import Foundation
import Highlightr
import SwiftUI
import UIKit

/// Adapted from hutch: Highlightr wraps a JavaScriptCore context and is
/// not thread-safe, so an instance stays where it was made. A `nil` result
/// means "show plain text", never an error.
nonisolated final class SyntaxHighlighter {

    private let highlightr: Highlightr?
    private let supported: Set<String>

    init(colorScheme: ColorScheme) {
        let engine = Highlightr()
        // Xcode-like in light, muted in dark, so code reads as native.
        engine?.setTheme(to: colorScheme == .dark ? "atom-one-dark" : "xcode")
        highlightr = engine
        supported = Set(engine?.supportedLanguages() ?? [])
    }

    func highlight(_ code: String, fileName: String, font: UIFont) -> NSAttributedString? {
        guard let highlightr, let language = Self.language(for: fileName),
              supported.contains(language) else {
            return nil
        }
        highlightr.theme.setCodeFont(font)
        return highlightr.highlight(code, as: language, fastRender: true)
    }

    /// File extension → highlight.js language name. Unknown is fine; the
    /// caller falls back to plain text.
    static func language(for fileName: String) -> String? {
        let name = fileName.lowercased()
        if name == "makefile" { return "makefile" }
        if name == "dockerfile" { return "dockerfile" }
        guard let ext = name.split(separator: ".").last, ext != name else { return nil }
        switch ext {
        case "swift": return "swift"
        case "go": return "go"
        case "rs": return "rust"
        case "py": return "python"
        case "rb": return "ruby"
        case "js", "mjs", "cjs": return "javascript"
        case "ts", "tsx": return "typescript"
        case "jsx": return "javascript"
        case "c", "h": return "c"
        case "cc", "cpp", "cxx", "hpp": return "cpp"
        case "m": return "objectivec"
        case "cs": return "csharp"
        case "java": return "java"
        case "kt", "kts": return "kotlin"
        case "sh", "bash", "zsh": return "bash"
        case "fish": return "shell"
        case "php": return "php"
        case "pl": return "perl"
        case "lua": return "lua"
        case "html", "htm": return "xml"
        case "xml", "plist", "storyboard", "xib": return "xml"
        case "css": return "css"
        case "scss", "sass": return "scss"
        case "json": return "json"
        case "yml", "yaml": return "yaml"
        case "toml", "ini", "cfg": return "ini"
        case "md", "markdown": return "markdown"
        case "org": return "plaintext"
        case "sql": return "sql"
        case "diff", "patch": return "diff"
        case "proto": return "protobuf"
        case "cmake": return "cmake"
        case "gradle": return "gradle"
        case "ex", "exs": return "elixir"
        case "erl": return "erlang"
        case "hs": return "haskell"
        case "ml", "mli": return "ocaml"
        case "clj", "cljs": return "clojure"
        case "scala": return "scala"
        case "r": return "r"
        case "dart": return "dart"
        case "zig": return "plaintext"
        case "vim": return "vim"
        case "tex": return "latex"
        case "txt", "text", "log": return nil
        default: return nil
        }
    }
}