feat: on-demand preview generation with progress messages for non-native formats

apps/api/src/routes/file-preview.ts

@@ -5,8 +5,10 @@
  * and document files. Generates browser-playable H.264 MP4 (video),
  * MP3 (audio), or PDF (documents) previews and caches them on disk.
  */
+import { randomUUID } from "node:crypto";
 import { createReadStream } from "node:fs";
-import { access, copyFile, mkdir, rename, rm } from "node:fs/promises";
+import { access, copyFile, mkdir, readFile, rename, rm, writeFile } from "node:fs/promises";
+import { tmpdir } from "node:os";
 import { join } from "node:path";
 import { convertDocument, sofficeAvailable } from "@snapotter/doc-engine";
 import { runFfmpeg } from "@snapotter/media-engine";
@@ -16,7 +18,7 @@ import { env } from "../config.js";
 import { db, schema } from "../db/index.js";
 import { getStoredFilePath } from "../lib/file-storage.js";
 import { hasEffectivePermission } from "../permissions.js";
-import { requireAuth } from "../plugins/auth.js";
+import { getAuthUser, requireAuth } from "../plugins/auth.js";
 
 const PREVIEW_DIR = ".previews";
 let previewDirReady = false;
@@ -207,5 +209,142 @@ export async function filePreviewRoutes(app: FastifyInstance): Promise<void> {
     },
   );
 
+  // ── On-demand preview for uploaded (non-stored) media files ─────
+  app.post("/api/v1/preview/generate", async (request: FastifyRequest, reply: FastifyReply) => {
+    // Optional auth -- the preview is for the user's own uploaded file
+    getAuthUser(request);
+
+    const parts = request.parts();
+    let fileBuffer: Buffer | null = null;
+    let filename = "input";
+
+    for await (const part of parts) {
+      if (part.type !== "file") continue;
+      const chunks: Buffer[] = [];
+      for await (const chunk of part.file) {
+        chunks.push(chunk);
+      }
+      fileBuffer = Buffer.concat(chunks);
+      filename = part.filename ?? "input";
+      break; // only process the first file
+    }
+
+    if (!fileBuffer || fileBuffer.length === 0) {
+      return reply.status(400).send({ error: "No file provided" });
+    }
+
+    const ext = filename.split(".").pop()?.toLowerCase() ?? "";
+    const videoExts = new Set([
+      "avi",
+      "mkv",
+      "wmv",
+      "flv",
+      "mov",
+      "mpg",
+      "mpeg",
+      "m4v",
+      "3gp",
+      "3g2",
+      "ts",
+      "mts",
+      "m2ts",
+      "vob",
+      "divx",
+      "asf",
+      "rm",
+      "rmvb",
+      "f4v",
+      "ogv",
+      "mp4",
+      "webm",
+      "ogg",
+    ]);
+    const audioExts = new Set([
+      "wav",
+      "flac",
+      "aac",
+      "wma",
+      "ogg",
+      "oga",
+      "opus",
+      "m4a",
+      "aiff",
+      "aif",
+      "amr",
+      "ape",
+      "ac3",
+      "dts",
+      "mp3",
+    ]);
+
+    const isVideo = videoExts.has(ext);
+    const isAudio = audioExts.has(ext);
+
+    if (!isVideo && !isAudio) {
+      return reply.status(400).send({ error: "Unsupported file type for preview" });
+    }
+
+    const id = randomUUID();
+    const inputPath = join(tmpdir(), `snapotter-preview-${id}.${ext}`);
+    const outputExt = isVideo ? "mp4" : "mp3";
+    const outputPath = join(tmpdir(), `snapotter-preview-${id}-out.${outputExt}`);
+
+    try {
+      await writeFile(inputPath, fileBuffer);
+
+      if (isVideo) {
+        await runFfmpeg([
+          "-i",
+          inputPath,
+          "-t",
+          "30",
+          "-vf",
+          "scale='min(720,iw)':-2",
+          "-c:v",
+          "libx264",
+          "-preset",
+          "ultrafast",
+          "-crf",
+          "28",
+          "-c:a",
+          "aac",
+          "-b:a",
+          "128k",
+          "-movflags",
+          "+faststart",
+          "-y",
+          outputPath,
+        ]);
+      } else {
+        await runFfmpeg([
+          "-i",
+          inputPath,
+          "-t",
+          "60",
+          "-c:a",
+          "libmp3lame",
+          "-b:a",
+          "128k",
+          "-y",
+          outputPath,
+        ]);
+      }
+
+      const outputBuffer = await readFile(outputPath);
+      const contentType = isVideo ? "video/mp4" : "audio/mpeg";
+
+      return reply
+        .header("Content-Type", contentType)
+        .header("Content-Length", outputBuffer.length)
+        .send(outputBuffer);
+    } catch (err) {
+      request.log.error({ err, filename }, "On-demand preview generation failed");
+      return reply.status(422).send({ error: "Could not generate preview" });
+    } finally {
+      await rm(inputPath, { force: true }).catch(() => {});
+      await rm(outputPath, { force: true }).catch(() => {});
+    }
+  });
+
   app.log.info("File preview routes registered");
 }