❌ Bad: "This is wrong."
✅ Good: "This could cause a race condition when multiple users
access simultaneously. Consider using a mutex here."

❌ Bad: "Why didn't you use X pattern?"
✅ Good: "Have you considered the Repository pattern? It would
make this easier to test. Here's an example: [link]"

❌ Bad: "Rename this variable."
✅ Good: "[nit] Consider `userCount` instead of `uc` for
clarity. Not blocking if you prefer to keep it."

Before diving into code, understand:

1. Read PR description and linked issue
2. Check PR size (>400 lines? Ask to split)
3. Review CI/CD status (tests passing?)
4. Understand the business requirement
5. Note any relevant architectural decisions

1. **Architecture & Design**
   - Does the solution fit the problem?
   - Are there simpler approaches?
   - Is it consistent with existing patterns?
   - Will it scale?

2. **File Organization**
   - Are new files in the right places?
   - Is code grouped logically?
   - Are there duplicate files?

3. **Testing Strategy**
   - Are there tests?
   - Do tests cover edge cases?
   - Are tests readable?

For each file:

1. **Logic & Correctness**
   - Edge cases handled?
   - Off-by-one errors?
   - Null/undefined checks?
   - Race conditions?

2. **Security**
   - Input validation?
   - SQL injection risks?
   - XSS vulnerabilities?
   - Sensitive data exposure?

3. **Performance**
   - N+1 queries?
   - Unnecessary loops?
   - Memory leaks?
   - Blocking operations?

4. **Maintainability**
   - Clear variable names?
   - Functions doing one thing?
   - Complex code commented?
   - Magic numbers extracted?

1. Summarize key concerns
2. Highlight what you liked
3. Make clear decision:
   - ✅ Approve
   - 💬 Comment (minor suggestions)
   - 🔄 Request Changes (must address)
4. Offer to pair if complex

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❌ "This will fail if the list is empty."
✅ "What happens if `items` is an empty array?"

❌ "You need error handling here."
✅ "How should this behave if the API call fails?"

❌ "This is inefficient."
✅ "I see this loops through all users. Have we considered
the performance impact with 100k users?"

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Use labels to indicate priority:

🔴 [blocking] - Must fix before merge
🟡 [important] - Should fix, discuss if disagree
🟢 [nit] - Nice to have, not blocking
💡 [suggestion] - Alternative approach to consider
📚 [learning] - Educational comment, no action needed
🎉 [praise] - Good work, keep it up!

Example:
"🔴 [blocking] This SQL query is vulnerable to injection.
Please use parameterized queries."

"🟢 [nit] Consider renaming `data` to `userData` for clarity."

"🎉 [praise] Excellent test coverage! This will catch edge cases."

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// Check for TypeScript-specific issues

// ❌ Using any defeats type safety
function processData(data: any) {  // Avoid any
    return data.value;
}

// ✅ Use proper types
interface DataPayload {
    value: string;
}
function processData(data: DataPayload) {
    return data.value;
}

// ❌ Not handling async errors
async function fetchUser(id: string) {
    const response = await fetch(`/api/users/${id}`);
    return response.json();  // What if network fails?
}

// ✅ Handle errors properly
async function fetchUser(id: string): Promise<User> {
    try {
        const response = await fetch(`/api/users/${id}`);
        if (!response.ok) {
            throw new Error(`HTTP ${response.status}`);
        }
        return await response.json();
    } catch (error) {
        console.error('Failed to fetch user:', error);
        throw error;
    }
}

// ❌ Mutation of props
function UserProfile({ user }: Props) {
    user.lastViewed = new Date();  // Mutating prop!
    return <div>{user.name}</div>;
}

// ✅ Don't mutate props
function UserProfile({ user, onView }: Props) {
    useEffect(() => {
        onView(user.id);  // Notify parent to update
    }, [user.id]);
    return <div>{user.name}</div>;
}

When reviewing significant changes:

1. **Design Document First**
   - For large features, request design doc before code
   - Review design with team before implementation
   - Agree on approach to avoid rework

2. **Review in Stages**
   - First PR: Core abstractions and interfaces
   - Second PR: Implementation
   - Third PR: Integration and tests
   - Easier to review, faster to iterate

3. **Consider Alternatives**
   - "Have we considered using [pattern/library]?"
   - "What's the tradeoff vs. the simpler approach?"
   - "How will this evolve as requirements change?"

// ❌ Poor test: Implementation detail testing
test('increments counter variable', () => {
    const component = render(<Counter />);
    const button = component.getByRole('button');
    fireEvent.click(button);
    expect(component.state.counter).toBe(1);  // Testing internal state
});

// ✅ Good test: Behavior testing
test('displays incremented count when clicked', () => {
    render(<Counter />);
    const button = screen.getByRole('button', { name: /increment/i });
    fireEvent.click(button);
    expect(screen.getByText('Count: 1')).toBeInTheDocument();
});

// Review questions for tests:
// - Do tests describe behavior, not implementation?
// - Are test names clear and descriptive?
// - Do tests cover edge cases?
// - Are tests independent (no shared state)?
// - Can tests run in any order?

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Traditional: Praise + Criticism + Praise (feels fake)

Better: Context + Specific Issue + Helpful Solution

Example:
"I noticed the payment processing logic is inline in the
controller. This makes it harder to test and reuse.

[Specific Issue]
The calculateTotal() function mixes tax calculation,
discount logic, and database queries, making it difficult
to unit test and reason about.

[Helpful Solution]
Could we extract this into a PaymentService class? That
would make it testable and reusable. I can pair with you
on this if helpful."

When author disagrees with your feedback:

1. **Seek to Understand**
   "Help me understand your approach. What led you to
   choose this pattern?"

2. **Acknowledge Valid Points**
   "That's a good point about X. I hadn't considered that."

3. **Provide Data**
   "I'm concerned about performance. Can we add a benchmark
   to validate the approach?"

4. **Escalate if Needed**
   "Let's get [architect/senior dev] to weigh in on this."

5. **Know When to Let Go**
   If it's working and not a critical issue, approve it.
   Perfection is the enemy of progress.

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