pandora_kit/

drag.rs

use ratatui::layout::Rect;

/// Minimum columns the popup must retain when dragged to an edge.
const MIN_VISIBLE_W: u16 = 20;

/// Minimum rows the popup must retain when dragged to an edge.
const MIN_VISIBLE_H: u16 = 5;

/// Minimum popup width when resizing.
const MIN_RESIZE_W: u16 = 20;

/// Minimum popup height when resizing.
const MIN_RESIZE_H: u16 = 5;

/// Which edges of the popup are being resized.
#[derive(Clone, Copy, Debug, Default, PartialEq)]
pub struct EdgeSet {
    pub left: bool,
    pub right: bool,
    pub top: bool,
    pub bottom: bool,
}

/// The interactive zone at a given screen position.
#[derive(Clone, Copy, Debug, PartialEq)]
pub enum Zone {
    None,
    Move,
    Resize(EdgeSet),
}

/// Result of a drag update.
#[derive(Clone, Copy, Debug, PartialEq)]
pub enum DragUpdate {
    None,
    Moved { x: u16, y: u16 },
    Resized { x: u16, y: u16, w: u16, h: u16 },
}

// ── Geometry helpers ──

pub fn contains(rect: Rect, col: u16, row: u16) -> bool {
    col >= rect.x
        && col < rect.x + rect.width
        && row >= rect.y
        && row < rect.y + rect.height
}

pub fn is_on_border(popup: Rect, col: u16, row: u16) -> bool {
    if !contains(popup, col, row) {
        return false;
    }
    let inner = Rect {
        x: popup.x + 1,
        y: popup.y + 1,
        width: popup.width.saturating_sub(2),
        height: popup.height.saturating_sub(2),
    };
    !contains(inner, col, row)
}

/// Default zone detection for standard popups:
/// - Border → Resize (with appropriate edges)
/// - Header (rows y+1 to y+3) → Move
/// - Else → None
pub fn default_zone_at(popup: Rect, col: u16, row: u16) -> Zone {
    if !contains(popup, col, row) {
        return Zone::None;
    }

    if is_on_border(popup, col, row) {
        let mut edges = EdgeSet { left: false, right: false, top: false, bottom: false };
        if row == popup.y { edges.top = true; }
        if row == popup.y + popup.height - 1 { edges.bottom = true; }
        if col == popup.x { edges.left = true; }
        if col == popup.x + popup.width - 1 { edges.right = true; }
        return Zone::Resize(edges);
    }

    // Header area (title + divider line)
    let header_top = popup.y + 1;
    let header_bottom = header_top + 2;
    if row >= header_top && row < header_bottom {
        return Zone::Move;
    }

    Zone::None
}

// ── Drag state machine ──

enum DragMode {
    Idle,
    Move,
    Resize(EdgeSet),
}

impl Default for DragMode {
    fn default() -> Self {
        Self::Idle
    }
}

/// State for tracking a popup drag or resize operation.
#[derive(Default)]
pub struct DragState {
    cursor_offset: (u16, u16),
    start_popup: Rect,
    mode: DragMode,
}

impl DragState {
    pub fn new() -> Self {
        Self::default()
    }

    /// Start a drag based on the zone at the click position.
    pub fn begin(&mut self, popup: Rect, col: u16, row: u16, zone: Zone) {
        match zone {
            Zone::None => {}
            Zone::Move => {
                let dx = col.saturating_sub(popup.x);
                let dy = row.saturating_sub(popup.y);
                self.cursor_offset = (dx, dy);
                self.start_popup = popup;
                self.mode = DragMode::Move;
            }
            Zone::Resize(edges) => {
                self.cursor_offset = (col, row);
                self.start_popup = popup;
                self.mode = DragMode::Resize(edges);
            }
        }
    }

    /// Update the drag and return the new popup state.
    /// Returns `None`/`DragUpdate::None` if no drag is in progress.
    pub fn update(&self, area: Rect, col: u16, row: u16) -> DragUpdate {
        match &self.mode {
            DragMode::Idle => DragUpdate::None,
            DragMode::Move => {
                let (dx, dy) = self.cursor_offset;
                let max_w = area.width.saturating_sub(MIN_VISIBLE_W);
                let max_h = area.height.saturating_sub(MIN_VISIBLE_H);
                let nx = (col as i16 - dx as i16).clamp(0, max_w as i16) as u16;
                let ny = (row as i16 - dy as i16).clamp(0, max_h as i16) as u16;
                DragUpdate::Moved { x: nx, y: ny }
            }
            DragMode::Resize(edges) => {
                let p = self.start_popup;
                let mut x = p.x;
                let mut y = p.y;
                let mut w = p.width;
                let mut h = p.height;

                if edges.right {
                    w = col.saturating_sub(p.x).max(MIN_RESIZE_W);
                }
                if edges.bottom {
                    h = row.saturating_sub(p.y).max(MIN_RESIZE_H);
                }
                if edges.left {
                    let right = p.x + p.width;
                    let new_x = col.min(right.saturating_sub(MIN_RESIZE_W));
                    w = right.saturating_sub(new_x);
                    x = new_x;
                }
                if edges.top {
                    let bottom = p.y + p.height;
                    let new_y = row.min(bottom.saturating_sub(MIN_RESIZE_H));
                    h = bottom.saturating_sub(new_y);
                    y = new_y;
                }

                DragUpdate::Resized { x, y, w, h }
            }
        }
    }

    /// Whether a drag is in progress.
    pub fn is_dragging(&self) -> bool {
        !matches!(self.mode, DragMode::Idle)
    }

    /// End the drag (called on mouse up).
    pub fn end(&mut self) {
        self.mode = DragMode::Idle;
    }
}

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

    // ── contains / is_on_border / default_zone_at ──

    #[test]
    fn contains_inside() {
        let r = Rect::new(10, 5, 20, 10);
        assert!(contains(r, 15, 8));
    }

    #[test]
    fn contains_outside() {
        let r = Rect::new(10, 5, 20, 10);
        assert!(!contains(r, 5, 8));
        assert!(!contains(r, 35, 8));
    }

    #[test]
    fn contains_excludes_right_and_bottom_edge() {
        let r = Rect::new(10, 5, 20, 10);
        assert!(!contains(r, 30, 8));
        assert!(!contains(r, 15, 15));
    }

    #[test]
    fn is_on_border_top_edge() {
        let r = Rect::new(10, 5, 20, 10);
        assert!(is_on_border(r, 15, 5));
    }

    #[test]
    fn is_on_border_left_edge() {
        let r = Rect::new(10, 5, 20, 10);
        assert!(is_on_border(r, 10, 8));
    }

    #[test]
    fn is_on_border_inside() {
        let r = Rect::new(10, 5, 20, 10);
        assert!(!is_on_border(r, 15, 8));
    }

    #[test]
    fn default_zone_at_header_is_move() {
        let r = Rect::new(0, 0, 60, 20);
        assert_eq!(default_zone_at(r, 5, 1), Zone::Move);
    }

    #[test]
    fn default_zone_at_border_is_resize() {
        let r = Rect::new(0, 0, 60, 20);
        assert!(matches!(default_zone_at(r, 0, 0), Zone::Resize(_)));
    }

    #[test]
    fn default_zone_at_body_is_none() {
        let r = Rect::new(0, 0, 60, 20);
        assert_eq!(default_zone_at(r, 30, 10), Zone::None);
    }

    #[test]
    fn default_zone_at_outside_is_none() {
        let r = Rect::new(0, 0, 60, 20);
        assert_eq!(default_zone_at(r, 100, 5), Zone::None);
    }

    #[test]
    fn default_zone_at_right_edge_is_resize_right() {
        let r = Rect::new(10, 5, 40, 30);
        let zone = default_zone_at(r, 49, 15);
        assert!(matches!(zone, Zone::Resize(e) if e.right && !e.left && !e.top && !e.bottom));
    }

    #[test]
    fn default_zone_at_bottom_edge_is_resize_bottom() {
        let r = Rect::new(10, 5, 40, 30);
        let zone = default_zone_at(r, 20, 34);
        assert!(matches!(zone, Zone::Resize(e) if e.bottom && !e.top && !e.left && !e.right));
    }

    #[test]
    fn default_zone_at_top_left_corner_is_resize_both() {
        let r = Rect::new(10, 5, 40, 30);
        let zone = default_zone_at(r, 10, 5);
        assert!(matches!(zone, Zone::Resize(e) if e.top && e.left));
    }

    // ── begin ──

    #[test]
    fn begin_move_sets_offset() {
        let popup = Rect::new(10, 5, 40, 30);
        let mut drag = DragState::new();
        drag.begin(popup, 15, 10, Zone::Move);
        assert!(drag.is_dragging());
    }

    #[test]
    fn begin_none_does_not_drag() {
        let popup = Rect::new(10, 5, 40, 30);
        let mut drag = DragState::new();
        drag.begin(popup, 15, 10, Zone::None);
        assert!(!drag.is_dragging());
    }

    #[test]
    fn begin_move_computes_correct_offset() {
        let popup = Rect::new(10, 5, 40, 30);
        let mut drag = DragState::new();
        drag.begin(popup, 25, 15, Zone::Move);
        let result = drag.update(Rect::new(0, 0, 100, 50), 25, 15);
        assert_eq!(result, DragUpdate::Moved { x: 10, y: 5 });
    }

    #[test]
    fn begin_resize_starts_dragging() {
        let popup = Rect::new(10, 5, 40, 30);
        let mut drag = DragState::new();
        drag.begin(popup, 49, 15, default_zone_at(popup, 49, 15));
        assert!(drag.is_dragging());
    }

    // ── update (move) ──

    #[test]
    fn update_returns_none_when_not_dragging() {
        let drag = DragState::new();
        assert_eq!(drag.update(Rect::new(0, 0, 100, 50), 50, 25), DragUpdate::None);
    }

    #[test]
    fn update_move_returns_origin() {
        let popup = Rect::new(10, 5, 40, 30);
        let mut drag = DragState::new();
        drag.begin(popup, 15, 10, Zone::Move);
        let result = drag.update(Rect::new(0, 0, 100, 50), 40, 30);
        assert_eq!(result, DragUpdate::Moved { x: 35, y: 25 });
    }

    #[test]
    fn update_move_clamps_nx_to_area_width_minus_min_w() {
        let popup = Rect::new(10, 5, 40, 30);
        let mut drag = DragState::new();
        drag.begin(popup, 15, 10, Zone::Move);
        let result = drag.update(Rect::new(0, 0, 100, 50), 999, 30);
        if let DragUpdate::Moved { x, .. } = result {
            assert!(x <= 80);
        } else {
            panic!("expected Move");
        }
    }

    #[test]
    fn update_move_clamps_ny_to_area_height_minus_min_h() {
        let popup = Rect::new(10, 5, 40, 30);
        let mut drag = DragState::new();
        drag.begin(popup, 15, 10, Zone::Move);
        let result = drag.update(Rect::new(0, 0, 100, 50), 30, 999);
        if let DragUpdate::Moved { y, .. } = result {
            assert!(y <= 45);
        } else {
            panic!("expected Move");
        }
    }

    #[test]
    fn update_move_keeps_minimum_visible_size() {
        let popup = Rect::new(10, 5, 40, 30);
        let mut drag = DragState::new();
        drag.begin(popup, 15, 10, Zone::Move);
        let result = drag.update(Rect::new(0, 0, 100, 50), 999, 999);
        assert_eq!(result, DragUpdate::Moved { x: 80, y: 45 });
    }

    #[test]
    fn update_move_clamps_to_zero_when_negative() {
        let popup = Rect::new(10, 5, 40, 30);
        let mut drag = DragState::new();
        drag.begin(popup, 15, 10, Zone::Move);
        let result = drag.update(Rect::new(0, 0, 100, 50), 0, 0);
        assert_eq!(result, DragUpdate::Moved { x: 0, y: 0 });
    }

    #[test]
    fn update_move_allows_drag_below_middle() {
        let popup = Rect::new(0, 0, 40, 35);
        let mut drag = DragState::new();
        drag.begin(popup, 5, 1, Zone::Move);
        let result = drag.update(Rect::new(0, 0, 100, 50), 5, 26);
        if let DragUpdate::Moved { y, .. } = result {
            assert!(y >= 25, "ny should reach middle of screen, got ny={}", y);
        } else {
            panic!("expected Move");
        }
    }

    // ── update (resize) ──

    #[test]
    fn update_resize_right_increases_width() {
        let popup = Rect::new(10, 5, 40, 30);
        let mut drag = DragState::new();
        drag.begin(popup, 49, 15, Zone::Resize(EdgeSet { left: false, right: true, top: false, bottom: false }));
        let result = drag.update(Rect::new(0, 0, 100, 50), 60, 15);
        assert_eq!(result, DragUpdate::Resized { x: 10, y: 5, w: 50, h: 30 });
    }

    #[test]
    fn update_resize_bottom_increases_height() {
        let popup = Rect::new(10, 5, 40, 30);
        let mut drag = DragState::new();
        drag.begin(popup, 20, 34, Zone::Resize(EdgeSet { left: false, right: false, top: false, bottom: true }));
        let result = drag.update(Rect::new(0, 0, 100, 50), 20, 40);
        assert_eq!(result, DragUpdate::Resized { x: 10, y: 5, w: 40, h: 35 });
    }

    #[test]
    fn update_resize_left_moves_and_shrinks() {
        let popup = Rect::new(20, 5, 40, 30);
        let mut drag = DragState::new();
        drag.begin(popup, 20, 15, Zone::Resize(EdgeSet { left: true, right: false, top: false, bottom: false }));
        let result = drag.update(Rect::new(0, 0, 100, 50), 30, 15);
        // left edge moved right → smaller width, x changes
        if let DragUpdate::Resized { x, w, .. } = result {
            assert_eq!(x, 30);
            assert!(w <= 30);
        } else {
            panic!("expected Resized");
        }
    }

    #[test]
    fn update_resize_enforces_min_width() {
        let popup = Rect::new(10, 5, 40, 30);
        let mut drag = DragState::new();
        drag.begin(popup, 49, 15, Zone::Resize(EdgeSet { left: false, right: true, top: false, bottom: false }));
        let result = drag.update(Rect::new(0, 0, 100, 50), 20, 15);
        if let DragUpdate::Resized { w, .. } = result {
            assert!(w >= MIN_RESIZE_W);
        } else {
            panic!("expected Resized");
        }
    }

    // ── multi-step resize ──

    fn unpack_resized(result: DragUpdate) -> Rect {
        match result {
            DragUpdate::Resized { x, y, w, h } => Rect::new(x, y, w, h),
            _ => panic!("expected Resized"),
        }
    }

    #[test]
    fn resize_right_then_right_again() {
        let area = Rect::new(0, 0, 100, 50);
        let popup = Rect::new(10, 5, 40, 30);

        // First drag: resize right to w=50
        let mut drag = DragState::new();
        drag.begin(popup, 49, 15, Zone::Resize(EdgeSet { right: true, ..Default::default() }));
        let r1 = unpack_resized(drag.update(area, 60, 15));
        assert_eq!(r1, Rect::new(10, 5, 50, 30));
        drag.end();

        // Second drag: resize right from new rect to w=55
        drag.begin(r1, r1.x + r1.width - 1, 15, Zone::Resize(EdgeSet { right: true, ..Default::default() }));
        let r2 = unpack_resized(drag.update(area, 65, 15));
        assert_eq!(r2, Rect::new(10, 5, 55, 30));

        // Right edge should be at 10+50=60, now at 10+55=65
        assert_eq!(r2.x + r2.width, 65);
    }

    #[test]
    fn resize_right_then_left_keeps_right_edge() {
        let area = Rect::new(0, 0, 100, 50);
        let popup = Rect::new(10, 5, 40, 30);
        // First drag: resize right to w=50
        let mut drag = DragState::new();
        drag.begin(popup, 49, 15, Zone::Resize(EdgeSet { right: true, ..Default::default() }));
        let r1 = unpack_resized(drag.update(area, 60, 15));
        assert_eq!(r1, Rect::new(10, 5, 50, 30));
        drag.end();

        // The right edge is now at 60
        let new_right = r1.x + r1.width; // 60

        // Second drag: resize left edge to col=5
        // Left click at x=10, drag to x=5
        drag.begin(r1, r1.x, 15, Zone::Resize(EdgeSet { left: true, ..Default::default() }));
        let r2 = unpack_resized(drag.update(area, 5, 15));
        // x should be 5, width should be 60-5=55
        assert_eq!(r2.x, 5);
        assert_eq!(r2.x + r2.width, new_right); // right edge preserved
    }

    #[test]
    fn resize_top_then_bottom_keeps_bottom_edge() {
        let area = Rect::new(0, 0, 100, 50);
        let popup = Rect::new(10, 5, 40, 30);
        let bottom_edge = popup.y + popup.height; // 35

        // First drag: resize top to row=10
        let mut drag = DragState::new();
        drag.begin(popup, 15, 5, Zone::Resize(EdgeSet { top: true, ..Default::default() }));
        let r1 = unpack_resized(drag.update(area, 15, 10));
        // y=10, h=35-10=25, bottom still at 35
        assert_eq!(r1, Rect::new(10, 10, 40, 25));
        assert_eq!(r1.y + r1.height, bottom_edge);
        drag.end();

        // Second drag: resize bottom from row=34 to row=40
        drag.begin(r1, 15, 34, Zone::Resize(EdgeSet { bottom: true, ..Default::default() }));
        let r2 = unpack_resized(drag.update(area, 15, 40));
        // y=10, h=40-10=30
        assert_eq!(r2, Rect::new(10, 10, 40, 30));
        assert_eq!(r2.y + r2.height, 40);
    }

    #[test]
    fn resize_top_then_right_independent_axes() {
        let area = Rect::new(0, 0, 100, 50);
        let popup = Rect::new(10, 5, 40, 30);

        // First drag: resize top to row=10
        let mut drag = DragState::new();
        drag.begin(popup, 15, 5, Zone::Resize(EdgeSet { top: true, ..Default::default() }));
        let r1 = unpack_resized(drag.update(area, 15, 10));
        assert_eq!(r1, Rect::new(10, 10, 40, 25));
        drag.end();

        // Second drag: resize right to col=70
        drag.begin(r1, 49, 15, Zone::Resize(EdgeSet { right: true, ..Default::default() }));
        let r2 = unpack_resized(drag.update(area, 70, 15));
        // y=10 (unchanged), w=70-10=60
        assert_eq!(r2, Rect::new(10, 10, 60, 25));
    }

    #[test]
    fn resize_left_then_top_corner_sequence() {
        let area = Rect::new(0, 0, 100, 50);
        let popup = Rect::new(20, 10, 40, 30);

        // First: resize left edge to col=10, makes popup wider
        let mut drag = DragState::new();
        drag.begin(popup, 20, 15, Zone::Resize(EdgeSet { left: true, ..Default::default() }));
        let r1 = unpack_resized(drag.update(area, 10, 15));
        // x=10, w=60-10=50 (right edge at 20+40=60)
        assert_eq!(r1, Rect::new(10, 10, 50, 30));
        drag.end();

        // Second: resize top to row=15
        drag.begin(r1, 15, 10, Zone::Resize(EdgeSet { top: true, ..Default::default() }));
        let r2 = unpack_resized(drag.update(area, 15, 15));
        // y=15, h=40-15=25 (bottom edge at 10+30=40)
        assert_eq!(r2, Rect::new(10, 15, 50, 25));
    }

    #[test]
    fn resize_single_drag_back_and_forth() {
        let area = Rect::new(0, 0, 100, 50);
        let popup = Rect::new(10, 5, 40, 30);

        let mut drag = DragState::new();
        drag.begin(popup, 49, 15, Zone::Resize(EdgeSet { right: true, ..Default::default() }));

        // Drag wide to w=60
        let r1 = unpack_resized(drag.update(area, 70, 15));
        assert_eq!(r1, Rect::new(10, 5, 60, 30));

        // Drag back narrower to w=45 (same drag, mouse moved left)
        let r2 = unpack_resized(drag.update(area, 55, 15));
        assert_eq!(r2, Rect::new(10, 5, 45, 30));

        // Drag wide again to w=55
        let r3 = unpack_resized(drag.update(area, 65, 15));
        assert_eq!(r3, Rect::new(10, 5, 55, 30));
    }

    // ── end ──

    #[test]
    fn end_clears_state() {
        let popup = Rect::new(10, 5, 40, 30);
        let mut drag = DragState::new();
        drag.begin(popup, 15, 10, Zone::Move);
        assert!(drag.is_dragging());
        drag.end();
        assert!(!drag.is_dragging());
        assert_eq!(drag.update(Rect::new(0, 0, 100, 50), 40, 30), DragUpdate::None);
    }

    // ── is_dragging ──

    #[test]
    fn is_dragging_false_by_default() {
        let drag = DragState::new();
        assert!(!drag.is_dragging());
    }

    #[test]
    fn is_dragging_true_after_move_begin() {
        let popup = Rect::new(10, 5, 40, 30);
        let mut drag = DragState::new();
        drag.begin(popup, 15, 10, Zone::Move);
        assert!(drag.is_dragging());
    }

    #[test]
    fn is_dragging_true_after_resize_begin() {
        let popup = Rect::new(10, 5, 40, 30);
        let mut drag = DragState::new();
        drag.begin(popup, 15, 10, Zone::Resize(EdgeSet { left: false, right: true, top: false, bottom: false }));
        assert!(drag.is_dragging());
    }

    #[test]
    fn is_dragging_false_after_end() {
        let popup = Rect::new(10, 5, 40, 30);
        let mut drag = DragState::new();
        drag.begin(popup, 15, 10, Zone::Move);
        drag.end();
        assert!(!drag.is_dragging());
    }
}