# IP Data API

A simple API for retrieving information about IP addresses.

## Prerequisites

- Go 1.20 or higher

## Installation

1. Clone the repository
2. Install dependencies:

```
go mod tidy
```

## Running the API

```
go run .
```

The server will start on port 8080 by default. You can change the port by setting the `PORT` environment variable.

## Configuration

The API can be configured using the following environment variables:

| Variable             | Description                                                                    | Default  |
| -------------------- | ------------------------------------------------------------------------------ | -------- |
| `PORT`               | Port to run the API server                                                     | `8080`   |
| `DNS_TIMEOUT_MS`     | Timeout for DNS hostname lookups in milliseconds                               | `500`    |
| `DISABLE_DNS_LOOKUP` | Disable hostname lookups completely for faster response (set to "true" or "1") | disabled |

Example:

```
DNS_TIMEOUT_MS=300 PORT=3000 go run .

# Run with DNS lookups disabled completely
DISABLE_DNS_LOOKUP=true go run .
```

## API Endpoints

### Get IP Information

```
GET /api/ip/:ip
```

Example:

```
GET /api/ip/8.8.8.8
```

Response:

```json
{
  "ip": "8.8.8.8",
  "hostname": "dns.google",
  "asn": "15169",
  "as_name": "Google LLC",
  "country_code": "US",
  "country": "United States",
  "region": "California",
  "city": "Mountain View",
  "latitude": 37.40599,
  "longitude": -122.078514,
  "zip_code": "94043",
  "time_zone": "-07:00"
}
```

## Performance Optimization

For maximum performance, you can completely disable hostname DNS lookups using the `DISABLE_DNS_LOOKUP=true` environment variable. This will make all API requests faster, but the `hostname` field will be empty in the response.

## Features

- IP geolocation data (country, region, city, coordinates, timezone)
- ASN information (ASN number and organization name)
- Hostname resolution via reverse DNS lookup (with configurable timeout or ability to disable)
- Support for both IPv4 and IPv6 addresses
- In-memory data storage with efficient binary search lookups

## Data Sources

The API uses four data files:

### IPv4 Files

- `IP2LOCATION-LITE-ASN.CSV` - ASN information for IPv4 addresses
- `IP2LOCATION-LITE-DB11.CSV` - Geolocation information for IPv4 addresses

### IPv6 Files

- `IP2LOCATION-LITE-ASN.IPV6.CSV` - ASN information for IPv6 addresses
- `IP2LOCATION-LITE-DB11.IPV6.CSV` - Geolocation information for IPv6 addresses

These files are loaded into memory when the API starts. The API automatically detects whether an IP is IPv4 or IPv6 and uses the appropriate dataset.