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Vijay Gangatharan
Vijay Gangatharan

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Building for the Long Term: The Architecture Behind File Insights 🏗️

#vscode #extensions #codenewbie #productivity

Part 2 of 5: From Hobby Project to Enterprise-Grade Extension

After my "aha moment" about solving the daily file size frustration, I faced a crucial decision: Build it quick and dirty, or build it right? 🤔

📊 TL;DR

Building File Insights taught me that good architecture is the difference between a weekend hack and professional software. Using a Manager-Service pattern with TypeScript strict mode and proper resource management transformed a "simple" file size display into an enterprise-grade VS Code extension.

Key Architecture Decisions:

  • 🏗️ Manager-Service pattern for clean separation of concerns
  • 🛡️ TypeScript strict mode with Result types for bulletproof error handling
  • ⚡ Debounced updates and resource management for zero performance impact
  • 🔄 Live configuration updates without VS Code restarts

I'd seen too many promising projects die slow deaths because they couldn't scale beyond their initial implementation. So I made a commitment that would define everything about File Insights: If I'm going to build this, I'm going to build it like it matters.

The Approaches That Failed First 😅

Before I landed on the current architecture, I tried several approaches that seemed "simpler":

❌ Attempt 1: Everything in extension.ts

// This was my first naive attempt
export function activate(context: vscode.ExtensionContext) {
  let statusBarItem = vscode.window.createStatusBarItem();

  vscode.window.onDidChangeActiveTextEditor(() => {
    // 200 lines of mixed concerns here...
    // UI logic, file operations, configuration, error handling
    // It became unreadable FAST
  });
}
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Result: Unmaintainable mess after adding just 3 features

❌ Attempt 2: Class-based but still mixed concerns

class FileInsights {
  updateDisplay() {
    // Still mixing UI, business logic, and file operations
    const stats = this.getFileStats(); // File operation
    const formatted = this.formatSize(); // Business logic  
    this.statusBar.text = formatted; // UI operation
    // When any layer changed, everything broke
  }
}
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Result: Brittle code that broke with every new feature

The Architecture Philosophy: SOLID Foundations 💪

Why Architecture Matters for "Simple" Extensions

Many developers think: "It's just a VS Code extension that shows file sizes—how complex can it be?"

Famous last words. 😅

Even simple tools can become maintenance nightmares without proper architecture. I wanted File Insights to be:

  • Maintainable: Easy to add features without breaking existing functionality
  • Testable: Every component isolated and verifiable
  • Scalable: Ready for features I haven't even imagined yet
  • Professional: Code quality that makes me proud, not embarrassed

The Breakthrough: Manager-Service Pattern 🎯

After those failures, I realized I needed true separation of concerns. Enter the Manager-Service pattern that saved File Insights:

src/
├── extension.ts              # Entry point (minimal, clean)
├── managers/
│   ├── extensionManager.ts   # Orchestration & lifecycle
│   └── statusBarManager.ts   # UI-specific logic
├── services/
│   ├── configurationService.ts  # Settings management
│   └── fileService.ts           # File system operations
├── utils/
│   ├── formatter.ts             # Size formatting logic
│   └── logger.ts               # Structured logging
└── types/
    ├── extension.ts             # Core interfaces
    └── common.ts               # Shared types
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Why this architecture works:

  • 📦 Single Responsibility: Each class has one job and does it well
  • 🔗 Clear Boundaries: Managers coordinate, Services execute, Utils assist
  • 🧪 Testable: Every component can be tested in isolation
  • 🔄 Maintainable: Adding features doesn't break existing functionality
  • 📈 Scalable: Easy to add new managers or services as needed

No more "god classes" that do everything! 🙏

The Heart of the System: ExtensionManager 💝

The ExtensionManager is the conductor of our orchestra. It doesn't do the work—it coordinates everyone else:

export class ExtensionManager {
  private statusBarManager: StatusBarManager;
  private config: FileInsightsConfig;
  private disposables: vscode.Disposable[] = [];
  private updateTimeout: NodeJS.Timeout | null = null;

  constructor(context: vscode.ExtensionContext) {
    // 1. Get configuration
    this.config = ConfigurationService.getConfiguration();

    // 2. Initialize UI
    this.statusBarManager = new StatusBarManager(this.config);

    // 3. Register everything
    this.registerCommands(context);
    this.registerEventListeners();
    this.registerConfigurationListener();

    // 4. Show initial state
    this.updateFileStats();
  }
}
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Real-world impact: When I added the "Show Details" command, it took 15 minutes instead of hours because the architecture told me exactly where everything belonged:

  • Command registration → ExtensionManager.registerCommands()
  • UI logic → StatusBarManager.showFileDetails()
  • File operations → FileService.getFileStats()
  • No existing code touched! ✨

The UI Layer: StatusBarManager 🎨

The StatusBarManager owns everything about the status bar display:

export class StatusBarManager {
  private statusBarItem: vscode.StatusBarItem | null = null;
  private config: FileInsightsConfig;

  updateFileStats(stats: FileStats | null): void {
    if (!this.config.enabled || !stats) {
      this.hide();
      return;
    }

    // Size limit check
    if (stats.size > this.config.maxFileSize) {
      this.showMessage('File too large to analyze');
      return;
    }

    // Format and display
    const formattedSize = SizeFormatter.formatSize(stats.size, this.config);
    this.showFileSize(formattedSize, stats);
  }
}
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Isolation success story: When VS Code changed their status bar API in version 1.94, I only had to update 12 lines in StatusBarManager. Zero changes to business logic, file operations, or configuration. The architecture protected me from breaking changes! 🎭

Features this enabled:

  • 🎨 Theme support without touching core logic
  • 📱 Different status bar positions as simple config change
  • ✨ Future animation support already architected
  • 🔄 Status bar recreation on position change

Data Layer: Services That Actually Serve 📊

ConfigurationService: Settings Made Simple 

export class ConfigurationService {
  static getConfiguration(): FileInsightsConfig {
    const config = vscode.workspace.getConfiguration('fileInsights');

    return {
      enabled: config.get('enabled', true),
      displayFormat: config.get('displayFormat', 'auto'),
      statusBarPosition: config.get('statusBarPosition', 'right'),
      showTooltip: config.get('showTooltip', true),
      refreshInterval: config.get('refreshInterval', 500),
      maxFileSize: config.get('maxFileSize', 1073741824) // 1GB
    };
  }
}
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Live updates breakthrough: This architecture enabled something most extensions can't do - true real-time configuration:

// When user changes ANY setting, everything updates instantly
static onDidChangeConfiguration(callback: (config: FileInsightsConfig) => void): vscode.Disposable {
  return vscode.workspace.onDidChangeConfiguration(event => {
    if (event.affectsConfiguration('fileInsights')) {
      const newConfig = this.getConfiguration();
      callback(newConfig); // Triggers cascade update
    }
  });
}
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User experience: Change display format from "auto" to "KB" → see effect immediately. Change status bar position → seamless transition. No restart required! 🔄

FileService: The Heavy Lifter 

export class FileService {
  static async getFileStats(uri?: vscode.Uri): Promise<Result<FileStats, string>> {
    try {
      const activeEditor = vscode.window.activeTextEditor;
      const fileUri = uri || activeEditor?.document.uri;

      if (!fileUri || fileUri.scheme !== 'file') {
        return { success: false, error: 'No valid file URI provided' };
      }

      const stats = statSync(fileUri.fsPath);

      return {
        success: true,
        data: {
          size: stats.size,
          path: fileUri.fsPath,
          lastModified: stats.mtime
        }
      };
    } catch (error: unknown) {
      return { success: false, error: 'Failed to access file' };
    }
  }
}
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Error handling evolution: I initially used try/catch everywhere. Disaster! 😱

// This was a nightmare to debug
try {
  const stats = getFileStats();
  updateDisplay(stats);
} catch (error) {
  // What failed? File access? Display update? Who knows!
  console.log('Something broke');
}
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Solution: Result pattern

// Now every operation is explicit about success/failure
const result = await FileService.getFileStats(uri);
if (result.success) {
  this.statusBarManager.updateFileStats(result.data);
} else {
  this.logger.warn('File access failed', result.error);
  this.statusBarManager.hide();
}
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Benefits: No silent failures, predictable control flow, better debugging! ✅

The Utilities: Small but Mighty 🔧

SizeFormatter: Making Bytes Human-Readable 

export class SizeFormatter {
  static formatSize(bytes: number, config: FileInsightsConfig): FormattedSize {
    if (bytes === 0) {
      return { value: 0, unit: 'B', formatted: '0 B' };
    }

    // Handle forced format (bytes, kb, mb)
    if (config.displayFormat !== 'auto') {
      return this.formatToSpecificUnit(bytes, config.displayFormat, config);
    }

    // Auto format based on size
    const unitIndex = Math.floor(Math.log(bytes) / Math.log(1024));
    const clampedIndex = Math.max(0, Math.min(unitIndex, 4)); // B, KB, MB, GB, TB

    const value = bytes / Math.pow(1024, clampedIndex);
    const unit = ['B', 'KB', 'MB', 'GB', 'TB'][clampedIndex];

    const decimals = clampedIndex === 0 ? 0 : 2;
    const formattedValue = Number(value.toFixed(decimals));

    return {
      value: formattedValue,
      unit,
      formatted: `${formattedValue} ${unit}`
    };
  }
}
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Smart formatting insights: This took 6 iterations to get right!

// Failed attempts:
// v1: Always show decimals → "1.00 B" looked weird
// v2: Round everything → Lost precision on edge cases  
// v3: Fixed 2 decimals → "1536.00 B" was overwhelming

// Final solution: Context-aware precision
const decimals = clampedIndex === 0 ? 0 : 2;
// Bytes = no decimals, everything else = 2 decimals
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User psychology: 1,048,576 bytes becomes "1 MB", but 1,024 bytes stays "1024 B". Small files need precision, large files need readability. 🎯

Logger: Debugging Made Beautiful 

export class Logger {
  private context: string;

  constructor(context: string) {
    this.context = context;
  }

  info(message: string, ...args: LoggableValue[]): void {
    this.log('INFO', message, ...args);
  }

  private log(level: LogLevel, message: string, ...args: LoggableValue[]): void {
    const timestamp = new Date().toISOString();
    const contextStr = picocolors.gray(`[${this.context}]`);
    const levelStr = this.colorizeLevel(level);
    const timestampStr = picocolors.gray(`[${timestamp}]`);

    console.log(`${timestampStr} ${levelStr} ${contextStr} ${message}`);
  }
}
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Debugging game-changer: Before structured logging, bug reports were impossible to debug:

// Old way - useless for debugging
console.log('Error occurred');

// New way - tells the whole story
[2024-12-15T10:30:45.123Z] [ERROR] [FileService] Failed to access file: Permission denied /Users/dev/secret.txt
[2024-12-15T10:30:45.124Z] [INFO] [StatusBarManager] Hiding status bar due to file access error
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Real impact: User reports went from "It's broken" to "Here's the exact error log from the Output Channel". Debugging time: 3 hours → 15 minutes. 🔍

TypeScript: The Foundation of Confidence 💎

Every interface, every type, every parameter is explicitly defined:

// Core configuration interface
export interface FileInsightsConfig {
  enabled: boolean;
  displayFormat: 'auto' | 'bytes' | 'kb' | 'mb';
  statusBarPosition: 'left' | 'right';
  showTooltip: boolean;
  refreshInterval: number;
  maxFileSize: number;
}

// File statistics interface
export interface FileStats {
  size: number;
  path: string;
  lastModified: Date;
}

// Result pattern for error handling
export type Result<T, E = Error> = 
  | { success: true; data: T }
  | { success: false; error: E };
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TypeScript discipline: Strict mode caught 47 bugs before users ever saw them:

// This would compile with loose TypeScript but fail at runtime
function formatSize(bytes: any): string { // ❌ 'any' type
  return bytes.toString(); // ❌ What if bytes is undefined?
}

// Strict mode forces explicit contracts
function formatSize(bytes: number, config: FileInsightsConfig): FormattedSize {
  // ✅ Compiler guarantees type safety
  // ✅ Runtime failures become impossible
}
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Strict mode rules I enforce:

  • ❌ No any types allowed
  • ❌ No implicit returns
  • ❌ No unsafe property access
  • ✅ Every function has explicit types
  • ✅ All error cases handled

Result: If it compiles, it works. Period. 🛡️

Development Workflow: Professional Grade 🚀

Build System: Webpack + TypeScript 

// webpack.config.js (simplified)
module.exports = {
  target: 'node',
  entry: './src/extension.ts',
  output: {
    path: path.resolve(__dirname, 'dist'),
    filename: 'extension.js',
    libraryTarget: 'commonjs2'
  },
  module: {
    rules: [{
      test: /\.ts$/,
      exclude: /node_modules/,
      use: 'ts-loader'
    }]
  },
  externals: {
    vscode: 'commonjs vscode'
  }
};
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Single bundle: The entire extension ships as one optimized extension.js file. Faster loading, simpler deployment. ⚡

Code Quality: ESLint + Prettier 

{
  "scripts": {
    "lint": "eslint src --ext ts",
    "format": "prettier --write .",
    "compile": "webpack",
    "watch": "webpack --watch",
    "package": "webpack --mode production"
  }
}
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Consistent quality: Every commit is linted and formatted. No more bike-shedding about code style! 🎨

Performance: Every Millisecond Matters ⚡

Debounced Updates 

private scheduleUpdate(): void {
  if (this.updateTimeout) {
    clearTimeout(this.updateTimeout);
  }

  this.updateTimeout = setTimeout(() => {
    this.updateFileStats();
  }, this.config.refreshInterval);
}
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Why this matters: When you're typing rapidly, File Insights doesn't spam the file system. Updates are batched intelligently. 🧠

Large File Protection 

if (stats.size > this.config.maxFileSize) {
  this.showMessage('File too large to analyze');
  return;
}
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User configurable: Default 1GB limit, but power users can adjust. No crashes from analyzing massive files! 💪

Lessons Learned: Architecture in Practice 📚

What Worked Brilliantly ✨

  1. Manager-Service Pattern: Adding new features is a joy, not a nightmare
  2. TypeScript Strict Mode: Caught dozens of bugs before they reached users
  3. Result Pattern: Error handling became predictable and testable
  4. Separation of Concerns: UI, business logic, and data access never mix

What I'd Do Differently 🤔

  1. More Granular Interfaces: Some interfaces grew a bit too large
  2. Better Dependency Injection: Would make testing even easier
  3. Event-Driven Architecture: Could reduce coupling between managers

The Human Side 💝

Building this architecture wasn't just about code—it was about future me. Every design decision was made thinking: "Will I understand this in 6 months? Will I be able to extend it without breaking things?"

The answer, looking back after multiple feature releases, is a resounding YES! 🎉

What's Next? 🗺️

In Part 3, we'll dive deep into the features that make File Insights special—from smart size formatting to real-time updates to the command palette integration.

Part 4 will cover the technical challenges and creative solutions, including performance optimization and error handling.

Part 5 wraps up with testing strategies, performance considerations, and the roadmap ahead.

Architecture nerds unite! 🤓 What's your favorite pattern for VS Code extensions? Share your thoughts in the comments!

🔗 **Useful Links:**

📖 **Next up: Part 3 - Feature Deep-Dive: The Magic Behind the User Experience

Building quality software takes time and care. If File Insights has made your development workflow smoother, please consider ⭐ starring the repository! 🙏

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