homeboy 0.70.0

//! File I/O primitives with consistent error handling.

use crate::error::{Error, Result};
use std::fs;
use std::path::Path;

/// Read file contents with standardized error handling.
///
/// Wraps `fs::read_to_string` with consistent `Error::internal_io` formatting.
pub fn read_file(path: &Path, operation: &str) -> Result<String> {
    fs::read_to_string(path)
        .map_err(|e| Error::internal_io(e.to_string(), Some(operation.to_string())))
}

/// Write content to file with standardized error handling.
///
/// Wraps `fs::write` with consistent `Error::internal_io` formatting.
pub fn write_file(path: &Path, content: &str, operation: &str) -> Result<()> {
    fs::write(path, content)
        .map_err(|e| Error::internal_io(e.to_string(), Some(operation.to_string())))
}

/// Write content to file atomically (write to .tmp, then rename).
///
/// Prevents data loss if the process crashes mid-write. The rename is
/// atomic on POSIX filesystems, so readers always see either the old
/// content or the new content — never a partial write.
pub fn write_file_atomic(path: &Path, content: &str, operation: &str) -> Result<()> {
    let parent = path.parent().ok_or_else(|| {
        Error::internal_io(
            format!("Invalid path: {}", path.display()),
            Some(operation.to_string()),
        )
    })?;

    let filename = path.file_name().ok_or_else(|| {
        Error::internal_io(
            format!("Invalid path: {}", path.display()),
            Some(operation.to_string()),
        )
    })?;

    let tmp_path = parent.join(format!("{}.tmp", filename.to_string_lossy()));

    fs::write(&tmp_path, content).map_err(|e| {
        Error::internal_io(e.to_string(), Some(format!("{} (write temp)", operation)))
    })?;

    fs::rename(&tmp_path, path)
        .map_err(|e| Error::internal_io(e.to_string(), Some(format!("{} (rename)", operation))))?;

    Ok(())
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::io::Write;
    use tempfile::NamedTempFile;

    #[test]
    fn read_file_succeeds_for_existing_file() {
        let mut temp = NamedTempFile::new().unwrap();
        writeln!(temp, "test content").unwrap();

        let content = read_file(temp.path(), "test read").unwrap();
        assert!(content.contains("test content"));
    }

    #[test]
    fn read_file_returns_error_for_missing_file() {
        let result = read_file(Path::new("/nonexistent/path.txt"), "test read");
        assert!(result.is_err());
        let err = result.unwrap_err();
        assert_eq!(err.code.as_str(), "internal.io_error");
    }

    #[test]
    fn write_file_succeeds_for_valid_path() {
        let temp = NamedTempFile::new().unwrap();
        let result = write_file(temp.path(), "new content", "test write");
        assert!(result.is_ok());

        let content = fs::read_to_string(temp.path()).unwrap();
        assert_eq!(content, "new content");
    }

    #[test]
    fn write_file_returns_error_for_invalid_path() {
        let result = write_file(
            Path::new("/nonexistent/dir/file.txt"),
            "content",
            "test write",
        );
        assert!(result.is_err());
        let err = result.unwrap_err();
        assert_eq!(err.code.as_str(), "internal.io_error");
    }
}