csvsc 2.2.1

Build processing chains for CSV files
Documentation 
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use crate::{
    Headers, Row, RowStream,
    error::{Error, RowResult},
};

pub struct Select<'a, I> {
    iter: I,
    columns: Vec<&'a str>,
    headers: Headers,
    old_headers: Headers,
}

impl<'a, I> Select<'a, I>
where
    I: RowStream,
{
    pub fn new(iter: I, columns: Vec<&'a str>) -> Select<I> {
        let headers: Headers = Row::from(columns.clone()).into();

        Select{
            old_headers: iter.headers().clone(),
            iter,
            columns,
            headers,
        }
    }
}

pub struct IntoIter<'a, I> {
    iter: I,
    columns: Vec<&'a str>,
    old_headers: Headers,
}

impl<'a, I> Iterator for IntoIter<'a, I>
where
    I: Iterator<Item = RowResult>,
{
    type Item = RowResult;

    fn next(&mut self) -> Option<Self::Item> {
        self.iter.next().map(|result| {
            result.and_then(|val| {
                let values = self.columns.iter()
                    .map(|header| {
                        self.old_headers
                            .get_field(&val, header)
                            .ok_or_else(|| Error::ColumnNotFound(header.to_string()))
                    })
                    .collect::<Result<Vec<_>, Error>>()?;

                Ok(values.into())
            })
        })
    }
}

impl<'a, I> IntoIterator for Select<'a, I>
where
    I: RowStream,
{
    type Item = RowResult;

    type IntoIter = IntoIter<'a, I::IntoIter>;

    fn into_iter(self) -> Self::IntoIter {
        Self::IntoIter {
            iter: self.iter.into_iter(),
            columns: self.columns,
            old_headers: self.old_headers,
        }
    }
}

impl<'a, I> RowStream for Select<'a, I>
where
    I: RowStream,
{
    fn headers(&self) -> &Headers {
        &self.headers
    }
}

#[cfg(test)]
mod tests {
    use super::Select;

    use crate::mock::MockStream;
    use crate::{Row, RowStream};

    #[test]
    fn keeps_the_correct_headers() {
        let iter = MockStream::from_rows(
            vec![
                Ok(Row::from(vec!["id", "val", "path"])),
                Ok(Row::from(vec!["1", "40", "/tmp/a1m.csv"])),
                Ok(Row::from(vec!["2", "39", "/tmp/a1m.csv"])),
                Ok(Row::from(vec!["3", "38", "/tmp/a2m.csv"])),
                Ok(Row::from(vec!["4", "37", "/tmp/a2m.csv"])),
            ]
            .into_iter(),
        )
        .unwrap();

        let del = Select::new(
            iter,
            vec!["id", "val"],
        );

        assert_eq!(
            *del.headers(),
            Row::from(vec!["id", "val"]).into(),
        );

        let mut del = del.into_iter();

        assert_eq!(
            del.next().unwrap().unwrap(),
            Row::from(vec!["1", "40"])
        );
        assert_eq!(
            del.next().unwrap().unwrap(),
            Row::from(vec!["2", "39"])
        );
        assert_eq!(
            del.next().unwrap().unwrap(),
            Row::from(vec!["3", "38"])
        );
        assert_eq!(
            del.next().unwrap().unwrap(),
            Row::from(vec!["4", "37"])
        );
    }

    #[test]
    fn keeps_them_in_the_correct_order() {
        let iter = MockStream::from_rows(
            vec![
                Ok(Row::from(vec!["id", "val", "path"])),
                Ok(Row::from(vec!["1", "40", "/tmp/a1m.csv"])),
                Ok(Row::from(vec!["2", "39", "/tmp/a1m.csv"])),
                Ok(Row::from(vec!["3", "38", "/tmp/a2m.csv"])),
                Ok(Row::from(vec!["4", "37", "/tmp/a2m.csv"])),
            ]
            .into_iter(),
        )
        .unwrap();

        let sel = Select::new(
            iter,
            vec!["path", "val"],
        );

        assert_eq!(
            *sel.headers(),
            Row::from(vec!["path", "val"]).into(),
        );

        let mut sel = sel.into_iter();

        assert_eq!(
            sel.next().unwrap().unwrap(),
            Row::from(vec!["/tmp/a1m.csv", "40"])
        );
        assert_eq!(
            sel.next().unwrap().unwrap(),
            Row::from(vec!["/tmp/a1m.csv", "39"])
        );
        assert_eq!(
            sel.next().unwrap().unwrap(),
            Row::from(vec!["/tmp/a2m.csv", "38"])
        );
        assert_eq!(
            sel.next().unwrap().unwrap(),
            Row::from(vec!["/tmp/a2m.csv", "37"])
        );
    }
}