Add Merge UI to V2 (#4235)

# Description of Changes
Add UI for Merge into V2.

frontend/src/tools/Automate.tsx

@@ -1,4 +1,4 @@
-import React, { useState, useMemo } from "react";
+import React, { useState } from "react";
 import { useTranslation } from "react-i18next";
 import { useFileSelection } from "../contexts/FileContext";
 import { useNavigationActions } from "../contexts/NavigationContext";
@@ -161,25 +161,10 @@ const Automate = ({ onPreviewFile, onComplete, onError }: BaseToolProps) => {
     content
   });
 
-  // Dynamic file placeholder based on supported types
-  const filesPlaceholder = useMemo(() => {
-    if (currentStep === AUTOMATION_STEPS.RUN && stepData.automation?.operations?.length) {
-      const firstOperation = stepData.automation.operations[0];
-      const toolConfig = toolRegistry[firstOperation.operation as keyof typeof toolRegistry];
-
-      // Check if the tool has supportedFormats that include non-PDF formats
-      if (toolConfig?.supportedFormats && toolConfig.supportedFormats.length > 1) {
-        return t('automate.files.placeholder.multiFormat', 'Select files to process (supports various formats)');
-      }
-    }
-    return t('automate.files.placeholder', 'Select PDF files to process with this automation');
-  }, [currentStep, stepData.automation, toolRegistry, t]);
-
   // Always create files step to avoid conditional hook calls
   const filesStep = createFilesToolStep(createStep, {
     selectedFiles,
     isCollapsed: hasResults,
-    placeholder: filesPlaceholder
   });
 
   const automationSteps = [

frontend/src/tools/Convert.tsx

@@ -100,7 +100,6 @@ const Convert = ({ onPreviewFile, onComplete, onError }: BaseToolProps) => {
     files: {
       selectedFiles,
       isCollapsed: hasResults,
-      placeholder: t("convert.selectFilesPlaceholder", "Select files in the main view to get started"),
     },
     steps: [
       {

frontend/src/tools/Flatten.tsx

@@ -22,7 +22,6 @@ const Flatten = (props: BaseToolProps) => {
     files: {
       selectedFiles: base.selectedFiles,
       isCollapsed: base.hasResults,
-      placeholder: t("flatten.files.placeholder", "Select a PDF file in the main view to get started"),
     },
     steps: [
       {
@@ -59,4 +58,4 @@ const Flatten = (props: BaseToolProps) => {
 // Static method to get the operation hook for automation
 Flatten.tool = () => useFlattenOperation;
 
-export default Flatten as ToolComponent;
+export default Flatten as ToolComponent;

frontend/src/tools/Merge.tsx

@@ -0,0 +1,98 @@
+import { useCallback } from "react";
+import { useTranslation } from "react-i18next";
+import { createToolFlow } from "../components/tools/shared/createToolFlow";
+import MergeSettings from "../components/tools/merge/MergeSettings";
+import MergeFileSorter from "../components/tools/merge/MergeFileSorter";
+import { useMergeParameters } from "../hooks/tools/merge/useMergeParameters";
+import { useMergeOperation } from "../hooks/tools/merge/useMergeOperation";
+import { useBaseTool } from "../hooks/tools/shared/useBaseTool";
+import { BaseToolProps, ToolComponent } from "../types/tool";
+import { useMergeTips } from "../components/tooltips/useMergeTips";
+import { useFileManagement, useSelectedFiles, useAllFiles } from "../contexts/FileContext";
+
+const Merge = (props: BaseToolProps) => {
+  const { t } = useTranslation();
+  const mergeTips = useMergeTips();
+
+  // File selection hooks for custom sorting
+  const { fileIds } = useAllFiles();
+  const { selectedRecords } = useSelectedFiles();
+  const { reorderFiles } = useFileManagement();
+
+  const base = useBaseTool(
+    'merge',
+    useMergeParameters,
+    useMergeOperation,
+    props,
+    { minFiles: 2 }
+  );
+
+  // Custom file sorting logic for merge tool
+  const sortFiles = useCallback((sortType: 'filename' | 'dateModified', ascending: boolean = true) => {
+    const sortedRecords = [...selectedRecords].sort((recordA, recordB) => {
+      let comparison = 0;
+      switch (sortType) {
+        case 'filename':
+          comparison = recordA.name.localeCompare(recordB.name);
+          break;
+        case 'dateModified':
+          comparison = recordA.lastModified - recordB.lastModified;
+          break;
+      }
+      return ascending ? comparison : -comparison;
+    });
+
+    const selectedIds = sortedRecords.map(record => record.id);
+    const deselectedIds = fileIds.filter(id => !selectedIds.includes(id));
+    reorderFiles([...selectedIds, ...deselectedIds]);
+  }, [selectedRecords, fileIds, reorderFiles]);
+
+  return createToolFlow({
+    files: {
+      selectedFiles: base.selectedFiles,
+      isCollapsed: base.hasResults,
+      minFiles: 2,
+    },
+    steps: [
+      {
+        title: "Sort Files",
+        isCollapsed: base.settingsCollapsed,
+        content: (
+          <MergeFileSorter
+            onSortFiles={sortFiles}
+            disabled={!base.hasFiles || base.endpointLoading}
+          />
+        ),
+      },
+      {
+        title: "Settings",
+        isCollapsed: base.settingsCollapsed,
+        onCollapsedClick: base.settingsCollapsed ? base.handleSettingsReset : undefined,
+        tooltip: mergeTips,
+        content: (
+          <MergeSettings
+            parameters={base.params.parameters}
+            onParameterChange={base.params.updateParameter}
+            disabled={base.endpointLoading}
+          />
+        ),
+      },
+    ],
+    executeButton: {
+      text: t("merge.submit", "Merge PDFs"),
+      isVisible: !base.hasResults,
+      loadingText: t("loading"),
+      onClick: base.handleExecute,
+      disabled: !base.params.validateParameters() || !base.hasFiles || !base.endpointEnabled,
+    },
+    review: {
+      isVisible: base.hasResults,
+      operation: base.operation,
+      title: t("merge.title", "Merge Results"),
+      onFileClick: base.handleThumbnailClick,
+      onUndo: base.handleUndo,
+    },
+  });
+};
+
+export default Merge as ToolComponent;

frontend/src/tools/RemoveCertificateSign.tsx

@@ -19,7 +19,6 @@ const RemoveCertificateSign = (props: BaseToolProps) => {
     files: {
       selectedFiles: base.selectedFiles,
       isCollapsed: base.hasResults,
-      placeholder: t("removeCertSign.files.placeholder", "Select a PDF file in the main view to get started"),
     },
     steps: [],
     executeButton: {

frontend/src/tools/Repair.tsx

@@ -19,7 +19,6 @@ const Repair = (props: BaseToolProps) => {
     files: {
       selectedFiles: base.selectedFiles,
       isCollapsed: base.hasResults,
-      placeholder: t("repair.files.placeholder", "Select a PDF file in the main view to get started"),
     },
     steps: [],
     executeButton: {

frontend/src/tools/Sanitize.tsx

@@ -20,7 +20,6 @@ const Sanitize = (props: BaseToolProps) => {
     files: {
       selectedFiles: base.selectedFiles,
       isCollapsed: base.hasResults,
-      placeholder: t("sanitize.files.placeholder", "Select a PDF file in the main view to get started"),
     },
     steps: [
       {

frontend/src/tools/SingleLargePage.tsx

@@ -19,7 +19,6 @@ const SingleLargePage = (props: BaseToolProps) => {
     files: {
       selectedFiles: base.selectedFiles,
       isCollapsed: base.hasResults,
-      placeholder: t("pdfToSinglePage.files.placeholder", "Select a PDF file in the main view to get started"),
     },
     steps: [],
     executeButton: {

frontend/src/tools/UnlockPdfForms.tsx

@@ -19,7 +19,6 @@ const UnlockPdfForms = (props: BaseToolProps) => {
     files: {
       selectedFiles: base.selectedFiles,
       isCollapsed: base.hasFiles || base.hasResults,
-      placeholder: t("unlockPDFForms.files.placeholder", "Select a PDF file in the main view to get started"),
     },
     steps: [],
     executeButton: {