# T7.2: Versioning API Reference

## Overview

Full version history for all entities and edges. Track changes, diffs, and point-in-time state.

---

## Entities

### GET /memory/entities/{id}/versions
List all versions of an entity

**Request**:
```bash
curl -H "Authorization: Bearer $TOKEN" \
  http://localhost:8080/memory/entities/e_kubernetes/versions
```

**Response** (200 OK):
```json
{
  "entity_id": "e_kubernetes",
  "versions": [
    {
      "version_num": 3,
      "operation": "update",
      "snapshot": {"id": "e_kubernetes", "name": "Kubernetes", ...},
      "changed_at": "2025-01-30T10:15:00Z",
      "changed_by": "alice@example.com",
      "fields_changed": ["name", "description"]
    },
    {
      "version_num": 2,
      "operation": "update",
      ...
    },
    {
      "version_num": 1,
      "operation": "create",
      ...
    }
  ],
  "total": 3
}
```

---

### GET /memory/entities/{id}/versions/{num}
Get specific version

**Request**:
```bash
curl -H "Authorization: Bearer $TOKEN" \
  http://localhost:8080/memory/entities/e_kubernetes/versions/2
```

**Response** (200 OK):
```json
{
  "entity_id": "e_kubernetes",
  "version": {
    "version_num": 2,
    "operation": "update",
    "snapshot": {...},
    "changed_at": "2025-01-30T10:10:00Z",
    "changed_by": "alice@example.com",
    "fields_changed": ["description"]
  }
}
```

**Response** (404 Not Found):
```json
{
  "error": "Version 99 not found for entity e_kubernetes"
}
```

---

### GET /memory/entities/{id}/diff?from={v1}&to={v2}
Diff two versions

**Request**:
```bash
curl -H "Authorization: Bearer $TOKEN" \
  "http://localhost:8080/memory/entities/e_kubernetes/diff?from=1&to=3"
```

**Response** (200 OK):
```json
{
  "entity_id": "e_kubernetes",
  "diff": {
    "from_version": 1,
    "to_version": 3,
    "added_fields": [
      {
        "name": "new_attribute",
        "from_value": null,
        "to_value": "some_value"
      }
    ],
    "removed_fields": [],
    "modified_fields": [
      {
        "name": "description",
        "from_value": "Old description",
        "to_value": "New description"
      }
    ]
  }
}
```

**Response** (400 Bad Request):
```json
{
  "error": "from version must be < to version"
}
```

---

### GET /memory/entities/{id}/at?as_of={timestamp}
Query entity state at point in time

**Request**:
```bash
curl -H "Authorization: Bearer $TOKEN" \
  "http://localhost:8080/memory/entities/e_kubernetes/at?as_of=2025-01-16T00:00:00Z"
```

**Response** (200 OK):
```json
{
  "entity_id": "e_kubernetes",
  "as_of": "2025-01-16T00:00:00Z",
  "snapshot": {
    "version_num": 1,
    "operation": "create",
    "snapshot": {...},
    "changed_at": "2025-01-15T10:00:00Z",
    "changed_by": "bob@example.com",
    "fields_changed": []
  }
}
```

**Response** (404 Not Found):
```json
{
  "error": "No version of e_kubernetes existed before 2025-01-16T00:00:00Z"
}
```

---

## Edges

### GET /memory/edges/{id}/versions
List all versions of an edge

**Request**:
```bash
curl -H "Authorization: Bearer $TOKEN" \
  "http://localhost:8080/memory/edges/550e8400-e29b-41d4-a716-446655440000/versions"
```

**Response** (200 OK):
```json
{
  "edge_id": "550e8400-e29b-41d4-a716-446655440000",
  "versions": [
    {
      "version_num": 2,
      "operation": "update",
      "snapshot": {...},
      "changed_at": "2025-01-30T10:15:00Z",
      "changed_by": "alice@example.com",
      "fields_changed": ["weight"]
    }
  ],
  "total": 2
}
```

---

### GET /memory/edges/{id}/diff?from={v1}&to={v2}
Diff two edge versions

**Request**:
```bash
curl -H "Authorization: Bearer $TOKEN" \
  "http://localhost:8080/memory/edges/550e8400-e29b-41d4-a716-446655440000/diff?from=1&to=2"
```

**Response** (200 OK):
```json
{
  "edge_id": "550e8400-e29b-41d4-a716-446655440000",
  "diff": {
    "from_version": 1,
    "to_version": 2,
    "added_fields": [],
    "removed_fields": [],
    "modified_fields": [
      {
        "name": "weight",
        "from_value": 0.5,
        "to_value": 0.8
      }
    ]
  }
}
```

---

## Use Cases

### Audit Trail
```bash
# See who changed what and when
curl -H "Authorization: Bearer $TOKEN" \
  http://localhost:8080/memory/entities/e_kubernetes/versions
```

### Rollback
```bash
# Get old version
curl -H "Authorization: Bearer $TOKEN" \
  http://localhost:8080/memory/entities/e_kubernetes/versions/1 | jq .version.snapshot

# Re-ingest to restore
curl -X POST http://localhost:8080/memory/ingest \
  -H "Authorization: Bearer $TOKEN" \
  -d '{...snapshot...}'
```

### Time Travel
```bash
# See memory as it was 2 weeks ago
curl -H "Authorization: Bearer $TOKEN" \
  "http://localhost:8080/memory/entities/e_kubernetes/at?as_of=2025-01-16T00:00:00Z"

# Query entire graph as it was then
curl -H "Authorization: Bearer $TOKEN" \
  "http://localhost:8080/memory/query?query=kubernetes&as_of=2025-01-16T00:00:00Z"
```

### Compliance
```bash
# Generate audit report
curl -H "Authorization: Bearer $TOKEN" \
  http://localhost:8080/memory/entities/e_kubernetes/versions \
  | jq '.versions[] | {changed_at, changed_by, fields_changed}'
```

---

## Error Codes

| Code | Meaning |
|------|---------|
| 200 | Success |
| 400 | Bad request (invalid query) |
| 401 | Unauthorized (missing/invalid JWT) |
| 403 | Forbidden (insufficient permissions) |
| 404 | Version not found |
| 429 | Rate limit exceeded (200 req/hr per endpoint) |
| 500 | Internal error |

---

## Rate Limits

| Endpoint | Limit |
|----------|-------|
| /versions | 200/hr |
| /versions/{num} | 200/hr |
| /diff | 100/hr |
| /at | 500/hr |

---

## Timestamps

All timestamps are RFC3339 format (ISO 8601 with timezone):
- `2025-01-30T10:15:00Z` ✅
- `2025-01-30T10:15:00+00:00` ✅
- `2025-01-30T10:15:00` ❌ (missing timezone)