app_for_reddit/App AI for Reddit/Views/Components/ThinCaretTextEditor.swift

import AppKit
import SwiftUI

private final class TextEditorScrollView: NSScrollView {
    override func layout() {
        super.layout()
        syncTextContainerWidth()
    }

    override func resizeSubviews(withOldSize oldSize: NSSize) {
        super.resizeSubviews(withOldSize: oldSize)
        syncTextContainerWidth()
    }

    fileprivate func syncTextContainerWidthIfNeeded() {
        syncTextContainerWidth()
    }

    private func syncTextContainerWidth() {
        guard let textView = documentView as? NSTextView,
              let container = textView.textContainer,
              let layoutManager = textView.layoutManager else { return }

        let width = contentView.bounds.width
        guard width > 1 else { return }

        textView.minSize = NSSize(width: width, height: 0)
        textView.maxSize = NSSize(width: width, height: .greatestFiniteMagnitude)
        container.lineBreakMode = .byWordWrapping

        if abs(textView.frame.width - width) > 0.5 {
            textView.setFrameSize(NSSize(width: width, height: textView.frame.height))
        }

        layoutManager.ensureLayout(for: container)

        let usedHeight = layoutManager.usedRect(for: container).height
        let insetHeight = textView.textContainerInset.height * 2
        let newHeight = max(usedHeight + insetHeight, contentView.bounds.height)

        if abs(textView.frame.height - newHeight) > 0.5 {
            textView.setFrameSize(NSSize(width: width, height: newHeight))
        }
    }
}

private final class ThinCaretTextView: NSTextView {
    private let caretWidth: CGFloat = 1

    var placeholder: String = "" {
        didSet {
            guard placeholder != oldValue else { return }
            needsDisplay = true
        }
    }

    var placeholderColor: NSColor = .placeholderTextColor

    override func viewDidMoveToWindow() {
        super.viewDidMoveToWindow()
        _ = layoutManager
        hideSystemInsertionIndicator()
    }

    override func becomeFirstResponder() -> Bool {
        let becameFirstResponder = super.becomeFirstResponder()
        hideSystemInsertionIndicator()
        return becameFirstResponder
    }

    override func layout() {
        super.layout()
        hideSystemInsertionIndicator()
    }

    override func drawInsertionPoint(in rect: NSRect, color: NSColor, turnedOn flag: Bool) {
        var caretRect = rect
        caretRect.size.width = caretWidth
        super.drawInsertionPoint(in: caretRect, color: color, turnedOn: flag)
    }

    override func setNeedsDisplay(_ rect: NSRect, avoidAdditionalLayout flag: Bool) {
        var invalidRect = rect
        invalidRect.size.width += caretWidth - 1
        super.setNeedsDisplay(invalidRect, avoidAdditionalLayout: flag)
    }

    override func draw(_ dirtyRect: NSRect) {
        drawPlaceholderIfNeeded()
        super.draw(dirtyRect)
    }

    override func didChangeText() {
        super.didChangeText()
        needsDisplay = true
    }

    private func hideSystemInsertionIndicator() {
        hideInsertionIndicators(in: self)
    }

    private func hideInsertionIndicators(in view: NSView) {
        for subview in view.subviews {
            if #available(macOS 14.0, *),
               let indicator = subview as? NSTextInsertionIndicator {
                indicator.displayMode = .hidden
            }
            hideInsertionIndicators(in: subview)
        }
    }

    private func drawPlaceholderIfNeeded() {
        guard string.isEmpty, !placeholder.isEmpty else { return }

        let font = font ?? NSFont.systemFont(ofSize: AppTheme.formFieldFontSize)
        let paragraphStyle = NSMutableParagraphStyle()
        paragraphStyle.lineBreakMode = .byWordWrapping

        let attributes: [NSAttributedString.Key: Any] = [
            .font: font,
            .foregroundColor: placeholderColor,
            .paragraphStyle: paragraphStyle
        ]

        let horizontalInset = textContainerInset.width + (textContainer?.lineFragmentPadding ?? 0)
        let verticalInset = textContainerInset.height
        let drawRect = NSRect(
            x: horizontalInset,
            y: verticalInset,
            width: bounds.width - horizontalInset - textContainerInset.width,
            height: bounds.height - verticalInset - textContainerInset.height
        )

        placeholder.draw(
            with: drawRect,
            options: [.usesLineFragmentOrigin, .usesFontLeading],
            attributes: attributes
        )
    }
}

struct ThinCaretTextEditor: NSViewRepresentable {
    @Binding var text: String
    var placeholder: String = ""
    var fontSize: CGFloat = AppTheme.formFieldFontSize
    var isEditable: Bool = true

    func makeCoordinator() -> Coordinator {
        Coordinator(parent: self)
    }

    func makeNSView(context: Context) -> NSScrollView {
        let scrollView = TextEditorScrollView()
        scrollView.hasVerticalScroller = true
        scrollView.hasHorizontalScroller = false
        scrollView.autohidesScrollers = true
        scrollView.borderType = .noBorder
        scrollView.drawsBackground = false
        scrollView.focusRingType = .none

        let textView = ThinCaretTextView()
        textView.isEditable = isEditable
        textView.isSelectable = true
        textView.isRichText = false
        textView.allowsUndo = true
        textView.drawsBackground = false
        textView.backgroundColor = .clear
        textView.focusRingType = .none
        textView.isVerticallyResizable = true
        textView.isHorizontallyResizable = false
        textView.autoresizingMask = [.width]
        textView.textContainer?.lineFragmentPadding = 0
        textView.textContainer?.lineBreakMode = .byWordWrapping
        textView.textContainer?.widthTracksTextView = true
        textView.textContainer?.containerSize = NSSize(
            width: 0,
            height: CGFloat.greatestFiniteMagnitude
        )
        textView.textContainerInset = NSSize(
            width: AppTheme.textEditorHorizontalInset,
            height: AppTheme.textEditorVerticalInset
        )
        textView.isAutomaticQuoteSubstitutionEnabled = false
        textView.isAutomaticDashSubstitutionEnabled = false
        textView.isAutomaticTextReplacementEnabled = false
        textView.font = NSFont.systemFont(ofSize: fontSize)
        textView.textColor = NSColor(AppTheme.textPrimary)
        textView.insertionPointColor = NSColor(AppTheme.textPrimary)
        textView.placeholder = placeholder
        textView.placeholderColor = NSColor(AppTheme.textTertiary.opacity(0.7))
        textView.delegate = context.coordinator
        textView.string = text

        scrollView.documentView = textView
        context.coordinator.textView = textView
        return scrollView
    }

    func updateNSView(_ scrollView: NSScrollView, context: Context) {
        guard let textView = scrollView.documentView as? ThinCaretTextView else { return }

        textView.isEditable = isEditable
        textView.placeholder = placeholder
        textView.placeholderColor = NSColor(AppTheme.textTertiary.opacity(0.7))
        textView.textContainerInset = NSSize(
            width: AppTheme.textEditorHorizontalInset,
            height: AppTheme.textEditorVerticalInset
        )

        if textView.string != text {
            textView.string = text
            textView.needsDisplay = true
        }

        textView.textColor = NSColor(AppTheme.textPrimary)
        textView.insertionPointColor = NSColor(AppTheme.textPrimary)
        textView.font = NSFont.systemFont(ofSize: fontSize)

        if let scrollView = scrollView as? TextEditorScrollView {
            scrollView.syncTextContainerWidthIfNeeded()
        }
    }

    final class Coordinator: NSObject, NSTextViewDelegate {
        var parent: ThinCaretTextEditor
        weak var textView: NSTextView?

        init(parent: ThinCaretTextEditor) {
            self.parent = parent
        }

        func textDidChange(_ notification: Notification) {
            guard let textView = notification.object as? NSTextView else { return }
            parent.text = textView.string
            textView.needsDisplay = true

            if let scrollView = textView.enclosingScrollView as? TextEditorScrollView {
                scrollView.syncTextContainerWidthIfNeeded()
            }
        }
    }
}