teksilo-data 0.9.0

// SPDX-License-Identifier: MPL-2.0
// SPDX-FileCopyrightText: 2026 FernTech

//! `CheckState` — tri-state checkbox value shared by the data layer and widgets.
//!
//! Represents the three visual states of a checkbox: unchecked, checked, and
//! indeterminate (partial — some but not all descendants are checked). Lives in
//! `teksilo-data` rather than `teksilo-widgets` so that [`crate::TreeCheckedModel`]
//! can produce `Signal<CheckState>` values without inverting the dependency graph.
//!
//! `From<bool>` converts a plain two-state boolean (e.g. from a filter predicate)
//! into `Unchecked` or `Checked`, making it easy to bridge non-tristate sources.
//!
//! ```rust
//! # use teksilo_data::CheckState;
//! let state = CheckState::Indeterminate;
//! assert!(state.is_filled());
//! assert_eq!(state.next_tristate(), CheckState::Unchecked);
//! assert_eq!(CheckState::from(true), CheckState::Checked);
//! ```

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub enum CheckState {
    /// The checkbox is unchecked (no fill, no mark).
    Unchecked,
    /// The checkbox is fully checked (filled with a check mark).
    Checked,
    /// Some but not all descendants are checked; shown as a dash or partial fill.
    Indeterminate,
}

impl CheckState {
    /// Whether the box shows a filled background (checked or indeterminate).
    pub fn is_filled(self) -> bool {
        self != CheckState::Unchecked
    }

    /// Cycle to the next state: Unchecked → Checked → Indeterminate → Unchecked.
    pub fn next_tristate(self) -> Self {
        match self {
            CheckState::Unchecked => CheckState::Checked,
            CheckState::Checked => CheckState::Indeterminate,
            CheckState::Indeterminate => CheckState::Unchecked,
        }
    }
}

impl From<bool> for CheckState {
    fn from(checked: bool) -> Self {
        if checked {
            CheckState::Checked
        } else {
            CheckState::Unchecked
        }
    }
}