71 lines
1.9 KiB
Rust
71 lines
1.9 KiB
Rust
use combine::parser::char::{char, digit, letter, spaces};
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use combine::{many1, optional, Parser};
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use thiserror::Error;
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enum ParsedValue {
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Valid(i32),
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Invalid,
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}
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#[derive(Error, Debug)]
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pub enum VariableParsingError {
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#[error("invalid variable value, must be a number")]
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InvalidValue,
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#[error("unconsumed input")]
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UnconsumedInput,
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#[error("parser error: {0}")]
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InternalParseError(#[from] combine::error::StringStreamError),
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}
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pub fn parse_set_variable(input: &str) -> Result<(String, i32), VariableParsingError> {
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let name = many1(letter()).map(|value: String| value);
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let maybe_minus = optional(char('-')).map(|value: Option<char>| match value {
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Some(minus_sign) => String::from(minus_sign),
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_ => "".to_owned(),
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});
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let value = maybe_minus
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.and(many1(digit()))
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.map(|value: (String, String)| {
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let number = format!("{}{}", value.0, value.1);
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match number.parse::<i32>() {
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Ok(num) => ParsedValue::Valid(num),
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_ => ParsedValue::Invalid,
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}
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});
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let mut parser = name.skip(spaces().silent()).and(value);
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let (result, rest) = parser.parse(input)?;
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if rest.len() == 0 {
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match result {
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(variable_name, ParsedValue::Valid(value)) => Ok((variable_name, value)),
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_ => Err(VariableParsingError::InvalidValue),
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}
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} else {
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Err(VariableParsingError::UnconsumedInput)
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}
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn parse_postive_number() {
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let result = parse_set_variable("myvar 5");
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assert!(result.is_ok());
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assert_eq!(("myvar".to_string(), 5), result.unwrap());
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}
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#[test]
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fn parse_negative_number() {
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let result = parse_set_variable("myvar -5");
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assert!(result.is_ok());
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assert_eq!(("myvar".to_string(), -5), result.unwrap());
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}
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}
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