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use crate::{Headers, Row, RowStream, RowResult};

pub struct FilterRow<I, F> {
    iter: I,
    f: F,
    headers: Headers,
}

impl<I, F> FilterRow<I, F>
where
    I: RowStream,
    F: Fn(&Headers, &Row) -> bool,
{
    pub fn new(
        iter: I,
        f: F,
    ) -> FilterRow<I, F> {
        let headers = iter.headers().clone();

        FilterRow {
            iter,
            f,
            headers,
        }
    }
}

pub struct IntoIter<I, F> {
    iter: I,
    f: F,
    headers: Headers,
}

impl<I, F> Iterator for IntoIter<I, F>
where
    I: Iterator<Item = RowResult>,
    F: Fn(&Headers, &Row) -> bool,
{
    type Item = RowResult;

    fn next(&mut self) -> Option<Self::Item> {
        while let Some(rs) = self.iter.next() {
            match rs {
                Ok(row) => if (self.f)(&self.headers, &row) {
                    return Some(Ok(row));
                }
                Err(e) => return Some(Err(e)),
            }
        }

        None
    }
}

impl<I, F> IntoIterator for FilterRow<I, F>
where
    I: RowStream,
    F: Fn(&Headers, &Row) -> bool,
{
    type Item = RowResult;

    type IntoIter = IntoIter<I::IntoIter, F>;

    fn into_iter(self) -> Self::IntoIter {
        Self::IntoIter {
            iter: self.iter.into_iter(),
            f: self.f,
            headers: self.headers,
        }
    }
}

impl<I, F> RowStream for FilterRow<I, F>
where
    I: RowStream,
    F: Fn(&Headers, &Row) -> bool,
{
    fn headers(&self) -> &Headers {
        &self.headers
    }
}

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

    use crate::{Row, MockStream, error};

    #[test]
    fn test_filter() {
        let iter = MockStream::from_rows(
            vec![
                Ok(Row::from(vec!["a", "b"])),
                Ok(Row::from(vec!["1", "2"])),
                Ok(Row::from(vec!["2", "7"])),
                Err(error::Error::InconsistentHeaders),
                Ok(Row::from(vec!["1", "1"])),
                Ok(Row::from(vec!["2", "9"])),
            ]
            .into_iter(),
        )
        .unwrap();

        let mut r = FilterRow::new(iter, |headers, row| {
            headers.get_field(row, "b").unwrap().parse::<i32>().unwrap() > 2
        })
            .into_iter();

        assert!(r.next().unwrap().is_ok());
        assert!(r.next().unwrap().is_err());
        assert!(r.next().unwrap().is_ok());
        assert!(r.next().is_none());
    }
}