swiftui-navigation/Sources/_SwiftUINavigationState/TextState.swift

import CustomDump
import SwiftUI

/// An equatable description of SwiftUI `Text`. Useful for storing rich text in feature models
/// that can still be tested for equality.
///
/// Although `SwiftUI.Text` and `SwiftUI.LocalizedStringKey` are value types that conform to
/// `Equatable`, their `==` do not return `true` when used with seemingly equal values. If we were
/// to naively store these values in state, our tests may begin to fail.
///
/// ``TextState`` solves this problem by providing an interface similar to `SwiftUI.Text` that can
/// be held in state and asserted against.
///
/// Let's say you wanted to hold some dynamic, styled text content in your app state. You could use
/// ``TextState``:
///
/// ```swift
/// class Model: Equatable {
///   @Published var label = TextState("")
/// }
/// ```
///
/// Your model can then assign a value to this state using an API similar to that of `SwiftUI.Text`.
///
/// ```swift
/// self.label = TextState("Hello, ") + TextState(name).bold() + TextState("!")
/// ```
///
/// And your view can render it by passing it to a `SwiftUI.Text` initializer:
///
/// ```swift
/// var body: some View {
///   Text(self.model.label)
/// }
/// ```
///
/// SwiftUI Navigation comes with a few convenience APIs for alerts and dialogs that wrap
/// ``TextState`` under the hood. See ``AlertState`` and ``ConfirmationDialogState`` accordingly.
///
/// In the future, should `SwiftUI.Text` and `SwiftUI.LocalizedStringKey` reliably conform to
/// `Equatable`, ``TextState`` may be deprecated.
///
/// - Note: ``TextState`` does not support _all_ `LocalizedStringKey` permutations at this time
///   (interpolated `SwiftUI.Image`s, for example). ``TextState`` also uses reflection to determine
///   `LocalizedStringKey` equatability, so be mindful of edge cases.
public struct TextState: Equatable, Hashable {
  fileprivate var modifiers: [Modifier] = []
  fileprivate let storage: Storage

  fileprivate enum Modifier: Equatable, Hashable {
    case accessibilityHeading(AccessibilityHeadingLevel)
    case accessibilityLabel(TextState)
    case accessibilityTextContentType(AccessibilityTextContentType)
    case baselineOffset(CGFloat)
    case bold(isActive: Bool)
    case font(Font?)
    case fontDesign(Font.Design?)
    case fontWeight(Font.Weight?)
    case fontWidth(FontWidth?)
    case foregroundColor(Color?)
    case italic(isActive: Bool)
    case kerning(CGFloat)
    case monospacedDigit
    case speechAdjustedPitch(Double)
    case speechAlwaysIncludesPunctuation(Bool)
    case speechAnnouncementsQueued(Bool)
    case speechSpellsOutCharacters(Bool)
    case strikethrough(isActive: Bool, pattern: LineStylePattern?, color: Color?)
    case tracking(CGFloat)
    case underline(isActive: Bool, pattern: LineStylePattern?, color: Color?)
  }

  public enum FontWidth: String, Equatable, Hashable {
    case compressed
    case condensed
    case expanded
    case standard

    #if swift(>=5.7.1)
      @available(iOS 16, macOS 13, tvOS 16, watchOS 9, *)
      var toSwiftUI: SwiftUI.Font.Width {
        switch self {
        case .compressed: return .compressed
        case .condensed: return .condensed
        case .expanded: return .expanded
        case .standard: return .standard
        }
      }
    #endif
  }

  public enum LineStylePattern: String, Equatable, Hashable {
    case dash
    case dashDot
    case dashDotDot
    case dot
    case solid

    @available(iOS 16, macOS 13, tvOS 16, watchOS 9, *)
    var toSwiftUI: SwiftUI.Text.LineStyle.Pattern {
      switch self {
      case .dash: return .dash
      case .dashDot: return .dashDot
      case .dashDotDot: return .dashDotDot
      case .dot: return .dot
      case .solid: return .solid
      }
    }
  }

  fileprivate enum Storage: Equatable, Hashable {
    indirect case concatenated(TextState, TextState)
    case localized(LocalizedStringKey, tableName: String?, bundle: Bundle?, comment: StaticString?)
    case verbatim(String)

    static func == (lhs: Self, rhs: Self) -> Bool {
      switch (lhs, rhs) {
      case let (.concatenated(l1, l2), .concatenated(r1, r2)):
        return l1 == r1 && l2 == r2

      case let (.localized(lk, lt, lb, lc), .localized(rk, rt, rb, rc)):
        return lk.formatted(tableName: lt, bundle: lb, comment: lc)
          == rk.formatted(tableName: rt, bundle: rb, comment: rc)

      case let (.verbatim(lhs), .verbatim(rhs)):
        return lhs == rhs

      case let (.localized(key, tableName, bundle, comment), .verbatim(string)),
        let (.verbatim(string), .localized(key, tableName, bundle, comment)):
        return key.formatted(tableName: tableName, bundle: bundle, comment: comment) == string

      // NB: We do not attempt to equate concatenated cases.
      default:
        return false
      }
    }

    func hash(into hasher: inout Hasher) {
      enum Key {
        case concatenated
        case localized
        case verbatim
      }

      switch self {
      case let (.concatenated(first, second)):
        hasher.combine(Key.concatenated)
        hasher.combine(first)
        hasher.combine(second)

      case let .localized(key, tableName, bundle, comment):
        hasher.combine(Key.localized)
        hasher.combine(key.formatted(tableName: tableName, bundle: bundle, comment: comment))

      case let .verbatim(string):
        hasher.combine(Key.verbatim)
        hasher.combine(string)
      }
    }
  }
}

// MARK: - API

extension TextState {
  public init(verbatim content: String) {
    self.storage = .verbatim(content)
  }

  @_disfavoredOverload
  public init<S: StringProtocol>(_ content: S) {
    self.init(verbatim: String(content))
  }

  public init(
    _ key: LocalizedStringKey,
    tableName: String? = nil,
    bundle: Bundle? = nil,
    comment: StaticString? = nil
  ) {
    self.storage = .localized(key, tableName: tableName, bundle: bundle, comment: comment)
  }

  public static func + (lhs: Self, rhs: Self) -> Self {
    .init(storage: .concatenated(lhs, rhs))
  }

  public func baselineOffset(_ baselineOffset: CGFloat) -> Self {
    var `self` = self
    `self`.modifiers.append(.baselineOffset(baselineOffset))
    return `self`
  }

  public func bold() -> Self {
    var `self` = self
    `self`.modifiers.append(.bold(isActive: true))
    return `self`
  }

  @available(iOS 16, macOS 13, tvOS 16, watchOS 9, *)
  public func bold(isActive: Bool) -> Self {
    var `self` = self
    `self`.modifiers.append(.bold(isActive: isActive))
    return `self`
  }

  public func font(_ font: Font?) -> Self {
    var `self` = self
    `self`.modifiers.append(.font(font))
    return `self`
  }

  public func fontDesign(_ design: Font.Design?) -> Self {
    var `self` = self
    `self`.modifiers.append(.fontDesign(design))
    return `self`
  }

  public func fontWeight(_ weight: Font.Weight?) -> Self {
    var `self` = self
    `self`.modifiers.append(.fontWeight(weight))
    return `self`
  }

  @available(iOS 16, macOS 13, tvOS 16, watchOS 9, *)
  public func fontWidth(_ width: FontWidth?) -> Self {
    var `self` = self
    `self`.modifiers.append(.fontWidth(width))
    return `self`
  }

  public func foregroundColor(_ color: Color?) -> Self {
    var `self` = self
    `self`.modifiers.append(.foregroundColor(color))
    return `self`
  }

  public func italic() -> Self {
    var `self` = self
    `self`.modifiers.append(.italic(isActive: true))
    return `self`
  }

  @available(iOS 16, macOS 13, tvOS 16, watchOS 9, *)
  public func italic(isActive: Bool) -> Self {
    var `self` = self
    `self`.modifiers.append(.italic(isActive: isActive))
    return `self`
  }

  public func kerning(_ kerning: CGFloat) -> Self {
    var `self` = self
    `self`.modifiers.append(.kerning(kerning))
    return `self`
  }

  @available(iOS 15, macOS 12, tvOS 15, watchOS 8, *)
  public func monospacedDigit() -> Self {
    var `self` = self
    `self`.modifiers.append(.monospacedDigit)
    return `self`
  }

  public func strikethrough(_ isActive: Bool = true, color: Color? = nil) -> Self {
    var `self` = self
    `self`.modifiers.append(.strikethrough(isActive: isActive, pattern: .solid, color: color))
    return `self`
  }

  @available(iOS 16, macOS 13, tvOS 16, watchOS 9, *)
  public func strikethrough(
    _ isActive: Bool = true,
    pattern: LineStylePattern,
    color: Color? = nil
  ) -> Self {
    var `self` = self
    `self`.modifiers.append(.strikethrough(isActive: isActive, pattern: pattern, color: color))
    return `self`
  }

  public func tracking(_ tracking: CGFloat) -> Self {
    var `self` = self
    `self`.modifiers.append(.tracking(tracking))
    return `self`
  }

  public func underline(_ isActive: Bool = true, color: Color? = nil) -> Self {
    var `self` = self
    `self`.modifiers.append(.underline(isActive: isActive, pattern: .solid, color: color))
    return `self`
  }

  @available(iOS 16, macOS 13, tvOS 16, watchOS 9, *)
  public func underline(
    _ isActive: Bool = true,
    pattern: LineStylePattern,
    color: Color? = nil
  ) -> Self {
    var `self` = self
    `self`.modifiers.append(.underline(isActive: isActive, pattern: pattern, color: color))
    return `self`
  }
}

// MARK: Accessibility

extension TextState {
  public enum AccessibilityTextContentType: String, Equatable, Hashable {
    case console, fileSystem, messaging, narrative, plain, sourceCode, spreadsheet, wordProcessing

    #if compiler(>=5.5.1)
      @available(iOS 15, macOS 12, tvOS 15, watchOS 8, *)
      var toSwiftUI: SwiftUI.AccessibilityTextContentType {
        switch self {
        case .console: return .console
        case .fileSystem: return .fileSystem
        case .messaging: return .messaging
        case .narrative: return .narrative
        case .plain: return .plain
        case .sourceCode: return .sourceCode
        case .spreadsheet: return .spreadsheet
        case .wordProcessing: return .wordProcessing
        }
      }
    #endif
  }

  public enum AccessibilityHeadingLevel: String, Equatable, Hashable {
    case h1, h2, h3, h4, h5, h6, unspecified

    #if compiler(>=5.5.1)
      @available(iOS 15, macOS 12, tvOS 15, watchOS 8, *)
      var toSwiftUI: SwiftUI.AccessibilityHeadingLevel {
        switch self {
        case .h1: return .h1
        case .h2: return .h2
        case .h3: return .h3
        case .h4: return .h4
        case .h5: return .h5
        case .h6: return .h6
        case .unspecified: return .unspecified
        }
      }
    #endif
  }
}

@available(iOS 15, macOS 12, tvOS 15, watchOS 8, *)
extension TextState {
  public func accessibilityHeading(_ headingLevel: AccessibilityHeadingLevel) -> Self {
    var `self` = self
    `self`.modifiers.append(.accessibilityHeading(headingLevel))
    return `self`
  }

  public func accessibilityLabel(_ label: Self) -> Self {
    var `self` = self
    `self`.modifiers.append(.accessibilityLabel(label))
    return `self`
  }

  public func accessibilityLabel(_ string: String) -> Self {
    var `self` = self
    `self`.modifiers.append(.accessibilityLabel(.init(string)))
    return `self`
  }

  public func accessibilityLabel<S: StringProtocol>(_ string: S) -> Self {
    var `self` = self
    `self`.modifiers.append(.accessibilityLabel(.init(string)))
    return `self`
  }

  public func accessibilityLabel(
    _ key: LocalizedStringKey, tableName: String? = nil, bundle: Bundle? = nil,
    comment: StaticString? = nil
  ) -> Self {
    var `self` = self
    `self`.modifiers.append(
      .accessibilityLabel(.init(key, tableName: tableName, bundle: bundle, comment: comment)))
    return `self`
  }

  public func accessibilityTextContentType(_ type: AccessibilityTextContentType) -> Self {
    var `self` = self
    `self`.modifiers.append(.accessibilityTextContentType(type))
    return `self`
  }

  public func speechAdjustedPitch(_ value: Double) -> Self {
    var `self` = self
    `self`.modifiers.append(.speechAdjustedPitch(value))
    return `self`
  }

  public func speechAlwaysIncludesPunctuation(_ value: Bool = true) -> Self {
    var `self` = self
    `self`.modifiers.append(.speechAlwaysIncludesPunctuation(value))
    return `self`
  }

  public func speechAnnouncementsQueued(_ value: Bool = true) -> Self {
    var `self` = self
    `self`.modifiers.append(.speechAnnouncementsQueued(value))
    return `self`
  }

  public func speechSpellsOutCharacters(_ value: Bool = true) -> Self {
    var `self` = self
    `self`.modifiers.append(.speechSpellsOutCharacters(value))
    return `self`
  }
}

extension Text {
  public init(_ state: TextState) {
    let text: Text
    switch state.storage {
    case let .concatenated(first, second):
      text = Text(first) + Text(second)
    case let .localized(content, tableName, bundle, comment):
      text = .init(content, tableName: tableName, bundle: bundle, comment: comment)
    case let .verbatim(content):
      text = .init(verbatim: content)
    }
    self = state.modifiers.reduce(text) { text, modifier in
      switch modifier {
      #if compiler(>=5.5.1)
        case let .accessibilityHeading(level):
          if #available(iOS 15, macOS 12, tvOS 15, watchOS 8, *) {
            return text.accessibilityHeading(level.toSwiftUI)
          } else {
            return text
          }
        case let .accessibilityLabel(value):
          if #available(iOS 15, macOS 12, tvOS 15, watchOS 8, *) {
            switch value.storage {
            case let .verbatim(string):
              return text.accessibilityLabel(string)
            case let .localized(key, tableName, bundle, comment):
              return text.accessibilityLabel(
                Text(key, tableName: tableName, bundle: bundle, comment: comment))
            case .concatenated(_, _):
              assertionFailure("`.accessibilityLabel` does not support concatenated `TextState`")
              return text
            }
          } else {
            return text
          }
        case let .accessibilityTextContentType(type):
          if #available(iOS 15, macOS 12, tvOS 15, watchOS 8, *) {
            return text.accessibilityTextContentType(type.toSwiftUI)
          } else {
            return text
          }
      #else
        case .accessibilityHeading,
          .accessibilityLabel,
          .accessibilityTextContentType:
          return text
      #endif
      case let .baselineOffset(baselineOffset):
        return text.baselineOffset(baselineOffset)
      case let .bold(isActive):
        #if swift(>=5.7.1)
          if #available(iOS 16, macOS 13, tvOS 16, watchOS 9, *) {
            return text.bold(isActive)
          } else {
            return text.bold()
          }
        #else
          _ = isActive
          return text.bold()
        #endif
      case let .font(font):
        return text.font(font)
      case let .fontDesign(design):
        #if swift(>=5.7.1)
          if #available(iOS 16.1, macOS 13, tvOS 16.1, watchOS 9.1, *) {
            return text.fontDesign(design)
          } else {
            return text
          }
        #else
          _ = design
          return text
        #endif
      case let .fontWeight(weight):
        return text.fontWeight(weight)
      case let .fontWidth(width):
        #if swift(>=5.7.1)
          if #available(iOS 16, macOS 13, tvOS 16, watchOS 9, *) {
            return text.fontWidth(width?.toSwiftUI)
          } else {
            return text
          }
        #else
          _ = width
          return text
        #endif
      case let .foregroundColor(color):
        return text.foregroundColor(color)
      case let .italic(isActive):
        #if swift(>=5.7.1)
          if #available(iOS 16, macOS 13, tvOS 16, watchOS 9, *) {
            return text.italic(isActive)
          } else {
            return text.italic()
          }
        #else
          _ = isActive
          return text.italic()
        #endif
      case let .kerning(kerning):
        return text.kerning(kerning)
      case .monospacedDigit:
        if #available(iOS 15, macOS 12, tvOS 15, watchOS 8, *) {
          return text.monospacedDigit()
        } else {
          return text
        }
      case let .speechAdjustedPitch(value):
        if #available(iOS 15, macOS 12, tvOS 15, watchOS 8, *) {
          return text.speechAdjustedPitch(value)
        } else {
          return text
        }
      case let .speechAlwaysIncludesPunctuation(value):
        if #available(iOS 15, macOS 12, tvOS 15, watchOS 8, *) {
          return text.speechAlwaysIncludesPunctuation(value)
        } else {
          return text
        }
      case let .speechAnnouncementsQueued(value):
        if #available(iOS 15, macOS 12, tvOS 15, watchOS 8, *) {
          return text.speechAnnouncementsQueued(value)
        } else {
          return text
        }
      case let .speechSpellsOutCharacters(value):
        if #available(iOS 15, macOS 12, tvOS 15, watchOS 8, *) {
          return text.speechSpellsOutCharacters(value)
        } else {
          return text
        }
      case let .strikethrough(isActive, pattern, color):
        #if swift(>=5.7.1)
          if #available(iOS 16, macOS 13, tvOS 16, watchOS 9, *), let pattern = pattern {
            return text.strikethrough(isActive, pattern: pattern.toSwiftUI, color: color)
          } else {
            return text.strikethrough(isActive, color: color)
          }
        #else
          _ = pattern
          return text.strikethrough(isActive, color: color)
        #endif
      case let .tracking(tracking):
        return text.tracking(tracking)
      case let .underline(isActive, pattern, color):
        #if swift(>=5.7.1)
          if #available(iOS 16, macOS 13, tvOS 16, watchOS 9, *), let pattern = pattern {
            return text.underline(isActive, pattern: pattern.toSwiftUI, color: color)
          } else {
            return text.underline(isActive, color: color)
          }
        #else
          _ = pattern
          return text.strikethrough(isActive, color: color)
        #endif
      }
    }
  }
}

extension String {
  public init(state: TextState, locale: Locale? = nil) {
    switch state.storage {
    case let .concatenated(lhs, rhs):
      self = String(state: lhs, locale: locale) + String(state: rhs, locale: locale)

    case let .localized(key, tableName, bundle, comment):
      self = key.formatted(
        locale: locale,
        tableName: tableName,
        bundle: bundle,
        comment: comment
      )

    case let .verbatim(string):
      self = string
    }
  }
}

extension LocalizedStringKey {
  // NB: `LocalizedStringKey` conforms to `Equatable` but returns false for equivalent format
  //     strings. To account for this we reflect on it to extract and string-format its storage.
  fileprivate func formatted(
    locale: Locale? = nil,
    tableName: String? = nil,
    bundle: Bundle? = nil,
    comment: StaticString? = nil
  ) -> String {
    let children = Array(Mirror(reflecting: self).children)
    let key = children[0].value as! String
    let arguments: [CVarArg] = Array(Mirror(reflecting: children[2].value).children)
      .compactMap {
        let children = Array(Mirror(reflecting: $0.value).children)
        let value: Any
        let formatter: Formatter?
        // `LocalizedStringKey.FormatArgument` differs depending on OS/platform.
        if children[0].label == "storage" {
          (value, formatter) =
            Array(Mirror(reflecting: children[0].value).children)[0].value as! (Any, Formatter?)
        } else {
          value = children[0].value
          formatter = children[1].value as? Formatter
        }
        return formatter?.string(for: value) ?? value as! CVarArg
      }

    let format = NSLocalizedString(
      key,
      tableName: tableName,
      bundle: bundle ?? .main,
      value: "",
      comment: comment.map(String.init) ?? ""
    )
    return String(format: format, locale: locale, arguments: arguments)
  }
}

// MARK: - CustomDumpRepresentable

extension TextState: CustomDumpRepresentable {
  public var customDumpValue: Any {
    func dumpHelp(_ textState: Self) -> String {
      var output: String
      switch textState.storage {
      case let .concatenated(lhs, rhs):
        output = dumpHelp(lhs) + dumpHelp(rhs)
      case let .localized(key, tableName, bundle, comment):
        output = key.formatted(tableName: tableName, bundle: bundle, comment: comment)
      case let .verbatim(string):
        output = string
      }
      func tag(_ name: String, attribute: String? = nil, _ value: String? = nil) {
        output = """
          <\(name)\(attribute.map { " \($0)" } ?? "")\(value.map { "=\($0)" } ?? "")>\
          \(output)\
          </\(name)>
          """
      }
      for modifier in textState.modifiers {
        switch modifier {
        case let .accessibilityHeading(headingLevel):
          tag("accessibility-heading-level", headingLevel.rawValue)
        case let .accessibilityLabel(value):
          tag("accessibility-label", dumpHelp(value))
        case let .accessibilityTextContentType(type):
          tag("accessibility-text-content-type", type.rawValue)
        case let .baselineOffset(baselineOffset):
          tag("baseline-offset", "\(baselineOffset)")
        case .bold(isActive: true), .fontWeight(.some(.bold)):
          output = "**\(output)**"
        case .font(.some):
          break  // TODO: capture Font description using DSL similar to TextState and print here
        case let .fontDesign(.some(design)):
          func describe(design: Font.Design) -> String {
            switch design {
            case .default: return "default"
            case .serif: return "serif"
            case .rounded: return "rounded"
            case .monospaced: return "monospaced"
            @unknown default: return "\(design)"
            }
          }
          tag("font-design", describe(design: design))
        case let .fontWeight(.some(weight)):
          func describe(weight: Font.Weight) -> String {
            switch weight {
            case .black: return "black"
            case .bold: return "bold"
            case .heavy: return "heavy"
            case .light: return "light"
            case .medium: return "medium"
            case .regular: return "regular"
            case .semibold: return "semibold"
            case .thin: return "thin"
            default: return "\(weight)"
            }
          }
          tag("font-weight", describe(weight: weight))
        case let .fontWidth(.some(width)):
          tag("font-width", width.rawValue)
        case let .foregroundColor(.some(color)):
          tag("foreground-color", "\(color)")
        case .italic(isActive: true):
          output = "_\(output)_"
        case let .kerning(kerning):
          tag("kerning", "\(kerning)")
        case let .speechAdjustedPitch(value):
          tag("speech-adjusted-pitch", "\(value)")
        case .speechAlwaysIncludesPunctuation(true):
          tag("speech-always-includes-punctuation")
        case .speechAnnouncementsQueued(true):
          tag("speech-announcements-queued")
        case .speechSpellsOutCharacters(true):
          tag("speech-spells-out-characters")
        case let .strikethrough(isActive: true, pattern: _, color: .some(color)):
          tag("s", attribute: "color", "\(color)")
        case .strikethrough(isActive: true, pattern: _, color: .none):
          output = "~~\(output)~~"
        case let .tracking(tracking):
          tag("tracking", "\(tracking)")
        case let .underline(isActive: true, pattern: _, .some(color)):
          tag("u", attribute: "color", "\(color)")
        case .underline(isActive: true, pattern: _, color: .none):
          tag("u")
        case .bold(isActive: false),
          .font(.none),
          .fontDesign(.none),
          .fontWeight(.none),
          .fontWidth(.none),
          .foregroundColor(.none),
          .italic(isActive: false),
          .monospacedDigit,
          .speechAlwaysIncludesPunctuation(false),
          .speechAnnouncementsQueued(false),
          .speechSpellsOutCharacters(false),
          .strikethrough(isActive: false, pattern: _, color: _),
          .underline(isActive: false, pattern: _, color: _):
          break
        }
      }
      return output
    }

    return dumpHelp(self)
  }
}