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use std::iter::Peekable;
use std::str::Chars;
pub type CSV = Vec<CSVRecord>;
pub type CSVRecord = Vec<CSVField>;
pub type CSVField = String;
const COMMA: char = ',';
const DQUOTE: char = '"';
const CR: char = '\r';
const LF: char = '\n';
#[derive(Debug)]
pub enum Error {
UnexpectedCharacterInEscapedField(char),
UnexpectedCharacterInNonEscapedField(char),
UnexpectedEndOfInput,
AteWrongCharacter(char, char),
}
pub fn parse_csv(input_csv: &str) -> Result<CSV, Error> {
let csv_string = input_csv.trim();
let mut csv_iterator = csv_string.chars().peekable();
let mut csv = CSV::new();
csv.push(parse_record(&mut csv_iterator)?);
while let Some(_) = csv_iterator.peek() {
eat(CR, &mut csv_iterator)?;
eat(LF, &mut csv_iterator)?;
if let Some(_) = csv_iterator.peek() {
csv.push(parse_record(&mut csv_iterator)?);
}
}
Ok(csv)
}
fn parse_record(csv_iterator: &mut Peekable<Chars>) -> Result<CSVRecord, Error> {
let mut record = CSVRecord::new();
record.push(parse_field(csv_iterator)?);
while let Some(&COMMA) = csv_iterator.peek() {
eat(COMMA, csv_iterator)?;
record.push(parse_field(csv_iterator)?);
}
Ok(record)
}
fn parse_field(csv_iterator: &mut Peekable<Chars>) -> Result<CSVField, Error> {
if let Some(&DQUOTE) = csv_iterator.peek() {
parse_escaped_field(csv_iterator)
} else {
parse_non_escaped_field(csv_iterator)
}
}
fn parse_escaped_field(csv_iterator: &mut Peekable<Chars>) -> Result<CSVField, Error> {
let mut field = CSVField::new();
eat(DQUOTE, csv_iterator)?;
while let Some(character) = csv_iterator.next() {
if is_textdata(character) || character == COMMA || character == CR || character == LF {
field.push(character);
} else if character == DQUOTE {
if let Some(&DQUOTE) = csv_iterator.peek() {
field.push(character);
csv_iterator.next();
} else {
break;
}
}
}
Ok(field)
}
fn parse_non_escaped_field(csv_iterator: &mut Peekable<Chars>) -> Result<CSVField, Error> {
let mut field = CSVField::new();
while let Some(character) = csv_iterator.peek() {
if *character == COMMA {
break;
} else if is_textdata(*character) {
field.push(*character);
csv_iterator.next();
} else if *character == CR {
break;
} else {
return Err(Error::UnexpectedCharacterInNonEscapedField(*character));
}
}
Ok(field)
}
fn eat(character: char, character_iterator: &mut Peekable<Chars>) -> Result<(), Error> {
if let Some(c) = character_iterator.next() {
if c == character {
Ok(())
} else {
Err(Error::AteWrongCharacter(character, c))
}
} else {
Err(Error::UnexpectedEndOfInput)
}
}
fn is_textdata(character: char) -> bool {
character == '\u{0020}'
|| character == '\u{0021}'
|| (character >= '\u{0023}' && character <= '\u{002B}')
|| (character >= '\u{002D}' && character <= '\u{007E}')
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn parse_empty() {
assert_eq!(parse_csv("").unwrap(), vec![vec!["".into()] as CSVRecord]);
}
#[test]
fn parse_single_field_non_escaped() {
assert_eq!(
parse_csv("value").unwrap(),
vec![vec!["value".into()] as CSVRecord]
);
}
#[test]
fn parse_multiple_fields_non_escaped() {
assert_eq!(
parse_csv("a,b,c").unwrap(),
vec![vec!["a".into(), "b".into(), "c".into()] as CSVRecord]
);
}
#[test]
fn parse_multiple_fields_escaped() {
assert_eq!(
parse_csv("\"a\"\"\",\"\"\"b\"\"\",\"c \r\ndef\"").unwrap(),
vec![vec!["a\"".into(), "\"b\"".into(), "c \r\ndef".into()] as CSVRecord]
);
}
#[test]
fn parse_multiple_records() {
assert_eq!(
parse_csv("5,10,15\r\n20,25,30").unwrap(),
vec![
vec!["5".into(), "10".into(), "15".into()] as CSVRecord,
vec!["20".into(), "25".into(), "30".into()] as CSVRecord
]
);
}
#[test]
fn parse_multiple_records_non_escaped() {
assert_eq!(
parse_csv("\"5\",10,15\r\n20,\"25\"\"baguette\"\" \r \"\"\n \r\n\",30").unwrap(),
vec![
vec!["5".into(), "10".into(), "15".into()] as CSVRecord,
vec![
"20".into(),
"25\"baguette\" \r \"\n \r\n".into(),
"30".into()
] as CSVRecord
]
);
}
}