.authenticatedAt = null;
    this.lastConnectionUptimeMs = 0;
    this.lastMessageAt = null;
    this.lastClose = null;
    this.bytesSent = 0;
    this.bytesReceived = 0;
    this.serverDiagnostics = null;
    this.diagnosticsTimer = null;
    this.handleOnline = () => this.reconnectNow("Network connection restored.");
    this.handleOffline = () => this.handleNetworkOffline();
    this.handleVisibility = () => this.checkHeartbeat();
    window.addEventListener("online", this.handleOnline);
    window.addEventListener("offline", this.handleOffline);
    document.addEventListener("visibilitychange", this.handleVisibility);
  }

  get url() { throw new Error("Socket URL not implemented"); }
  get kind() { return "room"; }

  clientDiagnostics() {
    return {
      language: navigator.language || null,
      timezone: Intl.DateTimeFormat().resolvedOptions().timeZone || null,
      platform: navigator.userAgentData?.platform || navigator.platform || null,
    };
  }

  connect() {
    clearTimeout(this.reconnectTimer);
    clearInterval(this.pingTimer);
    clearInterval(this.diagnosticsTimer);
    if (this.stopped) return;
    if (!navigator.onLine) {
      this.scheduleReconnect("Your device is offline.");
      return;
    }

    this.intentionalClose = false;
    this.onStatus?.(this.reconnectAttempt ? "reconnecting" : "connecting", {
      attempt: this.reconnectAttempt,
      message: this.reconnectAttempt ? "Re-establishing the live connection." : "Opening the live connection.",
    });
    this.emitDiagnostics();

    let socket;
    try {
      socket = new WebSocket(this.url);
    } catch (error) {
      logError("websocket.create", error, { kind: this.kind });
      this.scheduleReconnect("The live connection could not be opened.");
      return;
    }
    this.socket = socket;

    socket.addEventListener("open", () => {
      if (socket !== this.socket || this.stopped) return;
      logInfo("websocket.open", { kind: this.kind });
      this.serverDiagnostics = null;
      this.lastClose = null;
      this.send({
        type: "authenticate",
        password: this.password || null,
        access_token: this.accessToken || null,
        nickname: this.nickname || null,
        guest_id: this.guestId || null,
        color: this.color || null,
        diagnostics: this.clientDiagnostics(),
        client_id: this.clientId || null,
        known_revision_id: this.getKnownRevision?.() ?? null,
      });
      this.emitDiagnostics();
    });

    socket.addEventListener("message", event => {
      if (socket !== this.socket || this.stopped) return;
      let message;
      try { message = JSON.parse(event.data); } catch { return; }
      this.lastMessageAt = Date.now();
      this.bytesReceived += typeof event.data === "string" ? new Blob([event.data]).size : Number(event.data?.byteLength || 0);
      if (message.type === "password_required") {
        this.intentionalClose = true;
        this.onPasswordRequired?.();
        socket.close();
        return;
      }
      if (message.type === "password_changed") {
        this.intentionalClose = true;
        socket.close();
        return;
      }
      if (message.type === "error") {
        this.intentionalClose = true;
        this.onError?.(message.message);
        socket.close();
        return;
      }
      if (message.type === "authenticated") {
        const restored = this.reconnectAttempt > 0;
        this.reconnectAttempt = 0;
        this.authenticatedAt = Date.now();
        this.latencySamples = [];
        this.onStatus?.("online", { restored });
        this.onAuthenticated?.(message);
        this.startPing();
        this.startDiagnostics();
        this.emitDiagnostics();
        return;
      }
      if (message.type === "diagnostics") {
        this.applyServerDiagnostics(message.diagnostics || {});
        return;
      }
      if (message.type === "document") this.onDocument?.(message);
      if (message.type === "resync") this.onResync?.(message);
      if (message.type === "presence") this.onPresence?.(message.users || []);
      if (message.type === "chat") this.onChat?.(message);
      if (message.type === "pong") {
        const started = this.pendingPings.get(message.nonce);
        if (started !== undefined) {
          this.pendingPings.delete(message.nonce);
          const latency = Math.max(0, Math.round(performance.now() - started));
          this.latencySamples.push(latency);
          while (this.latencySamples.length > this.latencySampleWindow) this.latencySamples.shift();
          this.onLatency?.(latency);
          this.emitDiagnostics();
        }
      }
    });

    socket.addEventListener("close", event => {
      if (socket !== this.socket) return;
      clearInterval(this.pingTimer);
      clearInterval(this.diagnosticsTimer);
      this.pendingPings.clear();
      this.onPresence?.([]);
      this.onLatency?.(null);
      const closedAt = Date.now();
      this.lastConnectionUptimeMs = this.authenticatedAt ? Math.max(0, closedAt - this.authenticatedAt) : this.lastConnectionUptimeMs;
      this.authenticatedAt = null;
      this.lastClose = { code: event.code, reason: event.reason || "", at: closedAt };
      this.emitDiagnostics();
      logWarn("websocket.close", {
        kind: this.kind,
        code: event.code,
        reason: event.reason || "",
        intentional: this.intentionalClose || this.stopped,
      });
      if (!this.intentionalClose && !this.stopped) {
        this.scheduleReconnect(this.closeMessage(event));
      }
    });

    socket.addEventListener("error", event => {
      if (socket !== this.socket || this.stopped) return;
      logError("websocket.error", event, { kind: this.kind });
      if (socket.readyState !== WebSocket.CLOSING && socket.readyState !== WebSocket.CLOSED) {
        socket.close();
      }
    });
  }

  closeMessage(event) {
    if (!navigator.onLine) return "Your device is offline.";
    if (event.reason === "heartbeat timeout") return "The connection stopped responding after the tab was inactive.";
    return "The server connection was interrupted.";
  }

  scheduleReconnect(message) {
    if (this.stopped) return;
    clearTimeout(this.reconnectTimer);
    this.reconnectAttempt += 1;
    const baseDelay = Math.min(this.maxReconnectDelayMs, 750 * (2 ** Math.min(this.reconnectAttempt - 1, 4)));
    const retryInMs = navigator.onLine ? baseDelay : 3000;
    this.totalReconnects += 1;
    this.onStatus?.("reconnecting", { attempt: this.reconnectAttempt, message, retryInMs });
    this.emitDiagnostics();
    this.reconnectTimer = window.setTimeout(() => this.connect(), retryInMs);
  }

  reconnectNow(message) {
    if (this.stopped || this.socket?.readyState === WebSocket.OPEN || this.socket?.readyState === WebSocket.CONNECTING) return;
    clearTimeout(this.reconnectTimer);
    this.onStatus?.("reconnecting", { attempt: this.reconnectAttempt, message, retryInMs: 0 });
    this.connect();
  }

  handleNetworkOffline() {
    if (this.stopped) return;
    this.onStatus?.("reconnecting", { attempt: this.reconnectAttempt + 1, message: "Your device is offline.", retryInMs: 3000 });
    if (this.socket?.readyState === WebSocket.OPEN || this.socket?.readyState === WebSocket.CONNECTING) {
      this.socket.close();
    } else {
      this.scheduleReconnect("Your device is offline.");
    }
  }

  checkHeartbeat() {
    if (this.stopped || this.socket?.readyState !== WebSocket.OPEN) return;
    const now = performance.now();
    const expired = [...this.pendingPings.values()].some(started => now - started >= this.heartbeatTimeoutMs);
    if (expired) {
      logWarn("websocket.heartbeat_timeout", { kind: this.kind });
      this.socket.close(4000, "heartbeat timeout");
    }
  }

  startPing() {
    clearInterval(this.pingTimer);
    const ping = () => {
      this.checkHeartbeat();
      if (this.socket?.readyState !== WebSocket.OPEN) return;
      const nonce = Date.now();
      this.pendingPings.set(nonce, performance.now());
      this.send({ type: "ping", nonce });
    };
    ping();
    this.pingTimer = window.setInterval(ping, this.heartbeatIntervalMs);
  }

  startDiagnostics() {
    clearInterval(this.diagnosticsTimer);
    this.diagnosticsTimer = window.setInterval(() => this.emitDiagnostics(), 1000);
  }

  applyServerDiagnostics(diagnostics) {
    this.serverDiagnostics = diagnostics;
    const positiveNumber = (value, fallback, min, max) => {
      const parsed = Number(value);
      return Number.isFinite(parsed) && parsed >= min && parsed <= max ? parsed : fallback;
    };
    this.heartbeatIntervalMs = positiveNumber(diagnostics.heartbeat_interval_ms, this.heartbeatIntervalMs, 1000, 120000);
    this.heartbeatTimeoutMs = positiveNumber(diagnostics.heartbeat_timeout_ms, this.heartbeatTimeoutMs, this.heartbeatIntervalMs * 2, 300000);
    this.maxReconnectDelayMs = positiveNumber(diagnostics.max_reconnect_delay_ms, this.maxReconnectDelayMs, 1000, 120000);
    this.latencySampleWindow = Math.round(positiveNumber(diagnostics.latency_sample_window, this.latencySampleWindow, 3, 100));
    while (this.latencySamples.length > this.latencySampleWindow) this.latencySamples.shift();
    if (this.socket?.readyState === WebSocket.OPEN && this.authenticatedAt) this.startPing();
    this.emitDiagnostics();
  }

  latencyStats() {
    if (!this.latencySamples.length) return { current: null, average: null, minimum: null, maximum: null, jitter: null, quality: "unknown" };
    const samples = this.latencySamples;
    const current = samples.at(-1);
    const average = Math.round(samples.reduce((sum, value) => sum + value, 0) / samples.length);
    const minimum = Math.min(...samples);
    const maximum = Math.max(...samples);
    const differences = samples.slice(1).map((value, index) => Math.abs(value - samples[index]));
    const jitter = differences.length ? Math.round(differences.reduce((sum, value) => sum + value, 0) / differences.length) : 0;
    const thresholds = this.serverDiagnostics?.quality_thresholds || {};
    const excellent = Number(thresholds.excellent_max_ms ?? 100);
    const good = Number(thresholds.good_max_ms ?? 250);
    const degraded = Number(thresholds.degraded_max_ms ?? 600);
    const quality = current <= excellent ? "excellent" : current <= good ? "good" : current <= degraded ? "degraded" : "poor";
    return { current, average, minimum, maximum, jitter, quality };
  }

  emitDiagnostics() {
    const readyStates = ["connecting", "open", "closing", "closed"];
    this.onDiagnostics?.({
      server: this.serverDiagnostics,
      runtime: {
        state: readyStates[this.socket?.readyState ?? WebSocket.CLOSED] || "closed",
        visibility: document.visibilityState,
        uptime_ms: this.authenticatedAt ? Math.max(0, Date.now() - this.authenticatedAt) : 0,
        last_connection_uptime_ms: this.lastConnectionUptimeMs,
        reconnect_attempt: this.reconnectAttempt,
        total_reconnects: this.totalReconnects,
        authenticated_at: this.authenticatedAt,
        last_message_at: this.lastMessageAt,
        last_close: this.lastClose,
        buffered_amount: this.socket?.bufferedAmount || 0,
        bytes_sent: this.bytesSent,
        bytes_received: this.bytesReceived,
        latency: this.latencyStats(),
      },
    });
  }

  send(message) {
    if (this.socket?.readyState !== WebSocket.OPEN) return false;
    const payload = JSON.stringify(message);
    this.bytesSent += new Blob([payload]).size;
    this.socket.send(payload);
    return true;
  }

  update(baseRevisionId, updateId, operation, ownerReplacements = []) {
    return this.send({
      type: "update",
      base_revision_id: baseRevisionId,
      update_id: updateId,
      operation,
      owner_replacements: ownerReplacements,
    });
  }
  chat(text) { this.send({ type: "chat", text }); }
  setColor(color) { this.color = color || null; this.send({ type: "set_color", color: this.color }); }

  stop() {
    this.stopped = true;
    this.intentionalClose = true;
    clearTimeout(this.reconnectTimer);
    clearInterval(this.pingTimer);
    clearInterval(this.diagnosticsTimer);
    window.removeEventListener("online", this.handleOnline);
    window.removeEventListener("offline", this.handleOffline);
    document.removeEventListener("visibilitychange", this.handleVisibility);
    this.socket?.close();
  }
}

export class NoteSocket extends RoomSocket {
  get kind() { return "note"; }
  get url() { const p = location.protocol === "https:" ? "wss:" : "ws:"; return `${p}//${location.host}/ws/${encodeURIComponent(this.workspaceSlug)}/${encodeURIComponent(this.noteSlug)}`; }
}

export class PadSocket extends RoomSocket {
  get kind() { return "pad"; }
  get url() { const p = location.protocol === "https:" ? "wss:" : "ws:"; return `${p}//${location.host}/ws/p/${encodeURIComponent(this.slug)}`; }
}