wip: Can't seem to get the node modifiers working properly.

Sources/CliDoc2/Modifiers.swift

@@ -0,0 +1,118 @@
+import Rainbow
+
+public protocol NodeModifier {
+  // swiftlint:disable type_name
+  associatedtype _Body: TextNode
+  typealias Body = _Body
+  // swiftlint:enable type_name
+
+  associatedtype Content: TextNode
+
+  @TextBuilder
+  func render(content: Content) -> Body
+}
+
+public extension NodeModifier {
+
+  func concat<T: NodeModifier>(_ modifier: T) -> ConcatModifier<Self, T> {
+    print("Concat: \(type(of: modifier))")
+    return .init(firstModifier: self, secondModifier: modifier)
+  }
+}
+
+public struct ConcatModifier<M0: NodeModifier, M1: NodeModifier>: NodeModifier where M1.Content == M0.Body {
+  let firstModifier: M0
+  let secondModifier: M1
+
+  public func render(content: M0.Content) -> some TextNode {
+    let firstOutput = firstModifier.render(content: content)
+    return secondModifier.render(content: firstOutput)
+  }
+}
+
+public struct ModifiedNode<Content: TextNode, Modifier: NodeModifier> {
+  @usableFromInline
+  let content: Content
+
+  @usableFromInline
+  let modifier: Modifier
+
+  @usableFromInline
+  init(content: Content, modifier: Modifier) {
+    self.content = content
+    self.modifier = modifier
+  }
+}
+
+extension ModifiedNode: TextNode where Modifier.Content == Content {
+  public func render() -> String {
+    modifier.render(content: content).render()
+  }
+
+  @inlinable
+  func apply<M: NodeModifier>(_ modifier: M) -> ModifiedNode<Content, ConcatModifier<Modifier, M>> {
+    print("ModifiedNode modifier called.")
+    return .init(content: content, modifier: self.modifier.concat(modifier))
+  }
+}
+
+public extension TextNode {
+  @inlinable
+  func modifier<M: NodeModifier>(_ modifier: M) -> ModifiedNode<Self, M> {
+    .init(content: self, modifier: modifier)
+  }
+}
+
+@usableFromInline
+struct ColorModifier<Content: TextNode>: NodeModifier {
+  @usableFromInline
+  let color: NamedColor
+
+  @usableFromInline
+  init(color: NamedColor) {
+    self.color = color
+  }
+
+  @usableFromInline
+  func render(content: Content) -> some TextNode {
+    content.render().applyingColor(color)
+  }
+}
+
+public extension TextNode {
+  @inlinable
+  func color(_ color: NamedColor) -> some TextNode {
+    modifier(ColorModifier(color: color))
+  }
+}
+
+@usableFromInline
+struct StyleModifier<Content: TextNode>: NodeModifier {
+
+  @usableFromInline
+  let styles: [Style]
+
+  @usableFromInline
+  init(styles: [Style]) {
+    self.styles = styles
+  }
+
+  @usableFromInline
+  func render(content: Content) -> some TextNode {
+    styles.reduce(content.render()) {
+      $0.applyingStyle($1)
+    }
+  }
+}
+
+public extension TextNode {
+  @inlinable
+  func style(_ styles: Style...) -> some TextNode {
+    modifier(StyleModifier(styles: styles))
+  }
+
+  @inlinable
+  func style(_ styles: [Style]) -> some TextNode {
+    modifier(StyleModifier(styles: styles))
+  }
+}