+struct Reader<Input: Iterator<Item = Result<String, std::io::Error>>> {
+ input: std::iter::Enumerate<Input>,
+ row: Option<RowInput>,
+}
+impl<Input: Iterator<Item = Result<String, std::io::Error>>> Reader<Input> {
+ fn new(input: Input) -> Self {
+ Self {
+ input: input.enumerate(),
+ row: None,
+ }
+ }
+}
+impl<Input: Iterator<Item = Result<String, std::io::Error>>> Iterator for Reader<Input> {
+ type Item = Result<RowInput, std::io::Error>;
+ fn next(&mut self) -> Option<Self::Item> {
+ loop {
+ match self
+ .input
+ .next()
+ .map(|(n, r)| (n, r.map(|line| String::from(line.trim_end()))))
+ {
+ None => return Ok(std::mem::take(&mut self.row)).transpose(),
+ Some((_, Err(e))) => return Some(Err(e)),
+ Some((_, Ok(line))) if line.is_empty() && self.row.is_some() => {
+ return Ok(std::mem::take(&mut self.row)).transpose()
+ }
+ Some((_, Ok(line))) if line.is_empty() => {}
+ Some((n, Ok(line))) if line.starts_with(' ') => match &mut self.row {
+ None => {
+ return Some(Err(std::io::Error::other(format!(
+ "{}: Entry with no header",
+ n + 1
+ ))))
+ }
+ Some(ref mut row) => row.entries.push(Entry(String::from(line.trim()))),
+ },
+ Some((_, Ok(line))) => {
+ let prev = std::mem::take(&mut self.row);
+ self.row = Some(RowInput {
+ label: line,
+ entries: vec![],
+ });
+ if prev.is_some() {
+ return Ok(prev).transpose();
+ }
+ }
+ }
+ }
+ }
+}
+
+fn read_rows(input: impl std::io::Read) -> impl Iterator<Item = Result<RowInput, std::io::Error>> {
+ Reader::new(std::io::BufReader::new(input).lines())
+}
+
+fn column_counts(rows: &[RowInput]) -> Vec<(usize, String)> {
+ let mut counts: Vec<_> = rows
+ .iter()
+ .flat_map(|r| r.entries.iter().collect::<HashSet<_>>().into_iter())
+ .fold(HashMap::new(), |mut cs, e| {
+ cs.entry(String::from(&e.0))
+ .and_modify(|n| *n += 1)
+ .or_insert(1);
+ cs
+ })
+ .into_iter()
+ .map(|(col, n)| (n, col))
+ .collect();
+ counts.sort();
+ counts