DrillDownList

DrillDownList.swift

import SwiftUI

struct DrillDownList<Data, RowContent>: View
where
  Data: RandomAccessCollection,
  Data.Element: Identifiable,
  Data.Element: Hashable,
  RowContent: View
{
  @Environment(\.dismiss) private var dismiss
  var data: Data
  var children: KeyPath<Data.Element, Data>
  var headerTitle: String
  var itemName: KeyPath<Data.Element, String>
  @Binding var navigationPath: NavigationPath
  var rowContent: (Data.Element) -> RowContent
  var onSelect: (Data.Element) -> Void
  var onAppear: ((Data) -> Void)? = nil
  var onNextPage: ((Data.Element) -> Void)? = nil

  let chevronBack = Image(systemName: "chevron.backward")

  var body: some View {
    VStack(spacing: 0) {
      header
      ScrollView {
        VStack(alignment: .leading, spacing: 0) {
          Divider()
          ForEach(data) { item in
            drillDownItem(item: item)
            Divider()
          }
        }
        .padding(.horizontal, 16)
      }
    }
    .navigationBarHidden(true)
    .navigationDestination(for: Data.Element.self) { item in
      let child = item[keyPath: children]
      DrillDownList(
        data: child,
        children: children,
        headerTitle: item[keyPath: itemName],
        itemName: itemName,
        navigationPath: $navigationPath,
        rowContent: rowContent,
        onSelect: onSelect,
        onAppear: onAppear,
        onNextPage: onNextPage
      )
    }
    .onAppear { onAppear?(data) }

  }

  @ViewBuilder
  func drillDownItem(item: Data.Element) -> some View {
    DrillDownListItem(
      item: item,
      children: children,
      itemName: itemName,
      rowContent: rowContent,
      navigationPath: $navigationPath,
      onSelect: onSelect,
      onNextPage: onNextPage
    )
  }

  var header: some View {
    ZStack {
      Button {
        dismiss()
      } label: {
        chevronBack
      }
      .frame(maxWidth: .infinity, alignment: .leading)

      Text(headerTitle)
        .padding(13)
    }
    .padding(.vertical, 16)
    .padding(.horizontal, 16)
  }
}

struct DrillDownListItem<Data, RowContent>: View
where
  Data: RandomAccessCollection,
  Data.Element: Identifiable,
  Data.Element: Hashable,
  RowContent: View
{
  var item: Data.Element
  var children: KeyPath<Data.Element, Data>
  var itemName: KeyPath<Data.Element, String>
  var rowContent: (Data.Element) -> RowContent
  @Binding var navigationPath: NavigationPath
  var onSelect: (Data.Element) -> Void
  var onNextPage: ((Data.Element) -> Void)? = nil

  var body: some View {
    let child = item[keyPath: children]
    if child.isEmpty {
      Button {
        onSelect(item)
        navigationPath.removeLast(navigationPath.count)
      } label: {
        rowContent(item)
      }
    } else {
      Button {
        navigationPath.append(item)
      } label: {
        rowContent(item)
      }
    }
  }
}