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datafake-rs is a Rust library for generating realistic mock JSON data. It uses JSONLogic for its configuration, allowing you to define complex data structures with ease. The library extends JSONLogic with a custom fake operator, powered by the fake-rs crate, to generate a wide variety of data types for testing, development, and other use cases.

🚀 Key Features

• JSONLogic Based: Define data generation rules using JSONLogic expressions.
• Rich Fake Data: Over 50 fake data types, including names, addresses, and financial data.
• Variable System: Pre-generate and reuse values throughout your schema.
• Type-Safe: Ensures strong typing with thorough validation.
• Batch Generation: Easily create multiple, unique data records.
• High Performance: Built on datalogic-rs for efficient evaluation.
• Flexible Configuration: Use JSON for easy setup and integration.
• Thread-Safe: Designed for safe concurrent data generation.

🏗️ How It Works

Configuration-Driven Design

You define your data schema using a JSONLogic configuration with custom operators.

use datafake_rs::DataGenerator;
use serde_json::json;

let config = json!({
    "variables": {
        "userId": {"fake": ["uuid"]},
        "country": {"fake": ["country_code"]}
    },
    "schema": {
        "id": {"var": "userId"},
        "profile": {
            "name": {"fake": ["name"]},
            "email": {"fake": ["email"]},
            "age": {"fake": ["u8", 18, 65]}
        },
        "location": {
            "country": {"var": "country"},
            "city": {"fake": ["city_name"]},
            "coordinates": {
                "lat": {"fake": ["latitude"]},
                "lng": {"fake": ["longitude"]}
            }
        }
    }
});

let generator = DataGenerator::from_value(config)?;
let mock_data = generator.generate()?;

JSONLogic Integration

The library integrates with datalogic-rs and adds a fake operator, while still supporting all standard JSONLogic operators.

{
    "schema": {
        "active": {"==": [{"var": "status"}, "active"]},
        "discount": {"if": [
            {">": [{"var": "age"}, 65]},
            0.2,
            0.0
        ]},
        "code": {"fake": ["u32", 1000, 9999]}
    }
}

🎯 Fake Data Generation

Supported Data Types

The fake operator can generate over 50 different types of data.

Numeric

{"fake": ["u8"]}
{"fake": ["u16", 100, 1000]}
{"fake": ["i32", -50, 50]}
{"fake": ["f64", 0.0, 1.0]}

Personal

{"fake": ["name"]}
{"fake": ["first_name"]}
{"fake": ["last_name"]}
{"fake": ["title"]}
{"fake": ["email"]}
{"fake": ["phone_number"]}

Address

{"fake": ["street_address"]}
{"fake": ["city_name"]}
{"fake": ["state_name"]}
{"fake": ["country_name"]}
{"fake": ["zip_code"]}
{"fake": ["latitude"]}
{"fake": ["longitude"]}

Financial

{"fake": ["bic"]}              // Random 8 or 11 character BIC
{"fake": ["bic", 8]}            // Fixed 8 character BIC
{"fake": ["bic", 11]}           // Fixed 11 character BIC
{"fake": ["bic8"]}              // Fixed 8 character BIC (shorthand)
{"fake": ["bic11"]}             // Fixed 11 character BIC (shorthand)
{"fake": ["credit_card_number"]}
{"fake": ["currency_code"]}
{"fake": ["currency_symbol"]}

Internet

{"fake": ["username"]}
{"fake": ["password", 10, 20]}
{"fake": ["ipv4"]}
{"fake": ["ipv6"]}
{"fake": ["mac_address"]}
{"fake": ["user_agent"]}
{"fake": ["domain_suffix"]}

Company

{"fake": ["company_name"]}
{"fake": ["industry"]}
{"fake": ["profession"]}
{"fake": ["catch_phrase"]}

Content

{"fake": ["word"]}
{"fake": ["words", 5]}
{"fake": ["sentence", 5, 10]}
{"fake": ["paragraph", 3, 5]}
{"fake": ["uuid"]}

Variable System

You can pre-generate values and reuse them in your schema.

{
    "variables": {
        "sessionId": {"fake": ["uuid"]},
        "timestamp": {"fake": ["u64", 1600000000, 1700000000]},
        "userId": {"fake": ["u32", 1000, 9999]}
    },
    "schema": {
        "session": {"var": "sessionId"},
        "events": [
            {
                "id": {"fake": ["uuid"]},
                "session": {"var": "sessionId"},
                "user": {"var": "userId"},
                "timestamp": {"var": "timestamp"},
                "action": {"fake": ["word"]}
            }
        ]
    }
}

🔧 Installation

Add datafake-rs to your Cargo.toml:

[dependencies]
datafake-rs = "0.1.0"

Or use cargo:

cargo add datafake-rs

📖 Usage Examples

Basic Example

use datafake_rs::DataGenerator;

let config = r#"{
    "schema": {
        "id": {"fake": ["uuid"]},
        "name": {"fake": ["name"]},
        "email": {"fake": ["email"]},
        "age": {"fake": ["u8", 18, 65]},
        "active": {"fake": ["bool"]}
    }
}"#;

let generator = DataGenerator::from_json(config)?;
let mock_user = generator.generate()?;

println!("{}", serde_json::to_string_pretty(&mock_user)?);

Nested Structures

use datafake_rs::DataGenerator;
use serde_json::json;

let config = json!({
    "variables": {
        "companyId": {"fake": ["uuid"]},
        "createdAt": {"fake": ["u64", 1600000000, 1700000000]}
    },
    "schema": {
        "company": {
            "id": {"var": "companyId"},
            "name": {"fake": ["company_name"]},
            "employees": [
                {
                    "id": {"fake": ["uuid"]},
                    "name": {"fake": ["name"]},
                    "email": {"fake": ["email"]}
                }
            ]
        }
    }
});

let generator = DataGenerator::from_value(config)?;
let company_data = generator.generate()?;

Batch Generation

Generate a list of unique records.

let config = json!({
    "schema": {
        "id": {"fake": ["uuid"]},
        "transaction": {
            "amount": {"fake": ["f64", 10.0, 1000.0]},
            "currency": {"fake": ["currency_code"]}
        }
    }
});

let generator = DataGenerator::from_value(config)?;
let transactions = generator.generate_batch(100)?;

Conditional Logic

Use JSONLogic conditions to shape your data.

let config = json!({
    "variables": {
        "age": {"fake": ["u8", 10, 80]}
    },
    "schema": {
        "age": {"var": "age"},
        "ageGroup": {
            "if": [
                {"<": [{"var": "age"}, 18]}, "minor",
                {"<": [{"var": "age"}, 65]}, "adult",
                "senior"
            ]
        }
    }
});

🧪 Testing

To run the test suite:

# Run all tests
cargo test

# Run a specific test with output
cargo test test_generate_batch -- --nocapture

🤝 Contributing

Contributions are welcome! If you're submitting a change, please ensure it has good test coverage and documentation.

🏢 About Plasmatic

datafake-rs is an open-source project from Plasmatic. We build developer tools that are performant and based on open standards.

📄 License

This project is licensed under the Apache License, Version 2.0. See the LICENSE file for details.

🔗 See Also

• datalogic-rs: A high-performance JSONLogic implementation for Rust.
• fake-rs: A library for generating fake data in Rust.
• JSONLogic: The official JSONLogic specification.

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