using unified system

komp-app/src/csv.rs

@@ -0,0 +1,107 @@
+use anyhow::{Result, bail};
+use std::io::{BufRead, Write};
+
+pub struct CsvRecordReader<R> {
+    reader: R,
+    buffer: String,
+}
+
+impl<R: BufRead> CsvRecordReader<R> {
+    pub fn new(reader: R) -> Self {
+        Self {
+            reader,
+            buffer: String::new(),
+        }
+    }
+
+    pub fn next_record(&mut self) -> Result<Option<Vec<String>>> {
+        self.buffer.clear();
+        let mut line = String::new();
+        loop {
+            line.clear();
+            let bytes = self.reader.read_line(&mut line)?;
+            if bytes == 0 {
+                if self.buffer.is_empty() {
+                    return Ok(None);
+                }
+                break;
+            }
+            self.buffer.push_str(&line);
+            if csv_record_complete(&self.buffer) {
+                break;
+            }
+        }
+        Ok(Some(parse_csv_record(
+            self.buffer.trim_end_matches(['\r', '\n']),
+        )?))
+    }
+}
+
+fn csv_record_complete(record: &str) -> bool {
+    let mut in_quotes = false;
+    let mut chars = record.chars().peekable();
+    while let Some(character) = chars.next() {
+        if character == '"' {
+            if in_quotes && chars.peek() == Some(&'"') {
+                let _ = chars.next();
+            } else {
+                in_quotes = !in_quotes;
+            }
+        }
+    }
+    !in_quotes
+}
+
+pub fn parse_csv_record(record: &str) -> Result<Vec<String>> {
+    let mut fields = Vec::new();
+    let mut current = String::new();
+    let mut chars = record.chars().peekable();
+    let mut in_quotes = false;
+    while let Some(character) = chars.next() {
+        match character {
+            '"' if in_quotes && chars.peek() == Some(&'"') => {
+                current.push('"');
+                let _ = chars.next();
+            }
+            '"' => in_quotes = !in_quotes,
+            ',' if !in_quotes => {
+                fields.push(current);
+                current = String::new();
+            }
+            _ => current.push(character),
+        }
+    }
+    if in_quotes {
+        bail!("CSV record has an unterminated quote");
+    }
+    fields.push(current);
+    Ok(fields)
+}
+
+pub fn write_csv_record(writer: &mut impl Write, fields: &[String]) -> Result<()> {
+    for (index, field) in fields.iter().enumerate() {
+        if index > 0 {
+            writer.write_all(b",")?;
+        }
+        if field.contains([',', '"', '\n', '\r']) {
+            writer.write_all(b"\"")?;
+            writer.write_all(field.replace('"', "\"\"").as_bytes())?;
+            writer.write_all(b"\"")?;
+        } else {
+            writer.write_all(field.as_bytes())?;
+        }
+    }
+    writer.write_all(b"\n")?;
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn parses_quoted_fields() {
+        let row = parse_csv_record(r#"name,"hello, ""world""",42"#).unwrap();
+        assert_eq!(row, vec!["name", "hello, \"world\"", "42"]);
+    }
+}