csvsc 2.2.1

Build processing chains for CSV files
Documentation 
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use super::Aggregate;
use crate::{Headers, Row, error};

#[derive(Default, Debug)]
pub struct Avg {
    source: String,
    colname: String,
    sum: f64,
    count: u64,
}

impl Avg {
    pub fn new(colname: String, source: String) -> Avg {
        Avg {
            source,
            colname,
            ..Default::default()
        }
    }
}

impl Aggregate for Avg {
    fn update(&mut self, headers: &Headers, row: &Row) -> error::Result<()> {
        match headers.get_field(row, &self.source) {
            Some(data) => match data.parse::<f64>() {
                Ok(num) => {
                    self.sum += num;
                    self.count += 1;

                    Ok(())
                }
                Err(_) => Err(error::Error::ValueError {
                    data: data.into(),
                    to_type: "f64".into(),
                }),
            },
            None => Err(error::Error::ColumnNotFound(self.source.to_string())),
        }
    }

    fn value(&self) -> String {
        if self.count != 0 {
            (self.sum / self.count as f64).to_string()
        } else {
            "NaN".to_string()
        }
    }

    fn colname(&self) -> &str {
        &self.colname
    }
}

#[cfg(test)]
mod tests {
    use super::{Aggregate, Avg};
    use crate::{Row, error::Error};

    #[test]
    fn test_avg() {
        let mut avg = Avg::new("new".into(), "a".into());
        let h = Row::from(vec!["a"]).into();

        let r = Row::from(vec!["3.0"]);
        avg.update(&h, &r).unwrap();
        let r = Row::from(vec!["2"]);
        avg.update(&h, &r).unwrap();
        let r = Row::from(vec![".5"]);
        avg.update(&h, &r).unwrap();
        let r = Row::from(vec![".5"]);
        avg.update(&h, &r).unwrap();

        assert_eq!(avg.value(), "1.5");
    }

    #[test]
    fn test_missing_column() {
        let mut avg = Avg::new("new".into(), "a".into());
        let h = Row::from(vec!["b"]).into();

        let r = Row::from(vec!["3.0"]);

        match avg.update(&h, &r) {
            Err(Error::ColumnNotFound(val)) => assert_eq!(val, "a"),
            _ => panic!("Test failed"),
        }
    }

    #[test]
    fn test_value_error() {
        let mut avg = Avg::new("new".into(), "a".into());
        let h = Row::from(vec!["a"]).into();

        let r = Row::from(vec!["chicken"]);

        match avg.update(&h, &r) {
            Err(Error::ValueError{ data, to_type }) => {
                assert_eq!(data, "chicken");
                assert_eq!(to_type, "f64");
            }
            _ => panic!("Test failed"),
        }
    }
}