strict-path 0.1.2

mod fs;
mod iter;
mod links;
mod traits;

pub use iter::{StrictOpenOptions, StrictReadDir};

use crate::validator::path_history::{BoundaryChecked, Canonicalized, PathHistory, Raw};
use crate::{Result, StrictPathError};
use std::ffi::OsStr;
use std::marker::PhantomData;
use std::path::{Path, PathBuf};
use std::sync::Arc;

/// Strip the Windows verbatim `\\?\` prefix from a path if present.
///
/// The `junction` crate does not handle verbatim prefix paths correctly - it creates
/// broken junctions that return ERROR_INVALID_NAME (123) when accessed.
/// This helper strips the prefix so junction creation works correctly.
///
/// See: <https://github.com/tesuji/junction/issues/30>
#[cfg(all(windows, feature = "junctions"))]
pub(super) fn strip_verbatim_prefix(path: &Path) -> std::borrow::Cow<'_, Path> {
    use std::borrow::Cow;
    let s = path.as_os_str().to_string_lossy();
    if let Some(rest) = s.strip_prefix(r"\\?\") {
        Cow::Owned(PathBuf::from(rest))
    } else {
        Cow::Borrowed(path)
    }
}

/// SUMMARY:
/// Hold a validated, system-facing filesystem path guaranteed to be within a `PathBoundary`.
///
/// DETAILS:
/// Use when you need system-facing I/O with safety proofs. For user-facing display and rooted
/// virtual operations prefer `VirtualPath`. Operations like `strict_join` and
/// `strictpath_parent` preserve guarantees. `Display` shows the real system path. String
/// accessors are prefixed with `strictpath_` to avoid confusion.
#[derive(Clone)]
pub struct StrictPath<Marker = ()> {
    path: PathHistory<((Raw, Canonicalized), BoundaryChecked)>,
    boundary: Arc<crate::PathBoundary<Marker>>,
    _marker: PhantomData<Marker>,
}

impl<Marker> StrictPath<Marker> {
    /// SUMMARY:
    /// Create the base `StrictPath` anchored at the provided boundary directory.
    ///
    /// PARAMETERS:
    /// - `dir_path` (`AsRef<Path>`): Boundary directory (must exist).
    ///
    /// RETURNS:
    /// - `Result<StrictPath<Marker>>`: Base path ("" join) within the boundary.
    ///
    /// ERRORS:
    /// - `StrictPathError::InvalidRestriction`: If the boundary cannot be created/validated.
    ///
    /// NOTE: Prefer passing `PathBoundary` in reusable flows.
    ///
    /// EXAMPLE:
    /// ```rust
    /// # use strict_path::StrictPath;
    /// let base: StrictPath = StrictPath::with_boundary(std::env::temp_dir())?;
    /// assert!(base.is_dir());
    /// # Ok::<_, Box<dyn std::error::Error>>(())
    /// ```
    pub fn with_boundary<P: AsRef<Path>>(dir_path: P) -> Result<Self> {
        let validated_dir = crate::PathBoundary::try_new(dir_path)?;
        validated_dir.into_strictpath()
    }

    /// SUMMARY:
    /// Create the base `StrictPath`, creating the boundary directory if missing.
    ///
    /// PARAMETERS:
    /// - `dir_path` (`AsRef<Path>`): Boundary directory (created if absent).
    ///
    /// RETURNS:
    /// - `Result<StrictPath<Marker>>`: Base path ("" join) within the boundary.
    ///
    /// ERRORS:
    /// - `StrictPathError::InvalidRestriction`: If the directory cannot be created or canonicalized.
    ///
    /// EXAMPLE:
    /// ```rust
    /// # use strict_path::StrictPath;
    /// let dir = std::env::temp_dir().join("strict-path-wbc-example");
    /// let base: StrictPath = StrictPath::with_boundary_create(&dir)?;
    /// assert!(base.is_dir());
    /// # std::fs::remove_dir_all(&dir)?;
    /// # Ok::<_, Box<dyn std::error::Error>>(())
    /// ```
    pub fn with_boundary_create<P: AsRef<Path>>(dir_path: P) -> Result<Self> {
        let validated_dir = crate::PathBoundary::try_new_create(dir_path)?;
        validated_dir.into_strictpath()
    }

    pub(crate) fn new(
        boundary: Arc<crate::PathBoundary<Marker>>,
        validated_path: PathHistory<((Raw, Canonicalized), BoundaryChecked)>,
    ) -> Self {
        Self {
            path: validated_path,
            boundary,
            _marker: PhantomData,
        }
    }

    #[inline]
    pub(crate) fn boundary(&self) -> &crate::PathBoundary<Marker> {
        &self.boundary
    }

    /// Return the boundary path (always available, used internally by Debug and other impls).
    #[inline]
    pub(crate) fn boundary_path(&self) -> &Path {
        self.boundary.path()
    }

    #[inline]
    pub(crate) fn path(&self) -> &Path {
        &self.path
    }

    /// SUMMARY:
    /// Return a lossy `String` view of the system path. Prefer `.interop_path()` only for unavoidable third-party interop.
    ///
    /// PARAMETERS:
    /// - _none_
    ///
    /// RETURNS:
    /// - `Cow<'_, str>`: The path as a UTF-8 string, with replacement characters for non-UTF-8 bytes.
    ///
    /// ERRORS:
    /// - None (infallible).
    ///
    /// EXAMPLE:
    /// ```rust
    /// # use strict_path::PathBoundary;
    /// # let temp = tempfile::tempdir()?;
    /// # let data_dir: PathBoundary = PathBoundary::try_new(temp.path())?;
    /// let file_path = data_dir.strict_join("report.txt")?;
    /// let s = file_path.strictpath_to_string_lossy();
    /// assert!(s.ends_with("report.txt"));
    /// # Ok::<_, Box<dyn std::error::Error>>(())
    /// ```
    #[inline]
    pub fn strictpath_to_string_lossy(&self) -> std::borrow::Cow<'_, str> {
        self.path.to_string_lossy()
    }

    /// SUMMARY:
    /// Return the underlying system path as `&str` if valid UTF‑8; otherwise `None`.
    ///
    /// PARAMETERS:
    /// - _none_
    ///
    /// RETURNS:
    /// - `Option<&str>`: The path as a string slice, or `None` if the path contains non-UTF-8 bytes.
    ///
    /// ERRORS:
    /// - None (infallible).
    ///
    /// EXAMPLE:
    /// ```rust
    /// # use strict_path::PathBoundary;
    /// # let temp = tempfile::tempdir()?;
    /// # let data_dir: PathBoundary = PathBoundary::try_new(temp.path())?;
    /// let file_path = data_dir.strict_join("config.toml")?;
    /// if let Some(s) = file_path.strictpath_to_str() {
    ///     assert!(s.ends_with("config.toml"));
    /// }
    /// # Ok::<_, Box<dyn std::error::Error>>(())
    /// ```
    #[inline]
    pub fn strictpath_to_str(&self) -> Option<&str> {
        self.path.to_str()
    }

    /// SUMMARY:
    /// Return the underlying system path as `&OsStr` for unavoidable third-party `AsRef<Path>` interop.
    ///
    /// PARAMETERS:
    /// - _none_
    ///
    /// RETURNS:
    /// - `&OsStr`: The raw OS string representation of the system path.
    ///
    /// ERRORS:
    /// - None (infallible).
    ///
    /// EXAMPLE:
    /// ```rust
    /// # use strict_path::PathBoundary;
    /// # let temp = tempfile::tempdir()?;
    /// # let data_dir: PathBoundary = PathBoundary::try_new(temp.path())?;
    /// let file_path = data_dir.strict_join("data.bin")?;
    /// let os_str = file_path.interop_path();
    /// assert!(std::path::Path::new(os_str).exists() || !std::path::Path::new(os_str).exists());
    /// # Ok::<_, Box<dyn std::error::Error>>(())
    /// ```
    #[inline]
    pub fn interop_path(&self) -> &OsStr {
        self.path.as_os_str()
    }

    /// SUMMARY:
    /// Return a `Display` wrapper that shows the real system path.
    ///
    /// PARAMETERS:
    /// - _none_
    ///
    /// RETURNS:
    /// - `std::path::Display<'_>`: A display adapter suitable for use with `println!` or `format!`.
    ///
    /// ERRORS:
    /// - None (infallible).
    ///
    /// EXAMPLE:
    /// ```rust
    /// # use strict_path::PathBoundary;
    /// # let temp = tempfile::tempdir()?;
    /// # let data_dir: PathBoundary = PathBoundary::try_new(temp.path())?;
    /// let file_path = data_dir.strict_join("notes.txt")?;
    /// println!("Path: {}", file_path.strictpath_display());
    /// # Ok::<_, Box<dyn std::error::Error>>(())
    /// ```
    #[inline]
    pub fn strictpath_display(&self) -> std::path::Display<'_> {
        self.path.display()
    }

    /// SUMMARY:
    /// Consume and return the inner `PathBuf` (escape hatch). Prefer `.interop_path()` (third-party adapters only) to borrow.
    ///
    /// PARAMETERS:
    /// - _none_
    ///
    /// RETURNS:
    /// - `PathBuf`: The validated system path, relinquishing all boundary guarantees.
    ///
    /// ERRORS:
    /// - None (infallible).
    ///
    /// EXAMPLE:
    /// ```rust
    /// # use strict_path::PathBoundary;
    /// # let temp = tempfile::tempdir()?;
    /// # let data_dir: PathBoundary = PathBoundary::try_new(temp.path())?;
    /// let file_path = data_dir.strict_join("output.bin")?;
    /// let raw: std::path::PathBuf = file_path.unstrict();
    /// // raw is now a plain PathBuf — use only for unavoidable interop
    /// # Ok::<_, Box<dyn std::error::Error>>(())
    /// ```
    #[inline]
    pub fn unstrict(self) -> PathBuf {
        self.path.into_inner()
    }

    /// SUMMARY:
    /// Convert this `StrictPath` into a user‑facing `VirtualPath`.
    ///
    /// PARAMETERS:
    /// - _none_
    ///
    /// RETURNS:
    /// - `VirtualPath<Marker>`: A user-facing path derived from this strict path's boundary and location.
    ///
    /// ERRORS:
    /// - None (infallible).
    ///
    /// EXAMPLE:
    /// ```rust
    /// # use strict_path::PathBoundary;
    /// # let temp = tempfile::tempdir()?;
    /// # let data_dir: PathBoundary = PathBoundary::try_new(temp.path())?;
    /// let file_path = data_dir.strict_join("docs/readme.md")?;
    /// let vpath = file_path.virtualize();
    /// println!("{}", vpath.virtualpath_display());
    /// # Ok::<_, Box<dyn std::error::Error>>(())
    /// ```
    #[cfg(feature = "virtual-path")]
    #[inline]
    pub fn virtualize(self) -> crate::path::virtual_path::VirtualPath<Marker> {
        crate::path::virtual_path::VirtualPath::new(self)
    }

    /// SUMMARY:
    /// Change the compile-time marker while reusing the validated strict path.
    ///
    /// WHEN TO USE:
    /// - After authenticating/authorizing a user and granting them access to a path
    /// - When escalating or downgrading permissions (e.g., ReadOnly → ReadWrite)
    /// - When reinterpreting a path's domain (e.g., TempStorage → UserUploads)
    ///
    /// WHEN NOT TO USE:
    /// - When converting between path types - conversions preserve markers automatically
    /// - When the current marker already matches your needs - no transformation needed
    /// - When you haven't verified authorization - NEVER change markers without checking permissions
    ///
    /// PARAMETERS:
    /// - `_none_`
    ///
    /// RETURNS:
    /// - `StrictPath<NewMarker>`: Same boundary-checked system path encoded with the new marker.
    ///
    /// ERRORS:
    /// - `_none_`
    ///
    /// SECURITY:
    /// The caller MUST ensure the new marker reflects real-world permissions. This method does not
    /// perform any authorization checks.
    ///
    /// EXAMPLE:
    /// ```rust
    /// # use strict_path::{PathBoundary, StrictPath};
    /// # use std::io;
    /// # struct UserFiles;
    /// # struct ReadOnly;
    /// # struct ReadWrite;
    /// # let boundary_dir = std::env::temp_dir().join("strict-path-change-marker-example");
    /// # std::fs::create_dir_all(&boundary_dir.join("logs"))?;
    /// # let data_dir: PathBoundary = PathBoundary::try_new(&boundary_dir)?;
    /// #
    /// // Verify user can write before granting write access
    /// fn authorize_write_access(
    ///     user_id: &str,
    ///     path: StrictPath<(UserFiles, ReadOnly)>
    /// ) -> Result<StrictPath<(UserFiles, ReadWrite)>, &'static str> {
    ///     if user_id == "admin" {
    ///         Ok(path.change_marker())  // ✅ Transform after authorization check
    ///     } else {
    ///         Err("insufficient permissions")  // ❌ User lacks write permission
    ///     }
    /// }
    ///
    /// // Function requiring write permission - enforces type safety at compile time
    /// fn write_log_entry(path: StrictPath<(UserFiles, ReadWrite)>, content: &str) -> io::Result<()> {
    ///     path.write(content.as_bytes())
    /// }
    ///
    /// // Start with read-only access from untrusted input
    /// let requested_log = "logs/app.log"; // Untrusted input
    /// let read_only_path: StrictPath<(UserFiles, ReadOnly)> =
    ///     data_dir.strict_join(requested_log)?.change_marker();
    ///
    /// // Elevate permissions after authorization
    /// let read_write_path = authorize_write_access("admin", read_only_path)
    ///     .expect("user must have sufficient permissions");
    ///
    /// // Now we can call functions requiring write access
    /// write_log_entry(read_write_path, "Application started")?;
    /// #
    /// # std::fs::remove_dir_all(&boundary_dir)?;
    /// # Ok::<_, Box<dyn std::error::Error>>(())
    /// ```
    ///
    /// **Type Safety Guarantee:**
    ///
    /// The following code **fails to compile** because you cannot pass a path with one marker
    /// type to a function expecting a different marker type. This compile-time check enforces
    /// that permission changes are explicit and cannot be bypassed accidentally.
    ///
    /// ```compile_fail
    /// # use strict_path::{PathBoundary, StrictPath};
    /// # struct ReadOnly;
    /// # struct WritePermission;
    /// # let boundary_dir = std::env::temp_dir().join("strict-path-change-marker-deny");
    /// # std::fs::create_dir_all(&boundary_dir).unwrap();
    /// # let data_dir: PathBoundary<ReadOnly> = PathBoundary::try_new(&boundary_dir).unwrap();
    /// let read_only_path: StrictPath<ReadOnly> = data_dir.strict_join("logs/app.log").unwrap();
    /// fn require_write(_: StrictPath<WritePermission>) {}
    /// // ❌ Compile error: expected `StrictPath<WritePermission>`, found `StrictPath<ReadOnly>`
    /// require_write(read_only_path);
    /// ```
    #[inline]
    pub fn change_marker<NewMarker>(self) -> StrictPath<NewMarker> {
        let StrictPath { path, boundary, .. } = self;

        // Try to unwrap the Arc (zero-cost if this is the only reference).
        // If other references exist, clone the boundary (allocation needed).
        let boundary_owned = Arc::try_unwrap(boundary).unwrap_or_else(|arc| (*arc).clone());
        let new_boundary = Arc::new(boundary_owned.change_marker::<NewMarker>());

        StrictPath {
            path,
            boundary: new_boundary,
            _marker: PhantomData,
        }
    }

    /// SUMMARY:
    /// Consume and return a new `PathBoundary` anchored at this strict path.
    ///
    /// PARAMETERS:
    /// - _none_
    ///
    /// RETURNS:
    /// - `Result<PathBoundary<Marker>>`: Boundary anchored at the strict path's
    ///   system location (must already exist and be a directory).
    ///
    /// ERRORS:
    /// - `StrictPathError::InvalidRestriction`: If the strict path does not exist
    ///   or is not a directory.
    ///
    /// EXAMPLE:
    /// ```rust
    /// # use strict_path::PathBoundary;
    /// # let temp = tempfile::tempdir()?;
    /// # let data_dir: PathBoundary = PathBoundary::try_new(temp.path())?;
    /// let subdir = data_dir.strict_join("uploads")?;
    /// subdir.create_dir()?;
    /// let sub_boundary: PathBoundary = subdir.try_into_boundary()?;
    /// let _ = sub_boundary.strict_join("file.bin")?;
    /// # Ok::<_, Box<dyn std::error::Error>>(())
    /// ```
    #[inline]
    pub fn try_into_boundary(self) -> Result<crate::PathBoundary<Marker>> {
        let StrictPath { path, .. } = self;
        crate::PathBoundary::try_new(path.into_inner())
    }

    /// SUMMARY:
    /// Consume and return a `PathBoundary`, creating the directory if missing.
    ///
    /// PARAMETERS:
    /// - _none_
    ///
    /// RETURNS:
    /// - `Result<PathBoundary<Marker>>`: Boundary anchored at the strict path's
    ///   system location (created if necessary).
    ///
    /// ERRORS:
    /// - `StrictPathError::InvalidRestriction`: If creation or canonicalization fails.
    ///
    /// EXAMPLE:
    /// ```rust
    /// # use strict_path::PathBoundary;
    /// # let temp = tempfile::tempdir()?;
    /// # let data_dir: PathBoundary = PathBoundary::try_new(temp.path())?;
    /// let subdir = data_dir.strict_join("cache")?;
    /// // Directory does not exist yet — try_into_boundary_create will create it
    /// let sub_boundary: PathBoundary = subdir.try_into_boundary_create()?;
    /// let _ = sub_boundary.strict_join("item.bin")?;
    /// # Ok::<_, Box<dyn std::error::Error>>(())
    /// ```
    #[inline]
    pub fn try_into_boundary_create(self) -> Result<crate::PathBoundary<Marker>> {
        let StrictPath { path, .. } = self;
        crate::PathBoundary::try_new_create(path.into_inner())
    }

    /// SUMMARY:
    /// Join a path segment and re-validate against the boundary.
    ///
    /// NOTE:
    /// Never wrap `.interop_path()` in `Path::new()` to use `Path::join()` — that defeats all security. Always use this method.
    /// After `.unstrict()` (explicit escape hatch), you own a `PathBuf` and can do whatever you need.
    ///
    /// PARAMETERS:
    /// - `path` (`AsRef<Path>`): Segment or absolute path to validate.
    ///
    /// RETURNS:
    /// - `Result<StrictPath<Marker>>`: Validated path inside the boundary.
    ///
    /// ERRORS:
    /// - `StrictPathError::PathResolutionError`, `StrictPathError::PathEscapesBoundary`.
    #[inline]
    pub fn strict_join<P: AsRef<Path>>(&self, path: P) -> Result<Self> {
        let new_systempath = self.path.join(path);
        self.boundary.strict_join(new_systempath)
    }

    /// SUMMARY:
    /// Return the parent as a new `StrictPath`, or `None` at the boundary root.
    ///
    /// PARAMETERS:
    /// - _none_
    ///
    /// RETURNS:
    /// - `Result<Option<StrictPath<Marker>>>`: The parent path, or `None` if already at the boundary root.
    ///
    /// ERRORS:
    /// - `StrictPathError::PathResolutionError`: If the parent path cannot be resolved.
    /// - `StrictPathError::PathEscapesBoundary`: If the parent escapes the boundary (cannot occur in practice).
    ///
    /// EXAMPLE:
    /// ```rust
    /// # use strict_path::PathBoundary;
    /// # let temp = tempfile::tempdir()?;
    /// # let data_dir: PathBoundary = PathBoundary::try_new(temp.path())?;
    /// let file_path = data_dir.strict_join("logs/app.log")?;
    /// if let Some(parent) = file_path.strictpath_parent()? {
    ///     assert!(parent.strictpath_display().to_string().ends_with("logs"));
    /// }
    /// # Ok::<_, Box<dyn std::error::Error>>(())
    /// ```
    pub fn strictpath_parent(&self) -> Result<Option<Self>> {
        match self.path.parent() {
            Some(p) => match self.boundary.strict_join(p) {
                Ok(p) => Ok(Some(p)),
                Err(e) => Err(e),
            },
            None => Ok(None),
        }
    }

    /// SUMMARY:
    /// Return a new path with file name changed, re‑validating against the boundary.
    ///
    /// PARAMETERS:
    /// - `file_name` (`AsRef<OsStr>`): The new file name to substitute.
    ///
    /// RETURNS:
    /// - `Result<StrictPath<Marker>>`: A new strict path with the file name replaced, validated within the boundary.
    ///
    /// ERRORS:
    /// - `StrictPathError::PathResolutionError`: If the resulting path cannot be resolved.
    /// - `StrictPathError::PathEscapesBoundary`: If the new name would escape the boundary.
    ///
    /// EXAMPLE:
    /// ```rust
    /// # use strict_path::PathBoundary;
    /// # let temp = tempfile::tempdir()?;
    /// # let data_dir: PathBoundary = PathBoundary::try_new(temp.path())?;
    /// let original = data_dir.strict_join("docs/old.txt")?;
    /// let renamed = original.strictpath_with_file_name("new.txt")?;
    /// assert!(renamed.strictpath_display().to_string().ends_with("new.txt"));
    /// # Ok::<_, Box<dyn std::error::Error>>(())
    /// ```
    #[inline]
    pub fn strictpath_with_file_name<S: AsRef<OsStr>>(&self, file_name: S) -> Result<Self> {
        let new_systempath = self.path.with_file_name(file_name);
        self.boundary.strict_join(new_systempath)
    }

    /// SUMMARY:
    /// Return a new path with extension changed; error at the boundary root.
    ///
    /// PARAMETERS:
    /// - `extension` (`AsRef<OsStr>`): The new extension to apply (without leading dot).
    ///
    /// RETURNS:
    /// - `Result<StrictPath<Marker>>`: A new strict path with the extension replaced, validated within the boundary.
    ///
    /// ERRORS:
    /// - `StrictPathError::PathEscapesBoundary`: If called on the boundary root (no file name).
    /// - `StrictPathError::PathResolutionError`: If the resulting path cannot be resolved.
    ///
    /// EXAMPLE:
    /// ```rust
    /// # use strict_path::PathBoundary;
    /// # let temp = tempfile::tempdir()?;
    /// # let data_dir: PathBoundary = PathBoundary::try_new(temp.path())?;
    /// let original = data_dir.strict_join("report.txt")?;
    /// let converted = original.strictpath_with_extension("md")?;
    /// assert!(converted.strictpath_display().to_string().ends_with("report.md"));
    /// # Ok::<_, Box<dyn std::error::Error>>(())
    /// ```
    pub fn strictpath_with_extension<S: AsRef<OsStr>>(&self, extension: S) -> Result<Self> {
        let system_path = &self.path;
        if system_path.file_name().is_none() {
            return Err(StrictPathError::path_escapes_boundary(
                self.path.to_path_buf(),
                self.boundary.path().to_path_buf(),
            ));
        }
        let new_systempath = system_path.with_extension(extension);
        self.boundary.strict_join(new_systempath)
    }

    /// SUMMARY:
    /// Returns the file name component of the system path, if any.
    ///
    /// PARAMETERS:
    /// - _none_
    ///
    /// RETURNS:
    /// - `Option<&OsStr>`: The final path component, or `None` if the path ends with `..`.
    ///
    /// ERRORS:
    /// - None (infallible).
    ///
    /// EXAMPLE:
    /// ```rust
    /// # use strict_path::PathBoundary;
    /// # let temp = tempfile::tempdir()?;
    /// # let data_dir: PathBoundary = PathBoundary::try_new(temp.path())?;
    /// let file_path = data_dir.strict_join("notes.txt")?;
    /// assert_eq!(file_path.strictpath_file_name().unwrap(), "notes.txt");
    /// # Ok::<_, Box<dyn std::error::Error>>(())
    /// ```
    #[inline]
    pub fn strictpath_file_name(&self) -> Option<&OsStr> {
        self.path.file_name()
    }

    /// SUMMARY:
    /// Returns the file stem of the system path, if any.
    ///
    /// PARAMETERS:
    /// - _none_
    ///
    /// RETURNS:
    /// - `Option<&OsStr>`: The file name without its extension, or `None` if no file name.
    ///
    /// ERRORS:
    /// - None (infallible).
    ///
    /// EXAMPLE:
    /// ```rust
    /// # use strict_path::PathBoundary;
    /// # let temp = tempfile::tempdir()?;
    /// # let data_dir: PathBoundary = PathBoundary::try_new(temp.path())?;
    /// let file_path = data_dir.strict_join("report.txt")?;
    /// assert_eq!(file_path.strictpath_file_stem().unwrap(), "report");
    /// # Ok::<_, Box<dyn std::error::Error>>(())
    /// ```
    #[inline]
    pub fn strictpath_file_stem(&self) -> Option<&OsStr> {
        self.path.file_stem()
    }

    /// SUMMARY:
    /// Returns the extension of the system path, if any.
    ///
    /// PARAMETERS:
    /// - _none_
    ///
    /// RETURNS:
    /// - `Option<&OsStr>`: The file extension (without leading dot), or `None` if there is none.
    ///
    /// ERRORS:
    /// - None (infallible).
    ///
    /// EXAMPLE:
    /// ```rust
    /// # use strict_path::PathBoundary;
    /// # let temp = tempfile::tempdir()?;
    /// # let data_dir: PathBoundary = PathBoundary::try_new(temp.path())?;
    /// let file_path = data_dir.strict_join("archive.tar.gz")?;
    /// assert_eq!(file_path.strictpath_extension().unwrap(), "gz");
    /// # Ok::<_, Box<dyn std::error::Error>>(())
    /// ```
    #[inline]
    pub fn strictpath_extension(&self) -> Option<&OsStr> {
        self.path.extension()
    }

    /// SUMMARY:
    /// Returns `true` if the system path starts with the given prefix.
    ///
    /// PARAMETERS:
    /// - `p` (`AsRef<Path>`): The path prefix to check against.
    ///
    /// RETURNS:
    /// - `bool`: `true` if the system path starts with the given prefix, `false` otherwise.
    ///
    /// ERRORS:
    /// - None (infallible).
    ///
    /// EXAMPLE:
    /// ```rust
    /// # use strict_path::PathBoundary;
    /// # let temp = tempfile::tempdir()?;
    /// # let data_dir: PathBoundary = PathBoundary::try_new(temp.path())?;
    /// let file_path = data_dir.strict_join("logs/app.log")?;
    /// // Use the boundary's canonical path (interop_path) as the prefix to compare against
    /// assert!(file_path.strictpath_starts_with(data_dir.interop_path()));
    /// # Ok::<_, Box<dyn std::error::Error>>(())
    /// ```
    #[inline]
    pub fn strictpath_starts_with<P: AsRef<Path>>(&self, p: P) -> bool {
        self.path.starts_with(p.as_ref())
    }

    /// SUMMARY:
    /// Returns `true` if the system path ends with the given suffix.
    ///
    /// PARAMETERS:
    /// - `p` (`AsRef<Path>`): The path suffix to check against.
    ///
    /// RETURNS:
    /// - `bool`: `true` if the system path ends with the given suffix, `false` otherwise.
    ///
    /// ERRORS:
    /// - None (infallible).
    ///
    /// EXAMPLE:
    /// ```rust
    /// # use strict_path::PathBoundary;
    /// # let temp = tempfile::tempdir()?;
    /// # let data_dir: PathBoundary = PathBoundary::try_new(temp.path())?;
    /// let file_path = data_dir.strict_join("reports/summary.csv")?;
    /// assert!(file_path.strictpath_ends_with("summary.csv"));
    /// # Ok::<_, Box<dyn std::error::Error>>(())
    /// ```
    #[inline]
    pub fn strictpath_ends_with<P: AsRef<Path>>(&self, p: P) -> bool {
        self.path.ends_with(p.as_ref())
    }

    /// SUMMARY:
    /// Returns `true` if the system path exists.
    ///
    /// PARAMETERS:
    /// - _none_
    ///
    /// RETURNS:
    /// - `bool`: `true` if the path exists on the filesystem, `false` otherwise (including on permission errors).
    ///
    /// ERRORS:
    /// - None (infallible — permission errors return `false`; use `try_exists` to distinguish).
    ///
    /// EXAMPLE:
    /// ```rust
    /// # use strict_path::PathBoundary;
    /// # let temp = tempfile::tempdir()?;
    /// # let data_dir: PathBoundary = PathBoundary::try_new(temp.path())?;
    /// let file_path = data_dir.strict_join("data.txt")?;
    /// assert!(!file_path.exists());
    /// file_path.write("hello")?;
    /// assert!(file_path.exists());
    /// # Ok::<_, Box<dyn std::error::Error>>(())
    /// ```
    pub fn exists(&self) -> bool {
        self.path.exists()
    }

    /// SUMMARY:
    /// Returns `true` if the system path is a file.
    ///
    /// PARAMETERS:
    /// - _none_
    ///
    /// RETURNS:
    /// - `bool`: `true` if the path exists and is a regular file, `false` otherwise.
    ///
    /// ERRORS:
    /// - None (infallible).
    ///
    /// EXAMPLE:
    /// ```rust
    /// # use strict_path::PathBoundary;
    /// # let temp = tempfile::tempdir()?;
    /// # let data_dir: PathBoundary = PathBoundary::try_new(temp.path())?;
    /// let file_path = data_dir.strict_join("item.txt")?;
    /// file_path.write("x")?;
    /// assert!(file_path.is_file());
    /// assert!(!data_dir.strict_join(".")?.is_file());
    /// # Ok::<_, Box<dyn std::error::Error>>(())
    /// ```
    pub fn is_file(&self) -> bool {
        self.path.is_file()
    }

    /// SUMMARY:
    /// Returns `true` if the system path is a directory.
    ///
    /// PARAMETERS:
    /// - _none_
    ///
    /// RETURNS:
    /// - `bool`: `true` if the path exists and is a directory, `false` otherwise.
    ///
    /// ERRORS:
    /// - None (infallible).
    ///
    /// EXAMPLE:
    /// ```rust
    /// # use strict_path::PathBoundary;
    /// # let temp = tempfile::tempdir()?;
    /// # let data_dir: PathBoundary = PathBoundary::try_new(temp.path())?;
    /// let subdir = data_dir.strict_join("sub")?;
    /// subdir.create_dir()?;
    /// assert!(subdir.is_dir());
    /// # Ok::<_, Box<dyn std::error::Error>>(())
    /// ```
    pub fn is_dir(&self) -> bool {
        self.path.is_dir()
    }

    /// SUMMARY:
    /// Returns the metadata for the system path.
    ///
    /// PARAMETERS:
    /// - _none_
    ///
    /// RETURNS:
    /// - `std::fs::Metadata`: Filesystem metadata (size, permissions, timestamps, etc.).
    ///
    /// ERRORS:
    /// - `std::io::Error`: If the path does not exist or cannot be accessed.
    ///
    /// EXAMPLE:
    /// ```rust
    /// # use strict_path::PathBoundary;
    /// # let temp = tempfile::tempdir()?;
    /// # let data_dir: PathBoundary = PathBoundary::try_new(temp.path())?;
    /// let file_path = data_dir.strict_join("info.txt")?;
    /// file_path.write("hello")?;
    /// let meta = file_path.metadata()?;
    /// assert_eq!(meta.len(), 5);
    /// # Ok::<_, Box<dyn std::error::Error>>(())
    /// ```
    pub fn metadata(&self) -> std::io::Result<std::fs::Metadata> {
        std::fs::metadata(&self.path)
    }

    /// SUMMARY:
    /// Return the metadata for the system path without following symlinks (like `std::fs::symlink_metadata`).
    ///
    /// DETAILS:
    /// This retrieves metadata about the path entry itself. On symlinks, this reports
    /// information about the link, not the target.
    #[inline]
    pub fn symlink_metadata(&self) -> std::io::Result<std::fs::Metadata> {
        std::fs::symlink_metadata(&self.path)
    }

    /// SUMMARY:
    /// Set permissions on the file or directory at this path.
    ///
    /// PARAMETERS:
    /// - `perm` (`std::fs::Permissions`): The permissions to set.
    ///
    /// RETURNS:
    /// - `io::Result<()>`: Success or I/O error.
    ///
    /// EXAMPLE:
    /// ```rust
    /// use strict_path::PathBoundary;
    ///
    /// let temp = tempfile::tempdir()?;
    /// let data_dir: PathBoundary = PathBoundary::try_new(temp.path())?;
    /// let file = data_dir.strict_join("script.sh")?;
    /// file.write("#!/bin/bash\necho hello")?;
    ///
    /// // Make executable (Unix) or read-only (cross-platform)
    /// let mut perms = file.metadata()?.permissions();
    /// perms.set_readonly(true);
    /// file.set_permissions(perms)?;
    ///
    /// assert!(file.metadata()?.permissions().readonly());
    /// # Ok::<(), Box<dyn std::error::Error>>(())
    /// ```
    #[inline]
    pub fn set_permissions(&self, perm: std::fs::Permissions) -> std::io::Result<()> {
        std::fs::set_permissions(&self.path, perm)
    }

    /// SUMMARY:
    /// Check if the path exists, returning an error on permission issues.
    ///
    /// DETAILS:
    /// Unlike `exists()` which returns `false` on permission errors, this method
    /// distinguishes between "path does not exist" (`Ok(false)`) and "cannot check
    /// due to permission error" (`Err(...)`).
    ///
    /// RETURNS:
    /// - `Ok(true)`: Path exists
    /// - `Ok(false)`: Path does not exist
    /// - `Err(...)`: Permission or other I/O error prevented the check
    ///
    /// EXAMPLE:
    /// ```rust
    /// use strict_path::PathBoundary;
    ///
    /// let temp = tempfile::tempdir()?;
    /// let data_dir: PathBoundary = PathBoundary::try_new(temp.path())?;
    ///
    /// let existing = data_dir.strict_join("exists.txt")?;
    /// existing.write("content")?;
    /// assert_eq!(existing.try_exists()?, true);
    ///
    /// let missing = data_dir.strict_join("missing.txt")?;
    /// assert_eq!(missing.try_exists()?, false);
    /// # Ok::<(), Box<dyn std::error::Error>>(())
    /// ```
    #[inline]
    pub fn try_exists(&self) -> std::io::Result<bool> {
        self.path.try_exists()
    }

    /// SUMMARY:
    /// Create an empty file if it doesn't exist, or update the modification time if it does.
    ///
    /// DETAILS:
    /// This is a convenience method combining file creation and mtime update.
    /// Uses `OpenOptions` with `create(true).write(true)` which creates the file
    /// if missing or opens it for writing if it exists, updating mtime on close.
    ///
    /// RETURNS:
    /// - `io::Result<()>`: Success or I/O error.
    ///
    /// EXAMPLE:
    /// ```rust
    /// use strict_path::PathBoundary;
    ///
    /// let temp = tempfile::tempdir()?;
    /// let data_dir: PathBoundary = PathBoundary::try_new(temp.path())?;
    ///
    /// let file = data_dir.strict_join("marker.txt")?;
    /// assert!(!file.exists());
    ///
    /// file.touch()?;
    /// assert!(file.exists());
    /// assert_eq!(file.read_to_string()?, "");  // Empty file
    /// # Ok::<(), Box<dyn std::error::Error>>(())
    /// ```
    pub fn touch(&self) -> std::io::Result<()> {
        // Using truncate(false) to preserve existing content - touch only updates mtime
        std::fs::OpenOptions::new()
            .create(true)
            .write(true)
            .truncate(false)
            .open(&self.path)?;
        Ok(())
    }

    /// SUMMARY:
    /// Read directory entries at this path (discovery). Re‑join names through strict/virtual APIs before I/O.
    ///
    /// PARAMETERS:
    /// - _none_
    ///
    /// RETURNS:
    /// - `std::fs::ReadDir`: Raw iterator over directory entries (names are not yet re-validated).
    ///
    /// ERRORS:
    /// - `std::io::Error`: If the path is not a directory or cannot be read.
    ///
    /// EXAMPLE:
    /// ```rust
    /// # use strict_path::PathBoundary;
    /// # let temp = tempfile::tempdir()?;
    /// # let data_dir: PathBoundary = PathBoundary::try_new(temp.path())?;
    /// data_dir.strict_join("file.txt")?.write("x")?;
    /// for entry in data_dir.strict_join(".")?.read_dir()? {
    ///     let entry = entry?;
    ///     let child = data_dir.strict_join(entry.file_name())?;
    ///     println!("{}", child.strictpath_display());
    /// }
    /// # Ok::<_, Box<dyn std::error::Error>>(())
    /// ```
    pub fn read_dir(&self) -> std::io::Result<std::fs::ReadDir> {
        std::fs::read_dir(&self.path)
    }

    /// SUMMARY:
    /// Read directory entries as validated `StrictPath` values (auto re-joins each entry).
    ///
    /// DETAILS:
    /// Unlike `read_dir()` which returns raw `std::fs::DirEntry`, this method automatically
    /// validates each directory entry through `strict_join()`, returning an iterator of
    /// `Result<StrictPath<Marker>>`. This eliminates the need for manual re-validation loops.
    ///
    /// PARAMETERS:
    /// - _none_
    ///
    /// RETURNS:
    /// - `io::Result<StrictReadDir<Marker>>`: Iterator yielding validated `StrictPath` entries.
    ///
    /// ERRORS:
    /// - `std::io::Error`: If the directory cannot be read.
    /// - Each yielded item may also be `Err` if validation fails for that entry.
    ///
    /// EXAMPLE:
    /// ```rust
    /// # use strict_path::{PathBoundary, StrictPath};
    /// # let temp = tempfile::tempdir()?;
    /// # let data_dir: PathBoundary = PathBoundary::try_new(temp.path())?;
    /// # let dir = data_dir.strict_join("data")?;
    /// # dir.create_dir_all()?;
    /// # data_dir.strict_join("data/file1.txt")?.write("a")?;
    /// # data_dir.strict_join("data/file2.txt")?.write("b")?;
    /// // Iterate with automatic validation
    /// for entry in dir.strict_read_dir()? {
    ///     let child: StrictPath = entry?;
    ///     println!("{}", child.strictpath_display());
    /// }
    /// # Ok::<_, Box<dyn std::error::Error>>(())
    /// ```
    pub fn strict_read_dir(&self) -> std::io::Result<StrictReadDir<'_, Marker>> {
        let inner = std::fs::read_dir(&self.path)?;
        Ok(StrictReadDir {
            inner,
            parent: self,
        })
    }

    /// SUMMARY:
    /// Reads the file contents as `String`.
    ///
    /// PARAMETERS:
    /// - _none_
    ///
    /// RETURNS:
    /// - `String`: The entire file contents decoded as UTF-8.
    ///
    /// ERRORS:
    /// - `std::io::Error`: If the file cannot be read or contains invalid UTF-8.
    ///
    /// EXAMPLE:
    /// ```rust
    /// # use strict_path::PathBoundary;
    /// # let temp = tempfile::tempdir()?;
    /// # let data_dir: PathBoundary = PathBoundary::try_new(temp.path())?;
    /// let file_path = data_dir.strict_join("hello.txt")?;
    /// file_path.write("hello world")?;
    /// assert_eq!(file_path.read_to_string()?, "hello world");
    /// # Ok::<_, Box<dyn std::error::Error>>(())
    /// ```
    pub fn read_to_string(&self) -> std::io::Result<String> {
        std::fs::read_to_string(&self.path)
    }

    /// SUMMARY:
    /// Reads the file contents as raw bytes.
    ///
    /// PARAMETERS:
    /// - _none_
    ///
    /// RETURNS:
    /// - `Vec<u8>`: The entire file contents as a byte vector.
    ///
    /// ERRORS:
    /// - `std::io::Error`: If the file cannot be read.
    ///
    /// EXAMPLE:
    /// ```rust
    /// # use strict_path::PathBoundary;
    /// # let temp = tempfile::tempdir()?;
    /// # let data_dir: PathBoundary = PathBoundary::try_new(temp.path())?;
    /// let file_path = data_dir.strict_join("data.bin")?;
    /// file_path.write(b"\x00\x01\x02")?;
    /// assert_eq!(file_path.read()?, vec![0, 1, 2]);
    /// # Ok::<_, Box<dyn std::error::Error>>(())
    /// ```
    #[inline]
    pub fn read(&self) -> std::io::Result<Vec<u8>> {
        std::fs::read(&self.path)
    }

    /// SUMMARY:
    /// Write bytes to the file (create if missing). Accepts any `AsRef<[u8]>` (e.g., `&str`, `&[u8]`).
    ///
    /// PARAMETERS:
    /// - `contents` (`AsRef<[u8]>`): The bytes to write; replaces any existing file content.
    ///
    /// RETURNS:
    /// - `()`: File written successfully.
    ///
    /// ERRORS:
    /// - `std::io::Error`: If the file cannot be created or written (e.g., parent missing, permission denied).
    ///
    /// EXAMPLE:
    /// ```rust
    /// # use strict_path::PathBoundary;
    /// # let temp = tempfile::tempdir()?;
    /// # let data_dir: PathBoundary = PathBoundary::try_new(temp.path())?;
    /// let file_path = data_dir.strict_join("config.toml")?;
    /// file_path.write("[server]\nport = 8080\n")?;
    /// assert_eq!(file_path.read_to_string()?, "[server]\nport = 8080\n");
    /// # Ok::<_, Box<dyn std::error::Error>>(())
    /// ```
    #[inline]
    pub fn write<C: AsRef<[u8]>>(&self, contents: C) -> std::io::Result<()> {
        std::fs::write(&self.path, contents)
    }

    /// SUMMARY:
    /// Append bytes to the file (create if missing). Accepts any `AsRef<[u8]>` (e.g., `&str`, `&[u8]`).
    ///
    /// PARAMETERS:
    /// - `data` (`AsRef<[u8]>`): Bytes to append to the file.
    ///
    /// RETURNS:
    /// - `()`: Returns nothing on success.
    ///
    /// ERRORS:
    /// - `std::io::Error`: Propagates OS errors when the file cannot be opened or written.
    ///
    /// EXAMPLE:
    /// ```rust
    /// # use strict_path::{PathBoundary, StrictPath};
    /// # let boundary_dir = std::env::temp_dir().join("strict-path-append-example");
    /// # std::fs::create_dir_all(&boundary_dir)?;
    /// # let data_dir: PathBoundary = PathBoundary::try_new(&boundary_dir)?;
    /// // Untrusted input from request/CLI/config/etc.
    /// let log_file = "logs/audit.log";
    /// let log_path: StrictPath = data_dir.strict_join(log_file)?;
    /// log_path.create_parent_dir_all()?;
    /// log_path.append("[2025-01-01] Session started\n")?;
    /// log_path.append("[2025-01-01] User logged in\n")?;
    /// let contents = log_path.read_to_string()?;
    /// assert!(contents.contains("Session started"));
    /// assert!(contents.contains("User logged in"));
    /// # std::fs::remove_dir_all(&boundary_dir)?;
    /// # Ok::<_, Box<dyn std::error::Error>>(())
    /// ```
    #[inline]
    pub fn append<C: AsRef<[u8]>>(&self, data: C) -> std::io::Result<()> {
        use std::io::Write;
        let mut file = std::fs::OpenOptions::new()
            .create(true)
            .append(true)
            .open(&self.path)?;
        file.write_all(data.as_ref())
    }
}