fix: remove O(n²) bottleneck in large file scans (#46)

Removed redundant findMatchingVideoFile call and per-file WebSocket
broadcasts from the run:files_found handler. With 32k+ subtitle files,
the synchronous disk I/O and DB queries blocked the event loop entirely.

Video path matching now happens in processFile when the file is actually
processed, and video_path is stored in the DB at that point.

Co-authored-by: bridgemill-ch <bridgemill-ch@users.noreply.github.com>

Author: johnpc

src/coordinator.ts

@@ -1,7 +1,6 @@
 import { ProcessingEngine } from './processingEngine';
 import { StateManager } from './stateManager';
 import { ScanConfig } from './config';
-import { findMatchingVideoFile } from './findMatchingVideoFile';
 import { Run } from './database';
 import { once } from 'events';
 
@@ -33,16 +32,15 @@ export class ProcessingCoordinator {
     this.engine.on('run:files_found', (files: string[]) => {
       this.currentRunId = this.stateManager.startRun(files.length, this.enabledEngines);
 
-      // Add all files to database as pending
-      files.forEach((filePath) => {
-        const videoPath = findMatchingVideoFile(filePath);
-        this.stateManager.addFile(this.currentRunId!, filePath, videoPath);
-      });
+      // Add all files to database as pending (video matching happens during processing)
+      for (const filePath of files) {
+        this.stateManager.addFile(this.currentRunId!, filePath, null);
+      }
     });
 
-    this.engine.on('file:started', ({ srtPath }: { srtPath: string }) => {
+    this.engine.on('file:started', ({ srtPath, videoPath }: { srtPath: string; videoPath: string | null }) => {
       if (this.currentRunId) {
-        this.stateManager.updateFileStatus(this.currentRunId, srtPath, 'processing', null);
+        this.stateManager.updateFileStatus(this.currentRunId, srtPath, 'processing', null, videoPath);
       }
     });
 

src/stateManager.ts

@@ -105,14 +105,16 @@ export class StateManager extends EventEmitter {
   // File management
   addFile(runId: string, filePath: string, videoPath: string | null): void {
     this.db.createFileResult(runId, filePath, videoPath);
-    this.emitFileUpdate(runId, filePath);
   }
 
-  updateFileStatus(runId: string, filePath: string, status: FileResult['status'], currentEngine?: string | null): void {
+  updateFileStatus(runId: string, filePath: string, status: FileResult['status'], currentEngine?: string | null, videoPath?: string | null): void {
     const updates: Partial<FileResult> = { status };
     if (currentEngine !== undefined) {
       updates.current_engine = currentEngine;
     }
+    if (videoPath !== undefined) {
+      updates.video_path = videoPath;
+    }
 
     this.db.updateFileResult(runId, filePath, updates);
     this.emitFileUpdate(runId, filePath);