#if os(macOS)
import AppKit

extension NSAttributedString.Key {
    static let docsBaseFont = NSAttributedString.Key("OficinaDocsBaseFont")
    static let docsLeading = NSAttributedString.Key("OficinaDocsLeading")
}

/// CSS line boxes include the paragraph's font strut and each inline run's
/// half-leading. TextKit's single paragraph multiplier cannot express that when
/// a line mixes font families or sizes.
@MainActor final class DocsLayoutManager: NSLayoutManager, @preconcurrency NSLayoutManagerDelegate {
    private(set) var storageRevision: UInt64 = 0
    override func processEditing(for textStorage: NSTextStorage, edited editMask: NSTextStorageEditActions,
                                 range newCharRange: NSRange, changeInLength delta: Int, invalidatedRange invalidatedCharRange: NSRange) {
        super.processEditing(for: textStorage, edited: editMask, range: newCharRange,
                             changeInLength: delta, invalidatedRange: invalidatedCharRange)
        storageRevision &+= 1
        for container in textContainers {
            (container.textView as? DocsPagedTextView)?.invalidatePagination()
        }
    }
    override init() { super.init(); usesFontLeading = false; delegate = self }
    required init?(coder: NSCoder) { fatalError("init(coder:) is unavailable") }
    override func drawBackground(forGlyphRange glyphsToShow: NSRange, at origin: NSPoint) {
        super.drawBackground(forGlyphRange: glyphsToShow, at: origin)
        guard let storage = textStorage, let container = textContainers.first as? DocsPageTextContainer else { return }
        let characters = characterRange(forGlyphRange: glyphsToShow, actualGlyphRange: nil)
        storage.enumerateAttribute(.docsQuoteBorders, in: characters) { value, range, _ in
            guard let borders = value as? [CGFloat] else { return }
            let glyphs = self.glyphRange(forCharacterRange: range, actualCharacterRange: nil)
            var bounds = self.boundingRect(forGlyphRange: glyphs, in: container)
            bounds.origin.y += origin.y
            NSColor(white: 200.0 / 255, alpha: 1).setFill()
            for inset in borders {
                CGRect(x: origin.x + container.geometry.textX + inset, y: bounds.minY, width: 2.25, height: bounds.height).fill()
            }
        }
    }
    func layoutManager(_ layoutManager: NSLayoutManager, shouldSetLineFragmentRect lineFragmentRect: UnsafeMutablePointer<NSRect>,
                       lineFragmentUsedRect: UnsafeMutablePointer<NSRect>, baselineOffset: UnsafeMutablePointer<CGFloat>,
                       in textContainer: NSTextContainer, forGlyphRange glyphRange: NSRange) -> Bool {
        guard let storage = textStorage, glyphRange.length > 0 else { return false }
        let range = characterRange(forGlyphRange: glyphRange, actualGlyphRange: nil)
        guard range.location < storage.length,
              let base = storage.attribute(.docsBaseFont, at: range.location, effectiveRange: nil) as? NSFont,
              let leading = storage.attribute(.docsLeading, at: range.location, effectiveRange: nil) as? CGFloat else { return false }
        var above: CGFloat = 0, below: CGFloat = 0
        func include(_ font: NSFont) {
            let halfLeading = (font.pointSize * leading - font.ascender + font.descender) / 2
            above = max(above, font.ascender + halfLeading)
            below = max(below, -font.descender + halfLeading)
        }
        include(base)
        var attachment = false
        storage.enumerateAttributes(in: range) { attributes, _, _ in
            if let font = attributes[.font] as? NSFont { include(font) }
            if attributes[.attachment] != nil { attachment = true }
        }
        guard !attachment else { return false }
        let end = NSMaxRange(range)
        let endsParagraph = end > 0 && (storage.string as NSString).character(at: end - 1) == 10
        let style = storage.attribute(.paragraphStyle, at: range.location, effectiveRange: nil) as? NSParagraphStyle
        lineFragmentRect.pointee.size.height = above + below + (endsParagraph ? style?.paragraphSpacing ?? 0 : 0)
        lineFragmentUsedRect.pointee.size.height = above + below
        baselineOffset.pointee = above
        return true
    }
}
#endif