use config::{Config, Environment, File};
// re-export
pub use config::{ConfigError, FileFormat};

pub fn load<'a, T: serde::de::Deserialize<'a>>(
    file: &str,
    format: FileFormat,
) -> Result<T, ConfigError> {
    let builder = Config::builder();
    match std::env::var("CONFIG_PATH") {
        Ok(env_file_path) => builder.add_source(File::with_name(&env_file_path)),
        Err(_) => builder.add_source(File::from_str(file, format)),
    }
    .add_source(Environment::default().separator("."))
    .build()?
    .try_deserialize()
}

#[test]
fn test_load_yaml() {
    use serde::Deserialize;

    #[derive(Debug, Deserialize)]
    struct Author {
        pub name: String,
        pub books: Vec<String>,
    }

    #[derive(Debug, Deserialize)]
    struct Test {
        pub count: u32,
        pub author: Author,
    }

    let expected_data: Test = Test {
        count: 10,
        author: Author {
            name: "John Ronald Reuel Tolkien".to_string(),
            books: vec!["The Lord of the Rings".to_string()],
        },
    };

    let data: Test = load(include_str!("./test_config.yaml"), FileFormat::Yaml).unwrap();
    assert_eq!(data.count, expected_data.count);
    assert_eq!(data.author.name, expected_data.author.name);
    assert_eq!(data.author.books, expected_data.author.books);
}