Restructure frontend code to allow for extensions (#4721)

# Description of Changes
Move frontend code into `core` folder and add infrastructure for
`proprietary` folder to include premium, non-OSS features

frontend/src/core/hooks/tools/ocr/useOCROperation.ts

@@ -0,0 +1,125 @@
+import { useCallback } from 'react';
+import { useTranslation } from 'react-i18next';
+import { OCRParameters, defaultParameters } from '@app/hooks/tools/ocr/useOCRParameters';
+import { useToolOperation, ToolOperationConfig, ToolType } from '@app/hooks/tools/shared/useToolOperation';
+import { createStandardErrorHandler } from '@app/utils/toolErrorHandler';
+import { useToolResources } from '@app/hooks/tools/shared/useToolResources';
+
+// Helper: get MIME type based on file extension
+function getMimeType(filename: string): string {
+  const ext = filename.toLowerCase().split('.').pop();
+  switch (ext) {
+    case 'pdf': return 'application/pdf';
+    case 'txt': return 'text/plain';
+    case 'zip': return 'application/zip';
+    default: return 'application/octet-stream';
+  }
+}
+
+// Lightweight ZIP extractor (keep or replace with a shared util if you have one)
+async function extractZipFile(zipBlob: Blob): Promise<File[]> {
+  const JSZip = await import('jszip');
+  const zip = new JSZip.default();
+  const zipContent = await zip.loadAsync(await zipBlob.arrayBuffer());
+  const out: File[] = [];
+  for (const [filename, file] of Object.entries(zipContent.files)) {
+    if (!file.dir) {
+      const content = await file.async('blob');
+      out.push(new File([content], filename, { type: getMimeType(filename) }));
+    }
+  }
+  return out;
+}
+
+// Helper: strip extension
+function stripExt(name: string): string {
+  const i = name.lastIndexOf('.');
+  return i > 0 ? name.slice(0, i) : name;
+}
+
+// Static function that can be used by both the hook and automation executor
+export const buildOCRFormData = (parameters: OCRParameters, file: File): FormData => {
+  const formData = new FormData();
+  formData.append('fileInput', file);
+  parameters.languages.forEach((lang) => formData.append('languages', lang));
+  formData.append('ocrType', parameters.ocrType);
+  formData.append('ocrRenderType', parameters.ocrRenderType);
+  formData.append('sidecar', parameters.additionalOptions.includes('sidecar').toString());
+  formData.append('deskew', parameters.additionalOptions.includes('deskew').toString());
+  formData.append('clean', parameters.additionalOptions.includes('clean').toString());
+  formData.append('cleanFinal', parameters.additionalOptions.includes('cleanFinal').toString());
+  formData.append('removeImagesAfter', parameters.additionalOptions.includes('removeImagesAfter').toString());
+  return formData;
+};
+
+// Static response handler for OCR - can be used by automation executor
+export const ocrResponseHandler = async (blob: Blob, originalFiles: File[], extractZipFiles: (blob: Blob) => Promise<File[]>): Promise<File[]> => {
+  const headBuf = await blob.slice(0, 8).arrayBuffer();
+  const head = new TextDecoder().decode(new Uint8Array(headBuf));
+
+  // ZIP: sidecar or multi-asset output
+  if (head.startsWith('PK')) {
+    const base = stripExt(originalFiles[0].name);
+    try {
+      const extractedFiles = await extractZipFiles(blob);
+      if (extractedFiles.length > 0) return extractedFiles;
+    } catch { /* ignore and try local extractor */ }
+    try {
+      const local = await extractZipFile(blob); // local fallback
+      if (local.length > 0) return local;
+    } catch { /* fall through */ }
+    return [new File([blob], `ocr_${base}.zip`, { type: 'application/zip' })];
+  }
+
+  // Not a PDF: surface error details if present
+  if (!head.startsWith('%PDF')) {
+    const textBuf = await blob.slice(0, 1024).arrayBuffer();
+    const text = new TextDecoder().decode(new Uint8Array(textBuf));
+    if (/error|exception|html/i.test(text)) {
+      if (text.includes('OCR tools') && text.includes('not installed')) {
+        throw new Error('OCR tools (OCRmyPDF or Tesseract) are not installed on the server. Use the standard or fat Docker image instead of ultra-lite, or install OCR tools manually.');
+      }
+      const title =
+        text.match(/<title[^>]*>([^<]+)<\/title>/i)?.[1] ||
+        text.match(/<h1[^>]*>([^<]+)<\/h1>/i)?.[1] ||
+        'Unknown error';
+      throw new Error(`OCR service error: ${title}`);
+    }
+    throw new Error(`Response is not a valid PDF. Header: "${head}"`);
+  }
+
+  const originalName = originalFiles[0].name;
+  return [new File([blob], originalName, { type: 'application/pdf' })];
+};
+
+// Static configuration object (without t function dependencies)
+export const ocrOperationConfig = {
+  toolType: ToolType.singleFile,
+  buildFormData: buildOCRFormData,
+  operationType: 'ocr',
+  endpoint: '/api/v1/misc/ocr-pdf',
+  defaultParameters,
+} as const;
+
+export const useOCROperation = () => {
+  const { t } = useTranslation();
+  const { extractZipFiles } = useToolResources();
+
+  // OCR-specific parsing: ZIP (sidecar) vs PDF vs HTML error
+  const responseHandler = useCallback(async (blob: Blob, originalFiles: File[]): Promise<File[]> => {
+    // extractZipFiles from useToolResources already returns File[] directly
+    const simpleExtractZipFiles = extractZipFiles;
+    return ocrResponseHandler(blob, originalFiles, simpleExtractZipFiles);
+  }, [extractZipFiles]);
+
+  const ocrConfig: ToolOperationConfig<OCRParameters> = {
+    ...ocrOperationConfig,
+    responseHandler,
+    getErrorMessage: (error) =>
+      error.message?.includes('OCR tools') && error.message?.includes('not installed')
+        ? 'OCR tools (OCRmyPDF or Tesseract) are not installed on the server. Use the standard or fat Docker image instead of ultra-lite, or install OCR tools manually.'
+        : createStandardErrorHandler(t('ocr.error.failed', 'OCR operation failed'))(error),
+  };
+
+  return useToolOperation(ocrConfig);
+};

frontend/src/core/hooks/tools/ocr/useOCRParameters.ts

@@ -0,0 +1,29 @@
+import { BaseParameters } from '@app/types/parameters';
+import { useBaseParameters, BaseParametersHook } from '@app/hooks/tools/shared/useBaseParameters';
+
+export interface OCRParameters extends BaseParameters {
+  languages: string[];
+  ocrType: string;
+  ocrRenderType: string;
+  additionalOptions: string[];
+}
+
+export type OCRParametersHook = BaseParametersHook<OCRParameters>;
+
+export const defaultParameters: OCRParameters = {
+  languages: [],
+  ocrType: 'skip-text',
+  ocrRenderType: 'hocr',
+  additionalOptions: [],
+};
+
+export const useOCRParameters = (): OCRParametersHook => {
+  return useBaseParameters({
+    defaultParameters,
+    endpointName: 'ocr-pdf',
+    validateFn: (params) => {
+      // At minimum, we need at least one language selected
+      return params.languages.length > 0;
+    },
+  });
+};