qubit-fs 0.2.2

Provider-neutral synchronous and asynchronous filesystem abstraction for Rust
Documentation 
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// =============================================================================
//    Copyright (c) 2025 - 2026 Haixing Hu.
//
//    SPDX-License-Identifier: Apache-2.0
//
//    Licensed under the Apache License, Version 2.0.
// =============================================================================
// facade.
//! Immutable path constraints used by filesystem property snapshots.

use crate::error::FsError;
use crate::error::FsOperation;
use crate::error::FsResult;
use crate::path::Path;
use crate::path::PathForm;

/// Immutable path form constraints attached to one filesystem snapshot.
///
/// # Examples
///
/// ```rust
/// use qubit_fs::path::{PathConstraints, PathForm};
///
/// let constraints = PathConstraints::absolute();
/// assert_eq!(PathForm::Absolute, constraints.form());
/// ```
#[derive(Clone, Debug, Eq, PartialEq)]
pub struct PathConstraints {
    /// Accepted absolute-versus-relative path policy.
    form: PathForm,
}

impl PathConstraints {
    /// Creates constraints accepting only absolute paths.
    ///
    /// # Returns
    /// Constraints rejecting every relative path.
    #[inline]
    #[must_use]
    pub const fn absolute() -> Self {
        Self {
            form: PathForm::Absolute,
        }
    }

    /// Creates constraints accepting only relative paths.
    ///
    /// # Returns
    /// Constraints rejecting every absolute path.
    #[inline]
    #[must_use]
    pub const fn relative() -> Self {
        Self {
            form: PathForm::Relative,
        }
    }

    /// Creates constraints accepting either logical path form.
    ///
    /// # Returns
    /// Constraints accepting absolute and relative paths.
    #[inline]
    #[must_use]
    pub const fn either() -> Self {
        Self { form: PathForm::Either }
    }

    /// Returns the configured accepted path form.
    ///
    /// # Returns
    /// The immutable accepted path-form policy.
    #[inline]
    #[must_use]
    pub const fn form(&self) -> PathForm {
        self.form
    }

    /// Validates a logical path without performing I/O.
    ///
    /// # Parameters
    /// - `path`: Logical path whose absolute or relative form is checked.
    ///
    /// # Errors
    /// Returns an invalid-path error when `path` has a disallowed form.
    #[inline]
    pub fn validate(&self, path: &Path) -> FsResult<()> {
        let allowed = matches!(self.form, PathForm::Either)
            || matches!(
                (self.form, path.is_absolute()),
                (PathForm::Absolute, true) | (PathForm::Relative, false)
            );
        if allowed {
            Ok(())
        } else {
            Err(FsError::invalid_path(
                FsOperation::ParsePath,
                "path form is not accepted by this filesystem",
            ))
        }
    }
}

#[cfg(test)]
mod tests {
    use std::hint::black_box;

    use super::PathConstraints;
    use crate::path::PathForm;

    #[test]
    fn relative_constructor_is_executed_at_runtime() {
        let constructor: fn() -> PathConstraints = black_box(PathConstraints::relative);
        let either_constructor: fn() -> PathConstraints = black_box(PathConstraints::either);

        assert_eq!(PathForm::Relative, constructor().form());
        assert_eq!(PathForm::Either, either_constructor().form());
    }
}