import Highlightr
import OrgSwiftUI
import SwiftUI
import UIKit

/// Highlights `#+begin_src` blocks in org content, bridging Highlightr to `OrgCodeStyler`.
///
/// Highlightr already returns an `NSAttributedString`, so this walks its color runs straight
/// into an `AttributedString`. Colors are baked in, so a new instance is made per theme.
@MainActor
final class OrgSyntaxStyler: OrgCodeStyler {
    private let highlightr: Highlightr?
    private let supported: Set<String>

    init(colorScheme: ColorScheme) {
        let engine = Highlightr()
        engine?.setTheme(to: colorScheme == .dark ? "atom-one-dark" : "xcode")
        highlightr = engine
        supported = Set(engine?.supportedLanguages() ?? [])
    }

    func highlighted(code: String, language: String?) -> AttributedString? {
        guard let highlightr, let language = resolvedLanguage(language) else { return nil }
        highlightr.theme.setCodeFont(.monospacedSystemFont(ofSize: 13, weight: .regular))
        guard let attributed = highlightr.highlight(code, as: language, fastRender: true) else {
            return nil
        }
        return Self.attributedString(from: attributed)
    }

    private func resolvedLanguage(_ raw: String?) -> String? {
        guard let trimmed = raw?.trimmingCharacters(in: .whitespacesAndNewlines).lowercased(),
              !trimmed.isEmpty else { return nil }
        let mapped = Self.aliases[trimmed] ?? trimmed
        return supported.contains(mapped) ? mapped : nil
    }

    private static let aliases: [String: String] = [
        "js": "javascript", "jsx": "javascript", "ts": "typescript", "tsx": "typescript",
        "py": "python", "rb": "ruby", "rs": "rust", "sh": "bash", "shell": "bash", "zsh": "bash",
        "yml": "yaml", "c++": "cpp", "cc": "cpp", "kt": "kotlin", "cs": "csharp",
        "objc": "objectivec", "objective-c": "objectivec", "html": "xml", "htm": "xml",
    ]

    /// Carry Highlightr's colors across, in a monospaced font at the block's own size.
    private static func attributedString(from attributed: NSAttributedString) -> AttributedString {
        var result = AttributedString()
        let range = NSRange(location: 0, length: attributed.length)
        attributed.enumerateAttribute(.foregroundColor, in: range) { value, subrange, _ in
            var fragment = AttributedString((attributed.string as NSString).substring(with: subrange))
            fragment.font = .system(.footnote, design: .monospaced)
            if let color = value as? UIColor {
                fragment.foregroundColor = Color(uiColor: color)
            }
            result += fragment
        }
        return result
    }
}