feat(video): implement ffmpeg-based video operations backend

Add src/main/VideoOperations.js with pure argument-builder functions
(buildConvertArgs, buildCompressArgs, buildTrimArgs, buildFramesArgs,
buildGifArgs) and a single executeOperation entry point that spawns
ffmpeg via dependency-injected execFileFn, mirroring AudioOperations.js.

Wire ipcMain.handle('process-video-operation', ...) in main.js using
getFFmpegPath() and sanitizeErrorMessage(). Update preload.js's
ALLOWED_SEND_CHANNELS: remove 6 stale video-* channel names, add
process-video-operation.

Amit Haridas

src/main.js

@@ -7,6 +7,7 @@ const WordTemplateExporter = require('./wordTemplateExporter');
 const PDFOperations = require('./main/PDFOperations');
 const ImageOperations = require('./main/ImageOperations');
 const AudioOperations = require('./main/AudioOperations');
+const VideoOperations = require('./main/VideoOperations');
 const GitOperations = require('./main/GitOperations');
 const PdfFontHeader = require('./main/PdfFontHeader');
 const MonospaceFontConfig = require('./main/MonospaceFontConfig');
@@ -4651,6 +4652,20 @@ ipcMain.handle('process-audio-operation', async (event, { operation, data }) =>
   }
 });
 
+// ========================================
+// VIDEO OPERATIONS — delegates to main/VideoOperations.js
+// ========================================
+
+ipcMain.handle('process-video-operation', async (event, { operation, data }) => {
+  try {
+    return await VideoOperations.executeOperation(operation, data, {
+      ffmpegPath: getFFmpegPath(),
+    });
+  } catch (error) {
+    return { success: false, error: sanitizeErrorMessage(error.message) };
+  }
+});
+
 // IPC Handler for folder selection (for batch image operations)
 ipcMain.on('select-image-folder', (event, inputId) => {
   const folder = dialog.showOpenDialogSync(mainWindow, {

src/main/VideoOperations.js

@@ -0,0 +1,145 @@
+/**
+ * Video Operations Module
+ *
+ * Handles video manipulation via `ffmpeg`: format conversion, compression, trim,
+ * frame extraction, and GIF conversion. Because ffmpeg is an external binary, this
+ * module is split into pure/testable argument-builder functions and a single
+ * `executeOperation` that is the only piece which actually spawns ffmpeg — the
+ * ffmpeg binary path and the `execFile` implementation are both injected so tests
+ * can replace them with fakes, without invoking a real binary.
+ *
+ * @module VideoOperations
+ */
+
+const fs = require('fs');
+const path = require('path');
+const { execFile } = require('child_process');
+
+/**
+ * Build args for a straight format conversion. ffmpeg infers the output format
+ * from outputPath's extension.
+ */
+function buildConvertArgs({ inputPath, outputPath }) {
+  return ['-i', inputPath, '-y', outputPath];
+}
+
+/**
+ * Build args to re-encode inputPath with libx264 at the given CRF (Constant Rate
+ * Factor). Lower CRF = higher quality/larger file, per libx264 convention. crf
+ * must be an integer in [0, 51].
+ */
+function buildCompressArgs({ inputPath, outputPath, crf = 28 }) {
+  if (!Number.isInteger(crf) || crf < 0 || crf > 51) {
+    throw new Error('Invalid crf: must be an integer between 0 and 51');
+  }
+
+  return ['-i', inputPath, '-vcodec', 'libx264', '-crf', String(crf), '-y', outputPath];
+}
+
+/**
+ * Build args to trim inputPath to [startTime, startTime + duration) seconds.
+ * startTime/duration must be finite, non-negative numbers — they become argv
+ * elements passed straight to execFile with no shell involved, so there's no
+ * injection risk, but malformed values should still fail fast rather than reach
+ * ffmpeg with garbage.
+ */
+function buildTrimArgs({ inputPath, outputPath, startTime, duration }) {
+  const isValid = (n) => typeof n === 'number' && Number.isFinite(n) && n >= 0;
+
+  if (!isValid(startTime) || !isValid(duration)) {
+    throw new Error('Invalid trim range');
+  }
+
+  return ['-i', inputPath, '-ss', String(startTime), '-t', String(duration), '-y', outputPath];
+}
+
+/**
+ * Build args to extract frames from inputPath at fps frames-per-second, written
+ * as sequentially numbered PNGs into outputDir. fps must be a positive finite
+ * number.
+ */
+function buildFramesArgs({ inputPath, outputDir, fps = 1 }) {
+  if (typeof fps !== 'number' || !Number.isFinite(fps) || fps <= 0) {
+    throw new Error('Invalid fps: must be a positive finite number');
+  }
+
+  return ['-i', inputPath, '-vf', `fps=${fps}`, path.join(outputDir, 'frame-%04d.png')];
+}
+
+/**
+ * Build args to convert inputPath to an animated GIF at the given fps and width
+ * (height scales automatically via -1), using the lanczos scaling filter.
+ */
+function buildGifArgs({ inputPath, outputPath, fps = 10, width = 480 }) {
+  return ['-i', inputPath, '-vf', `fps=${fps},scale=${width}:-1:flags=lanczos`, '-y', outputPath];
+}
+
+/**
+ * Run ffmpeg with the given args via the injected execFileFn, wrapped in a Promise.
+ */
+function runFfmpeg(ffmpegPath, args, execFileFn) {
+  return new Promise((resolve, reject) => {
+    execFileFn(ffmpegPath, args, { maxBuffer: 10 * 1024 * 1024 }, (error, stdout, stderr) => {
+      if (error) {
+        reject(new Error(stderr || error.message));
+        return;
+      }
+      resolve();
+    });
+  });
+}
+
+async function executeOperation(operation, data, { ffmpegPath, execFileFn } = {}) {
+  const resolvedFfmpegPath = ffmpegPath || 'ffmpeg';
+  const resolvedExecFileFn = execFileFn || execFile;
+
+  switch (operation) {
+    case 'convert': {
+      const { inputPath, outputPath } = data || {};
+      const args = buildConvertArgs({ inputPath, outputPath });
+      await runFfmpeg(resolvedFfmpegPath, args, resolvedExecFileFn);
+      return { success: true, outputPath };
+    }
+
+    case 'compress': {
+      const { inputPath, outputPath, crf } = data || {};
+      const args = buildCompressArgs({ inputPath, outputPath, crf });
+      await runFfmpeg(resolvedFfmpegPath, args, resolvedExecFileFn);
+      return { success: true, outputPath };
+    }
+
+    case 'trim': {
+      const { inputPath, outputPath, startTime, duration } = data || {};
+      const args = buildTrimArgs({ inputPath, outputPath, startTime, duration });
+      await runFfmpeg(resolvedFfmpegPath, args, resolvedExecFileFn);
+      return { success: true, outputPath };
+    }
+
+    case 'frames': {
+      const { inputPath, outputDir, fps } = data || {};
+      const args = buildFramesArgs({ inputPath, outputDir, fps });
+      fs.mkdirSync(outputDir, { recursive: true });
+      await runFfmpeg(resolvedFfmpegPath, args, resolvedExecFileFn);
+      return { success: true, outputDir };
+    }
+
+    case 'gif': {
+      const { inputPath, outputPath, fps, width } = data || {};
+      const args = buildGifArgs({ inputPath, outputPath, fps, width });
+      await runFfmpeg(resolvedFfmpegPath, args, resolvedExecFileFn);
+      return { success: true, outputPath };
+    }
+
+    default:
+      throw new Error(`Unknown operation: ${operation}`);
+  }
+}
+
+module.exports = {
+  executeOperation,
+  buildConvertArgs,
+  buildCompressArgs,
+  buildTrimArgs,
+  buildFramesArgs,
+  buildGifArgs,
+};

src/preload.js

@@ -52,12 +52,7 @@ const ALLOWED_SEND_CHANNELS = [
   'process-audio-operation',
 
   // Video converter
-  'video-convert',
-  'video-batch-convert',
-  'video-compress',
-  'video-trim',
-  'video-frames',
-  'video-gif',
+  'process-video-operation',
 
   // Header/Footer
   'get-header-footer-settings',