Refactor model

Sources/SwiftUIMath/Internal/Model/Atoms/Fraction.swift

@@ -0,0 +1,71 @@
+import Foundation
+
+extension Math {
+  final class Fraction: Atom {
+    var hasRule: Bool
+    var leftDelimiter: String
+    var rightDelimiter: String
+    var numerator: AtomList?
+    var denominator: AtomList?
+
+    var isContinuedFraction: Bool = false
+    var alignment: String  // "l", "r", "c" for left, right, center
+
+    override var description: String {
+      [
+        hasRule ? "\\frac" : "\\atop",
+        leftDelimiter.isEmpty ? nil : "[\(leftDelimiter)]",
+        rightDelimiter.isEmpty ? nil : "[\(rightDelimiter)]",
+        "{\(numerator?.description ?? "placeholder")}",
+        "{\(denominator?.description ?? "placeholder")}",
+        superscript.map { "^{\($0)}" },
+        `subscript`.map { "_{\($0)}" },
+      ]
+      .compactMap(\.self)
+      .joined()
+    }
+
+    override var finalized: Math.Atom {
+      let finalized = super.finalized
+
+      if let fraction = finalized as? Fraction {
+        fraction.numerator = fraction.numerator?.finalized
+        fraction.denominator = fraction.denominator?.finalized
+      }
+
+      return finalized
+    }
+
+    init(_ fraction: Fraction) {
+      self.hasRule = fraction.hasRule
+      self.leftDelimiter = fraction.leftDelimiter
+      self.rightDelimiter = fraction.rightDelimiter
+      self.numerator = fraction.numerator.map { AtomList($0) }
+      self.denominator = fraction.denominator.map { AtomList($0) }
+      self.isContinuedFraction = fraction.isContinuedFraction
+      self.alignment = fraction.alignment
+
+      super.init(fraction)
+    }
+
+    init(
+      hasRule: Bool = true,
+      leftDelimiter: String = "",
+      rightDelimiter: String = "",
+      numerator: AtomList? = nil,
+      denominator: AtomList? = nil,
+      isContinuedFraction: Bool = false,
+      alignment: String = "c"
+    ) {
+      self.hasRule = hasRule
+      self.leftDelimiter = leftDelimiter
+      self.rightDelimiter = rightDelimiter
+      self.numerator = numerator
+      self.denominator = denominator
+      self.isContinuedFraction = isContinuedFraction
+      self.alignment = alignment
+
+      super.init(type: .fraction)
+    }
+  }
+}