# API Reference

Arbiter provides a REST API for managing reviews, monitoring metrics, and receiving
webhook events from GitHub and GitLab.

## Interactive Documentation

The API provides auto-generated interactive documentation:

- **Swagger UI:** `http://localhost:8000/docs`
- **ReDoc:** `http://localhost:8000/redoc`
- **OpenAPI Schema:** `http://localhost:8000/openapi.json`

## Base URL

All API endpoints are relative to the base URL:

```
http://localhost:8000
```

In production, use your configured domain with HTTPS.

## Authentication

### Webhook Authentication

Webhooks use signature/token verification:

**GitHub:**
- Header: `X-Hub-Signature-256`
- Format: `sha256=<hmac_hex_digest>`
- Algorithm: HMAC-SHA256 using `ARBITER_GITHUB_WEBHOOK_SECRET`

**GitLab:**
- Header: `X-GitLab-Token`
- Format: Plain token string
- Verification: Constant-time comparison with `ARBITER_GITLAB_WEBHOOK_TOKEN`

### API Authentication

The REST API currently does not require authentication. For production deployments,
place it behind a reverse proxy with authentication or configure network-level access
controls.

## REST Endpoints

### Reviews

#### List Reviews

```http
GET /api/reviews
```

**Query Parameters:**

| Parameter | Type | Default | Description |
|-----------|------|---------|-------------|
| `page` | integer | 1 | Page number (1-indexed) |
| `page_size` | integer | 20 | Items per page (1-100) |
| `repository` | string | - | Filter by repository name |
| `status` | string | - | Filter by status (pending, processing, completed, failed) |
| `verdict` | string | - | Filter by verdict (approve, request_changes, comment) |
| `author` | string | - | Filter by PR author |

**Response:**

```json
{
  "items": [
    {
      "id": "abc123",
      "repository": "owner/repo",
      "pr_number": 42,
      "pr_title": "Add new feature",
      "author": "username",
      "status": "completed",
      "verdict": "request_changes",
      "verdict_confidence": 0.92,
      "finding_count": 5,
      "critical_count": 1,
      "high_count": 2,
      "total_cost_usd": 0.12,
      "created_at": "2025-06-04T10:00:00Z",
      "completed_at": "2025-06-04T10:02:30Z"
    }
  ],
  "total": 150,
  "page": 1,
  "page_size": 20,
  "pages": 8
}
```

#### Get Review Detail

```http
GET /api/reviews/{review_id}
```

**Response:**

```json
{
  "id": "abc123",
  "repository": "owner/repo",
  "pr_number": 42,
  "pr_title": "Add new feature",
  "base_sha": "abc1234",
  "head_sha": "def5678",
  "author": "username",
  "is_draft": false,
  "status": "completed",
  "verdict": "request_changes",
  "verdict_confidence": 0.92,
  "verdict_reasoning": "Critical security issue requires resolution",
  "total_tokens": 15000,
  "total_cost_usd": 0.12,
  "tokens_by_agent": {"security": 5000, "style": 5000, "complexity": 5000},
  "cost_by_agent": {"security": 0.04, "style": 0.04, "complexity": 0.04},
  "created_at": "2025-06-04T10:00:00Z",
  "started_at": "2025-06-04T10:00:05Z",
  "completed_at": "2025-06-04T10:02:30Z",
  "error_message": null,
  "findings": [
    {
      "id": "finding-1",
      "agent": "security",
      "file": "src/auth.py",
      "line_start": 42,
      "line_end": 45,
      "severity": "critical",
      "confidence": 0.95,
      "title": "SQL Injection Vulnerability",
      "description": "User input is passed directly to SQL query",
      "reasoning": "String interpolation in SQL queries allows injection",
      "suggestion": "Use parameterized queries",
      "references": ["https://owasp.org/..."],
      "prompt_version": "security-v1.0"
    }
  ],
  "conflicts": [
    {
      "id": "conflict-1",
      "finding_ids": ["finding-2", "finding-3"],
      "nature": "opposing_recommendation",
      "description": "Style suggests splitting function, complexity wants to keep it",
      "severity_weight": 0.5,
      "resolution": "Keep function together for readability",
      "winning_finding_id": "finding-3"
    }
  ]
}
```

#### Get Deliberation Log

```http
GET /api/reviews/{review_id}/deliberation
```

**Response:**

```json
{
  "review_id": "abc123",
  "steps": [
    {
      "id": "step-1",
      "step_type": "agent_start",
      "timestamp": "2025-06-04T10:00:10Z",
      "description": "Security agent started review",
      "details": {"agent": "security"},
      "sequence": 1
    },
    {
      "id": "step-2",
      "step_type": "finding_added",
      "timestamp": "2025-06-04T10:00:45Z",
      "description": "Security agent found SQL injection",
      "details": {"finding_id": "finding-1", "severity": "critical"},
      "sequence": 2
    },
    {
      "id": "step-3",
      "step_type": "conflict_detected",
      "timestamp": "2025-06-04T10:01:30Z",
      "description": "Detected conflict between style and complexity",
      "details": {"conflict_id": "conflict-1"},
      "sequence": 3
    },
    {
      "id": "step-4",
      "step_type": "verdict_determined",
      "timestamp": "2025-06-04T10:02:00Z",
      "description": "Final verdict: request_changes",
      "details": {"verdict": "request_changes", "confidence": 0.92},
      "sequence": 4
    }
  ]
}
```

#### Trigger Manual Review

```http
POST /api/reviews
```

**Request Body:**

```json
{
  "repository": "owner/repo",
  "pr_number": 42,
  "base_sha": "abc1234",
  "head_sha": "def5678",
  "pr_title": "Add new feature",
  "author": "username",
  "is_draft": false,
  "policy_name": "default",
  "diff_content": "diff --git a/file.py b/file.py\n..."
}
```

**Response (202 Accepted):**

```json
{
  "status": "queued",
  "job_id": "job-abc123",
  "review_id": null,
  "message": "Review queued with job ID job-abc123"
}
```

#### Get Metrics

```http
GET /api/reviews/metrics
```

**Response:**

```json
{
  "total_reviews": 500,
  "completed_reviews": 485,
  "average_cost_usd": 0.15,
  "verdict_counts": {
    "approve": 300,
    "request_changes": 150,
    "comment": 35
  },
  "severity_counts": {
    "critical": 50,
    "high": 200,
    "medium": 500,
    "low": 1000,
    "info": 300
  },
  "reviews_by_day": [
    {"date": "2025-06-01", "count": 15},
    {"date": "2025-06-02", "count": 22},
    {"date": "2025-06-03", "count": 18}
  ],
  "cost_by_agent": {
    "security": 25.50,
    "style": 20.00,
    "complexity": 22.00
  }
}
```

### Conversations

#### List Conversations

```http
GET /api/conversations
```

**Query Parameters:**

| Parameter | Type | Default | Description |
|-----------|------|---------|-------------|
| `page` | integer | 1 | Page number |
| `page_size` | integer | 20 | Items per page |
| `repository` | string | - | Filter by repository |
| `review_id` | string | - | Filter by review ID |

**Response:**

```json
{
  "items": [
    {
      "id": "conv-123",
      "review_id": "abc123",
      "platform": "github",
      "repository": "owner/repo",
      "pr_number": 42,
      "message_count": 4,
      "total_tokens": 2000,
      "total_cost_usd": 0.02,
      "started_at": "2025-06-04T11:00:00Z",
      "last_activity": "2025-06-04T11:15:00Z"
    }
  ],
  "total": 25,
  "page": 1,
  "page_size": 20,
  "pages": 2
}
```

#### Get Conversation Detail

```http
GET /api/conversations/{conversation_id}
```

#### Get Conversation for Review

```http
GET /api/conversations/review/{review_id}
```

Returns `null` if no conversation exists for the review.

### Health Endpoints

#### Basic Health Check

```http
GET /health
```

**Response:**

```json
{
  "status": "healthy",
  "version": "0.5.0"
}
```

#### Readiness Check

```http
GET /health/ready
```

**Response:**

```json
{
  "status": "ready",
  "components": {
    "database": {"status": "healthy"},
    "redis": {"status": "healthy"},
    "worker": {"status": "healthy", "queue_size": 3}
  }
}
```

#### Liveness Probe

```http
GET /health/live
```

**Response:**

```json
{
  "status": "alive"
}
```

#### Prometheus Metrics

```http
GET /metrics
```

Returns Prometheus-formatted metrics.

## Webhook Endpoints

### GitHub Webhook

```http
POST /webhooks/github
```

**Headers:**

| Header | Description |
|--------|-------------|
| `X-Hub-Signature-256` | HMAC-SHA256 signature |
| `X-GitHub-Event` | Event type (pull_request, issue_comment) |

**Supported Events:**

- `pull_request` — PR opened, synchronized, or reopened
- `issue_comment` — Comment created on PR (for follow-up questions)

#### Pull Request Payload

```json
{
  "action": "opened",
  "pull_request": {
    "number": 42,
    "title": "Add new feature",
    "draft": false,
    "base": {"sha": "abc1234"},
    "head": {"sha": "def5678"},
    "user": {"login": "username"}
  },
  "repository": {
    "full_name": "owner/repo"
  }
}
```

#### Issue Comment Payload

```json
{
  "action": "created",
  "issue": {
    "number": 42,
    "pull_request": {}
  },
  "comment": {
    "id": 123456,
    "body": "Can you explain the SQL injection warning?",
    "user": {"login": "username"}
  },
  "repository": {
    "full_name": "owner/repo"
  }
}
```

**Responses:**

```json
{"status": "queued", "job_id": "abc123", "repository": "owner/repo", "pr_number": 42}
```

```json
{"status": "ignored", "reason": "Event type 'push' not processed"}
```

```json
{"status": "duplicate", "reason": "Review already queued for this commit"}
```

### GitLab Webhook

```http
POST /webhooks/gitlab
```

**Headers:**

| Header | Description |
|--------|-------------|
| `X-GitLab-Token` | Verification token |

**Supported Events:**

- `merge_request` — MR opened, reopened, or updated
- `note` — Comment (note) on MR (for follow-up questions)

#### Merge Request Payload

```json
{
  "object_kind": "merge_request",
  "object_attributes": {
    "iid": 42,
    "title": "Add new feature",
    "action": "open",
    "target_branch": "main",
    "work_in_progress": false,
    "last_commit": {"id": "def5678"}
  },
  "project": {
    "path_with_namespace": "owner/repo"
  },
  "user": {
    "username": "username"
  }
}
```

#### Note Payload

```json
{
  "object_kind": "note",
  "object_attributes": {
    "id": 123456,
    "note": "Can you explain this warning?",
    "noteable_type": "MergeRequest"
  },
  "merge_request": {
    "iid": 42
  },
  "project": {
    "path_with_namespace": "owner/repo"
  },
  "user": {
    "username": "username"
  }
}
```

## Error Responses

All endpoints return standard HTTP error codes with JSON error details:

### 400 Bad Request

```json
{
  "detail": "Missing required fields"
}
```

### 401 Unauthorized

```json
{
  "detail": "Invalid signature"
}
```

### 404 Not Found

```json
{
  "detail": "Review abc123 not found"
}
```

### 422 Validation Error

```json
{
  "detail": [
    {
      "loc": ["body", "pr_number"],
      "msg": "value is not a valid integer",
      "type": "type_error.integer"
    }
  ]
}
```

### 500 Internal Server Error

```json
{
  "detail": "Internal server error"
}
```

## Rate Limiting

The API applies rate limiting per client IP:

- Default: 60 requests per minute
- Configurable via `ARBITER_API_RATE_LIMIT_PER_MINUTE`

Rate limit headers are included in responses:

```
X-RateLimit-Limit: 60
X-RateLimit-Remaining: 55
X-RateLimit-Reset: 1707048120
```

## CORS

Cross-Origin Resource Sharing is configured via `ARBITER_CORS_ORIGINS`:

```bash
ARBITER_CORS_ORIGINS=["http://localhost:3000","https://dashboard.example.com"]
```

The API allows:
- Specified origins
- All standard headers
- Credentials
- GET, POST, PUT, DELETE methods