use bson::DecoderError;
use mongodb::options::AggregateOptions;

impl super::Database {
    pub fn aggregate<R>(
        &self,
        collection: &str,
        pipeline: Vec<bson::Document>,
        options: Option<AggregateOptions>,
    ) -> Result<Vec<R>, DecoderError>
    where
        for<'r> R: serde::Deserialize<'r>,
    {
        let collection = self.db.collection(&String::from(collection));
        match collection.aggregate(pipeline.into_iter(), options) {
            Ok(cursor) => {
                let mut data: Vec<R> = vec![];

                for doc in cursor {
                    match bson::from_bson::<R>(bson::Bson::Document(doc.expect("cannot_get_doc"))) {
                        Ok(document) => {
                            data.push(document);
                        }
                        Err(e) => return Err(e),
                    }
                }
                Ok(data)
            }
            Err(e) => return Err(DecoderError::Unknown(e.to_string())),
        }
    }
}