Config

Source: examples/config.ion in the repo.

// Configuration and JSON processing

// Build a config from defaults + overrides
let defaults = #{
    host: "0.0.0.0",
    port: 8080,
    debug: false,
    max_connections: 100,
    timeout_ms: 30000,
    features: ["logging", "metrics"],
};

let overrides = #{
    port: 3000,
    debug: true,
    features: ["logging", "metrics", "tracing"],
};

// Merge configs (overrides win)
let config = defaults.merge(overrides);
io::println(f"Server config:");
io::println(f"  Host: {config.host}");
io::println(f"  Port: {config.port}");
io::println(f"  Debug: {config.debug}");
io::println(f"  Features: {config.features.join(", ")}");

// Validate config
fn validate(config) {
    if config.port < 1 || config.port > 65535 {
        Err("invalid port")
    } else if config.max_connections < 1 {
        Err("max_connections must be positive")
    } else if config.timeout_ms < 100 {
        Err("timeout too low")
    } else {
        Ok(config)
    }
}

match validate(config) {
    Ok(c) => io::println(f"\nConfig valid! Listening on {c.host}:{c.port}"),
    Err(e) => io::println(f"\nConfig error: {e}"),
}

// Serialize to JSON
let json = json::pretty(config);
io::println(f"\nJSON output:\n{json}");

// Round-trip: encode then decode
let decoded = json::decode(json::encode(config));
io::println(f"\nRound-trip port: {decoded.port}");