nut-shell 0.1.2

//! Path parsing and navigation.
//!
//! Unix-style path resolution with `.` and `..` support.

use crate::error::CliError;

/// Unix-style path parser and representation.
///
/// Handles absolute and relative paths with `.` and `..` navigation.
/// Zero-allocation parsing using string slices.
///
/// # Path Syntax
///
/// - **Absolute paths**: Start with `/` (e.g., `/system/reboot`)
/// - **Relative paths**: No leading `/` (e.g., `network/status`, `../hw`)
/// - **Parent navigation**: `..` goes up one level
/// - **Current directory**: `.` stays at current level
///
/// # Memory
///
/// Uses `MAX_DEPTH` const generic to limit nesting depth.
/// All parsing is zero-allocation, working with string slices.
#[derive(Debug, PartialEq)]
pub struct Path<'a, const MAX_DEPTH: usize> {
    /// Whether path starts with `/`
    is_absolute: bool,

    /// Path segments (includes `.` and `..` for resolution)
    segments: heapless::Vec<&'a str, MAX_DEPTH>,
}

impl<'a, const MAX_DEPTH: usize> Path<'a, MAX_DEPTH> {
    /// Parse path string into Path structure.
    ///
    /// Supports absolute (`/system/reboot`), relative (`cmd`, `./cmd`), and parent (`..`) paths.
    ///
    /// Returns `InvalidPath` for empty input or `PathTooDeep` if MAX_DEPTH exceeded.
    pub fn parse(input: &'a str) -> Result<Self, CliError> {
        // Handle empty path
        if input.is_empty() {
            return Err(CliError::InvalidPath);
        }

        // Check if absolute (starts with /)
        let is_absolute = input.starts_with('/');

        // Remove leading slash for parsing
        let path_str = if is_absolute { &input[1..] } else { input };

        // Parse segments
        let mut segments = heapless::Vec::new();

        // Empty path after removing leading slash means root directory
        if path_str.is_empty() {
            // Absolute path "/" refers to root
            if is_absolute {
                return Ok(Self {
                    is_absolute,
                    segments,
                });
            } else {
                // Relative empty path is invalid
                return Err(CliError::InvalidPath);
            }
        }

        // Split by '/' and filter empty segments
        for segment in path_str.split('/') {
            // Skip empty segments (e.g., from "//" or trailing "/")
            if segment.is_empty() {
                continue;
            }

            // Add segment
            segments.push(segment).map_err(|_| CliError::PathTooDeep)?;
        }

        Ok(Self {
            is_absolute,
            segments,
        })
    }

    /// Returns true if this is an absolute path (starts with `/`).
    pub fn is_absolute(&self) -> bool {
        self.is_absolute
    }

    /// Get path segments as slice.
    pub fn segments(&self) -> &[&'a str] {
        &self.segments
    }

    /// Returns the number of segments in this path.
    pub fn segment_count(&self) -> usize {
        self.segments.len()
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::config::{DefaultConfig, MinimalConfig, ShellConfig};

    // Use DefaultConfig's MAX_PATH_DEPTH = 8 for most tests
    type TestPath<'a> = Path<'a, { DefaultConfig::MAX_PATH_DEPTH }>;

    #[test]
    fn test_empty_path_is_invalid() {
        let result = TestPath::parse("");
        assert_eq!(result, Err(CliError::InvalidPath));
    }

    #[test]
    fn test_absolute_root() {
        let path = TestPath::parse("/").unwrap();
        assert!(path.is_absolute());
        assert_eq!(path.segments(), &[] as &[&str]);
        assert_eq!(path.segment_count(), 0);
    }

    #[test]
    fn test_absolute_single_segment() {
        let path = TestPath::parse("/system").unwrap();
        assert!(path.is_absolute());
        assert_eq!(path.segments(), &["system"]);
        assert_eq!(path.segment_count(), 1);
    }

    #[test]
    fn test_absolute_multiple_segments() {
        let path = TestPath::parse("/system/network/status").unwrap();
        assert!(path.is_absolute());
        assert_eq!(path.segments(), &["system", "network", "status"]);
        assert_eq!(path.segment_count(), 3);
    }

    #[test]
    fn test_relative_single_segment() {
        let path = TestPath::parse("help").unwrap();
        assert!(!path.is_absolute());
        assert_eq!(path.segments(), &["help"]);
    }

    #[test]
    fn test_relative_multiple_segments() {
        let path = TestPath::parse("system/network").unwrap();
        assert!(!path.is_absolute());
        assert_eq!(path.segments(), &["system", "network"]);
    }

    #[test]
    fn test_parent_navigation() {
        let path = TestPath::parse("..").unwrap();
        assert!(!path.is_absolute());
        assert_eq!(path.segments(), &[".."]);

        let path = TestPath::parse("../system").unwrap();
        assert_eq!(path.segments(), &["..", "system"]);

        let path = TestPath::parse("../../hw/led").unwrap();
        assert_eq!(path.segments(), &["..", "..", "hw", "led"]);
    }

    #[test]
    fn test_current_directory() {
        let path = TestPath::parse(".").unwrap();
        assert!(!path.is_absolute());
        assert_eq!(path.segments(), &["."]);

        let path = TestPath::parse("./cmd").unwrap();
        assert_eq!(path.segments(), &[".", "cmd"]);
    }

    #[test]
    fn test_mixed_navigation() {
        let path = TestPath::parse("../system/./network").unwrap();
        assert_eq!(path.segments(), &["..", "system", ".", "network"]);
    }

    #[test]
    fn test_trailing_slash_ignored() {
        let path = TestPath::parse("/system/").unwrap();
        assert!(path.is_absolute());
        assert_eq!(path.segments(), &["system"]);

        let path = TestPath::parse("network/").unwrap();
        assert!(!path.is_absolute());
        assert_eq!(path.segments(), &["network"]);
    }

    #[test]
    fn test_double_slash_treated_as_single() {
        let path = TestPath::parse("/system//network").unwrap();
        assert_eq!(path.segments(), &["system", "network"]);

        let path = TestPath::parse("//system").unwrap();
        assert!(path.is_absolute());
        assert_eq!(path.segments(), &["system"]);
    }

    #[test]
    fn test_path_too_deep() {
        // Build a path that exceeds MAX_PATH_DEPTH (8 for DefaultConfig)
        let deep_path = "a/b/c/d/e/f/g/h/i/j/k";
        let result = TestPath::parse(deep_path);
        assert_eq!(result, Err(CliError::PathTooDeep));
    }

    #[test]
    fn test_max_depth_exactly() {
        // MAX_PATH_DEPTH = 8 for DefaultConfig
        let path = TestPath::parse("a/b/c/d/e/f/g/h").unwrap();
        assert_eq!(path.segment_count(), 8);
    }

    #[test]
    fn test_absolute_path_with_parent() {
        let path = TestPath::parse("/../system").unwrap();
        assert!(path.is_absolute());
        assert_eq!(path.segments(), &["..", "system"]);
    }

    #[test]
    fn test_minimal_config_respects_depth() {
        type MinimalPath<'a> = Path<'a, { MinimalConfig::MAX_PATH_DEPTH }>;

        // MinimalConfig has MAX_PATH_DEPTH = 4
        // Exactly 4 segments should succeed
        let path = MinimalPath::parse("a/b/c/d").unwrap();
        assert_eq!(path.segment_count(), 4);

        // 5 segments should fail
        let result = MinimalPath::parse("a/b/c/d/e");
        assert_eq!(result, Err(CliError::PathTooDeep));
    }

    #[test]
    fn test_default_config_allows_deeper_paths() {
        // DefaultConfig has MAX_PATH_DEPTH = 8
        let path = TestPath::parse("a/b/c/d/e/f/g/h").unwrap();
        assert_eq!(path.segment_count(), 8);

        // But MinimalConfig (depth=4) doesn't allow this
        type MinimalPath<'a> = Path<'a, { MinimalConfig::MAX_PATH_DEPTH }>;
        let result = MinimalPath::parse("a/b/c/d/e/f/g/h");
        assert_eq!(result, Err(CliError::PathTooDeep));
    }
}