guise-ui 1.5.2

//! `TabBar` — a document-style tab strip (gpui entity).
//!
//! Owns the tab list and active index. Renders a horizontally scrollable
//! strip of tabs, each with a close button (shown while hovered or active),
//! plus an optional trailing add button. Emits [`TabBarEvent`] for selection,
//! close, and add clicks — closing does **not** remove the tab by itself, the
//! parent decides (e.g. after an unsaved-changes prompt) and calls
//! [`TabBar::remove_tab`].
//!
//! ```ignore
//! let bar = cx.new(|cx| TabBar::new(cx).tabs(["main.rs", "lib.rs"]).active(0));
//! cx.subscribe(&bar, |_this, bar, event: &TabBarEvent, cx| match event {
//!     TabBarEvent::Close(i) => {
//!         let i = *i;
//!         bar.update(cx, |b, cx| b.remove_tab(i, cx));
//!     }
//!     TabBarEvent::Add => bar.update(cx, |b, cx| b.add_tab("untitled", cx)),
//!     TabBarEvent::Select(_) => {}
//! })
//! .detach();
//! ```

use gpui::prelude::*;
use gpui::{div, px, Context, EventEmitter, IntoElement, SharedString, Window};

use crate::devtools::Probed;
use crate::theme::{theme, Size};
use crate::{ActionIcon, CloseButton};

/// Emitted by [`TabBar`] on user interaction.
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum TabBarEvent {
  /// A tab was clicked; carries its index. The bar has already switched to it.
  Select(usize),
  /// A tab's close button was clicked; carries its index. The tab is *not*
  /// removed automatically — call [`TabBar::remove_tab`] to drop it.
  Close(usize),
  /// The trailing `+` button was clicked.
  Add,
}

/// Where the active index lands after removing `removed` from a list that is
/// now `new_len` items long.
fn active_after_remove(active: usize, removed: usize, new_len: usize) -> usize {
  if new_len == 0 {
    return 0;
  }
  let shifted = if removed < active { active - 1 } else { active };
  shifted.min(new_len - 1)
}

/// A document-style tab strip. Create with
/// `cx.new(|cx| TabBar::new(cx).tabs(["one", "two"]))`.
pub struct TabBar {
  tabs: Vec<SharedString>,
  active: usize,
  hovered: Option<usize>,
  with_add_button: bool,
}

impl EventEmitter<TabBarEvent> for TabBar {}

impl TabBar {
  pub fn new(_cx: &mut Context<Self>) -> Self {
    TabBar {
      tabs: Vec::new(),
      active: 0,
      hovered: None,
      with_add_button: true,
    }
  }

  /// Replace the tab labels (builder form; see [`TabBar::set_tabs`] for the
  /// post-construction method).
  pub fn tabs<I, S>(mut self, tabs: I) -> Self
  where
    I: IntoIterator<Item = S>,
    S: Into<SharedString>,
  {
    self.tabs = tabs.into_iter().map(Into::into).collect();
    self
  }

  /// The initially active tab.
  pub fn active(mut self, index: usize) -> Self {
    self.active = index;
    self
  }

  /// Show the trailing `+` button (default `true`).
  pub fn with_add_button(mut self, show: bool) -> Self {
    self.with_add_button = show;
    self
  }

  /// The index of the active tab.
  pub fn active_index(&self) -> usize {
    self.active
  }

  /// Number of tabs.
  pub fn len(&self) -> usize {
    self.tabs.len()
  }

  pub fn is_empty(&self) -> bool {
    self.tabs.is_empty()
  }

  /// Append a tab and make it active. Does not emit an event.
  pub fn add_tab(&mut self, label: impl Into<SharedString>, cx: &mut Context<Self>) {
    self.tabs.push(label.into());
    self.active = self.tabs.len() - 1;
    cx.notify();
  }

  /// Remove the tab at `index` (no-op when out of range), keeping the
  /// active selection on the same document where possible. Does not emit.
  pub fn remove_tab(&mut self, index: usize, cx: &mut Context<Self>) {
    if index >= self.tabs.len() {
      return;
    }
    self.tabs.remove(index);
    self.active = active_after_remove(self.active, index, self.tabs.len());
    self.hovered = None;
    cx.notify();
  }

  /// Replace every tab, clamping the active index. Does not emit.
  pub fn set_tabs(&mut self, tabs: Vec<SharedString>, cx: &mut Context<Self>) {
    self.tabs = tabs;
    self.active = self.active.min(self.tabs.len().saturating_sub(1));
    self.hovered = None;
    cx.notify();
  }

  /// Programmatically switch tabs (clamped). Does not emit.
  pub fn set_active(&mut self, index: usize, cx: &mut Context<Self>) {
    let clamped = index.min(self.tabs.len().saturating_sub(1));
    if self.active != clamped {
      self.active = clamped;
      cx.notify();
    }
  }
}

impl Render for TabBar {
  fn render(&mut self, _window: &mut Window, cx: &mut Context<Self>) -> impl IntoElement {
    let t = theme(cx);
    let surface = t.surface().hsla();
    let strip_bg = t.surface_hover().hsla();
    let border = t.border().hsla();
    let text = t.text().hsla();
    let dimmed = t.dimmed().hsla();
    let font = t.font_size(Size::Sm);

    let count = self.tabs.len();
    let active = if count == 0 {
      0
    } else {
      self.active.min(count - 1)
    };
    let hovered = self.hovered;

    let mut strip = div()
      .id("guise-tabbar-strip")
      .flex_1()
      .min_w(px(0.0))
      .flex()
      .overflow_x_scroll();

    for (i, label) in self.tabs.iter().enumerate() {
      let is_active = i == active;
      let show_close = is_active || hovered == Some(i);

      // The close button keeps its slot when hidden so tab widths stay
      // stable; a hidden div paints nothing (no hitbox, no clicks).
      let mut close_slot = div().flex_none();
      if !show_close {
        close_slot = close_slot.invisible();
      }
      close_slot = close_slot.child(
        CloseButton::new(("guise-tabbar-close", i))
          .size(Size::Xs)
          .on_click(cx.listener(move |_this, _ev, _window, cx| {
            // Don't let the click bubble into the tab (which
            // would also select it).
            cx.stop_propagation();
            cx.emit(TabBarEvent::Close(i));
          })),
      );

      let mut tab = div()
        .id(("guise-tabbar-tab", i))
        .flex_none()
        .flex()
        .items_center()
        .gap(px(6.0))
        .pl(px(12.0))
        .pr(px(6.0))
        .py(px(6.0))
        .border_r_1()
        .border_color(border)
        .text_size(px(font))
        .text_color(if is_active { text } else { dimmed })
        .child(label.clone())
        .child(close_slot)
        .on_hover(cx.listener(move |this, entered: &bool, _window, cx| {
          if *entered {
            this.hovered = Some(i);
          } else if this.hovered == Some(i) {
            this.hovered = None;
          }
          cx.notify();
        }))
        .on_click(cx.listener(move |this, _ev, _window, cx| {
          this.active = i;
          cx.emit(TabBarEvent::Select(i));
          cx.notify();
        }));
      if is_active {
        tab = tab.bg(surface);
      } else {
        tab = tab.hover(move |s| s.text_color(text));
      }
      strip = strip.child(tab);
    }

    let mut bar = div()
      .flex()
      .items_center()
      .w_full()
      .bg(strip_bg)
      .border_b_1()
      .border_color(border)
      .child(strip);

    if self.with_add_button {
      bar = bar.child(
        div().flex_none().px(px(4.0)).child(
          ActionIcon::new("guise-tabbar-add", "+")
            .label("Add tab")
            .size(Size::Sm)
            .on_click(cx.listener(|_this, _ev, _window, cx| cx.emit(TabBarEvent::Add))),
        ),
      );
    }

    bar.probe("TabBar")
  }
}

#[cfg(test)]
mod tests {
  use super::active_after_remove;

  #[test]
  fn removing_before_active_shifts_it_left() {
    assert_eq!(active_after_remove(2, 0, 3), 1);
    assert_eq!(active_after_remove(3, 2, 3), 2);
  }

  #[test]
  fn removing_the_active_tab_keeps_its_slot_clamped() {
    // [a b c] active=1, remove 1 -> [a c] active=1 (c takes the slot).
    assert_eq!(active_after_remove(1, 1, 2), 1);
    // Removing the last while it is active clamps to the new tail.
    assert_eq!(active_after_remove(2, 2, 2), 1);
  }

  #[test]
  fn removing_after_active_leaves_it_alone() {
    assert_eq!(active_after_remove(0, 2, 2), 0);
    assert_eq!(active_after_remove(1, 3, 3), 1);
  }

  #[test]
  fn emptying_the_bar_resets_to_zero() {
    assert_eq!(active_after_remove(0, 0, 0), 0);
  }
}