# Change Impact Analysis

## Overview

Framework for analyzing the impact of proposed changes on a system.

---

## Impact Analysis Process

```
┌──────────┐    ┌──────────┐    ┌──────────┐    ┌──────────┐
│ Identify │───▶│ Analyze  │───▶│ Assess   │───▶│ Document │
│  Change  │    │ Impact   │    │  Risk    │    │ Decision │
└──────────┘    └──────────┘    └──────────┘    └──────────┘
```

---

## Change Request Template

```markdown
# Change Impact Analysis: [Change Name]

## Change Overview

| Field        | Value                                      |
| ------------ | ------------------------------------------ |
| Request ID   | CHG-[XXX]                                  |
| Requested By | [Name]                                     |
| Date         | YYYY-MM-DD                                 |
| Priority     | Low / Medium / High / Critical             |
| Status       | Draft / Under Review / Approved / Rejected |

---

## 1. Change Description

### What is being changed?

[Clear description of the proposed change]

### Why is this change needed?

[Business justification]

### What is the expected outcome?

[Success criteria]

---

## 2. Scope Analysis

### Files Affected

| File/Module        | Change Type | Effort |
| ------------------ | ----------- | ------ |
| src/auth/login.ts  | Modify      | Medium |
| src/api/users.ts   | Modify      | Low    |
| tests/auth.test.ts | Add         | Medium |

### Dependencies

| Dependency   | Impact        | Action Needed |
| ------------ | ------------- | ------------- |
| User Service | Breaking      | Update API    |
| Auth Library | Compatible    | None          |
| Database     | Schema change | Migration     |

### APIs Affected

| API         | Change             | Breaking |
| ----------- | ------------------ | -------- |
| POST /login | New field          | No       |
| GET /user   | New response field | No       |

---

## 3. Impact Matrix

### Technical Impact

| Area            | Impact Level | Description           |
| --------------- | ------------ | --------------------- |
| Performance     | Low          | No significant change |
| Security        | Medium       | New auth flow         |
| Scalability     | Low          | No change             |
| Maintainability | Medium       | Added complexity      |

### Business Impact

| Area       | Impact Level | Description    |
| ---------- | ------------ | -------------- |
| Users      | Medium       | New login step |
| Operations | Low          | Minor training |
| Revenue    | None         | N/A            |

---

## 4. Risk Assessment

### Risks

| Risk                   | Probability | Impact | Mitigation        |
| ---------------------- | ----------- | ------ | ----------------- |
| User confusion         | Medium      | Medium | Clear UI guidance |
| Integration failure    | Low         | High   | Thorough testing  |
| Performance regression | Low         | Medium | Load testing      |

### Rollback Plan

1. [Step 1 to revert]
2. [Step 2 to revert]
3. [Verification steps]

---

## 5. Implementation Plan

### Tasks

| Task                 | Owner  | Estimate | Dependencies   |
| -------------------- | ------ | -------- | -------------- |
| Update auth logic    | [Name] | 2 days   | None           |
| Add tests            | [Name] | 1 day    | Auth logic     |
| Update documentation | [Name] | 0.5 days | Implementation |

### Timeline

| Phase       | Start | End   | Owner    |
| ----------- | ----- | ----- | -------- |
| Development | MM/DD | MM/DD | Dev Team |
| Testing     | MM/DD | MM/DD | QA Team  |
| Deployment  | MM/DD | MM/DD | DevOps   |

---

## 6. Testing Requirements

- [ ] Unit tests for changed code
- [ ] Integration tests for affected APIs
- [ ] Regression testing
- [ ] Performance testing
- [ ] User acceptance testing

---

## 7. Communication Plan

| Audience     | Channel | When          | Owner  |
| ------------ | ------- | ------------- | ------ |
| Dev Team     | Slack   | Before start  | [Name] |
| Stakeholders | Email   | Before deploy | [Name] |
| Users        | In-app  | After deploy  | [Name] |

---

## 8. Approval

| Approver | Role          | Decision | Date |
| -------- | ------------- | -------- | ---- |
| [Name]   | Tech Lead     |          |      |
| [Name]   | Product Owner |          |      |
| [Name]   | Security      |          |      |

---

## 9. Post-Implementation

### Verification Steps

- [ ] [Verification 1]
- [ ] [Verification 2]

### Monitoring

- [ ] Error rates checked
- [ ] Performance baseline compared
- [ ] User feedback collected
```

---

## Dependency Analysis

### Code Dependency Map

```
┌─────────────────┐
│   Changed File   │
└────────┬────────┘
         │
    ┌────┴────┐
    ▼         ▼
┌───────┐  ┌───────┐
│Direct │  │Direct │
│Dep 1  │  │Dep 2  │
└───┬───┘  └───┬───┘
    │          │
    ▼          ▼
┌───────┐  ┌───────┐
│Indirect│ │Indirect│
│Dep    │  │Dep    │
└───────┘  └───────┘
```

### Finding Dependencies

```bash
# Find files that import the changed file
grep -r "import.*from.*'./changed-file'" src/

# TypeScript: Find usages
npx ts-unused-exports tsconfig.json

# Git: Find files that change together
git log --oneline --name-only -- src/changed-file.ts | \
  grep -v "^[a-f0-9]" | sort | uniq -c | sort -rn
```

---

## Impact Severity Matrix

| Probability ↓ / Impact → | Low    | Medium | High     |
| ------------------------ | ------ | ------ | -------- |
| **High**                 | Medium | High   | Critical |
| **Medium**               | Low    | Medium | High     |
| **Low**                  | Low    | Low    | Medium   |

---

## Quick Impact Checklist

### Before Approving

- [ ] All affected files identified
- [ ] Breaking changes documented
- [ ] Dependencies analyzed
- [ ] Risks assessed
- [ ] Rollback plan exists
- [ ] Testing requirements defined
- [ ] Timeline realistic
- [ ] Stakeholders notified

### Red Flags

- 🚩 Many files affected
- 🚩 Database schema changes
- 🚩 Public API breaking changes
- 🚩 Security-related changes
- 🚩 No rollback plan
- 🚩 No testing plan
- 🚩 Rushed timeline