Scroll SingleChoicePrompt when larger than terminal height

Sources/Noora/Components/SingleChoicePrompt.swift

@@ -77,27 +77,69 @@ struct SingleChoicePrompt {
     private func renderOptions<T: Equatable>(selectedOption: (T, String), options: [(T, String)]) {
         let titleOffset = title != nil ? "  " : ""
 
-        let questions = options.map { option in
-            if option == selectedOption {
-                return "\(titleOffset)  \("❯".hex(theme.primary)) \(option.1)"
-            } else {
-                return "\(titleOffset)    \(option.1)"
-            }
-        }.joined(separator: "\n")
+        // Header
 
-        var content = ""
+        var header = ""
         if let title {
-            content = "◉ \(title.formatted(theme: theme, terminal: terminal))".hexIfColoredTerminal(theme.primary, terminal)
+            header = "◉ \(title.formatted(theme: theme, terminal: terminal))".hexIfColoredTerminal(theme.primary, terminal)
                 .boldIfColoredTerminal(terminal)
         }
 
-        content += "\(title != nil ? "\n" : "")\(titleOffset)\(question.formatted(theme: theme, terminal: terminal))"
+        header += "\(title != nil ? "\n" : "")\(titleOffset)\(question.formatted(theme: theme, terminal: terminal))"
         if let description {
-            content +=
+            header +=
                 "\n\(titleOffset)\(description.formatted(theme: theme, terminal: terminal).hexIfColoredTerminal(theme.muted, terminal))"
         }
-        content += "\n\(questions)"
-        content += "\n\(titleOffset)\("↑/↓/k/j up/down • enter confirm".hexIfColoredTerminal(theme.muted, terminal))"
+
+        // Footer
+
+        let footer = "\n\(titleOffset)\("↑/↓/k/j up/down • enter confirm".hexIfColoredTerminal(theme.muted, terminal))"
+
+        func numberOfLines(for text: String) -> Int {
+            guard let terminalWidth = terminal.size?.columns else { return 1 }
+            let lines = text.raw.split(separator: "\n")
+            return lines.reduce(0) { sum, line in
+                let lineCount = (line.count + terminalWidth - 1) / terminalWidth
+                return sum + lineCount
+            }
+        }
+
+        let headerLines = numberOfLines(for: header)
+        let footerLines = numberOfLines(for: footer) + 1 /// `Renderer.render` adds a newline at the end
+
+        let maxVisibleOptions = if let terminalSize = terminal.size {
+            max(1, terminalSize.rows - headerLines - footerLines)
+        } else {
+            options.count
+        }
+
+        let currentIndex = options.firstIndex(where: { $0 == selectedOption })!
+        let middleIndex = maxVisibleOptions / 2
+
+        var startIndex = max(0, currentIndex - middleIndex)
+        if startIndex + maxVisibleOptions > options.count {
+            startIndex = max(0, options.count - maxVisibleOptions)
+        }
+
+        let endIndex = min(options.count, startIndex + maxVisibleOptions)
+
+        // Questions
+
+        var visibleOptions = [String]()
+        for (index, option) in options.enumerated() {
+            if (startIndex ..< endIndex) ~= index {
+                if option == selectedOption {
+                    visibleOptions.append("\(titleOffset)  \("❯".hex(theme.primary)) \(option.1)")
+                } else {
+                    visibleOptions.append("\(titleOffset)    \(option.1)")
+                }
+            }
+        }
+        let questions = visibleOptions.joined(separator: "\n")
+
+        // Render
+
+        let content = "\(header)\n\(questions)\(footer)"
         renderer.render(content, standardPipeline: standardPipelines.output)
     }
 }

Sources/Noora/Utilities/Terminal.swift

@@ -9,6 +9,7 @@ import Foundation
 public protocol Terminaling {
     var isInteractive: Bool { get }
     var isColored: Bool { get }
+    var size: (rows: Int, columns: Int)? { get }
     func withoutCursor(_ body: () throws -> Void) rethrows
     func inRawMode(_ body: @escaping () throws -> Void) rethrows
     func readCharacter() -> Character?
@@ -18,6 +19,8 @@ public struct Terminal: Terminaling {
     public let isInteractive: Bool
     public let isColored: Bool
 
+    public var size: (rows: Int, columns: Int)? { Terminal.size() }
+
     public init(isInteractive: Bool = Terminal.isInteractive(), isColored: Bool = Terminal.isColored()) {
         self.isInteractive = isInteractive
         self.isColored = isColored
@@ -105,4 +108,14 @@ public struct Terminal: Terminaling {
             return true
         }
     }
+
+    /// Returns the size of the terminal.
+    public static func size() -> (rows: Int, columns: Int)? {
+        var w = winsize()
+        if ioctl(STDOUT_FILENO, TIOCGWINSZ, &w) == 0 {
+            return (Int(w.ws_row), Int(w.ws_col))
+        } else {
+            return nil
+        }
+    }
 }

Tests/NooraTests/Components/SingleChoicePromptTests.swift

@@ -14,7 +14,7 @@ struct SingleChoicePromptTests {
     }
 
     let renderer = MockRenderer()
-    let terminal = MockTerminal()
+    let terminal = MockTerminal(size: (rows: 10, columns: 80))
     let keyStrokeListener = MockKeyStrokeListener()
 
     @Test func renders_the_right_content() throws {
@@ -118,4 +118,47 @@ struct SingleChoicePromptTests {
         ✔︎ How would you like to integrate Tuist?: option1 
         """)
     }
+
+    @Test func renders_the_right_content_when_more_options_than_terminal_height() throws {
+        // Given
+        let subject = SingleChoicePrompt(
+            title: nil,
+            question: "How would you like to integrate Tuist?",
+            description: nil,
+            theme: Theme.test(),
+            terminal: terminal,
+            collapseOnSelection: true,
+            renderer: renderer,
+            standardPipelines: StandardPipelines(),
+            keyStrokeListener: keyStrokeListener
+        )
+        keyStrokeListener.keyPressStub = .init(repeating: .downArrowKey, count: 10)
+
+        // When
+        _ = subject.run(options: (1 ... 20).map { "Option \($0)" })
+
+        // Then
+        #expect(renderer.renders[0] == """
+        How would you like to integrate Tuist?
+          ❯ Option 1
+            Option 2
+            Option 3
+            Option 4
+            Option 5
+            Option 6
+            Option 7
+        ↑/↓/k/j up/down • enter confirm
+        """)
+        #expect(renderer.renders[renderer.renders.count - 2] == """
+        How would you like to integrate Tuist?
+            Option 8
+            Option 9
+            Option 10
+          ❯ Option 11
+            Option 12
+            Option 13
+            Option 14
+        ↑/↓/k/j up/down • enter confirm
+        """)
+    }
 }

Tests/NooraTests/Mocks/MockTerminal.swift

@@ -3,13 +3,16 @@ import Noora
 class MockTerminal: Terminaling {
     var isInteractive: Bool = true
     var isColored: Bool = true
+    var size: (rows: Int, columns: Int)? = nil
 
     init(
         isInteractive: Bool = true,
-        isColored: Bool = true
+        isColored: Bool = true,
+        size: (rows: Int, columns: Int)? = nil
     ) {
         self.isInteractive = isInteractive
         self.isColored = isColored
+        self.size = size
     }
 
     func inRawMode(_ body: @escaping () throws -> Void) rethrows {