BrewBar/BrewBar/LogWindowController.swift

import Cocoa

class LogWindowController: NSWindowController {
    var textView: NSTextView!

    convenience init() {
        let contentRect = NSRect(x: 0, y: 0, width: 600, height: 400)
        let styleMask: NSWindow.StyleMask = [.titled, .closable, .resizable]

        let window = NSWindow(contentRect: contentRect,
                              styleMask: styleMask,
                              backing: .buffered,
                              defer: false)

        self.init(window: window)

        window.title = "BrewBar Logs"
        // the controller keeps the window alive; without this, closing the
        // window would deallocate it and reopening would crash
        window.isReleasedWhenClosed = false
        window.center()

        let scrollView = NSScrollView(frame: window.contentView!.bounds)
        scrollView.autoresizingMask = [.width, .height]
        scrollView.hasVerticalScroller = true

        textView = NSTextView(frame: scrollView.bounds)
        textView.isEditable = false
        textView.autoresizingMask = [.width, .height]
        textView.font = .monospacedSystemFont(ofSize: 12, weight: .regular)
        textView.textColor = .textColor // adapts to light/dark mode
        textView.backgroundColor = .textBackgroundColor
        textView.textContainerInset = NSSize(width: 8, height: 8)

        scrollView.documentView = textView
        window.contentView?.addSubview(scrollView)
    }

    func update(text: String) {
        // only follow the tail if the user is already at the bottom — don't
        // yank the scroll position away while they are reading older output
        let wasAtBottom: Bool = if let scrollView = textView.enclosingScrollView {
            scrollView.contentView.bounds.maxY >= textView.frame.height - 30
        } else {
            true
        }

        textView.string = text

        if wasAtBottom {
            textView.scrollToEndOfDocument(nil)
        }
    }
}