scarf/scarf/scarf/Features/Kanban/Views/KanbanColumnView.swift

import SwiftUI
import ScarfCore
import ScarfDesign

/// One column of the Kanban board. Owns its drop target, header chrome,
/// scroll viewport, and per-column empty state. Cards are rendered via
/// `KanbanCardView`.
struct KanbanColumnView: View {
    let column: KanbanBoardColumn
    let tasks: [HermesKanbanTask]
    /// Live indicator for the Running column — true when polling has
    /// ticked within the last 6 seconds.
    let isLive: Bool
    /// "ready: N →" pill on the To Do column.
    let readyPillCount: Int
    let onTaskTap: (HermesKanbanTask) -> Void
    let onCreate: () -> Void
    let onDrop: (KanbanTaskRef) -> Void
    let canCreate: Bool

    @State private var isTargeted = false

    var body: some View {
        VStack(spacing: 0) {
            header
                .padding(.horizontal, ScarfSpace.s3)
                .padding(.vertical, ScarfSpace.s2)
                .background(ScarfColor.backgroundSecondary.opacity(0.001))
                .background(.ultraThinMaterial)
            Divider()
                .opacity(0.5)
            ScrollView {
                LazyVStack(spacing: ScarfSpace.s2) {
                    if tasks.isEmpty {
                        emptyState
                            .padding(.top, ScarfSpace.s4)
                    } else {
                        ForEach(tasks) { task in
                            KanbanCardView(task: task) {
                                onTaskTap(task)
                            }
                        }
                    }
                }
                .padding(ScarfSpace.s3)
            }
        }
        .frame(minWidth: 240, idealWidth: 300, maxWidth: 360)
        .frame(maxHeight: .infinity)
        .background(
            RoundedRectangle(cornerRadius: ScarfRadius.xl, style: .continuous)
                .fill(ScarfColor.backgroundSecondary.opacity(0.6))
        )
        .overlay(
            RoundedRectangle(cornerRadius: ScarfRadius.xl, style: .continuous)
                .stroke(borderColor, lineWidth: isTargeted ? 2 : 1)
        )
        .animation(.easeInOut(duration: 0.12), value: isTargeted)
        .dropDestination(for: KanbanTaskRef.self) { items, _ in
            if let ref = items.first {
                onDrop(ref)
                return true
            }
            return false
        } isTargeted: { targeted in
            isTargeted = targeted
        }
    }

    // MARK: - Header

    private var header: some View {
        HStack(spacing: ScarfSpace.s2) {
            Text(column.displayName.uppercased())
                .scarfStyle(.captionUppercase)
                .foregroundStyle(ScarfColor.foregroundMuted)
            ScarfBadge(String(tasks.count), kind: .neutral)
            if column == .upNext, readyPillCount > 0 {
                Text("ready: \(readyPillCount) →")
                    .scarfStyle(.caption)
                    .foregroundStyle(ScarfColor.info)
            }
            if column == .running, isLive {
                liveIndicator
            }
            Spacer(minLength: 0)
            if canCreate {
                Button(action: onCreate) {
                    Image(systemName: "plus")
                        .font(.system(size: 12, weight: .semibold))
                }
                .buttonStyle(ScarfGhostButton())
                .help("New task in \(column.displayName)")
            }
        }
    }

    private var liveIndicator: some View {
        HStack(spacing: 4) {
            Circle()
                .fill(ScarfColor.success)
                .frame(width: 6, height: 6)
            Text("live")
                .scarfStyle(.caption)
                .foregroundStyle(ScarfColor.foregroundMuted)
        }
    }

    private var borderColor: Color {
        isTargeted ? ScarfColor.accent : ScarfColor.border
    }

    // MARK: - Empty state

    private var emptyState: some View {
        Text(emptyCopy)
            .scarfStyle(.footnote)
            .foregroundStyle(ScarfColor.foregroundFaint)
            .multilineTextAlignment(.center)
            .frame(maxWidth: .infinity)
            .padding(.vertical, ScarfSpace.s4)
    }

    private var emptyCopy: String {
        switch column {
        case .triage:   return "Nothing waiting on you."
        case .upNext:   return "Empty queue. Drop a task here."
        case .running:  return "No live workers."
        case .blocked:  return "Nothing blocked."
        case .done:     return "Recent completions appear here."
        case .archived: return "No archived tasks."
        }
    }
}