import SwiftUI

/// The **shadow placeholder** — the outline occupying an item's proposed landing spot
/// (DRAG-REORDER.md § The pieces).
///
/// One shape for both the drag's shadows and the lane resize's resting footprint, because they are
/// the same thing said twice: "here is the space this item occupies in the layout". They differ only
/// in whether the space is a *proposal* — the drag's is dashed, because a dashed outline is what
/// 03-board-ui.md's placeholder vocabulary asks for and what makes "the drop lands exactly here"
/// legible; the resize's is a plain fill, because the lane is already there.
///
/// **Hit-transparent, always.** The strip's own drop target has to stay live beneath the shadows
/// (DRAG-REORDER.md § Single-target dispatch: "shadow placeholders are hit-transparent, so the strip
/// target stays live beneath them"), and a shadow that swallowed the release would strand the drop.
///
/// **A drag's shadow lives exactly as long as the drag does.** The moment the mouse comes up the
/// slot it was holding draws the dropped card itself (`LaneView`'s `runSlots`, `DroppedCardFace`) —
/// "a lingering shadow over a hidden card is the hold failing its one job" (03-board-ui.md § Motion,
/// sharpened 2026-07-28). The one shadow that outlives a release is the cross-board *lane* arrival's,
/// which has no column to draw until the echo lands (`BoardView.runSlots`).
struct DragShadow: View {

    /// Matched to the surface it stands in for — a lane's plate is 10, a card's is 8.
    var cornerRadius: CGFloat = 10

    /// A drop proposal (dashed) or a resting footprint (plain).
    var dashed: Bool = true

    var body: some View {
        RoundedRectangle(cornerRadius: cornerRadius)
            .fill(.quaternary.opacity(0.5))
            .overlay {
                if dashed {
                    RoundedRectangle(cornerRadius: cornerRadius)
                        .strokeBorder(
                            Color.accentColor.opacity(0.55),
                            style: StrokeStyle(lineWidth: 1.5, dash: [6])
                        )
                }
            }
            .allowsHitTesting(false)
            .accessibilityHidden(true)
    }
}

/// The count badge a multi-drag's replica wears — Finder's own affordance for "this many are coming
/// with me" (04-interactions.md ▸ Drag and drop: "dragging any member of a multi-selection drags the
/// whole selection").
///
/// Draws nothing for a single item, so every replica can carry it unconditionally.
struct DragCountBadge: View {

    let count: Int

    var body: some View {
        if count > 1 {
            Text("\(count)")
                .font(.caption2.bold())
                .monospacedDigit()
                .foregroundStyle(.white)
                .padding(.horizontal, 6)
                .padding(.vertical, 3)
                .background(Circle().fill(Color.accentColor))
                .offset(x: 10, y: -10)
        }
    }
}