app-template/packages/trpc/src/services/danmaku.service.ts

import { createHash } from "node:crypto";
import { danmakuCacheDao, mediaItemDao, mountDao } from "@app/dao";
import type { DanmakuFetchOutput } from "@app/types";
import { decryptSecret } from "./secret.js";
import { createWebdav } from "./webdav-client.js";

const CACHE_TTL_MS = 24 * 60 * 60 * 1000;
/** 官方文件识别 hash：文件前 16MB 的 MD5（doc.dandanplay.com/open） */
const HASH_HEAD_BYTES = 16 * 1024 * 1024;

type OpenComment = {
    p?: string;
    m?: string;
    text?: string;
    mode?: number;
    time?: number;
};

function openApiBase(): string {
    return (process.env["OPEN_DANMAKU_API_BASE"] ?? "https://api.dandanplay.net").replace(
        /\/+$/,
        "",
    );
}

function openCredentials(): { appId: string; appSecret: string } | null {
    const appId = process.env["OPEN_DANMAKU_APP_ID"];
    const appSecret = process.env["OPEN_DANMAKU_APP_SECRET"];
    if (!appId || !appSecret) return null;
    return { appId, appSecret };
}

/** 官方签名：base64(sha256(AppId + Timestamp + Path + AppSecret)) */
export function generateOpenSignature(
    appId: string,
    timestamp: number,
    path: string,
    appSecret: string,
): string {
    return createHash("sha256").update(`${appId}${timestamp}${path}${appSecret}`).digest("base64");
}

/** 文件头部 MD5（样本应已截到 16MB 内） */
export function headMd5(sample: Buffer): string {
    return createHash("md5").update(sample).digest("hex");
}

function escapeXml(s: string): string {
    return s
        .replace(/&/g, "&")
        .replace(/</g, "&lt;")
        .replace(/>/g, "&gt;")
        .replace(/"/g, "&quot;");
}

/** 开放网络 comments → Bilibili 式 XML（`<d p="time,mode,0,0">text</d>`） */
export function openCommentsToXml(comments: OpenComment[]): string {
    const nodes: string[] = [];
    for (const c of comments) {
        let time = Number.NaN;
        let mode = 1;
        let text = "";
        if (typeof c.p === "string") {
            const [t, m] = c.p.split(",");
            time = Number(t);
            mode = Number(m) || 1;
            text = c.m ?? "";
        } else {
            time = Number(c.time);
            mode = Number(c.mode) || 1;
            text = c.text ?? c.m ?? "";
        }
        if (!Number.isFinite(time) || !text) continue;
        nodes.push(`<d p="${time},${mode},0,0">${escapeXml(text)}</d>`);
    }
    return `<?xml version="1.0" encoding="UTF-8"?><i>${nodes.join("")}</i>`;
}

function openHeaders(path: string): Record<string, string> {
    const creds = openCredentials();
    if (!creds) return {};
    const timestamp = Math.floor(Date.now() / 1000);
    return {
        "Content-Type": "application/json",
        "X-AppId": creds.appId,
        "X-Timestamp": String(timestamp),
        "X-Signature": generateOpenSignature(creds.appId, timestamp, path, creds.appSecret),
    };
}

function matchKeyFor(path: string, size: number): string {
    return createHash("sha256").update(`${path}:${size}`).digest("hex");
}

/** 取 WebDAV 文件前 16MB 的 MD5（开放网络文件识别用） */
async function remoteFileHash(userId: string, mediaId: string): Promise<string | null> {
    const item = await mediaItemDao.getByIdForUser(mediaId, userId);
    if (!item?.mountId) return null;
    const mount = await mountDao.getByIdForUser(item.mountId, userId);
    if (!mount) return null;
    const client = createWebdav({
        baseUrl: mount.baseUrl,
        username: mount.username ?? undefined,
        password: mount.secretEnc ? decryptSecret(mount.secretEnc) : undefined,
    });
    try {
        const abs = mount.rootPath.replace(/\/+$/, "") + item.path;
        const stream = client.createReadStream(abs, {
            range: { start: 0, end: HASH_HEAD_BYTES - 1 },
        });
        const sample = await new Promise<Buffer>((resolve, reject) => {
            const chunks: Buffer[] = [];
            stream.on("data", (chunk: Buffer) => {
                chunks.push(Buffer.isBuffer(chunk) ? chunk : Buffer.from(String(chunk)));
            });
            stream.on("end", () => resolve(Buffer.concat(chunks)));
            stream.on("error", reject);
        });
        return headMd5(sample.subarray(0, HASH_HEAD_BYTES));
    } catch {
        return null;
    }
}

async function fetchOpenNetworkXml(
    path: string,
    size: number,
    hash: string | null,
): Promise<string | null> {
    const base = openApiBase();
    const matchPath = "/api/v2/match";
    try {
        const matchRes = await fetch(`${base}${matchPath}`, {
            method: "POST",
            headers: openHeaders(matchPath),
            body: JSON.stringify({
                fileName: path.split("/").pop() ?? path,
                fileHash: hash ?? "",
                fileSize: size,
                matchMode: hash ? "hashAndFileName" : "fileNameOnly",
            }),
        });
        if (!matchRes.ok) return null;
        const matched = (await matchRes.json()) as {
            isMatched?: boolean;
            success?: boolean;
            matches?: Array<{ episodeId?: number | string }>;
        };
        if (matched.success === false) return null;
        const episodeId = matched.matches?.[0]?.episodeId;
        if (!episodeId || !matched.isMatched) return null;

        const commentPath = `/api/v2/comment/${episodeId}`;
        const commentRes = await fetch(`${base}${commentPath}?withRelated=true`, {
            headers: openHeaders(commentPath),
        });
        if (!commentRes.ok) return null;
        const body = (await commentRes.json()) as { comments?: OpenComment[] };
        const comments = body.comments ?? [];
        return openCommentsToXml(comments);
    } catch {
        return null;
    }
}

export const danmakuService = {
    async fetch(userId: string, mediaItemId: string): Promise<DanmakuFetchOutput> {
        const item = await mediaItemDao.getByIdForUser(mediaItemId, userId);
        if (!item) return { ok: false, source: "none", xml: "", message: "媒体不存在" };

        if (!openCredentials()) {
            return { ok: true, source: "none", xml: "", message: "未配置开放网络" };
        }

        const matchKey = matchKeyFor(item.path, item.size);
        const cached = await danmakuCacheDao.getValid(matchKey);
        if (cached) {
            return { ok: true, source: "cache", xml: cached.payload };
        }

        const hash = await remoteFileHash(userId, mediaItemId);
        const xml = await fetchOpenNetworkXml(item.path, item.size, hash);
        if (xml === null) {
            return { ok: true, source: "none", xml: "", message: "开放网络未匹配到弹幕" };
        }
        await danmakuCacheDao.upsert({
            matchKey,
            payload: xml,
            source: "open-network",
            expiresAt: new Date(Date.now() + CACHE_TTL_MS),
        });
        return { ok: true, source: "open-network", xml };
    },

    /** 本地 XML 由前端解析后直接喂播放器；此处仅确认媒体存在并记 size 日志约束 */
    async importMeta(userId: string, mediaItemId: string, byteSize: number): Promise<{ ok: true }> {
        const item = await mediaItemDao.getByIdForUser(mediaItemId, userId);
        if (!item) return Promise.reject(new Error("媒体不存在"));
        if (byteSize > 20_000_000) return Promise.reject(new Error("XML 过大"));
        return { ok: true };
    },
};