qubit-redact 0.3.0

// =============================================================================
//    Copyright (c) 2025 - 2026 Haixing Hu.
//
//    SPDX-License-Identifier: Apache-2.0
//
//    Licensed under the Apache License, Version 2.0.
// =============================================================================
//! Thread-local bounded-mask formatting context.

use std::cell::Cell;

use super::mask_byte_limit_reset::MaskByteLimitReset;

thread_local! {
    /// Active per-thread allocation ceiling for masks rendered by this adapter.
    static MASK_BYTE_LIMIT: Cell<Option<usize>> = const { Cell::new(None) };
}

/// Executes `operation` while bounding each materialized mask on this thread.
///
/// A nested operation may tighten the active ceiling but cannot widen a
/// ceiling established by an outer bounded formatter.
///
/// # Type Parameters
///
/// * `T` - Result type produced by the bounded operation.
///
/// # Parameters
///
/// * `max_bytes` - Maximum bytes retained by one materialized mask.
/// * `operation` - Formatting operation executed inside the bounded context.
///
/// # Returns
///
/// The result produced by `operation` after restoring any previous context.
pub(crate) fn with_mask_byte_limit<T>(
    max_bytes: usize,
    operation: impl FnOnce() -> T,
) -> T {
    MASK_BYTE_LIMIT.with(|context| {
        let previous = context.get();
        let effective =
            previous.map_or(max_bytes, |previous| previous.min(max_bytes));
        context.set(Some(effective));
        let _reset = MaskByteLimitReset::new(context, previous);
        operation()
    })
}

/// Returns the active per-thread materialized-mask ceiling, when bounded.
///
/// # Returns
///
/// `Some(max_bytes)` while bounded display formatting is active, or `None`
/// for ordinary unbounded redaction.
#[inline(always)]
pub(crate) fn mask_byte_limit() -> Option<usize> {
    MASK_BYTE_LIMIT.with(Cell::get)
}