import { writable, readonly, get } from 'svelte/store';
import { browser } from '$app/environment';
import type { GameTelemetry } from '$lib/telemetry.js';

export const telemetryByServer = writable<Map<string, GameTelemetry>>(new Map());
export const matchEventsByServer = writable<Map<string, GameTelemetry>>(new Map());

export type { StatusPlayer as RosterPlayer } from '$lib/server-observation.js';
import type { StatusPlayer as RosterPlayer, GameObservation } from '$lib/server-observation.js';

export type Health = 'online' | 'stale' | 'offline' | 'starting' | 'provisioning';
export type RconFailure = 'no-config' | 'no-port' | 'send-error' | 'timeout' | 'bad-reply' | 'no-players';

export interface RconEndpoint {
    host: string;
    port: number;
}

export interface ServerStatus {
    receivedAt?: number;
    server: string;
    containerState?: string | null;
    containerCheckedAt?: string | null;
    telemetryAfter?: string | null;
    rconStatus?: GameObservation;
    telemetry?: GameTelemetry;
    players: number | null;
    map: string | null;
    gametype: string | null;
    roster: RosterPlayer[] | null;
    health: Health;
    lastSeenAt: string | null;
    lastError: string | null;
    endpoint: RconEndpoint | null;
    reason: RconFailure | null;
    replySnippet: string | null;
    activeSince: string | null;
    inactiveSince: string | null;
    gameStartedAt: string | null;
    gameEndedAt: string | null;
}

export const statusByServer = writable<Map<string, ServerStatus>>(new Map());
export const statusReceivedAt = writable(0);

// Shared 1s ticker for elapsed-time displays. One interval feeds every card
// on the page instead of N per-card timers. Timer starts on the first
// startServerStream() call in the browser.
const _uiNow = writable(Date.now());
export const uiNow = readonly(_uiNow);
let serverClock: { time: number; receivedAt: number } | null = null;

// Report timestamps belong to the backend clock, which can differ from the
// browser's wall clock. Advance that clock locally even if updates stop.
export function serverTimeNow(): number {
    return serverClock ? serverClock.time + performance.now() - serverClock.receivedAt : Date.now();
}

function updateServerClock(serverNow?: number): void {
    if (typeof serverNow === 'number' && Number.isFinite(serverNow)) {
        // A delayed HTTP snapshot must not rewind time behind a newer stream
        // update and make that update look like it came from the future.
        const time = serverClock ? Math.max(serverNow, serverTimeNow()) : serverNow;
        serverClock = { time, receivedAt: performance.now() };
    }
}

export function syncServerTime(serverNow?: number): void {
    updateServerClock(serverNow);
    // Refresh immediately: a suspended tab's interval may be well behind.
    _uiNow.set(serverTimeNow());
}

let tickInterval: ReturnType<typeof setInterval> | null = null;

let source: EventSource | null = null;

export function startServerStream(): (() => void) | undefined {
    if (!browser || source) return;
    syncServerTime();
    const stream = source = new EventSource('/api/events/servers');
    let stopped = false;
    let frame: number | null = null;
    let pendingStatus: Map<string, ServerStatus> | null = null;
    let pendingTelemetry: Map<string, GameTelemetry> | null = null;
    let pendingMatches: Map<string, GameTelemetry> | null = null;
    let receivedAt = 0;
    const flush = () => {
        frame = null;
        if (stopped) return;
        const statuses = pendingStatus, telemetry = pendingTelemetry, matches = pendingMatches;
        const statusAt = receivedAt;
        pendingStatus = pendingTelemetry = pendingMatches = null;
        // Publish the latest clock before exposing reports, including after a
        // suspended frame. Every changed store is published at most once per frame.
        syncServerTime();
        if (statuses) { statusByServer.set(statuses); statusReceivedAt.set(statusAt); }
        if (matches) matchEventsByServer.set(matches);
        if (telemetry) telemetryByServer.set(telemetry);
    };
    const schedule = () => { if (frame === null) frame = requestAnimationFrame(flush); };
    stream.addEventListener('server-telemetry', (evt) => {
        if (stopped) return;
        const data = JSON.parse((evt as MessageEvent).data) as { entries: GameTelemetry[]; snapshot?: boolean; serverNow?: number };
        updateServerClock(data.serverNow);
        // Merge into one private map per frame. Snapshots replace all earlier
        // evidence; later deltas still apply in arrival order.
        if (data.snapshot) {
            pendingTelemetry = new Map();
            pendingMatches = new Map();
        }
        pendingTelemetry ??= new Map(get(telemetryByServer));
        for (const entry of data.entries) {
            pendingTelemetry.set(entry.server, entry);
            if (entry.event === 'game_start' || entry.event === 'game_end') {
                pendingMatches ??= new Map(get(matchEventsByServer));
                pendingMatches.set(entry.server, entry);
            }
        }
        schedule();
    });
    stream.addEventListener('server-status', (evt) => {
        if (stopped) return;
        const data = JSON.parse((evt as MessageEvent).data) as { entries: ServerStatus[]; serverNow?: number; delta?: boolean };
        updateServerClock(data.serverNow);
        receivedAt = Date.now();
        if (!data.delta) pendingStatus = new Map();
        pendingStatus ??= new Map(get(statusByServer));
        for (const entry of data.entries) pendingStatus.set(entry.server, { ...entry, receivedAt });
        schedule();
    });
    if (tickInterval === null) {
        tickInterval = setInterval(() => { if (typeof document === 'undefined' || document.visibilityState !== 'hidden') _uiNow.set(serverTimeNow()); }, 1000);
    }
    return () => {
        if (stopped) return;
        stopped = true;
        if (frame !== null) cancelAnimationFrame(frame);
        pendingStatus = pendingTelemetry = pendingMatches = null;
        stream.close(); source = null;
        if (tickInterval) clearInterval(tickInterval);
        tickInterval = null;
    };
}