# History API Endpoints Documentation

## Overview

The History API provides complete access to historical changes for all major entities in the ThrillTrack system. Built on top of the django-pghistory library, this API enables:

- **Historical Tracking**: View complete history of changes to entities
- **Event Comparison**: Compare different versions of entities over time
- **Field History**: Track changes to specific fields
- **Activity Summaries**: Get statistics about entity modifications
- **Rollback Capabilities**: Restore entities to previous states (admin only)

## Supported Entities

The History API is available for the following entities:

- **Parks** (`/api/v1/parks/{park_id}/history/`)
- **Rides** (`/api/v1/rides/{ride_id}/history/`)
- **Companies** (`/api/v1/companies/{company_id}/history/`)
- **Ride Models** (`/api/v1/ride-models/{model_id}/history/`)
- **Reviews** (`/api/v1/reviews/{review_id}/history/`)

Additionally, generic history endpoints are available:
- **Generic Event Access** (`/api/v1/history/events/{event_id}`)
- **Generic Event Comparison** (`/api/v1/history/compare`)

## Authentication & Authorization

### Access Levels

The History API implements a tiered access control system:

#### 1. Public (Unauthenticated)
- **Access Window**: Last 30 days
- **Permissions**: Read-only access to recent history
- **Use Cases**: Public transparency, recent changes visibility

#### 2. Authenticated Users
- **Access Window**: Last 1 year
- **Permissions**: Read-only access to extended history
- **Use Cases**: User research, tracking their contributions

#### 3. Moderators/Admins/Superusers
- **Access Window**: Unlimited (entire history)
- **Permissions**: Full read access + rollback capabilities
- **Use Cases**: Moderation, auditing, data recovery

### Rollback Permissions

Only users with moderator, admin, or superuser privileges can perform rollbacks:
- Check via `can_rollback` field in responses
- Requires explicit permission check
- Creates audit trail of rollback actions

## Endpoint Reference

### 1. List Entity History

Get paginated history of changes to an entity.

**Endpoint Pattern**: `GET /{entity-type}/{entity-id}/history/`

**Query Parameters**:
- `page` (integer, default: 1): Page number
- `page_size` (integer, default: 50, max: 100): Items per page
- `date_from` (string, format: YYYY-MM-DD): Filter from date
- `date_to` (string, format: YYYY-MM-DD): Filter to date

**Response**: `200 OK`
```json
{
  "entity_id": "uuid-string",
  "entity_type": "park|ride|company|ridemodel|review",
  "entity_name": "Entity Display Name",
  "total_events": 150,
  "accessible_events": 150,
  "access_limited": false,
  "access_reason": "Full access (moderator)",
  "events": [
    {
      "id": 12345,
      "timestamp": "2024-01-15T10:30:00Z",
      "operation": "insert|update|delete",
      "snapshot": {
        "id": "uuid",
        "name": "Example Park",
        "status": "operating",
        ...
      },
      "changed_fields": ["name", "status"],
      "change_summary": "Updated name and status",
      "can_rollback": true
    }
  ],
  "pagination": {
    "page": 1,
    "page_size": 50,
    "total_pages": 3,
    "total_items": 150
  }
}
```

**Examples**:
```bash
# Get park history
GET /api/v1/parks/123e4567-e89b-12d3-a456-426614174000/history/

# Get ride history with date filter
GET /api/v1/rides/987fcdeb-51a2-43f1-9876-543210fedcba/history/?date_from=2024-01-01&date_to=2024-12-31

# Get company history, page 2
GET /api/v1/companies/456e789a-b12c-34d5-e678-901234567890/history/?page=2&page_size=100
```

### 2. Get Specific History Event

Retrieve detailed information about a single historical event.

**Endpoint Pattern**: `GET /{entity-type}/{entity-id}/history/{event-id}/`

**Response**: `200 OK`
```json
{
  "id": 12345,
  "timestamp": "2024-01-15T10:30:00Z",
  "operation": "update",
  "entity_id": "uuid-string",
  "entity_type": "park",
  "entity_name": "Example Park",
  "snapshot": {
    "id": "uuid",
    "name": "Example Park",
    "status": "operating",
    ...
  },
  "changed_fields": ["name", "status"],
  "metadata": {},
  "can_rollback": true,
  "rollback_preview": null
}
```

**Examples**:
```bash
# Get specific park event
GET /api/v1/parks/123e4567-e89b-12d3-a456-426614174000/history/12345/

# Get specific review event
GET /api/v1/reviews/67890/history/54321/
```

### 3. Compare Two History Events

Compare two historical snapshots to see what changed between them.

**Endpoint Pattern**: `GET /{entity-type}/{entity-id}/history/compare/`

**Query Parameters**:
- `event1` (integer, required): First event ID
- `event2` (integer, required): Second event ID

**Response**: `200 OK`
```json
{
  "entity_id": "uuid-string",
  "entity_type": "park",
  "entity_name": "Example Park",
  "event1": {
    "id": 12345,
    "timestamp": "2024-01-15T10:30:00Z",
    "snapshot": {...}
  },
  "event2": {
    "id": 12346,
    "timestamp": "2024-01-16T14:20:00Z",
    "snapshot": {...}
  },
  "differences": {
    "name": {
      "old_value": "Old Park Name",
      "new_value": "New Park Name",
      "changed": true
    },
    "status": {
      "old_value": "closed",
      "new_value": "operating",
      "changed": true
    }
  },
  "changed_field_count": 2,
  "unchanged_field_count": 15,
  "time_between": "1 day, 3:50:00"
}
```

**Examples**:
```bash
# Compare two park events
GET /api/v1/parks/123e4567-e89b-12d3-a456-426614174000/history/compare/?event1=12345&event2=12346

# Compare ride events
GET /api/v1/rides/987fcdeb-51a2-43f1-9876-543210fedcba/history/compare/?event1=100&event2=105
```

### 4. Compare Event with Current State

Compare a historical event with the entity's current state.

**Endpoint Pattern**: `GET /{entity-type}/{entity-id}/history/{event-id}/diff-current/`

**Response**: `200 OK`
```json
{
  "entity_id": "uuid-string",
  "entity_type": "park",
  "entity_name": "Example Park",
  "event": {
    "id": 12345,
    "timestamp": "2024-01-15T10:30:00Z",
    "snapshot": {...}
  },
  "current_state": {
    "name": "Current Park Name",
    "status": "operating",
    ...
  },
  "differences": {
    "name": {
      "old_value": "Historical Name",
      "new_value": "Current Park Name",
      "changed": true
    }
  },
  "changed_field_count": 3,
  "time_since": "45 days, 2:15:30"
}
```

**Examples**:
```bash
# Compare historical park state with current
GET /api/v1/parks/123e4567-e89b-12d3-a456-426614174000/history/12345/diff-current/

# Compare historical company state with current
GET /api/v1/companies/456e789a-b12c-34d5-e678-901234567890/history/98765/diff-current/
```

### 5. Rollback to Historical State

Restore an entity to a previous state. **Requires moderator/admin/superuser permissions**.

**Endpoint Pattern**: `POST /{entity-type}/{entity-id}/history/{event-id}/rollback/`

**Authentication**: Required (JWT)

**Request Body**:
```json
{
  "fields": ["name", "status"],  // Optional: specific fields to rollback
  "comment": "Reverting vandalism",  // Optional: reason for rollback
  "create_backup": true  // Optional: create backup event before rollback
}
```

**Response**: `200 OK`
```json
{
  "success": true,
  "message": "Successfully rolled back to event 12345",
  "rolled_back_fields": ["name", "status"],
  "backup_event_id": 12350,
  "new_event_id": 12351
}
```

**Error Responses**:
- `401 Unauthorized`: Authentication required
- `403 Forbidden`: Insufficient permissions
- `404 Not Found`: Event or entity not found
- `400 Bad Request`: Invalid rollback request

**Examples**:
```bash
# Full rollback of park
POST /api/v1/parks/123e4567-e89b-12d3-a456-426614174000/history/12345/rollback/
{
  "comment": "Reverting accidental changes",
  "create_backup": true
}

# Partial rollback (specific fields only)
POST /api/v1/rides/987fcdeb-51a2-43f1-9876-543210fedcba/history/54321/rollback/
{
  "fields": ["name", "description"],
  "comment": "Restoring original name and description",
  "create_backup": true
}
```

### 6. Get Field History

Track all changes to a specific field over time.

**Endpoint Pattern**: `GET /{entity-type}/{entity-id}/history/field/{field-name}/`

**Response**: `200 OK`
```json
{
  "entity_id": "uuid-string",
  "entity_type": "park",
  "entity_name": "Example Park",
  "field": "status",
  "field_type": "CharField",
  "changes": [
    {
      "event_id": 12346,
      "timestamp": "2024-01-16T14:20:00Z",
      "old_value": "closed",
      "new_value": "operating"
    },
    {
      "event_id": 12345,
      "timestamp": "2024-01-15T10:30:00Z",
      "old_value": "operating",
      "new_value": "closed"
    }
  ],
  "total_changes": 2,
  "first_recorded": "2023-06-01T08:00:00Z",
  "last_changed": "2024-01-16T14:20:00Z"
}
```

**Examples**:
```bash
# Track park status changes
GET /api/v1/parks/123e4567-e89b-12d3-a456-426614174000/history/field/status/

# Track ride height changes
GET /api/v1/rides/987fcdeb-51a2-43f1-9876-543210fedcba/history/field/height/

# Track company name changes
GET /api/v1/companies/456e789a-b12c-34d5-e678-901234567890/history/field/name/
```

### 7. Get Activity Summary

Get statistics about modifications to an entity.

**Endpoint Pattern**: `GET /{entity-type}/{entity-id}/history/summary/`

**Response**: `200 OK`
```json
{
  "entity_id": "uuid-string",
  "entity_type": "park",
  "entity_name": "Example Park",
  "total_events": 150,
  "total_updates": 145,
  "total_creates": 1,
  "total_deletes": 0,
  "first_event": "2023-01-01T00:00:00Z",
  "last_event": "2024-03-15T16:45:00Z",
  "most_active_period": "2024-01",
  "average_updates_per_month": 12.5,
  "most_changed_fields": [
    {"field": "status", "changes": 25},
    {"field": "description", "changes": 18},
    {"field": "ride_count", "changes": 15}
  ]
}
```

**Examples**:
```bash
# Get park activity summary
GET /api/v1/parks/123e4567-e89b-12d3-a456-426614174000/history/summary/

# Get review activity summary
GET /api/v1/reviews/67890/history/summary/
```

## Generic History Endpoints

### Get Any Event by ID

Retrieve any historical event by its ID, regardless of entity type.

**Endpoint**: `GET /api/v1/history/events/{event-id}`

**Response**: `200 OK`
```json
{
  "id": 12345,
  "timestamp": "2024-01-15T10:30:00Z",
  "operation": "update",
  "entity_type": "park",
  "entity_id": "uuid-string",
  "snapshot": {...},
  "changed_fields": ["name", "status"],
  "can_rollback": true
}
```

### Compare Any Two Events

Compare any two events, even across different entities.

**Endpoint**: `GET /api/v1/history/compare`

**Query Parameters**:
- `event1` (integer, required): First event ID
- `event2` (integer, required): Second event ID

**Response**: Similar to entity-specific comparison endpoint

## Access Control Details

### Time-Based Access Windows

Access windows are enforced based on user authentication level:

```python
# Access limits
PUBLIC_WINDOW = 30 days
AUTHENTICATED_WINDOW = 1 year
PRIVILEGED_WINDOW = Unlimited
```

### Access Reason Messages

The API provides clear feedback about access limitations:

- **"Full access (moderator)"**: Unlimited access
- **"Full access (admin)"**: Unlimited access
- **"Full access (superuser)"**: Unlimited access
- **"Access limited to last 365 days (authenticated user)"**: 1-year limit
- **"Access limited to last 30 days (public)"**: 30-day limit

## Rollback Safety Guidelines

### Before Performing a Rollback

1. **Review the Target State**: Use `diff-current` to see what will change
2. **Check Dependencies**: Consider impact on related entities
3. **Create Backup**: Always set `create_backup: true` for safety
4. **Add Comment**: Document why the rollback is being performed
5. **Use Partial Rollback**: When possible, rollback only specific fields

### Rollback Best Practices

```json
{
  "fields": ["name", "description"],  // Limit scope
  "comment": "Reverting vandalism on 2024-03-15",  // Document reason
  "create_backup": true  // Always true in production
}
```

### Audit Trail

All rollbacks create:
1. **Backup Event**: Snapshot before rollback (if `create_backup: true`)
2. **Rollback Event**: New event with restored state
3. **Audit Log**: Metadata tracking who performed rollback and why

## Error Handling

### Common Error Responses

**404 Not Found**
```json
{
  "error": "Entity not found"
}
```

**400 Bad Request**
```json
{
  "error": "Invalid date format. Use YYYY-MM-DD"
}
```

**403 Forbidden**
```json
{
  "error": "Only moderators and administrators can perform rollbacks"
}
```

**401 Unauthorized**
```json
{
  "error": "Authentication required"
}
```

### Error Codes

| Status Code | Meaning |
|-------------|---------|
| 200 | Success |
| 201 | Created |
| 400 | Bad Request (invalid parameters) |
| 401 | Unauthorized (authentication required) |
| 403 | Forbidden (insufficient permissions) |
| 404 | Not Found (entity or event not found) |
| 500 | Internal Server Error |

## Rate Limiting

The History API implements standard rate limiting:

- **Authenticated Users**: 100 requests per minute
- **Unauthenticated Users**: 20 requests per minute
- **Rollback Operations**: 10 per minute (additional limit)

Rate limit headers:
```
X-RateLimit-Limit: 100
X-RateLimit-Remaining: 95
X-RateLimit-Reset: 1617181723
```

## Performance Considerations

### Pagination

- Default page size: 50 events
- Maximum page size: 100 events
- Use pagination for large result sets

### Caching

- Event data is cached for 5 minutes
- Comparison results are cached for 2 minutes
- Current state comparisons are not cached

### Query Optimization

- Use date filters to reduce result sets
- Prefer field-specific history for focused queries
- Use summary endpoints for overview data

## Integration Examples

### Python (requests)

```python
import requests

# Get park history
response = requests.get(
    'https://api.thrilltrack.com/v1/parks/123/history/',
    params={'page': 1, 'page_size': 50},
    headers={'Authorization': 'Bearer YOUR_TOKEN'}
)
history = response.json()

# Compare two events
response = requests.get(
    'https://api.thrilltrack.com/v1/parks/123/history/compare/',
    params={'event1': 100, 'event2': 105}
)
comparison = response.json()

# Perform rollback
response = requests.post(
    'https://api.thrilltrack.com/v1/parks/123/history/100/rollback/',
    json={
        'comment': 'Reverting vandalism',
        'create_backup': True
    },
    headers={'Authorization': 'Bearer YOUR_TOKEN'}
)
```

### JavaScript (fetch)

```javascript
// Get ride history
const response = await fetch(
  'https://api.thrilltrack.com/v1/rides/456/history/',
  {
    headers: {
      'Authorization': `Bearer ${token}`
    }
  }
);
const history = await response.json();

// Compare with current state
const diffResponse = await fetch(
  'https://api.thrilltrack.com/v1/rides/456/history/200/diff-current/'
);
const diff = await diffResponse.json();
```

### cURL

```bash
# Get company history
curl -H "Authorization: Bearer TOKEN" \
  "https://api.thrilltrack.com/v1/companies/789/history/"

# Rollback to previous state
curl -X POST \
  -H "Authorization: Bearer TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"comment": "Reverting changes", "create_backup": true}' \
  "https://api.thrilltrack.com/v1/companies/789/history/150/rollback/"
```

## Troubleshooting

### Common Issues

**Issue**: "Access limited to last 30 days"
- **Solution**: Authenticate with valid credentials to extend access window

**Issue**: "Event not found or not accessible"
- **Solution**: Event may be outside your access window or doesn't exist

**Issue**: "Cannot rollback: Event not found"
- **Solution**: Verify event ID and ensure you have rollback permissions

**Issue**: Rate limit exceeded
- **Solution**: Implement exponential backoff or reduce request frequency

## Support

For additional support:
- **Documentation**: https://docs.thrilltrack.com/history-api
- **GitHub Issues**: https://github.com/thrilltrack/api/issues
- **Email**: api-support@thrilltrack.com

## Changelog

### Version 1.0 (Current)
- Initial release of History API
- Support for Parks, Rides, Companies, Ride Models, and Reviews
- Complete CRUD history tracking
- Comparison and rollback capabilities
- Tiered access control system