import AppKit

final class DocumentNode: NSObject, SourceListItem, Identifiable {
	let id: UUID
	
	@objc dynamic var title: String
	@objc dynamic var displaysSectionHeading: Bool
	@objc dynamic var content: String
	@objc dynamic var children: [Any]
	
	required init(id: UUID, title: String = "", displaysSectionHeading: Bool = false, content: String = "", children: [DocumentNode] = []) {
		self.id = id
		self.title = title
		self.displaysSectionHeading = displaysSectionHeading
		self.content = content
		self.children = children
	}

	convenience init(id: UUID) {
		self.init(id: id, title: "", children: [])
	}

	@objc dynamic var leaf: Bool { children.isEmpty }
	@objc class func keyPathsForValuesAffectingLeaf() -> Set<String> {
		[#keyPath(children)]
	}

	@objc dynamic var isGroupItem: Bool { false }
	
	@objc dynamic var asDocumentNode: Self? { self }

	@objc dynamic var imageValue: NSImage! {
		let systemSymbolName = leaf ? "text.page" : "text.book.closed"
		let configuration = NSImage.SymbolConfiguration(pointSize: NSFont.systemFontSize, weight: .regular)
		return NSImage(systemSymbolName: systemSymbolName, accessibilityDescription: nil)?.withSymbolConfiguration(configuration)
	}

	@objc class func keyPathsForValuesAffectingImageValue() -> Set<String> {
		return [#keyPath(leaf)]
	}

	func update(from string: NSString, blockRanges: [UUID: NSRange]) {
		if let currentBlockRange = blockRanges[id] {
			content = ""

			let displaysSectionHeading = displaysSectionHeading
			var titleOffset = 0
			
			if displaysSectionHeading {
				string.enumerateSubstrings(in: currentBlockRange, options: .byParagraphs) { substring, substringRange, enclosingRange, shouldStop in
					titleOffset = enclosingRange.length
					self.title = substring ?? ""
					shouldStop.pointee = true
				}
			}
			
			var contentRange = currentBlockRange
			contentRange.location += titleOffset
			contentRange.length -= titleOffset
			
			content = string.substring(with: contentRange)
		}

		for index in children.indices {
			guard let documentNode = children[index] as? DocumentNode else { continue }
			documentNode.update(from: string, blockRanges: blockRanges)
		}
	}

	func update(from attributedString: NSAttributedString, firstBlockID: UUID) {
		let string = NSString(string: attributedString.string)
		let blockRanges = attributedString.blockRanges(firstBlockID: firstBlockID)
		update(from: string, blockRanges: blockRanges)
	}
}

struct DocumentNodeAccumulator {
	 var seen: Set<UUID> = []
	 var items: [DocumentNode] = []

	 mutating func visit(_ item: DocumentNode) {
		 guard !seen.contains(item.id) else { return }
		 seen.insert(item.id)
		 items.append(item)

		 for child in item.children {
			 guard let child = child as? DocumentNode else { continue }
			 visit(child)
		 }
	 }
 }