package solutions.tretter.githugandroid

data class GitHelpInvocation(
    val topic: String,
    val command: String,
)

fun parseGitHelpInvocation(command: String): GitHelpInvocation? {
    val tokens = GitSandboxEngine.tokenizeCommand(command)
    if (tokens.size >= 2 && tokens[0] == "man") {
        val topic = when {
            tokens[1] == "git" -> tokens.getOrNull(2) ?: "git"
            tokens[1].startsWith("git-") -> tokens[1].removePrefix("git-")
            tokens[1].startsWith("git") && tokens[1].length > 3 -> tokens[1].removePrefix("git")
            else -> tokens[1]
        }
            .takeIf { it.matches(Regex("[A-Za-z0-9_-]+")) }
            ?: return null
        return GitHelpInvocation(topic = topic, command = command)
    }
    if (tokens.size < 3 || tokens[0] != "git") return null
    val topic = when {
        tokens[1] == "help" -> tokens[2]
        tokens[1] == "--help" -> tokens[2]
        tokens.drop(2).any { it == "--help" } -> tokens[1]
        else -> return null
    }.takeIf { it.matches(Regex("[A-Za-z0-9_-]+")) } ?: return null
    return GitHelpInvocation(topic = topic, command = command)
}