Multi file Project Navigation

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Inspecting a repository

cwd: /Users/jeremy/Repos/Claude Code Course/Express-login-demo

> show me the file structure of this application

• List(~/Repos/Claude Code Course/Express-login-demo)
└ Listed 12 paths (ctrl+r to expand)

• Express-login-demo/
├─ config/
│  └─ database.js
├─ examples.md
├─ node_modules/
├─ package.json
├─ package-lock.json
├─ routes/
│  └─ auth.js
├─ schema.sql
└─ server.js

Summary of main components:
– server.js – Main Express application entry point
– config/database.js – PostgreSQL database connection pool
– routes/auth.js – Authentication routes (currently only login)
– schema.sql – Database schema definition

Route-Controller Architecture:
– Routes are mounted using Express Router patterns:
  • server.js mounts auth routes at /api/auth (e.g., server.js:11)
  • routes/auth.js handles the /login endpoint (inline controller logic)
– No separate controller layer — business logic is embedded in route handlers

Database:
– PostgreSQL (pg) with a connection pool (config/database.js)
– Single users table: id, email, name, password, timestamps (schema.sql)
– Email index for performance
– Uses bcrypt for password hashing and JWT for authentication tokens

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Example: Files affected by a database migration

• Using parameterized queries and a query builder/ORM improves portability.
• Placeholder syntax and pool configuration are the main code-level differences.

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Example file: current PostgreSQL pool (before migration)

const { Pool } = require('pg');

const pool = new Pool({
  host: process.env.DB_HOST,
  port: process.env.DB_PORT,
  database: process.env.DB_NAME,
  user: process.env.DB_USER,
  password: process.env.DB_PASSWORD,
});

pool.on('connect', () => {
  console.log('Connected to PostgreSQL database');
});

module.exports = pool;

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How Claude performs multi-file edits safely

• Inspect: Ask Claude to summarize the project structure and identify key components to target.
• Plan: Request a list of files and specific changes required for a migration or refactor.
• Restrict: Specify which files may be changed and which must remain unchanged.
• Apply & Verify: Have Claude perform the changes and then verify that the specified files were refactored.

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Practical dos and don’ts for multi-file work with Claude

• Do provide contextual groupings (for example, “the auth system consists of these three files”) instead of pasting every file.
• Do ask Claude to analyze relationships between files (routes → controllers → database) before making large changes.
• Don’t paste a massive, unrelated list of files without context; Claude already knows the repo structure and will reprocess unnecessarily.
• Don’t copy code from an unrelated stack (for example, React components) and expect it to work unmodified in a Node/Express application.

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Why multi-file awareness matters

• Refactors where business logic moves between layers (routes → controllers → services).
• Migrations (databases, auth providers) that touch configuration, schema, and queries.
• Understanding legacy codebases where relationships span several files.

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Links and references

• Express - Node.js web framework
• PostgreSQL Documentation
• mysql2 on npm
• MariaDB Documentation