data-alchemist-json 0.1.2

use std::io::Error;

use data_alchemist::writer::{OutputSink, OutputWriter};

pub struct JsonWriter;

pub struct JsonProperties {}

impl<T> OutputWriter<T> for JsonWriter where T: serde::Serialize {
    type Properties = JsonProperties;

    fn write(data: T, sink: &dyn OutputSink, _: Self::Properties) -> Result<(), Error> {
        let serialized = serde_json::to_vec(&data)?;
        sink.write_data(&serialized)
    }
}


#[cfg(test)]
mod test {
    use mockall::mock;
    use mockall::predicate::eq;
    use serde::Serialize;

    use super::*;

    mock! {
        pub OutputSink {}

        impl OutputSink for OutputSink {
            fn write_data(&self, data: &[u8]) -> Result<(), Error>;
        }
    }

    #[derive(Serialize, Debug, PartialEq)]
    struct TestStruct {
        name: String,
        age: u32,
    }

    #[test]
    fn given_valid_struct_should_serialize_and_write() {
        // given        
        let test_data = TestStruct {
            name: "Alice".to_string(),
            age: 30,
        };
        let expected_json = serde_json::to_vec(&test_data).unwrap();

        let mut mock_sink = MockOutputSink::new();
        mock_sink.expect_write_data()
            .with(eq(expected_json.clone()))  // Ensure the serialized data is passed
            .times(1)
            .returning(|_| Ok(()));

        // when
        let result = JsonWriter::write(test_data, &mut mock_sink, JsonProperties {});

        // then
        assert!(result.is_ok());
    }

    #[test]
    fn given_sink_write_error_should_return_error() {
        // given        
        let test_data = TestStruct {
            name: "Bob".to_string(),
            age: 42,
        };

        let mut mock_sink = MockOutputSink::new();
        mock_sink.expect_write_data()
            .times(1)
            .returning(|_| Err(std::io::Error::from(std::io::ErrorKind::Other)));

        // when
        let result = JsonWriter::write(test_data, &mut mock_sink, JsonProperties {});

        // then
        assert!(result.is_err());
    }
}