use clap::{Parser, Subcommand, ValueEnum};

// region: Clap Declaration

#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, ValueEnum)]
enum Target {
    #[value(name = "user")]
    User,
    #[value(name = "system")]
    System,
}

/// Simple program to manage Windows file associations
#[derive(Parser)]
#[command(name = "Windows File Association Operator", version, about)]
struct Cli {
    /// The TOML manifest file representing the complete program
    #[arg(
        short = 'm',
        long = "manifest",
        value_name = "PROG_MANIFEST",
        required = true
    )]
    manifest_file: String,
    #[command(subcommand)]
    command: CliCommands,
}

#[derive(Subcommand)]
enum CliCommands {
    /// Register the program
    #[command(name = "register")]
    #[command(about = "Register application with given manifest and scope.")]
    Register {
        /// The scope where wfassoc operate
        #[arg(short = 't', long = "target", value_name = "TARGET", required = true, value_enum, default_value_t = Target::User)]
        target: Target,
    },
    /// Unregister the program
    #[command(name = "unregister")]
    #[command(about = "Unregister application with given manifest and scope.")]
    Unregister {
        /// The scope where wfassoc operate
        #[arg(short = 't', long = "target", value_name = "TARGET", required = true, value_enum, default_value_t = Target::User)]
        target: Target,
    },
    /// Fetch current registration status
    #[command(name = "status")]
    #[command(
        about = "Fetch the status of registration for given manifest represented application."
    )]
    Status,
    #[command(name = "ext")]
    #[command(about = "File extension related operations according to given program manifest.")]
    Ext {
        #[command(subcommand)]
        command: CliExtCommands,
    },
}

#[derive(Subcommand)]
enum CliExtCommands {
    #[command(name = "link")]
    #[command(about = "Link user given file extension to the program declared in manifest file.")]
    Link {
        // The file extensions used for this operation. Specify * for all file extension.
        #[arg(required = true, value_name = "EXTS", num_args = 1..)]
        exts: Vec<String>,
    },
    #[command(name = "unlink")]
    #[command(
        about = "Unlink user given file extension from the program declared in manifest file."
    )]
    Unlink {
        // The file extensions used for this operation. Specify * for all file extension.
        #[arg(required = true, value_name = "EXTS", num_args = 1..)]
        exts: Vec<String>,
    },
    #[command(name = "list")]
    #[command(
        about = "List the association status for all extensions declared in given program manifest."
    )]
    List,
}

// endregion

// region: Exposed Type

#[derive(Debug)]
pub struct Request {

}

#[derive(Debug)]
pub struct RequestCommand {

}

#[derive(Debug)]
pub struct RequestExtCommand {

}

// endregion

///
/// 
/// Please note that if there is "help" or "version" command matched,
/// or any command line parse error occurs,
/// this function will order program exit immediately.
/// This is the mechanism of clap crate.
pub fn parse() -> Request {
    let cli = Cli::parse();
    todo!()
}