blizz_ui/components/

selector.rs

use std::io::Write;

use crossterm::{
  cursor::MoveTo,
  queue,
  style::{Attribute, Color, Print, ResetColor, SetAttribute, SetForegroundColor},
};
use rand::Rng;

use crate::decode;
use crate::layout::centered_column;
use crate::prompt::text_entry;
use crate::select_option::SelectOption;

const PREFIX_ACTIVE: &str = "\u{25b8} ";
const PREFIX_INACTIVE: &str = "  ";
const ARROW_UP: char = '\u{25b2}';
const ARROW_DOWN: char = '\u{25bc}';
const ELLIPSIS: &str = " \u{00b7}\u{00b7}\u{00b7} ";
const BORDER_VERTICAL: &str = "\u{2502}";
const BORDER_HORIZONTAL: &str = "\u{2500}";
const CORNER_TOP_LEFT: &str = "\u{256d}";
const CORNER_TOP_RIGHT: &str = "\u{256e}";
const CORNER_BOTTOM_LEFT: &str = "\u{2570}";
const CORNER_BOTTOM_RIGHT: &str = "\u{256f}";
const BORDER_TOP_OFFSET: u16 = 1;

const MAX_VISIBLE_OPTIONS: usize = 8;

/// Vertical list navigation (↑/↓); map from the host wizard’s up/down actions.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum ListNavigate {
  Up,
  Down,
}

/// Select list with scroll, open/reveal animation progress, and bordered layout.
#[derive(Debug, Clone)]
pub struct SelectorComponent {
  pub options: Vec<SelectOption>,
  pub selected: usize,
  pub scroll_offset: usize,
  pub visible: bool,
  pub open: f64,
  pub reveal: f64,
}

impl SelectorComponent {
  pub fn hidden() -> Self {
    Self {
      options: Vec::new(),
      selected: 0,
      scroll_offset: 0,
      visible: false,
      open: 0.0,
      reveal: 0.0,
    }
  }

  pub fn from_options(options: Vec<SelectOption>, default_index: usize) -> Self {
    Self {
      options,
      selected: default_index,
      scroll_offset: 0,
      visible: true,
      open: 0.0,
      reveal: 0.0,
    }
  }

  pub fn is_fully_open(&self) -> bool {
    self.open >= 1.0
  }

  pub fn is_fully_closed(&self) -> bool {
    self.open <= 0.0
  }

  pub fn is_fully_revealed(&self) -> bool {
    self.reveal >= 1.0
  }

  pub fn is_fully_hidden(&self) -> bool {
    self.reveal <= 0.0
  }

  /// How many option rows are visible for a list of this length (same cap as [`SelectorComponent::render`]).
  pub fn viewport_row_count(option_count: usize) -> usize {
    option_count.min(MAX_VISIBLE_OPTIONS)
  }

  pub fn navigate(&mut self, direction: ListNavigate) {
    let len = self.options.len();
    if len == 0 {
      return;
    }

    match direction {
      ListNavigate::Up => {
        self.selected = if self.selected == 0 {
          len - 1
        } else {
          self.selected - 1
        };
      }
      ListNavigate::Down => {
        self.selected = (self.selected + 1) % len;
      }
    }

    let max_visible = Self::viewport_row_count(len);
    if self.selected < self.scroll_offset {
      self.scroll_offset = self.selected;
    } else if self.selected >= self.scroll_offset + max_visible {
      self.scroll_offset = self.selected + 1 - max_visible;
    }

    if self.selected == 0 {
      self.scroll_offset = 0;
    } else if self.selected == len - 1 {
      self.scroll_offset = len.saturating_sub(max_visible);
    }
  }

  /// Wizard decode phase: waits until the question’s reveal progress crosses 0.5 (same gate as text entry).
  pub fn tick_decode(&mut self, question_reveal: f64, box_open_speed: f64, reveal_speed: f64) {
    if !self.visible || question_reveal < 0.5 {
      return;
    }
    self.open = (self.open + box_open_speed).min(1.0);
    if self.open >= 1.0 {
      self.reveal = (self.reveal + reveal_speed).min(1.0);
    }
  }

  pub fn tick_transition_encode(
    &mut self,
    next_has_selector: bool,
    encode_speed: f64,
    morph_speed: f64,
  ) {
    if !self.visible {
      return;
    }
    self.reveal = (self.reveal - encode_speed).max(0.0);
    if !next_has_selector && self.is_fully_hidden() {
      self.open = (self.open - morph_speed).max(0.0);
    }
  }

  pub fn tick_transition_decode(&mut self, encode_speed: f64, morph_speed: f64) {
    if !self.visible {
      return;
    }
    if self.open < 1.0 {
      self.open = (self.open + morph_speed).min(1.0);
    } else {
      self.reveal = (self.reveal + encode_speed).min(1.0);
    }
  }

  pub fn tick_exit_close(&mut self, encode_speed: f64, box_close_speed: f64) {
    if !self.visible {
      return;
    }
    self.reveal = (self.reveal - encode_speed).max(0.0);
    if self.reveal <= 0.0 {
      self.open = (self.open - box_close_speed).max(0.0);
    }
  }

  #[cfg(not(tarpaulin_include))]
  pub fn render<W: Write, R: Rng>(
    &self,
    writer: &mut W,
    tw: u16,
    start_row: u16,
    rng: &mut R,
  ) -> std::io::Result<usize> {
    if self.options.is_empty() {
      return Ok(0);
    }

    let layout = SelectorLayout::compute(self, tw);

    if self.open < 1.0 {
      return render_partial_border(writer, self.open, &layout, start_row);
    }

    let scroll_offset = self.scroll_offset;
    let has_scroll_up = scroll_offset > 0;
    let has_scroll_down = scroll_offset + layout.max_visible < self.options.len();

    let mut row = start_row;

    let top = selector_border(layout.inner_width, has_scroll_up, true);
    queue!(
      writer,
      MoveTo(layout.col, row),
      SetForegroundColor(Color::DarkGrey),
      Print(&top),
      ResetColor
    )?;
    row += 1;

    render_selector_items(
      writer,
      self,
      &layout,
      row,
      has_scroll_up,
      has_scroll_down,
      rng,
    )?;
    row += layout.max_visible as u16;

    let bottom = selector_border(layout.inner_width, has_scroll_down, false);
    queue!(
      writer,
      MoveTo(layout.col, row),
      SetForegroundColor(Color::DarkGrey),
      Print(&bottom),
      ResetColor
    )?;

    Ok(layout.max_visible + 2)
  }
}

struct SelectorLayout {
  tw: u16,
  inner_width: u16,
  col: u16,
  max_visible: usize,
}

impl SelectorLayout {
  fn compute(sel: &SelectorComponent, tw: u16) -> Self {
    let total = sel.options.len();
    let max_visible = total.min(MAX_VISIBLE_OPTIONS);
    let inner_width = selector_inner_width(sel, tw);
    let outer_width = inner_width + 4;
    let col = centered_column(tw, outer_width);
    Self {
      tw,
      inner_width,
      col,
      max_visible,
    }
  }
}

fn selector_inner_width(sel: &SelectorComponent, tw: u16) -> u16 {
  let max_label = sel
    .options
    .iter()
    .map(|o| o.label.chars().count())
    .max()
    .unwrap_or(0);
  let prefix_width = PREFIX_ACTIVE.chars().count();
  let content_min = (prefix_width + max_label + 2) as u16;
  let entry_width = text_entry("", "", tw).inner_width;
  content_min.max(entry_width)
}

fn selector_border(inner_width: u16, has_overflow: bool, top: bool) -> String {
  let fill_total = inner_width as usize + 2;
  let (left_corner, right_corner) = if top {
    (CORNER_TOP_LEFT, CORNER_TOP_RIGHT)
  } else {
    (CORNER_BOTTOM_LEFT, CORNER_BOTTOM_RIGHT)
  };

  if !has_overflow {
    let fill: String = BORDER_HORIZONTAL.repeat(fill_total);
    return format!("{left_corner}{fill}{right_corner}");
  }

  let text_col = PREFIX_ACTIVE.chars().count() + 1;
  let leading_space = ELLIPSIS.chars().take_while(|c| *c == ' ').count();
  let prefix_offset = text_col.saturating_sub(leading_space);
  let ellipsis_len = ELLIPSIS.chars().count();
  let right_fill = fill_total.saturating_sub(prefix_offset + ellipsis_len);
  format!(
    "{}{}{}{}{}",
    left_corner,
    BORDER_HORIZONTAL.repeat(prefix_offset),
    ELLIPSIS,
    BORDER_HORIZONTAL.repeat(right_fill),
    right_corner,
  )
}

#[cfg(not(tarpaulin_include))]
fn render_partial_border<W: Write>(
  writer: &mut W,
  open_progress: f64,
  layout: &SelectorLayout,
  start_row: u16,
) -> std::io::Result<usize> {
  let raw = ((layout.inner_width as f64) * open_progress).round() as u16;
  let even = (raw / 2) * 2;
  let current_width = if even == 0 && raw > 0 {
    2
  } else {
    even.min(layout.inner_width)
  };

  if current_width == 0 {
    return Ok(0);
  }

  let col = centered_column(layout.tw, current_width + 4);

  let top = selector_border(current_width, false, true);
  let bottom = selector_border(current_width, false, false);
  let empty_inner: String = " ".repeat(current_width as usize + 2);

  queue!(
    writer,
    MoveTo(col, start_row),
    SetForegroundColor(Color::DarkGrey),
    Print(&top),
    ResetColor
  )?;

  for i in 0..layout.max_visible {
    let row = start_row + BORDER_TOP_OFFSET + i as u16;
    queue!(
      writer,
      MoveTo(col, row),
      SetForegroundColor(Color::DarkGrey),
      Print(BORDER_VERTICAL),
      Print(&empty_inner),
      Print(BORDER_VERTICAL),
      ResetColor
    )?;
  }

  let bottom_row = start_row + BORDER_TOP_OFFSET + layout.max_visible as u16;
  queue!(
    writer,
    MoveTo(col, bottom_row),
    SetForegroundColor(Color::DarkGrey),
    Print(&bottom),
    ResetColor
  )?;

  Ok(layout.max_visible + 2)
}

struct SelectorRowPaint<'a> {
  layout: &'a SelectorLayout,
  row: u16,
  opt_idx: usize,
  max_label_width: usize,
  pad_width: usize,
  arrow_char: char,
}

#[cfg(not(tarpaulin_include))]
fn render_selector_items<W: Write, R: Rng>(
  writer: &mut W,
  sel: &SelectorComponent,
  layout: &SelectorLayout,
  start_row: u16,
  has_scroll_up: bool,
  has_scroll_down: bool,
  rng: &mut R,
) -> std::io::Result<()> {
  let max_label_width = sel
    .options
    .iter()
    .map(|o| o.label.chars().count())
    .max()
    .unwrap_or(0);
  let pad_width = (layout.inner_width as usize)
    .saturating_sub(PREFIX_ACTIVE.chars().count() + max_label_width + 2);

  for i in 0..layout.max_visible {
    let opt_idx = sel.scroll_offset + i;
    if opt_idx >= sel.options.len() {
      break;
    }
    render_selector_item(
      writer,
      sel,
      SelectorRowPaint {
        layout,
        row: start_row + i as u16,
        opt_idx,
        max_label_width,
        pad_width,
        arrow_char: scroll_arrow_for(i, layout.max_visible, has_scroll_up, has_scroll_down),
      },
      rng,
    )?;
  }

  Ok(())
}

#[cfg(not(tarpaulin_include))]
fn render_selector_item<W: Write, R: Rng>(
  writer: &mut W,
  sel: &SelectorComponent,
  paint: SelectorRowPaint<'_>,
  rng: &mut R,
) -> std::io::Result<()> {
  let SelectorRowPaint {
    layout,
    row,
    opt_idx,
    max_label_width,
    pad_width,
    arrow_char,
  } = paint;

  let opt = &sel.options[opt_idx];
  let is_selected = opt_idx == sel.selected;

  let label = if sel.reveal < 1.0 {
    let revealed = (opt.label.chars().count() as f64 * sel.reveal).round() as usize;
    decode::decode_frame(&opt.label, revealed, rng)
  } else {
    opt.label.clone()
  };

  let prefix = if is_selected {
    PREFIX_ACTIVE
  } else {
    PREFIX_INACTIVE
  };

  let padded_label = format!("{:<width$}", label, width = max_label_width);

  queue!(
    writer,
    MoveTo(layout.col, row),
    SetForegroundColor(Color::DarkGrey),
    Print(BORDER_VERTICAL),
    Print(" "),
  )?;

  if is_selected {
    queue!(
      writer,
      SetForegroundColor(Color::White),
      SetAttribute(Attribute::Bold),
      Print(prefix),
      Print(&padded_label),
      SetAttribute(Attribute::Reset),
    )?;
  } else {
    queue!(
      writer,
      SetForegroundColor(Color::DarkGrey),
      Print(prefix),
      Print(&padded_label),
    )?;
  }

  let gap: String = " ".repeat(pad_width + 1);
  queue!(
    writer,
    SetForegroundColor(Color::DarkGrey),
    Print(format!("{gap}{arrow_char}")),
    Print(format!(" {BORDER_VERTICAL}")),
    ResetColor
  )
}

fn scroll_arrow_for(
  i: usize,
  max_visible: usize,
  has_scroll_up: bool,
  has_scroll_down: bool,
) -> char {
  if i == 0 && has_scroll_up {
    ARROW_UP
  } else if i == max_visible - 1 && has_scroll_down {
    ARROW_DOWN
  } else {
    ' '
  }
}

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

  fn option(label: &str, value: &str) -> SelectOption {
    SelectOption {
      label: label.to_string(),
      value: value.to_string(),
    }
  }

  #[test]
  fn viewport_row_count_matches_render_cap() {
    assert_eq!(SelectorComponent::viewport_row_count(0), 0);
    assert_eq!(SelectorComponent::viewport_row_count(5), 5);
    assert_eq!(SelectorComponent::viewport_row_count(8), 8);
    assert_eq!(
      SelectorComponent::viewport_row_count(200),
      MAX_VISIBLE_OPTIONS
    );
  }

  #[test]
  fn is_fully_thresholds() {
    let mut s = SelectorComponent::from_options(vec![option("a", "a")], 0);
    s.open = 1.0;
    assert!(s.is_fully_open());
    s.open = 0.999;
    assert!(!s.is_fully_open());
    s.open = 0.0;
    assert!(s.is_fully_closed());
    s.open = -0.1;
    assert!(s.is_fully_closed());

    s.reveal = 1.0;
    assert!(s.is_fully_revealed());
    s.reveal = 0.999;
    assert!(!s.is_fully_revealed());
    s.reveal = 0.0;
    assert!(s.is_fully_hidden());
    s.reveal = 0.01;
    assert!(!s.is_fully_hidden());
  }

  #[test]
  fn scroll_arrow_for_branches() {
    assert_eq!(scroll_arrow_for(0, 4, true, false), ARROW_UP);
    assert_eq!(scroll_arrow_for(3, 4, false, true), ARROW_DOWN);
    assert_eq!(scroll_arrow_for(1, 4, true, true), ' ');
    assert_eq!(scroll_arrow_for(3, 4, true, false), ' ');
  }

  #[test]
  fn selector_layout_compute_places_column() {
    let sel = SelectorComponent::from_options(
      vec![option("short", "s"), option("much longer label", "m")],
      0,
    );
    let layout = SelectorLayout::compute(&sel, 120);
    assert_eq!(layout.max_visible, 2);
    assert_eq!(layout.tw, 120);
    assert!(layout.inner_width > 0);
    assert!(layout.col < 120);

    let empty = SelectorComponent::hidden();
    let layout_empty = SelectorLayout::compute(&empty, 80);
    assert_eq!(layout_empty.max_visible, 0);
  }

  #[test]
  fn selector_inner_width_tracks_longest_label() {
    let sel = SelectorComponent::from_options(vec![option("ab", "a"), option("abcdef", "b")], 0);
    let w = selector_inner_width(&sel, 200);
    assert!(w >= 6);

    let sel_empty = SelectorComponent::hidden();
    let w0 = selector_inner_width(&sel_empty, 80);
    assert!(w0 > 0);
  }

  #[test]
  fn selector_border_plain_and_overflow() {
    let plain_top = selector_border(10, false, true);
    assert!(plain_top.starts_with(CORNER_TOP_LEFT));
    assert!(plain_top.ends_with(CORNER_TOP_RIGHT));

    let plain_bot = selector_border(10, false, false);
    assert!(plain_bot.starts_with(CORNER_BOTTOM_LEFT));

    let overflow_top = selector_border(20, true, true);
    assert!(overflow_top.contains('\u{00b7}'));
  }

  #[test]
  fn navigate_down_increments_selection() {
    let mut sel = SelectorComponent::from_options(
      vec![option("A", "a"), option("B", "b"), option("C", "c")],
      0,
    );
    sel.navigate(ListNavigate::Down);
    assert_eq!(sel.selected, 1);
  }

  #[test]
  fn navigate_down_wraps_to_first() {
    let mut sel = SelectorComponent::from_options(vec![option("A", "a"), option("B", "b")], 1);
    sel.navigate(ListNavigate::Down);
    assert_eq!(sel.selected, 0);
  }

  #[test]
  fn navigate_up_decrements_selection() {
    let mut sel = SelectorComponent::from_options(
      vec![option("A", "a"), option("B", "b"), option("C", "c")],
      2,
    );
    sel.navigate(ListNavigate::Up);
    assert_eq!(sel.selected, 1);
  }

  #[test]
  fn navigate_up_wraps_to_last() {
    let mut sel = SelectorComponent::from_options(
      vec![option("A", "a"), option("B", "b"), option("C", "c")],
      0,
    );
    sel.navigate(ListNavigate::Up);
    assert_eq!(sel.selected, 2);
  }

  #[test]
  fn navigate_empty_options_is_noop() {
    let mut sel = SelectorComponent::hidden();
    sel.navigate(ListNavigate::Down);
    assert_eq!(sel.selected, 0);
  }
}