feat: refactor MailViewer and add utility functions for email handling and attachment processing

frontend/src/lib/utils/mail/email-loader.ts

@@ -0,0 +1,163 @@
+/**
+ * Email loading and processing utilities
+ */
+
+import {
+  ReadEML,
+  ReadMSG,
+  ReadPEC,
+  ShowOpenFileDialog,
+  SetCurrentMailFilePath,
+  ConvertToUTF8,
+} from '$lib/wailsjs/go/main/App';
+import type { internal } from '$lib/wailsjs/go/models';
+import { isBase64, isHtml } from '$lib/utils';
+import { looksLikeBase64, tryDecodeBase64 } from './data-utils';
+
+export interface LoadEmailResult {
+  success: boolean;
+  email?: internal.EmailData;
+  filePath?: string;
+  error?: string;
+  cancelled?: boolean;
+}
+
+/**
+ * Determines the email file type from the path
+ */
+export function getEmailFileType(filePath: string): 'eml' | 'msg' | null {
+  const lowerPath = filePath.toLowerCase();
+  if (lowerPath.endsWith('.eml')) return 'eml';
+  if (lowerPath.endsWith('.msg')) return 'msg';
+  return null;
+}
+
+/**
+ * Checks if a file path is a valid email file
+ */
+export function isEmailFile(filePath: string): boolean {
+  return getEmailFileType(filePath) !== null;
+}
+
+/**
+ * Loads an email from a file path
+ * @param filePath - Path to the email file
+ * @returns LoadEmailResult with the email data or error
+ */
+export async function loadEmailFromPath(filePath: string): Promise<LoadEmailResult> {
+  const fileType = getEmailFileType(filePath);
+
+  if (!fileType) {
+    return {
+      success: false,
+      error: 'Invalid file type. Only .eml and .msg files are supported.',
+    };
+  }
+
+  try {
+    let email: internal.EmailData;
+
+    if (fileType === 'msg') {
+      email = await ReadMSG(filePath, true);
+    } else {
+      // Try PEC first, fall back to regular EML
+      try {
+        email = await ReadPEC(filePath);
+      } catch {
+        email = await ReadEML(filePath);
+      }
+    }
+
+    // Process body if needed (decode base64)
+    if (email?.body) {
+      const trimmed = email.body.trim();
+      if (looksLikeBase64(trimmed)) {
+        const decoded = tryDecodeBase64(trimmed);
+        if (decoded) {
+          email.body = decoded;
+        }
+      }
+    }
+
+    return {
+      success: true,
+      email,
+      filePath,
+    };
+  } catch (error: unknown) {
+    const errorMessage = error instanceof Error ? error.message : String(error);
+    console.error('Failed to load email:', error);
+    return {
+      success: false,
+      error: errorMessage,
+    };
+  }
+}
+
+/**
+ * Opens a file dialog and loads the selected email
+ * @returns LoadEmailResult with the email data or error
+ */
+export async function openAndLoadEmail(): Promise<LoadEmailResult> {
+  try {
+    const filePath = await ShowOpenFileDialog();
+
+    if (!filePath || filePath.length === 0) {
+      return { success: false, cancelled: true };
+    }
+
+    const result = await loadEmailFromPath(filePath);
+
+    if (result.success && result.email) {
+      // Track the current mail file path for bug reports
+      await SetCurrentMailFilePath(filePath);
+    }
+
+    return result;
+  } catch (error: unknown) {
+    const errorMessage = error instanceof Error ? error.message : String(error);
+    console.error('Failed to open email file:', error);
+    return {
+      success: false,
+      error: errorMessage,
+    };
+  }
+}
+
+/**
+ * Processes and fixes the email body content
+ * - Decodes base64 content if needed
+ * - Fixes character encoding issues
+ * @param body - The raw email body
+ * @returns Processed body content
+ */
+export async function processEmailBody(body: string): Promise<string> {
+  if (!body) return body;
+
+  let content = body;
+
+  // 1. Try to decode if not HTML
+  if (!isHtml(content)) {
+    const clean = content.replace(/[\s\r\n]+/g, '');
+    if (isBase64(clean)) {
+      const decoded = tryDecodeBase64(clean);
+      if (decoded) {
+        content = decoded;
+      }
+    }
+  }
+
+  // 2. If it is HTML (original or decoded), try to fix encoding
+  if (isHtml(content)) {
+    try {
+      const fixed = await ConvertToUTF8(content);
+      if (fixed) {
+        content = fixed;
+      }
+    } catch (e) {
+      console.warn('Failed to fix encoding:', e);
+    }
+  }
+
+  return content;
+}