import Foundation

/// Reconcile against optimistic native storage, not the last published snapshot.
/// Equal visible text can still carry a new CRDT node mapping after publication.
@MainActor enum DocumentRenderReconciliation {
    static func apply(_ content: NSAttributedString, to storage: NSMutableAttributedString) {
        guard !storage.isEqual(to: content) else { return }
        storage.beginEditing()
        defer { storage.endEditing() }
        if let (range, replacement) = DocumentComposition.replacement(before: storage.string, after: content.string) {
            storage.replaceCharacters(in: range, with: replacement)
        }
        content.enumerateAttributes(in: NSRange(location: 0, length: content.length)) { attributes, range, _ in
            var changed = false
            storage.enumerateAttributes(in: range) { current, _, stop in
                if !NSDictionary(dictionary: current).isEqual(to: attributes) { changed = true; stop.pointee = true }
            }
            if changed { storage.setAttributes(attributes, range: range) }
        }
    }
}