diff --git a/src/auth.js b/src/auth.js
index 3a4b5c6..7d8e9f0 100644
--- a/src/auth.js
+++ b/src/auth.js
@@ -12,7 +12,9 @@ function authenticate(user) {
   const token = generateToken(user.id);
   const expiry = Date.now() + 3600000;
 
-  return { token, expiry };
+  return {
+    token,
+    expiry,
+    refreshToken: generateRefreshToken(user.id)
+  };
 }

@@ -5,7 +5,7 @@ const config = {
   port: 3000,
-  host: "localhost",
+  host: "0.0.0.0",
   debug: false
 };
@@ -45,6 +45,8 @@ function startServer() {
   app.listen(config.port);
+  console.log(`Server running on ${config.host}:${config.port}`);
+  monitor.ping();
 }

# Show unstaged changes (what you've modified but haven't git-added)
git diff
 
# Same thing, explicit
git diff --

# Show staged changes (what will go into the next commit)
git diff --staged
 
# Older alias, same thing
git diff --cached

# Show ALL changes — both staged and unstaged
git diff HEAD

# Any variant can take file paths
git diff -- src/app.js
git diff --staged -- src/app.js src/config.js
git diff HEAD -- "*.test.js"

# Diff between any two commits (by SHA, tag, or branch)
git diff abc1234 def5678
git diff v1.0 v2.0
git diff main feature

# These are equivalent:
git diff main feature
git diff main..feature

# Show only changes on feature since it diverged from main
git diff main...feature
 
# Equivalent to:
git diff $(git merge-base main feature) feature

git diff --stat main..feature

# Limit the width of the stat output
git diff --stat=80 main..feature
 
# Stat with a count limit (only top N files)
git diff --stat main..feature | head -20

git diff --name-only main..feature

git diff --name-status main..feature

git diff --shortstat main..feature

# Show only added files
git diff --diff-filter=A --name-only main..feature
 
# Show only deleted files
git diff --diff-filter=D --name-only main..feature
 
# Show only modified files (exclude additions and deletions)
git diff --diff-filter=M --name-only main..feature
 
# Exclude renames
git diff --diff-filter=d --name-only main..feature   # lowercase = exclude

git diff --word-diff

git diff --word-diff=color

# Treat each character as a "word" (useful for comparing hashes, IDs)
git diff --word-diff-regex=.
 
# Split on whitespace only (default is more aggressive)
git diff --word-diff-regex='[^ ]+'
 
# Split on programming tokens
git diff --word-diff-regex='[a-zA-Z_][a-zA-Z0-9_]*|[^[:space:]]'

# Ignore all whitespace changes
git diff -w
git diff --ignore-all-space
 
# Ignore changes in amount of whitespace (but not addition/removal)
git diff -b
git diff --ignore-space-change
 
# Ignore blank lines added or removed
git diff --ignore-blank-lines
 
# Ignore whitespace at end of lines
git diff --ignore-space-at-eol

# Highlight trailing whitespace and other problems
git diff --check

# Show 5 lines of context instead of the default 3
git diff -U5
 
# Show 10 lines of context
git diff -U10
 
# Show zero context (only changed lines)
git diff -U0
 
# Show the entire file (maximum context)
git diff -U99999

# First parent (default)
HEAD^     # = HEAD^1 = C
 
# Second parent (the merged branch)
HEAD^2    # = F

# Go back 2, then take the second parent
HEAD~2^2
 
# Go to merge commit's second parent, then back 1
HEAD^2~1

# Compare current commit with its parent
git diff HEAD~1 HEAD
 
# Compare two commits ago with current
git diff HEAD~2 HEAD
 
# Compare the two parents of a merge commit
git diff HEAD^1 HEAD^2
 
# What changed in just the last commit?
git diff HEAD~1..HEAD
# Or simply:
git show HEAD

# See what SHA a reference resolves to
git rev-parse HEAD
git rev-parse HEAD~3
git rev-parse main^2
 
# Short SHA
git rev-parse --short HEAD
git rev-parse --short=7 HEAD~2

# Set VS Code as the diff tool
git config --global diff.tool vscode
 
# Tell Git how to launch it
git config --global difftool.vscode.cmd 'code --wait --diff $LOCAL $REMOTE'
 
# Disable the "Launch VS Code?" prompt
git config --global difftool.prompt false

git config --global diff.tool smerge
git config --global difftool.smerge.cmd 'smerge "$LOCAL" "$REMOTE"'

git config --global diff.tool vimdiff

git config --global diff.tool meld
# Meld auto-detects, no cmd config needed

git config --global diff.tool kdiff3
# KDiff3 auto-detects, no cmd config needed

# Launch the configured diff tool
git difftool main..feature
 
# Use a specific tool (overrides config)
git difftool --tool=meld main..feature
 
# Skip the confirmation prompt
git difftool --no-prompt main..feature
 
# Compare staged changes in a tool
git difftool --staged
 
# Open all changed files at once (directory diff)
git difftool --dir-diff main..feature

git difftool --dir-diff main..feature

# This is what a PR diff shows:
git diff main...feature
 
# NOT this:
git diff main..feature

# Fetch the PR branch
git fetch origin pull/123/head:pr-123
git checkout pr-123
 
# See the summary
git diff --stat main...pr-123
 
# See file-level changes
git diff --name-status main...pr-123
 
# Review the full diff
git diff main...pr-123
 
# Or file by file in a diff tool
git difftool main...pr-123

# Focus on a specific file in the PR
git diff main...feature -- src/critical-file.js
 
# Ignore whitespace (focus on logic changes)
git diff -w main...feature
 
# Word-level diff for config or documentation changes
git diff --word-diff main...feature -- "*.md"
 
# How many lines changed per file?
git diff --stat main...feature
 
# Show only the list of changed files
git diff --name-only main...feature

mkdir diff-lab && cd diff-lab
git init
 
# Create initial project structure
mkdir -p src tests docs
 
cat > src/calculator.js << 'EOF'
function add(a, b) {
  return a + b;
}
 
function subtract(a, b) {
  return a - b;
}
 
function multiply(a, b) {
  return a * b;
}
 
function divide(a, b) {
  return a / b;
}
 
module.exports = { add, subtract, multiply, divide };
EOF
 
cat > src/formatter.js << 'EOF'
function formatCurrency(amount) {
  return "$" + amount.toFixed(2);
}
 
function formatPercent(value) {
  return (value * 100).toFixed(1) + "%";
}
 
module.exports = { formatCurrency, formatPercent };
EOF
 
cat > docs/README.md << 'EOF'
# Calculator App
 
A simple calculator with basic arithmetic operations.
 
## Features
- Addition
- Subtraction
- Multiplication
- Division
EOF
 
cat > tests/calculator.test.js << 'EOF'
const { add, subtract, multiply, divide } = require('../src/calculator');
 
test('add', () => expect(add(2, 3)).toBe(5));
test('subtract', () => expect(subtract(5, 3)).toBe(2));
test('multiply', () => expect(multiply(3, 4)).toBe(12));
test('divide', () => expect(divide(10, 2)).toBe(5));
EOF
 
git add .
git commit -m "Initial project setup"
git tag v1.0

# Make changes to two files WITHOUT staging
cat > src/calculator.js << 'EOF'
function add(a, b) {
  if (typeof a !== 'number' || typeof b !== 'number') {
    throw new TypeError('Arguments must be numbers');
  }
  return a + b;
}
 
function subtract(a, b) {
  return a - b;
}
 
function multiply(a, b) {
  return a * b;
}
 
function divide(a, b) {
  if (b === 0) {
    throw new Error('Division by zero');
  }
  return a / b;
}
 
module.exports = { add, subtract, multiply, divide };
EOF
 
echo "// v1.1 update" >> src/formatter.js

# 1. See unstaged changes (working dir vs. index)
git diff
# You should see changes in BOTH calculator.js and formatter.js
 
# 2. Stage only calculator.js
git add src/calculator.js
 
# 3. Now check each area
git diff
# Only formatter.js appears (calculator.js is staged, no longer "unstaged")
 
git diff --staged
# Only calculator.js appears (it's staged, waiting to be committed)
 
git diff HEAD
# BOTH files appear (everything different from last commit)

# Commit the staged changes
git commit -m "feat: add input validation to calculator"
 
# Stage and commit the remaining change
git add src/formatter.js
git commit -m "chore: add version comment"
 
# Now look at the diff between v1.0 and current
git diff v1.0 HEAD

# Verify your answers
git diff --stat v1.0 HEAD
git diff --shortstat v1.0 HEAD
git diff --name-status v1.0 HEAD

# Create a feature branch
git checkout -b feature/advanced-math
 
cat > src/calculator.js << 'EOF'
function add(a, b) {
  if (typeof a !== 'number' || typeof b !== 'number') {
    throw new TypeError('Arguments must be numbers');
  }
  return a + b;
}
 
function subtract(a, b) {
  return a - b;
}
 
function multiply(a, b) {
  return a * b;
}
 
function divide(a, b) {
  if (b === 0) {
    throw new Error('Division by zero');
  }
  return a / b;
}
 
function power(base, exp) {
  return Math.pow(base, exp);
}
 
function sqrt(n) {
  if (n < 0) throw new Error('Cannot sqrt negative number');
  return Math.sqrt(n);
}
 
module.exports = { add, subtract, multiply, divide, power, sqrt };
EOF
 
git add src/calculator.js
git commit -m "feat: add power and sqrt functions"
 
# Now make a change on main too (simulating team activity)
git checkout main
 
cat > docs/README.md << 'EOF'
# Calculator App
 
A simple calculator with basic arithmetic operations.
 
## Features
- Addition
- Subtraction
- Multiplication
- Division
 
## Installation
Run `npm install` to get started.
EOF
 
git add docs/README.md
git commit -m "docs: add installation instructions"

# Two-dot: raw difference between branch tips
git diff main..feature/advanced-math --stat
 
# Three-dot: only what the feature branch changed (since diverging)
git diff main...feature/advanced-math --stat

git checkout main
 
# Make prose changes to README
cat > docs/README.md << 'EOF'
# Calculator Application
 
A powerful calculator with comprehensive arithmetic operations and input validation.
 
## Features
- Addition
- Subtraction
- Multiplication
- Division (with zero-check)
 
## Installation
Run `npm install` to get started.
EOF
 
git add docs/README.md
 
# Compare with standard diff vs word diff
echo "=== Standard diff ==="
git diff --staged -- docs/README.md
 
echo ""
echo "=== Word diff ==="
git diff --staged --word-diff -- docs/README.md

git commit -m "docs: improve README descriptions"

# Merge the feature branch to create a merge commit
git merge --no-ff feature/advanced-math -m "Merge feature/advanced-math"
 
# Explore graph traversal
echo "Current commit (HEAD):"
git log --oneline -1
 
echo ""
echo "One commit back (HEAD~1):"
git log --oneline -1 HEAD~1
 
echo ""
echo "Two commits back (HEAD~2):"
git log --oneline -1 HEAD~2
 
echo ""
echo "Merge commit's first parent (HEAD^1):"
git log --oneline -1 HEAD^1
 
echo ""
echo "Merge commit's second parent (HEAD^2):"
git log --oneline -1 HEAD^2

# What did the merge commit bring in?
# (Compare the two parents of the merge)
git diff HEAD^1 HEAD^2 --stat
 
# What changed in the last 3 commits?
git diff HEAD~3 HEAD --stat
 
# What's different between the merge's parents?
git diff HEAD^1..HEAD^2

# Create multiple types of changes
git checkout -b feature/cleanup
 
# Add a new file
cat > src/utils.js << 'EOF'
function clamp(value, min, max) {
  return Math.min(Math.max(value, min), max);
}
module.exports = { clamp };
EOF
 
# Delete a file
rm src/formatter.js
 
# Modify a file
echo "// Updated" >> src/calculator.js
 
git add .
git commit -m "refactor: add utils, remove formatter, update calculator"

# What files were added?
git diff --diff-filter=A --name-only HEAD~1..HEAD
 
# What files were deleted?
git diff --diff-filter=D --name-only HEAD~1..HEAD
 
# What files were modified?
git diff --diff-filter=M --name-only HEAD~1..HEAD
 
# Full name-status view
git diff --name-status HEAD~1..HEAD