import { createLogger } from '@snowluma/common/logger';
import type { DownloadRKeyInfo } from '@snowluma/core/bridge';
import type { BridgeInterface } from '@snowluma/core/bridge-interface';
import type { MessageElement } from '@snowluma/protocol/events';
import type { RKeyConfig } from './types';

const log = createLogger('OneBot');

interface CachedRKey {
    value: string;
    expiresAt: number;
}

const RKEY_REFRESH_SKEW = 60;
const RKEY_REFRESH_COOLDOWN = 30;
// When the cache holds NO usable image rkey, the alternative to refreshing is
// handing out a bare URL the CDN rejects with `invalid rkey` (issue #156). So
// retry far more eagerly than the 30s steady-state backoff — but still throttled
// so a persistently-failing fetch isn't hammered once per inbound image.
const RKEY_EMPTY_COOLDOWN = 10;
// Upper bound on how long URL resolution may block on a refresh round-trip.
// A stuck packet send must never wedge message conversion — past this we
// fall back to whatever the cache holds (possibly nothing).
const RKEY_REFRESH_TIMEOUT_MS = 5000;
const PRIVATE_IMAGE_RKEY_TYPE = 10;
const GROUP_IMAGE_RKEY_TYPE = 20;
const PRIVATE_VIDEO_RKEY_TYPE = 12;
const GROUP_VIDEO_RKEY_TYPE = 22;
const PRIVATE_PTT_RKEY_TYPE = 14;
const GROUP_PTT_RKEY_TYPE = 24;
const FALLBACK_IMAGE_RKEY_TYPE = 2;

export class RKeyCache {
    private cache = new Map<number, CachedRKey>();
    private lastRefreshAttempt = 0;
    private refreshInflight: Promise<void> | null = null;
    /** Opt-in remote rkey endpoints; empty = feature off (the default). */
    private fallbackServers: string[];

    constructor(config?: RKeyConfig) {
        this.fallbackServers = config?.fallbackServers ?? [];
    }

    /** Replace the fallback endpoint list (global-config hot-reload). */
    setFallbackServers(servers: string[]): void {
        this.fallbackServers = servers;
    }

    warmUp(bridge: BridgeInterface, uin: string): void {
        this.ensureFresh(bridge).then(
            () => log.info('rkeys loaded: UIN=%s count=%d', uin, this.cache.size),
            (err) =>
                log.warn(
                    'failed to load rkeys for UIN %s: %s',
                    uin,
                    err instanceof Error ? err.message : String(err),
                ),
        );
    }

    resolveImageUrl(
        bridge: BridgeInterface,
        element: MessageElement,
        isGroup: boolean,
    ): Promise<string> {
        const url = element.imageUrl ?? '';
        // Forwarded images retain their upload scene, encoded by appid in the URL.
        const type =
            imageRKeyTypeFromUrl(url) ??
            (isGroup ? GROUP_IMAGE_RKEY_TYPE : PRIVATE_IMAGE_RKEY_TYPE);
        return this.resolveUrl(bridge, url, type);
    }

    resolveMediaUrl(
        bridge: BridgeInterface,
        element: MessageElement,
        isGroup: boolean,
    ): Promise<string> {
        let type: number;

        if (element.type === 'video') {
            type = isGroup ? GROUP_VIDEO_RKEY_TYPE : PRIVATE_VIDEO_RKEY_TYPE;
        } else if (element.type === 'record') {
            type = isGroup ? GROUP_PTT_RKEY_TYPE : PRIVATE_PTT_RKEY_TYPE;
        } else {
            type = isGroup ? GROUP_IMAGE_RKEY_TYPE : PRIVATE_IMAGE_RKEY_TYPE;
        }

        return this.resolveUrl(bridge, element.url ?? '', type);
    }

    private async resolveUrl(bridge: BridgeInterface, url: string, type: number): Promise<string> {
        if (!urlNeedsRKey(url)) {
            return url;
        }

        const rkey = await this.findRKeyForType(bridge, type);

        if (!rkey) {
            return url;
        }

        const separator = url.includes('?') ? '&rkey=' : '?rkey=';
        return url + separator + encodeURIComponent(stripRKeyPrefix(rkey));
    }

    private updateCache(rkeys: DownloadRKeyInfo[]): void {
        const now = Math.floor(Date.now() / 1000);

        for (const rk of rkeys) {
            if (!rk.rkey || !rk.type) {
                continue;
            }

            const baseTime = rk.createTime || now;
            const ttl = rk.ttlSeconds || 3600;
            this.cache.set(rk.type, {
                value: rk.rkey,
                expiresAt: baseTime + ttl,
            });
        }
    }

    /** True when at least one common image rkey (group or private) is cached and
     *  still valid — i.e. we can sign a typical image without a fresh fetch. */
    private hasUsableRkey(): boolean {
        return (
            this.findInCache(GROUP_IMAGE_RKEY_TYPE) !== null ||
            this.findInCache(PRIVATE_IMAGE_RKEY_TYPE) !== null
        );
    }

    /** Pull a still-valid rkey out of the cache, or null if missing/expiring. */
    private findInCache(primaryType: number): string | null {
        const now = Math.floor(Date.now() / 1000);

        const tryFind = (type: number): string | null => {
            const cached = this.cache.get(type);

            if (!cached || !cached.value) {
                return null;
            }

            if (cached.expiresAt !== 0 && now + RKEY_REFRESH_SKEW >= cached.expiresAt) {
                return null;
            }

            return cached.value;
        };

        return tryFind(primaryType) ?? tryFind(FALLBACK_IMAGE_RKEY_TYPE);
    }

    private async findRKeyForType(
        bridge: BridgeInterface,
        primaryType: number,
    ): Promise<string | null> {
        const cached = this.findInCache(primaryType);

        if (cached) {
            return cached;
        }

        // Cache miss or inside the expiry skew: block on a fresh fetch rather
        // than hand back a URL with a stale/absent rkey — the CDN rejects those
        // with `{"retcode":-5503010,"retmsg":"invalid rkey"}`. Mirrors NapCat's
        // getImageUrl path, which does `if (isExpired()) await refreshRkey()`
        // before building the URL instead of refreshing in the background.
        await this.ensureFresh(bridge);
        return this.findInCache(primaryType);
    }

    /**
     * Refresh the rkey cache via OIDB 0x9067_202, coalescing concurrent
     * callers onto one in-flight request and backing off (RKEY_REFRESH_COOLDOWN
     * when a usable rkey is held, RKEY_EMPTY_COOLDOWN while none is) so a
     * persistently-failing fetch isn't hammered once per inbound image. The await
     * is bounded by RKEY_REFRESH_TIMEOUT_MS.
     */
    private async ensureFresh(bridge: BridgeInterface): Promise<void> {
        if (!this.refreshInflight) {
            const now = Math.floor(Date.now() / 1000);
            // Back off hard once we hold a usable rkey; retry quickly while we don't,
            // so a transient empty/failed fetch self-heals in seconds, not 30s (#156).
            const cooldown = this.hasUsableRkey() ? RKEY_REFRESH_COOLDOWN : RKEY_EMPTY_COOLDOWN;

            if (now - this.lastRefreshAttempt < cooldown) {
                return;
            }

            this.lastRefreshAttempt = now;
            this.refreshInflight = this.runRefresh(bridge).finally(() => {
                this.refreshInflight = null;
            });
        }

        const inflight = this.refreshInflight;

        let timer: ReturnType<typeof setTimeout> | undefined;
        const timeout = new Promise<void>((resolve) => {
            timer = setTimeout(resolve, RKEY_REFRESH_TIMEOUT_MS);
        });

        try {
            await Promise.race([inflight, timeout]);
        } finally {
            clearTimeout(timer);
        }
    }

    /** One refresh round: native OIDB fetch, then — only if that left us without
     *  a usable image rkey AND fallback servers are configured — the remote
     *  fallback. Never throws; logs and degrades to whatever the cache holds. */
    private async runRefresh(bridge: BridgeInterface): Promise<void> {
        try {
            const rkeys = await bridge.apis.contacts.fetchDownloadRKeys();
            this.updateCache(rkeys);
        } catch (err) {
            log.warn('rkey refresh failed: %s', err instanceof Error ? err.message : String(err));
        }

        if (this.fallbackServers.length > 0 && !this.hasUsableRkey()) {
            await this.refreshFromFallback();
        }
    }

    /** Ask each configured fallback server in turn for an rkey, stopping at the
     *  first that yields one. Populates the group/private image rkey types. */
    private async refreshFromFallback(): Promise<void> {
        for (const server of this.fallbackServers) {
            try {
                const data = await fetchFallbackRkey(server);

                if (!data) {
                    continue;
                }

                const now = Math.floor(Date.now() / 1000);
                const expiresAt = data.expiredTime > now ? data.expiredTime : now + 3600;

                if (data.groupRkey) {
                    this.setFallbackRkey(GROUP_IMAGE_RKEY_TYPE, data.groupRkey, expiresAt);
                }

                if (data.privateRkey) {
                    this.setFallbackRkey(PRIVATE_IMAGE_RKEY_TYPE, data.privateRkey, expiresAt);
                }

                if (data.groupRkey || data.privateRkey) {
                    log.info('rkey loaded from fallback server %s', server);
                    return;
                }
            } catch (err) {
                log.warn(
                    'rkey fallback server %s failed: %s',
                    server,
                    err instanceof Error ? err.message : String(err),
                );
            }
        }
    }

    private setFallbackRkey(type: number, value: string, expiresAt: number): void {
        this.cache.set(type, { value, expiresAt });
    }
}

interface FallbackRkeyData {
    groupRkey: string;
    privateRkey: string;
    /** Absolute unix-seconds expiry (0 when the server omits it). */
    expiredTime: number;
}

/** Fetch + parse one fallback server's response. Accepts the bare
 *  `{ group_rkey, private_rkey, expired_time }` shape and an OneBot
 *  `{ retcode, data: {...} }` wrapper. Returns null when neither rkey is
 *  present. The stored values keep any leading `&rkey=`/`?rkey=` — resolveImageUrl
 *  strips it before re-appending, so both prefixed and bare tokens work. */
async function fetchFallbackRkey(server: string): Promise<FallbackRkeyData | null> {
    const res = await fetch(server, { signal: AbortSignal.timeout(RKEY_REFRESH_TIMEOUT_MS) });

    if (!res.ok) {
        throw new Error(`http ${res.status}`);
    }

    let body = (await res.json()) as Record<string, unknown>;

    if (body && typeof body === 'object' && 'retcode' in body && isRecord(body.data)) {
        body = body.data;
    }

    if (!isRecord(body)) {
        return null;
    }

    const groupRkey = typeof body.group_rkey === 'string' ? body.group_rkey : '';
    const privateRkey = typeof body.private_rkey === 'string' ? body.private_rkey : '';

    if (!groupRkey && !privateRkey) {
        return null;
    }

    const expiredTime = typeof body.expired_time === 'number' ? body.expired_time : 0;
    return { groupRkey, privateRkey, expiredTime };
}

function isRecord(value: unknown): value is Record<string, unknown> {
    return typeof value === 'object' && value !== null && !Array.isArray(value);
}

// QQ-NT download appids embedded in the image URL query string. The scene
// they encode is a property of the image (where it was uploaded), so they
// outrank the carrying message's group/private context — see resolveImageUrl.
const APPID_PRIVATE_IMAGE = '1406';
const APPID_GROUP_IMAGE = '1407';

/** Map the `appid` baked into an NT download URL to its rkey type. Returns
 *  null when the URL carries no recognised appid, leaving the caller to fall
 *  back to the message's group/private context. */
function imageRKeyTypeFromUrl(url: string): number | null {
    const match = url.match(/[?&]appid=(\d+)/);

    if (!match) {
        return null;
    }

    if (match[1] === APPID_PRIVATE_IMAGE) {
        return PRIVATE_IMAGE_RKEY_TYPE;
    }

    if (match[1] === APPID_GROUP_IMAGE) {
        return GROUP_IMAGE_RKEY_TYPE;
    }

    return null;
}

function urlNeedsRKey(url: string): boolean {
    if (!url || url.includes('rkey=')) {
        return false;
    }

    if (url.includes('gchat.qpic.cn')) {
        return false;
    }

    return (
        url.includes('multimedia.nt.qq.com.cn') ||
        url.includes('.nt.qq.com.cn') ||
        url.includes('/download')
    );
}

function stripRKeyPrefix(rkey: string): string {
    for (const prefix of ['&rkey=', '?rkey=']) {
        if (rkey.startsWith(prefix)) {
            return rkey.slice(prefix.length);
        }
    }

    return rkey;
}