Add SExpPrinter (#145)

Sources/OpenSwiftUICore/Util/SExpPrinter.swift

@@ -0,0 +1,67 @@
+//
+//  SExpPrinter.swift
+//  OpenSwiftUICore
+//
+//  Audited for RELEASE_2024
+//  Status: Complete
+
+package struct SExpPrinter {
+    var output: String
+    var depth: Int
+    package internal(set) var indent: String
+
+    package init(tag: String, singleLine: Bool = false) {
+        output = "(\(tag)"
+        depth = singleLine ? 0 : 1
+        indent = singleLine ? "" : "  "
+    }
+
+    package mutating func end() -> String {
+        if depth == 0 {
+            output.append(")")
+            return output
+        } else {
+            depth -= 1
+            indent.removeLast(2)
+            output.append(")")
+            return output
+        }
+    }
+
+    package mutating func print(_ string: String, newline: Bool = true) {
+        if newline, depth != 0 {
+            output.append("\n\(indent)")
+        } else {
+            output.append(" ")
+        }
+        output.append(string)
+    }
+
+    package mutating func newline() {
+        guard depth != 0 else {
+            return
+        }
+        output.append("\n")
+        output.append(indent)
+    }
+
+    package mutating func push(_ tag: String) {
+        if depth == 0 {
+            output.append("(\(tag)")
+        } else {
+            output.append("\n\(indent)(\(tag)")
+            depth += 1
+            indent.append("  ")
+        }
+    }
+
+    package mutating func pop() {
+        if depth == 0 {
+            output.append(")")
+        }  else {
+            depth -= 1
+            indent.removeLast(2)
+            output.append(")")
+        }
+    }
+}

Tests/OpenSwiftUICoreTests/Util/SExpPrinterTests.swift

@@ -0,0 +1,135 @@
+//
+//  SExpPrinterTests.swift
+//  OpenSwiftUICoreTests
+
+import OpenSwiftUICore
+import OpenGraphShims
+import Testing
+
+struct SExpPrinterTests {
+    @Test
+    func singleLine() {
+        var printer = SExpPrinter(tag: "(test", singleLine: true)
+        printer.push("A")
+        printer.push("B")
+        printer.pop()
+        printer.pop()
+        let end = printer.end()
+        #expect(end == "((test(A(B)))")
+    }
+
+    @Test
+    func multiLine() {
+        var printer = SExpPrinter(tag: "(test", singleLine: false)
+        printer.push("A")
+        printer.push("B")
+        printer.pop()
+        printer.pop()
+        let end = printer.end()
+        #expect(end == """
+        ((test
+          (A
+            (B)))
+        """)
+    }
+
+    @Test
+    func newline() {
+        var printer = SExpPrinter(tag: "(test", singleLine: false)
+        printer.push("A")
+        printer.newline()
+        printer.push("B")
+        printer.newline()
+        printer.pop()
+        printer.pop()
+        let end = printer.end()
+        #expect(end == """
+        ((test
+          (A
+            
+            (B
+              )))
+        """)
+        printer.newline()
+        let newEnd = printer.end()
+        #expect(newEnd == """
+        ((test
+          (A
+            
+            (B
+              ))))
+        """)
+    }
+
+    @Test
+    func printString() {
+        do {
+            var printer = SExpPrinter(tag: "(test", singleLine: false)
+            printer.push("A")
+            printer.print("B")
+            printer.print("C")
+            printer.pop()
+            let end = printer.end()
+            #expect(end == """
+            ((test
+              (A
+                B
+                C))
+            """)
+        }
+        do {
+            var printer = SExpPrinter(tag: "(test", singleLine: false)
+            printer.push("A")
+            printer.print("B")
+            printer.pop()
+            _ = printer.end()
+            printer.print("C")
+            let end = printer.end()
+            #expect(end == """
+            ((test
+              (A
+                B)) C)
+            """)
+        }
+        do {
+            var printer = SExpPrinter(tag: "(test", singleLine: true)
+            printer.push("A")
+            printer.print("B")
+            printer.print("C")
+            printer.pop()
+            let end = printer.end()
+            #expect(end == """
+            ((test(A B C))
+            """)
+        }
+        do {
+            var printer = SExpPrinter(tag: "(test", singleLine: true)
+            printer.push("A")
+            printer.print("B")
+            printer.pop()
+            printer.print("C")
+            let end = printer.end()
+            #expect(end == """
+            ((test(A B) C)
+            """)
+        }
+    }
+
+    @Test
+    func pushPop() {
+        var printer = SExpPrinter(tag: "(test", singleLine: false)
+        printer.push("A")
+        printer.push("B")
+        printer.pop()
+        printer.push("C")
+        printer.pop()
+        printer.pop()
+        let end = printer.end()
+        #expect(end == """
+        ((test
+          (A
+            (B)
+            (C)))
+        """)
+    }
+}