Add Playwright assistant regression coverage

frontend/e2e/video-render.ts

@@ -0,0 +1,88 @@
+import { execFile, execFileSync } from "node:child_process";
+import fs from "node:fs";
+import path from "node:path";
+import { promisify } from "node:util";
+import { buildSrt, type Clip } from "./subtitles";
+
+const execFileAsync = promisify(execFile);
+
+function hasFfmpeg() {
+  try {
+    execFileSync("ffmpeg", ["-version"], { stdio: "ignore" });
+    return true;
+  } catch {
+    return false;
+  }
+}
+
+const SUBTITLE_STYLE =
+  "FontSize=22,PrimaryColour=&H00FFFFFF,BackColour=&H80000000,BorderStyle=3,Outline=1,Shadow=0,MarginV=40";
+
+function escapeForFilter(p: string) {
+  // ffmpeg filter arguments treat ':' and '\' specially — escape both.
+  return p.replace(/\\/g, "\\\\").replace(/:/g, "\\:");
+}
+
+export async function renderFinalVideo({
+  rawWebmPath,
+  clips,
+  outDir,
+}: {
+  rawWebmPath: string;
+  clips: Clip[];
+  outDir: string;
+}): Promise<{ videoFile: string; degraded: string[] }> {
+  const degraded: string[] = [];
+  const srtPath = path.join(outDir, "captions.srt");
+  fs.writeFileSync(srtPath, buildSrt(clips));
+
+  if (!hasFfmpeg()) {
+    const dest = path.join(outDir, "video.webm");
+    fs.renameSync(rawWebmPath, dest);
+    degraded.push("ffmpeg not found — kept raw video.webm, no subtitles burned in, no narration.");
+    return { videoFile: dest, degraded };
+  }
+
+  const narrated = clips.filter((c) => c.narration);
+  const mp4Path = path.join(outDir, "video.mp4");
+  const srtArg = `subtitles=${escapeForFilter(srtPath)}:force_style='${SUBTITLE_STYLE}'`;
+
+  if (narrated.length === 0) {
+    degraded.push("No narration available — burned-in subtitles only.");
+    await execFileAsync("ffmpeg", [
+      "-y", "-i", rawWebmPath,
+      "-vf", srtArg,
+      "-c:v", "libx264", "-crf", "20", "-pix_fmt", "yuv420p",
+      "-movflags", "+faststart",
+      "-an",
+      mp4Path,
+    ]);
+  } else {
+    const audioInputs = narrated.flatMap((c) => ["-i", c.narration!.path]);
+    const adelayParts = narrated.map(
+      (c, i) => `[${i + 1}:a]adelay=${Math.max(0, Math.round(c.startMs))}|${Math.max(0, Math.round(c.startMs))}[a${i}]`,
+    );
+    const mixInputs = narrated.map((_, i) => `[a${i}]`).join("");
+    const filterComplex = [
+      `[0:v]${srtArg}[vout]`,
+      ...adelayParts,
+      `${mixInputs}amix=inputs=${narrated.length}:normalize=0[aout]`,
+    ].join(";");
+
+    await execFileAsync("ffmpeg", [
+      "-y", "-i", rawWebmPath, ...audioInputs,
+      "-filter_complex", filterComplex,
+      "-map", "[vout]", "-map", "[aout]",
+      "-c:v", "libx264", "-crf", "20", "-pix_fmt", "yuv420p",
+      "-c:a", "aac",
+      "-shortest",
+      "-movflags", "+faststart",
+      mp4Path,
+    ]);
+  }
+
+  fs.rmSync(rawWebmPath, { force: true });
+  for (const c of narrated) fs.rmSync(c.narration!.path, { force: true });
+
+  return { videoFile: mp4Path, degraded };
+}