string-auto-indent 0.1.2

#[cfg(doctest)]
doc_comment::doctest!("../README.md");

pub use line_ending::LineEnding;

/// Struct that encapsulates auto-indentation logic.
struct AutoIndent {
    line_ending: LineEnding,
}

impl AutoIndent {
    /// Creates a new instance by detecting the line ending from the input.
    fn new(input: &str) -> Self {
        Self {
            line_ending: LineEnding::from(input),
        }
    }

    /// Applies auto-indentation rules.
    fn apply(&self, input: &str) -> String {
        if input.trim().is_empty() {
            return String::new();
        }

        let mut lines: Vec<String> = LineEnding::split(input);

        // Take first line exactly as is
        let first_line = Some(lines.remove(0));

        // Find the minimum indentation for all remaining lines
        let min_indent = lines
            .iter()
            .filter(|line| !line.trim().is_empty()) // Ignore empty lines
            .map(|line| line.chars().take_while(|c| c.is_whitespace()).count())
            .min()
            .unwrap_or(0);

        // Adjust indentation for all lines except the first
        let mut result: Vec<String> = Vec::new();

        if let Some(first) = first_line {
            result.push(first.to_string()); // Preserve the first line exactly
        }

        result.extend(lines.iter().map(|line| {
            if line.trim().is_empty() {
                String::new() // Convert empty lines to actual empty lines
            } else {
                line.chars().skip(min_indent).collect() // Trim only relative indentation
            }
        }));

        // Ensure the final line is empty if it originally contained only whitespace
        if result.last().map(|s| s.trim()).unwrap_or("").is_empty() {
            *result.last_mut().unwrap() = String::new();
        }

        // Preserve the original trailing newline behavior
        self.line_ending.join(result)
    }
}

/// Auto-indents a string while preserving original line endings.
pub fn auto_indent(input: &str) -> String {
    AutoIndent::new(input).apply(input)
}

#[cfg(test)]
mod tests {
    use super::*;
    use line_ending::LineEnding;

    fn get_readme_contents() -> String {
        use std::fs::File;
        use std::io::Read;

        let readme_file = "README.md";

        // Read file contents
        let mut read_content = String::new();
        File::open(readme_file)
            .unwrap_or_else(|_| panic!("Failed to open {}", readme_file))
            .read_to_string(&mut read_content)
            .unwrap_or_else(|_| panic!("Failed to read {}", readme_file));

        read_content
    }

    #[test]
    fn test_preserves_formatting() {
        let readme_contents = get_readme_contents();

        assert_eq!(auto_indent(&readme_contents), readme_contents);

        // Validate the content was actually read
        let lines = LineEnding::split(&readme_contents);
        assert_eq!(lines.first().unwrap(), "# Multi-line String Auto-Indent");

        // Ensure the README has more than 5 lines
        assert!(
            lines.len() > 5,
            "Expected README to have more than 5 lines, but got {}",
            lines.len()
        );
    }

    #[test]
    fn test_basic_implementation() {
        let input = r#"Basic Test
        1
            2
                3
        "#;

        let line_ending = LineEnding::from(input);

        // With auto-indent
        assert_eq!(
            auto_indent(input),
            // string_replace_all("Basic Test\n1\n    2\n        3\n", "\n", e.as_str())
            line_ending.denormalize("Basic Test\n1\n    2\n        3\n")
        );

        // Without auto-indent
        assert_eq!(
            input,
            line_ending
                .denormalize("Basic Test\n        1\n            2\n                3\n        ")
        );
    }

    #[test]
    fn test_empty_first_line() {
        let input = r#"
        1
            2
                3
        "#;

        let line_ending = LineEnding::from(input);

        // With auto-indent
        assert_eq!(
            auto_indent(input),
            line_ending.denormalize("\n1\n    2\n        3\n")
        );

        // Without auto-indent
        assert_eq!(
            input,
            line_ending.denormalize("\n        1\n            2\n                3\n        "),
        );
    }

    #[test]
    fn test_indented_first_line() {
        let input = r#"     <- First Line
        Second Line
        "#;

        let line_ending = LineEnding::from(input);

        // With auto-indent
        assert_eq!(
            auto_indent(input),
            line_ending.denormalize("     <- First Line\nSecond Line\n")
        );

        // Without auto-indent
        assert_eq!(
            input,
            line_ending.denormalize("     <- First Line\n        Second Line\n        "),
        );
    }

    #[test]
    fn test_mixed_indentation() {
        let input = r#"First Line
        Second Line
Third Line
        "#;

        let line_ending = LineEnding::from(input);

        // With auto-indent
        assert_eq!(
            auto_indent(input),
            line_ending.denormalize("First Line\n        Second Line\nThird Line\n",)
        );

        // Without auto-indent
        assert_eq!(
            input,
            line_ending.denormalize("First Line\n        Second Line\nThird Line\n        "),
        );
    }

    #[test]
    fn test_single_line_no_change() {
        let input = "Single line no change";

        let line_ending = LineEnding::from(input);

        // With auto-indent
        assert_eq!(
            auto_indent(input),
            line_ending.denormalize("Single line no change")
        );

        // Without auto-indent
        assert_eq!(input, line_ending.denormalize("Single line no change"));
    }

    #[test]
    fn test_multiple_blank_lines() {
        let input = r#"First Line
        
            A

            B

            C

                D

        E
        "#;

        let line_ending = LineEnding::from(input);

        // With auto-indent
        assert_eq!(
            auto_indent(input),
            line_ending.denormalize("First Line\n\n    A\n\n    B\n\n    C\n\n        D\n\nE\n")
        );

        // Without auto-indent
        assert_eq!(
            input,
            line_ending.denormalize(
                "First Line\n        \n            A\n\n            B\n\n            C\n\n                D\n\n        E\n        "
            ),
        );
    }
}