//! Types that flow between the menu engine and frontends.
//!
//! - [`Action`]: commands sent into the menu (keypresses,
//!   script actions).
//! - [`MenuEvent`]: notifications sent out to subscribers
//!   (state changes, terminal events).
//! - [`ViewState`]: snapshot of what the frontend should
//!   render right now.

use std::sync::Arc;

use serde_json::Value;

/// Input mode. Insert mode sends keystrokes to the filter,
/// normal mode uses vim-style navigation keybinds.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
pub enum Mode {
    #[default]
    Insert,
    Normal,
}

/// A command the menu should process. Frontends and headless
/// scripts both produce these. The menu loop consumes them
/// sequentially.
#[derive(Debug, Clone, PartialEq)]
pub enum Action {
    UpdateFilter(String),
    MoveUp(usize),
    MoveDown(usize),
    MoveToTop,
    MoveToBottom,
    PageUp(usize),
    PageDown(usize),
    HalfPageUp(usize),
    HalfPageDown(usize),
    SetMode(Mode),
    Confirm,
    Cancel,
    Resize { height: u16 },
    AddItems(Vec<Value>),
}

/// Broadcast from the menu loop to all subscribers
/// (frontends, tests).
#[derive(Debug, Clone)]
pub enum MenuEvent {
    StateChanged(ViewState),
    Selected(Value),
    Cancelled,
}

/// Snapshot of the menu's visible state. Sent on every state
/// change so frontends can render without querying back into
/// the engine.
#[must_use]
#[derive(Debug, Clone)]
pub struct ViewState {
    pub visible_items: Vec<VisibleItem>,
    /// Index of the cursor within `visible_items`
    /// (not the full list).
    pub cursor: usize,
    pub filter_text: Arc<str>,
    pub total_items: usize,
    pub total_filtered: usize,
    pub mode: Mode,
}

/// A single item in the current viewport window. Has the
/// display label pre-resolved and the position in the
/// filtered list.
#[must_use]
#[derive(Debug, Clone)]
pub struct VisibleItem {
    pub label: String,
    pub index: usize,
}

/// Final outcome of [`crate::menu::MenuRunner::run`]. The
/// user either picked something or bailed.
#[must_use]
#[derive(Debug)]
pub enum MenuResult {
    Selected(Value),
    Cancelled,
}