import Foundation
#if os(macOS)
import AppKit
#else
import UIKit
#endif

extension NSAttributedString.Key { static let docsCodeStart = NSAttributedString.Key("OficinaDocsCodeStart") }

/// Inline decoration uses glyph advances, never extra characters: CRDT and
/// clipboard offsets continue to refer to the authored text.
@MainActor enum DocumentInlineCode {
    static func apply(to output: NSMutableAttributedString) {
        var spans: [NSRange] = []
        output.enumerateAttribute(.docsMarks, in: NSRange(location: 0, length: output.length)) { value, range, _ in
            guard let data = value as? Data,
                  let marks = try? JSONDecoder().decode([String: JSONValue].self, from: data), marks["code"] != nil else { return }
            if let last = spans.last, NSMaxRange(last) == range.location { spans[spans.count - 1] = NSUnionRange(last, range) }
            else { spans.append(range) }
        }
        for range in spans where range.length > 0 {
            guard let font = output.attribute(.font, at: range.location, effectiveRange: nil) as? DocsPlatformFont else { continue }
            let padding = font.pointSize * 0.35
            let paragraph = (output.string as NSString).paragraphRange(for: NSRange(location: range.location, length: 0))
            output.addAttribute(.docsCodeStart, value: padding,
                                range: (output.string as NSString).rangeOfComposedCharacterSequence(at: range.location))
            if paragraph.location != range.location && range.location > 0 {
                output.addAttribute(.kern, value: padding, range: (output.string as NSString).rangeOfComposedCharacterSequence(at: range.location - 1))
            }
            output.addAttribute(.kern, value: padding, range: (output.string as NSString).rangeOfComposedCharacterSequence(at: NSMaxRange(range) - 1))
            #if os(macOS)
            output.addAttribute(.backgroundColor, value: NSColor(white: 240.0 / 255, alpha: 1), range: range)
            #else
            output.addAttribute(.backgroundColor, value: UIColor(white: 240.0 / 255, alpha: 1), range: range)
            #endif
        }
    }
}