use std::path::{Path, PathBuf};

const MODEL_LIBRARY_DIR: &str = "model-library";
const INDEX_FILE: &str = "index.json";
const MANAGED_MODELS_DIR: &str = "managed-models";
const DEFAULT_MODELS_DIR: &str = "models";

/// Resolves the models directory from the user-configured `models_dir`.
/// - `None`        → `./models` (relative to the app's working directory)
/// - `Some("")`    → `./models`
/// - `Some(path)`  → that exact path
pub fn resolve_models_dir(models_dir: Option<&str>) -> PathBuf {
    match models_dir {
        None | Some("") => PathBuf::from(DEFAULT_MODELS_DIR),
        Some(path) => PathBuf::from(path),
    }
}

pub fn model_library_dir(app_data_dir: &Path) -> PathBuf {
    app_data_dir.join(MODEL_LIBRARY_DIR)
}

pub fn model_library_index_path(app_data_dir: &Path) -> PathBuf {
    model_library_dir(app_data_dir).join(INDEX_FILE)
}

/// Legacy path for the managed-models location inside AppData.
/// Used only for index persistence — downloads now go to the user-configured
/// `models_dir` (defaults to `./models` in the project root).
pub fn managed_models_dir(app_data_dir: &Path) -> PathBuf {
    model_library_dir(app_data_dir).join(MANAGED_MODELS_DIR)
}

#[cfg(test)]
mod tests {
    use super::{managed_models_dir, model_library_dir, model_library_index_path};

    #[test]
    fn model_library_paths_live_under_app_data_dir() {
        let root = std::path::Path::new("C:/Users/demo/AppData/Roaming/ForgeLM");

        assert_eq!(model_library_dir(root), root.join("model-library"));
        assert_eq!(
            model_library_index_path(root),
            root.join("model-library").join("index.json")
        );
        assert_eq!(
            managed_models_dir(root),
            root.join("model-library").join("managed-models")
        );
    }
}