dc-recorder/src/muxer.ts

import fs from "fs";
import path from "path";
import ffmpeg from "fluent-ffmpeg";

const recordingsDir = process.env.RECORDINGS_DIR ?? "./recordings";

interface EventMetadata {
    userId: string;
    username: string;
    tag: string;
    startTime: number;
    endTime: number;
    durationMs: number;
    filename: string;
}

interface ClipInfo {
    oggPath: string;
    jsonPath: string;
    meta: EventMetadata;
}

async function startMuxing() {
    console.log("[muxer] Scanning recordings directory...");
    if (!fs.existsSync(recordingsDir)) {
        console.error("[muxer] Recordings directory not found.");
        return;
    }

    const clips: ClipInfo[] = [];

    // Scan user directories
    const items = fs.readdirSync(recordingsDir);
    console.log(`[muxer] Found ${items.length} directories to scan...`);
    
    let processedDirs = 0;
    for (const item of items) {
        const itemPath = path.join(recordingsDir, item);
        if (fs.statSync(itemPath).isDirectory()) {
            const files = fs.readdirSync(itemPath);
            for (const file of files) {
                if (file.endsWith(".json")) {
                    const jsonPath = path.join(itemPath, file);
                    const oggPath = jsonPath.replace(/\.json$/, ".ogg");
                    if (fs.existsSync(oggPath)) {
                        try {
                            // Check if OGG file is valid (not empty and has reasonable size)
                            const oggStats = fs.statSync(oggPath);
                            if (oggStats.size === 0) {
                                console.warn(`[muxer] Skipping empty OGG file: ${oggPath}`);
                                continue;
                            }
                            
                            // Skip files that are too small (less than 1KB likely corrupted)
                            if (oggStats.size < 1024) {
                                console.warn(`[muxer] Skipping too small OGG file (${oggStats.size} bytes): ${oggPath}`);
                                continue;
                            }
                            
                            // Check if OGG file has valid header (starts with "OggS")
                            const oggBuffer = fs.readFileSync(oggPath);
                            const oggHeader = oggBuffer.slice(0, 4).toString();
                            if (oggHeader !== "OggS") {
                                console.warn(`[muxer] Skipping invalid OGG file (bad header): ${oggPath}`);
                                continue;
                            }
                            
                            const meta: EventMetadata = JSON.parse(fs.readFileSync(jsonPath, "utf-8"));
                            clips.push({ oggPath, jsonPath, meta });
                        } catch (e) {
                            console.error(`[muxer] Failed to read/parse JSON: ${jsonPath}`, e);
                        }
                    }
                }
            }
            processedDirs++;
            const progress = ((processedDirs / items.length) * 100).toFixed(2);
            console.log(`[muxer] Scanning progress: ${progress}% (${processedDirs}/${items.length} directories)`);
        }
    }

    if (clips.length === 0) {
        console.log("[muxer] No recording clips found to mux.");
        return;
    }

    // Sort by startTime so chronologically they are in order
    clips.sort((a, b) => a.meta.startTime - b.meta.startTime);

    // Find the global start time
    const globalStartTime = clips[0].meta.startTime;
    console.log(`[muxer] Found ${clips.length} clips. Base timestamp: ${globalStartTime}`);

    const command = ffmpeg();
    const filterParts: string[] = [];

    console.log(`[muxer] Creating audio filters for ${clips.length} clips...`);
    clips.forEach((clip, index) => {
        command.input(clip.oggPath);

        // Calculate delay relative to the global start time
        const delayMs = clip.meta.startTime - globalStartTime;

        // FFmpeg filter structure: [0:a]adelay=1000|1000[a0]
        // Setting adelay multiple times covers stereo channels.
        // We ensure all multiple channels get delayed.
        const inputSpecifier = `[${index}:a]`;
        const outputSpecifier = `[pad${index}]`;

        filterParts.push(`${inputSpecifier}adelay=${delayMs}|${delayMs}${outputSpecifier}`);
        
        const progress = (((index + 1) / clips.length) * 100).toFixed(2);
        console.log(`[muxer] Filter creation progress: ${progress}% (${index + 1}/${clips.length} clips)`);
    });

    // Merge them using amix
    const amixInputs = clips.map((_, i) => `[pad${i}]`).join("");
    // We add the amix command. dropout_transition=0 avoids volume drop when streams end.
    filterParts.push(`${amixInputs}amix=inputs=${clips.length}:dropout_transition=0[out]`);

    const outputFilename = path.join(recordingsDir, `muxed-${Date.now()}.mp3`);

    console.log(`[muxer] Combining clips. This might take a while...`);

    // Using fluent-ffmpeg's complexFilter
    command
        .complexFilter(filterParts, "out")
        .audioCodec("libmp3lame")
        .save(outputFilename)
        .on("progress", (progress) => {
            if (progress.percent) {
                console.log(`[muxer] Progress: ${progress.percent.toFixed(2)}%`);
            }
        })
        .on("end", () => {
            console.log(`[muxer] Successfully muxed! Output saved to: ${outputFilename}`);
        })
        .on("error", (err) => {
            console.error(`[muxer] FFmpeg Error:`, err);
        });
}

startMuxing();