soukoban 0.1.4

A library provides the implementation of some algorithms and data structures related to Sokoban
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//! Utilities for run-length encoding encoding and decoding.

use crate::error::{DecodeRleError, EncodeRleError};

/// Encodes a string using run-length encoding (RLE).
///
/// # Examples
///
/// ```
/// # use std::error::Error;
/// #
/// # fn main() -> Result<(), Box<dyn Error>> {
/// use soukoban::run_length::rle_encode;
///
/// assert_eq!(rle_encode("aaabbbcdd")?, "3a3bc2d");
/// #
/// #     Ok(())
/// # }
/// ```
pub fn rle_encode(str: &str) -> Result<String, EncodeRleError> {
    let mut result = String::new();
    let mut chars = str.chars().peekable();
    let mut count = 0;
    while let Some(char) = chars.next() {
        if char.is_numeric() {
            return Err(EncodeRleError::NumericCharacter(char));
        }
        count += 1;
        if chars.peek() != Some(&char) {
            if count > 1 {
                result.push_str(&count.to_string());
            }
            result.push(char);
            count = 0;
        }
    }
    Ok(result)
}

/// Decodes a string encoded with run-length encoding (RLE).
///
/// # Examples
///
/// ```
/// # use std::error::Error;
/// #
/// # fn main() -> Result<(), Box<dyn Error>> {
/// use soukoban::run_length::rle_decode;
///
/// assert_eq!(rle_decode("-#$.*+@")?, "-#$.*+@");
/// assert_eq!(rle_decode("3-##3(.$2(+*))-#")?, "---##.$+*+*.$+*+*.$+*+*-#");
/// #
/// #     Ok(())
/// # }
/// ```
pub fn rle_decode(str: &str) -> Result<String, DecodeRleError> {
    let mut result = String::new();

    let mut length_string = String::new();
    let mut iter = str.chars();
    while let Some(char) = iter.next() {
        if char.is_ascii_digit() {
            length_string.push(char);
            continue;
        }
        let mut token = String::new();
        if char == '(' {
            let mut nesting_level = 0;
            for char in &mut iter {
                if char == '(' {
                    nesting_level += 1;
                } else if char == ')' {
                    if nesting_level == 0 {
                        break;
                    }
                    nesting_level -= 1;
                }
                token.push(char);
            }
        } else {
            token = char.to_string();
        }
        let length = length_string.parse().unwrap_or(1);
        result += &token.repeat(length);
        length_string.clear();
    }
    if !length_string.is_empty() {
        return Err(DecodeRleError::EndWithDigits(
            length_string.parse().unwrap(),
        ));
    }
    if result.contains('(') {
        return rle_decode(&result);
    }
    Ok(result)
}