# GigaBrain API Documentation

GigaBrain provides both REST and gRPC APIs for graph database operations. This documentation covers both interfaces.

## Table of Contents

- [Authentication](#authentication)
- [REST API](#rest-api)
- [gRPC API](#grpc-api)
- [Error Handling](#error-handling)
- [Examples](#examples)

## Authentication

GigaBrain uses JWT (JSON Web Tokens) for authentication. Include the token in the `Authorization` header:

```
Authorization: Bearer <your-jwt-token>
```

### Roles

- **Admin**: Full access to all operations including user management
- **ReadWrite**: Can read and modify graph data
- **ReadOnly**: Can only read graph data

## REST API

Base URL: `http://localhost:3000/api/v1`

### Health Check

**GET** `/health`

Returns server health status.

**Response:**
```json
{
  "status": "healthy",
  "version": "0.1.0",
  "uptime_seconds": 3600
}
```

### Nodes

#### Create Node

**POST** `/nodes`

Creates a new node in the graph.

**Request Body:**
```json
{
  "labels": ["Person", "Employee"],
  "properties": {
    "name": "John Doe",
    "age": 30,
    "active": true,
    "salary": 75000.50
  }
}
```

**Response:**
```json
{
  "node_id": 12345
}
```

#### Get Node

**GET** `/nodes/{node_id}`

Retrieves a node by its ID.

**Response:**
```json
{
  "node": {
    "id": 12345,
    "labels": ["Person", "Employee"],
    "properties": {
      "name": "John Doe",
      "age": 30,
      "active": true,
      "salary": 75000.50
    }
  }
}
```

#### Update Node

**PUT** `/nodes/{node_id}`

Updates an existing node's labels and/or properties. Labels are completely replaced if provided, while properties are merged with existing ones.

**Request Body:**
```json
{
  "labels": ["Person", "Manager"],
  "properties": {
    "title": "Engineering Manager",
    "department": "Technology",
    "team_size": 8
  }
}
```

**Response:**
```json
{
  "id": 12345,
  "labels": ["Person", "Manager"],
  "properties": {
    "name": "John Doe",
    "age": 30,
    "title": "Engineering Manager",
    "department": "Technology",
    "team_size": 8
  }
}
```

**Notes:**
- Labels: If provided, completely replace existing labels
- Properties: If provided, merge with existing properties (new properties are added, existing ones are updated)
- Both `labels` and `properties` fields are optional

#### Delete Node Property

**DELETE** `/nodes/{node_id}/properties/{property_key}`

Deletes a specific property from a node.

**Response:**
```json
{
  "id": 12345,
  "labels": ["Person", "Manager"],
  "properties": {
    "name": "John Doe",
    "age": 30,
    "department": "Technology"
  }
}
```

**Error Response (404):**
```json
{
  "error": "Property 'salary' not found",
  "code": 404
}
```

#### Delete Node

**DELETE** `/nodes/{node_id}`

Deletes a node from the graph.

**Response:**
- Status: `204 No Content`
- Body: Empty

### Relationships

#### Create Relationship

**POST** `/relationships`

Creates a new relationship between two nodes.

**Request Body:**
```json
{
  "start_node": {
    "id": 12345
  },
  "end_node": {
    "id": 67890
  },
  "rel_type": "WORKS_FOR",
  "properties": [
    {
      "key": "since",
      "value": {
        "string_value": "2023-01-01"
      }
    }
  ]
}
```

**Response:**
```json
{
  "relationship_id": {
    "id": 98765
  }
}
```

#### Get Relationship

**GET** `/relationships/{relationship_id}`

Retrieves a relationship by its ID.

**Response:**
```json
{
  "relationship": {
    "id": {
      "id": 98765
    },
    "start_node": {
      "id": 12345
    },
    "end_node": {
      "id": 67890
    },
    "rel_type": "WORKS_FOR",
    "properties": []
  }
}
```

#### Delete Relationship

**DELETE** `/relationships/{relationship_id}`

Deletes a relationship from the graph.

**Response:**
```json
{
  "success": true
}
```

### Cypher Queries

#### Execute Cypher Query

**POST** `/cypher`

Executes a Cypher query against the graph.

**Request Body:**
```json
{
  "query": "MATCH (n:Person) WHERE n.age > 25 RETURN n.name, n.age",
  "parameters": {}
}
```

**Response:**
```json
{
  "results": [
    {
      "columns": ["n.name", "n.age"],
      "data": [
        ["John Doe", 30],
        ["Jane Smith", 28]
      ]
    }
  ],
  "error": "",
  "execution_time_ms": 15
}
```

### Graph Algorithms

#### Shortest Path

**POST** `/algorithms/shortest-path`

Finds the shortest path between two nodes.

**Request Body:**
```json
{
  "start_node": {
    "id": 12345
  },
  "end_node": {
    "id": 67890
  },
  "max_depth": 10
}
```

**Response:**
```json
{
  "path": [
    {"id": 12345},
    {"id": 54321},
    {"id": 67890}
  ],
  "total_weight": 2.0
}
```

#### PageRank

**POST** `/algorithms/pagerank`

Calculates PageRank scores for specified nodes.

**Request Body:**
```json
{
  "nodes": [
    {"id": 12345},
    {"id": 67890}
  ],
  "damping_factor": 0.85,
  "max_iterations": 100,
  "tolerance": 0.0001
}
```

**Response:**
```json
{
  "rankings": {
    "12345": 0.15,
    "67890": 0.25
  }
}
```

#### Centrality

**POST** `/algorithms/centrality`

Calculates various centrality measures.

**Request Body:**
```json
{
  "algorithm": "betweenness",
  "nodes": [
    {"id": 12345},
    {"id": 67890}
  ]
}
```

**Response:**
```json
{
  "centrality": {
    "12345": 0.35,
    "67890": 0.42
  }
}
```

#### Community Detection

**POST** `/algorithms/community-detection`

Detects communities in the graph.

**Request Body:**
```json
{
  "algorithm": "louvain",
  "resolution": 1.0
}
```

**Response:**
```json
{
  "communities": [
    [12345, 23456, 34567],
    [67890, 78901, 89012]
  ],
  "modularity": 0.45
}
```

### Graph Statistics

#### Get Graph Stats

**GET** `/stats`

Returns statistics about the graph.

**Response:**
```json
{
  "node_count": 1000,
  "relationship_count": 2500,
  "relationship_types": ["KNOWS", "WORKS_FOR", "LIVES_IN"],
  "labels": ["Person", "Company", "City"]
}
```

### API Documentation

#### Get API Documentation

**GET** `/docs`

Returns this API documentation in JSON format.

### Schema Constraints

#### Create Constraint

**POST** `/constraints`

Creates a new schema constraint to enforce data integrity rules.

**Request Body:**
```json
{
  "constraint_type": "required",
  "label": "Employee",
  "property": "email"
}
```

**Constraint Types:**

1. **Required Constraint**
```json
{
  "constraint_type": "required",
  "label": "Employee",
  "property": "email"
}
```

2. **Type Constraint**
```json
{
  "constraint_type": "type",
  "label": "Employee",
  "property": "salary",
  "type_value": "integer"
}
```
Supported types: `string`, `integer`, `float`, `boolean`

3. **Range Constraint**
```json
{
  "constraint_type": "range",
  "label": "Employee",
  "property": "salary",
  "min_value": 30000,
  "max_value": 200000
}
```

4. **Pattern Constraint**
```json
{
  "constraint_type": "pattern",
  "label": "User",
  "property": "email",
  "pattern": "@"
}
```

5. **Enum Constraint**
```json
{
  "constraint_type": "enum",
  "label": "Task",
  "property": "status",
  "allowed_values": ["pending", "in_progress", "completed"]
}
```

**Response:**
```json
{
  "id": "required:Employee:email",
  "constraint_type": "required",
  "label": "Employee",
  "property": "email",
  "details": {}
}
```

#### List Constraints

**GET** `/constraints`

Lists all defined schema constraints.

**Response:**
```json
[
  {
    "id": "required:Employee:email",
    "constraint_type": "required",
    "label": "Employee",
    "property": "email",
    "details": {}
  },
  {
    "id": "type:Employee:salary",
    "constraint_type": "type",
    "label": "Employee",
    "property": "salary",
    "details": {
      "type": "Integer"
    }
  }
]
```

## gRPC API

The gRPC API provides the same functionality as the REST API but uses Protocol Buffers for serialization. The service is defined in `proto/gigabrain.proto`.

### Service Definition

```protobuf
service GigaBrainService {
  // Node operations
  rpc CreateNode(CreateNodeRequest) returns (CreateNodeResponse);
  rpc GetNode(GetNodeRequest) returns (GetNodeResponse);
  rpc UpdateNode(UpdateNodeRequest) returns (UpdateNodeResponse);
  rpc DeleteNode(DeleteNodeRequest) returns (DeleteNodeResponse);
  
  // Relationship operations
  rpc CreateRelationship(CreateRelationshipRequest) returns (CreateRelationshipResponse);
  rpc GetRelationship(GetRelationshipRequest) returns (GetRelationshipResponse);
  rpc DeleteRelationship(DeleteRelationshipRequest) returns (DeleteRelationshipResponse);
  
  // Query operations
  rpc ExecuteCypher(CypherQueryRequest) returns (CypherQueryResponse);
  
  // Algorithm operations
  rpc ShortestPath(ShortestPathRequest) returns (ShortestPathResponse);
  rpc PageRank(PageRankRequest) returns (PageRankResponse);
  rpc Centrality(CentralityRequest) returns (CentralityResponse);
  rpc CommunityDetection(CommunityDetectionRequest) returns (CommunityDetectionResponse);
  
  // Stats operations
  rpc GetGraphStats(GraphStatsRequest) returns (GraphStatsResponse);
}
```

### Connection

Connect to the gRPC server at `localhost:50051`.

### Property Values

Property values can be one of the following types:

- `string_value`: String data
- `int_value`: 64-bit integer
- `float_value`: 64-bit floating point
- `bool_value`: Boolean
- `bytes_value`: Binary data

## Error Handling

### HTTP Status Codes

- `200 OK`: Successful operation
- `400 Bad Request`: Invalid request data
- `401 Unauthorized`: Authentication required
- `403 Forbidden`: Insufficient permissions
- `404 Not Found`: Resource not found
- `500 Internal Server Error`: Server error

### Error Response Format

```json
{
  "error": "Node ID is required",
  "code": 400
}
```

### gRPC Status Codes

- `OK`: Successful operation
- `INVALID_ARGUMENT`: Invalid request parameters
- `NOT_FOUND`: Resource not found
- `INTERNAL`: Internal server error
- `UNAUTHENTICATED`: Authentication failed
- `PERMISSION_DENIED`: Authorization failed

## Examples

### Creating a Social Network

```bash
# Create users
curl -X POST http://localhost:3000/api/v1/nodes \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer <token>" \
  -d '{
    "labels": ["Person"],
    "properties": {
      "name": "Alice",
      "age": 25
    }
  }'

curl -X POST http://localhost:3000/api/v1/nodes \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer <token>" \
  -d '{
    "labels": ["Person"],
    "properties": {
      "name": "Bob",
      "age": 30
    }
  }'

# Create friendship
curl -X POST http://localhost:3000/api/v1/relationships \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer <token>" \
  -d '{
    "start_node": 1,
    "end_node": 2,
    "rel_type": "FRIENDS",
    "properties": {
      "since": "2023-01-01"
    }
  }'

# Find mutual friends
curl -X POST http://localhost:3000/api/v1/cypher \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer <token>" \
  -d '{
    "query": "MATCH (a:Person)-[:FRIENDS]-(mutual)-[:FRIENDS]-(b:Person) WHERE a.name = $name1 AND b.name = $name2 RETURN mutual.name",
    "parameters": {"name1": "Alice", "name2": "Bob"}
  }'

# Update a node
curl -X PUT http://localhost:3000/api/v1/nodes/1 \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer <token>" \
  -d '{
    "labels": ["Person", "VIP"],
    "properties": {
      "status": "premium",
      "last_seen": "2023-12-01"
    }
  }'

# Delete a specific property
curl -X DELETE http://localhost:3000/api/v1/nodes/1/properties/age \
  -H "Authorization: Bearer <token>"
```

### Working with Schema Constraints

```bash
# Create a required email constraint for Employee nodes
curl -X POST http://localhost:3000/api/v1/constraints \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer <token>" \
  -d '{
    "constraint_type": "required",
    "label": "Employee",
    "property": "email"
  }'

# Create a type constraint for salary
curl -X POST http://localhost:3000/api/v1/constraints \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer <token>" \
  -d '{
    "constraint_type": "type",
    "label": "Employee",
    "property": "salary",
    "type_value": "integer"
  }'

# Create a range constraint for salary
curl -X POST http://localhost:3000/api/v1/constraints \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer <token>" \
  -d '{
    "constraint_type": "range",
    "label": "Employee",
    "property": "salary",
    "min_value": 30000,
    "max_value": 200000
  }'

# Try to create an employee without email (will fail)
curl -X POST http://localhost:3000/api/v1/nodes \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer <token>" \
  -d '{
    "labels": ["Employee"],
    "properties": {
      "name": "John Doe",
      "salary": 50000
    }
  }'
# Response: {"error": "Validation error: Required property 'email' is missing", "code": 400}

# Create an employee with all required properties
curl -X POST http://localhost:3000/api/v1/nodes \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer <token>" \
  -d '{
    "labels": ["Employee"],
    "properties": {
      "name": "John Doe",
      "email": "john@example.com",
      "salary": 50000
    }
  }'
```

### Running Graph Algorithms

```bash
# Calculate shortest path
curl -X POST http://localhost:3000/api/v1/algorithms/shortest-path \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer <token>" \
  -d '{
    "start_node": 1,
    "end_node": 10,
    "relationship_types": ["FRIENDS", "KNOWS"]
  }'

# Run PageRank
curl -X POST http://localhost:3000/api/v1/algorithms/pagerank \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer <token>" \
  -d '{
    "nodes": [1, 2, 3],
    "damping_factor": 0.85
  }'
```

## Performance Considerations

- Use batch operations when creating multiple nodes/relationships
- Enable request compression for large payloads
- Consider using gRPC for high-performance scenarios
- Implement connection pooling for production use
- Use streaming for large result sets

## Rate Limiting

The API implements rate limiting to prevent abuse:

- **Default limit**: 1000 requests per minute per IP
- **Burst limit**: 100 requests per second
- **Headers**: `X-RateLimit-Remaining`, `X-RateLimit-Reset`

## Monitoring

Monitor API performance using the built-in metrics:

- Request count and duration
- Error rates by endpoint
- Active connections
- Memory and CPU usage

Access metrics at: `GET /metrics` (Prometheus format)