use config::{Config, RawConfig};
use libc;
use nitrokey_sys;
use std::ffi::CString;
use std::ops::Deref;
use std::os::raw::c_int;
use misc::Authenticate;
use otp::{ConfigureOtp, GenerateOtp, OtpMode, OtpSlotData, RawOtpSlotData};
use util::{generate_password, get_last_error, result_from_string, CommandError, CommandStatus};

static TEMPORARY_PASSWORD_LENGTH: usize = 25;

/// Available Nitrokey models.
#[derive(Debug, PartialEq)]
enum Model {
    /// The Nitrokey Storage.
    Storage,
    /// The Nitrokey Pro.
    Pro,
}

/// A wrapper for a Nitrokey device of unknown type.
///
/// Use the function [`connect`][] to obtain a wrapped instance.  The wrapper implements all traits
/// that are shared between all Nitrokey devices so that the shared functionality can be used
/// without knowing the type of the underlying device.  If you want to use functionality that is
/// not available for all devices, you have to extract the device.
///
/// # Examples
///
/// Authentication with error handling:
///
/// ```no_run
/// use nitrokey::{Authenticate, DeviceWrapper, User};
/// # use nitrokey::CommandError;
///
/// fn perform_user_task(device: &User<DeviceWrapper>) {}
/// fn perform_other_task(device: &DeviceWrapper) {}
///
/// # fn try_main() -> Result<(), CommandError> {
/// let device = nitrokey::connect()?;
/// let device = match device.authenticate_user("123456") {
///     Ok(user) => {
///         perform_user_task(&user);
///         user.device()
///     },
///     Err((device, err)) => {
///         println!("Could not authenticate as user: {:?}", err);
///         device
///     },
/// };
/// perform_other_task(&device);
/// #     Ok(())
/// # }
/// ```
///
/// [`connect`]: fn.connect.html
// TODO: add example for Storage-specific code
#[derive(Debug)]
pub enum DeviceWrapper {
    /// A Nitrokey Storage device.
    Storage(()),
    /// A Nitrokey Pro device.
    Pro(Pro),
}

/// A Nitrokey Pro device without user or admin authentication.
///
/// Use the global function [`connect`][] to obtain an instance wrapper or the method
/// [`connect`][`Pro::connect`] to directly obtain an instance.  If you want to execute a command
/// that requires user or admin authentication, use [`authenticate_admin`][] or
/// [`authenticate_user`][].
///
/// # Examples
///
/// Authentication with error handling:
///
/// ```no_run
/// use nitrokey::{Authenticate, User, Pro};
/// # use nitrokey::CommandError;
///
/// fn perform_user_task(device: &User<Pro>) {}
/// fn perform_other_task(device: &Pro) {}
///
/// # fn try_main() -> Result<(), CommandError> {
/// let device = nitrokey::Pro::connect()?;
/// let device = match device.authenticate_user("123456") {
///     Ok(user) => {
///         perform_user_task(&user);
///         user.device()
///     },
///     Err((device, err)) => {
///         println!("Could not authenticate as user: {:?}", err);
///         device
///     },
/// };
/// perform_other_task(&device);
/// #     Ok(())
/// # }
/// ```
///
/// [`authenticate_admin`]: trait.Authenticate.html#method.authenticate_admin
/// [`authenticate_user`]: trait.Authenticate.html#method.authenticate_user
/// [`connect`]: fn.connect.html
/// [`Pro::connect`]: #method.connect
#[derive(Debug)]
pub struct Pro {}

/// A Nitrokey device with user authentication.
///
/// To obtain an instance of this struct, use the [`authenticate_user`][] method from the
/// [`Authenticate`][] trait.  To get back to an unauthenticated device, use the [`device`][]
/// method.
///
/// [`Authenticate`]: trait.Authenticate.html
/// [`authenticate_admin`]: trait.Authenticate.html#method.authenticate_admin
/// [`device`]: #method.device
#[derive(Debug)]
pub struct User<T: Device> {
    device: T,
    temp_password: Vec<u8>,
}

/// A Nitrokey device with admin authentication.
///
/// To obtain an instance of this struct, use the [`authenticate_admin`][] method from the
/// [`Authenticate`][] trait.  To get back to an unauthenticated device, use the [`device`][]
/// method.
///
/// [`Authenticate`]: trait.Authenticate.html
/// [`authenticate_admin`]: trait.Authenticate.html#method.authenticate_admin
/// [`device`]: #method.device
#[derive(Debug)]
pub struct Admin<T: Device> {
    device: T,
    temp_password: Vec<u8>,
}

/// A Nitrokey device.
///
/// This trait provides the commands that can be executed without authentication and that are
/// present on all supported Nitrokey devices.
pub trait Device: GenerateOtp {
    /// Returns the serial number of the Nitrokey device.  The serial number is the string
    /// representation of a hex number.
    ///
    /// # Example
    ///
    /// ```no_run
    /// use nitrokey::Device;
    /// # use nitrokey::CommandError;
    ///
    /// # fn try_main() -> Result<(), CommandError> {
    /// let device = nitrokey::connect()?;
    /// match device.get_serial_number() {
    ///     Ok(number) => println!("serial no: {:?}", number),
    ///     Err(err) => println!("Could not get serial number: {:?}", err),
    /// };
    /// #     Ok(())
    /// # }
    /// ```
    fn get_serial_number(&self) -> Result<String, CommandError> {
        unsafe { result_from_string(nitrokey_sys::NK_device_serial_number()) }
    }

    /// Returns the number of remaining authentication attempts for the user.  The total number of
    /// available attempts is three.
    ///
    /// # Example
    ///
    /// ```no_run
    /// use nitrokey::Device;
    /// # use nitrokey::CommandError;
    ///
    /// # fn try_main() -> Result<(), CommandError> {
    /// let device = nitrokey::connect()?;
    /// let count = device.get_user_retry_count();
    /// println!("{} remaining authentication attempts (user)", count);
    /// #     Ok(())
    /// # }
    /// ```
    fn get_user_retry_count(&self) -> u8 {
        unsafe { nitrokey_sys::NK_get_user_retry_count() }
    }

    /// Returns the number of remaining authentication attempts for the admin.  The total number of
    /// available attempts is three.
    ///
    /// # Example
    ///
    /// ```no_run
    /// use nitrokey::Device;
    /// # use nitrokey::CommandError;
    ///
    /// # fn try_main() -> Result<(), CommandError> {
    /// let device = nitrokey::connect()?;
    /// let count = device.get_admin_retry_count();
    /// println!("{} remaining authentication attempts (admin)", count);
    /// #     Ok(())
    /// # }
    /// ```
    fn get_admin_retry_count(&self) -> u8 {
        unsafe { nitrokey_sys::NK_get_admin_retry_count() }
    }

    /// Returns the major part of the firmware version (should be zero).
    ///
    /// # Example
    ///
    /// ```no_run
    /// use nitrokey::Device;
    /// # use nitrokey::CommandError;
    ///
    /// # fn try_main() -> Result<(), CommandError> {
    /// let device = nitrokey::connect()?;
    /// println!(
    ///     "Firmware version: {}.{}",
    ///     device.get_major_firmware_version(),
    ///     device.get_minor_firmware_version(),
    /// );
    /// #     Ok(())
    /// # }
    /// ```
    fn get_major_firmware_version(&self) -> i32 {
        unsafe { nitrokey_sys::NK_get_major_firmware_version() }
    }

    /// Returns the minor part of the firmware version (for example 8 for version 0.8).
    ///
    /// # Example
    ///
    /// ```no_run
    /// use nitrokey::Device;
    /// # use nitrokey::CommandError;
    ///
    /// # fn try_main() -> Result<(), CommandError> {
    /// let device = nitrokey::connect()?;
    /// println!(
    ///     "Firmware version: {}.{}",
    ///     device.get_major_firmware_version(),
    ///     device.get_minor_firmware_version(),
    /// );
    /// #     Ok(())
    /// # }
    fn get_minor_firmware_version(&self) -> i32 {
        unsafe { nitrokey_sys::NK_get_minor_firmware_version() }
    }

    /// Returns the current configuration of the Nitrokey device.
    ///
    /// # Example
    ///
    /// ```no_run
    /// use nitrokey::Device;
    /// # use nitrokey::CommandError;
    ///
    /// # fn try_main() -> Result<(), CommandError> {
    /// let device = nitrokey::connect()?;
    /// let config = device.get_config()?;
    /// println!("numlock binding:          {:?}", config.numlock);
    /// println!("capslock binding:         {:?}", config.capslock);
    /// println!("scrollock binding:        {:?}", config.scrollock);
    /// println!("require password for OTP: {:?}", config.user_password);
    /// #     Ok(())
    /// # }
    /// ```
    fn get_config(&self) -> Result<Config, CommandError> {
        unsafe {
            let config_ptr = nitrokey_sys::NK_read_config();
            if config_ptr.is_null() {
                return Err(get_last_error());
            }
            let config_array_ptr = config_ptr as *const [u8; 5];
            let raw_config = RawConfig::from(*config_array_ptr);
            libc::free(config_ptr as *mut libc::c_void);
            return Ok(raw_config.into());
        }
    }

    /// Changes the administrator PIN.
    ///
    /// # Errors
    ///
    /// - [`InvalidString`][] if one of the provided passwords contains a null byte
    /// - [`WrongPassword`][] if the current admin password is wrong
    ///
    /// # Example
    ///
    /// ```no_run
    /// use nitrokey::{CommandStatus, Device};
    /// # use nitrokey::CommandError;
    ///
    /// # fn try_main() -> Result<(), CommandError> {
    /// let device = nitrokey::connect()?;
    /// match device.change_admin_pin("12345678", "12345679") {
    ///     CommandStatus::Success => println!("Updated admin PIN."),
    ///     CommandStatus::Error(err) => println!("Failed to update admin PIN: {:?}", err),
    /// };
    /// #     Ok(())
    /// # }
    /// ```
    ///
    /// [`InvalidString`]: enum.CommandError.html#variant.InvalidString
    /// [`WrongPassword`]: enum.CommandError.html#variant.WrongPassword
    fn change_admin_pin(&self, current: &str, new: &str) -> CommandStatus {
        let current_string = CString::new(current);
        let new_string = CString::new(new);
        if current_string.is_err() || new_string.is_err() {
            return CommandStatus::Error(CommandError::InvalidString);
        }
        let current_string = current_string.unwrap();
        let new_string = new_string.unwrap();
        unsafe {
            CommandStatus::from(nitrokey_sys::NK_change_admin_PIN(
                current_string.as_ptr(),
                new_string.as_ptr(),
            ))
        }
    }

    /// Changes the user PIN.
    ///
    /// # Errors
    ///
    /// - [`InvalidString`][] if one of the provided passwords contains a null byte
    /// - [`WrongPassword`][] if the current user password is wrong
    ///
    /// # Example
    ///
    /// ```no_run
    /// use nitrokey::{CommandStatus, Device};
    /// # use nitrokey::CommandError;
    ///
    /// # fn try_main() -> Result<(), CommandError> {
    /// let device = nitrokey::connect()?;
    /// match device.change_user_pin("123456", "123457") {
    ///     CommandStatus::Success => println!("Updated admin PIN."),
    ///     CommandStatus::Error(err) => println!("Failed to update admin PIN: {:?}", err),
    /// };
    /// #     Ok(())
    /// # }
    /// ```
    ///
    /// [`InvalidString`]: enum.CommandError.html#variant.InvalidString
    /// [`WrongPassword`]: enum.CommandError.html#variant.WrongPassword
    fn change_user_pin(&self, current: &str, new: &str) -> CommandStatus {
        let current_string = CString::new(current);
        let new_string = CString::new(new);
        if current_string.is_err() || new_string.is_err() {
            return CommandStatus::Error(CommandError::InvalidString);
        }
        let current_string = current_string.unwrap();
        let new_string = new_string.unwrap();
        unsafe {
            CommandStatus::from(nitrokey_sys::NK_change_user_PIN(
                current_string.as_ptr(),
                new_string.as_ptr(),
            ))
        }
    }
}

trait AuthenticatedDevice<T> {
    fn new(device: T, temp_password: Vec<u8>) -> Self;
}

/// Connects to a Nitrokey device.  This method can be used to connect to any connected device,
/// both a Nitrokey Pro and a Nitrokey Storage.
///
/// # Example
///
/// ```
/// use nitrokey::DeviceWrapper;
///
/// fn do_something(device: DeviceWrapper) {}
///
/// match nitrokey::connect() {
///     Ok(device) => do_something(device),
///     Err(err) => println!("Could not connect to a Nitrokey: {:?}", err),
/// }
/// ```
pub fn connect() -> Result<DeviceWrapper, CommandError> {
    unsafe {
        match nitrokey_sys::NK_login_auto() {
            1 => match get_connected_device() {
                Some(wrapper) => Ok(wrapper),
                None => Err(CommandError::Unknown),
            },
            _ => Err(CommandError::Unknown),
        }
    }
}

fn get_connected_device() -> Option<DeviceWrapper> {
    // TODO: check connected device
    Some(DeviceWrapper::Pro(Pro {}))
}

fn connect_model(model: Model) -> bool {
    let model = match model {
        Model::Storage => nitrokey_sys::NK_device_model_NK_STORAGE,
        Model::Pro => nitrokey_sys::NK_device_model_NK_PRO,
    };
    unsafe { nitrokey_sys::NK_login_enum(model) == 1 }
}

impl DeviceWrapper {
    fn device(&self) -> &Device {
        match *self {
            DeviceWrapper::Storage(_) => panic!("..."),
            DeviceWrapper::Pro(ref pro) => pro,
        }
    }
}

impl GenerateOtp for DeviceWrapper {
    fn get_hotp_slot_name(&self, slot: u8) -> Result<String, CommandError> {
        self.device().get_hotp_slot_name(slot)
    }

    fn get_totp_slot_name(&self, slot: u8) -> Result<String, CommandError> {
        self.device().get_totp_slot_name(slot)
    }

    fn get_hotp_code(&self, slot: u8) -> Result<String, CommandError> {
        self.device().get_hotp_code(slot)
    }

    fn get_totp_code(&self, slot: u8) -> Result<String, CommandError> {
        self.device().get_totp_code(slot)
    }
}

impl Device for DeviceWrapper {}

impl Authenticate for DeviceWrapper {
    fn authenticate_user(self, password: &str) -> Result<User<Self>, (Self, CommandError)> {
        match self {
            DeviceWrapper::Storage(_) => panic!("..."),
            DeviceWrapper::Pro(pro) => {
                let result = pro.authenticate_user(password);
                match result {
                    Ok(user) => Ok(User::new(
                        DeviceWrapper::Pro(user.device),
                        user.temp_password,
                    )),
                    Err((pro, err)) => Err((DeviceWrapper::Pro(pro), err)),
                }
            }
        }
    }

    fn authenticate_admin(self, password: &str) -> Result<Admin<Self>, (Self, CommandError)> {
        match self {
            DeviceWrapper::Storage(_) => panic!("..."),
            DeviceWrapper::Pro(pro) => {
                let result = pro.authenticate_admin(password);
                match result {
                    Ok(admin) => Ok(Admin::new(
                        DeviceWrapper::Pro(admin.device),
                        admin.temp_password,
                    )),
                    Err((pro, err)) => Err((DeviceWrapper::Pro(pro), err)),
                }
            }
        }
    }
}

impl Pro {
    pub fn connect() -> Result<Pro, CommandError> {
        // TODO: maybe Option instead of Result?
        match connect_model(Model::Pro) {
            true => Ok(Pro {}),
            false => Err(CommandError::Unknown),
        }
    }

    fn authenticate<D, T>(self, password: &str, callback: T) -> Result<D, (Self, CommandError)>
    where
        D: AuthenticatedDevice<Pro>,
        T: Fn(*const i8, *const i8) -> c_int,
    {
        let temp_password = match generate_password(TEMPORARY_PASSWORD_LENGTH) {
            Ok(pw) => pw,
            Err(_) => return Err((self, CommandError::RngError)),
        };
        let password = CString::new(password);
        if password.is_err() {
            return Err((self, CommandError::InvalidString));
        }

        let pw = password.unwrap();
        let password_ptr = pw.as_ptr();
        let temp_password_ptr = temp_password.as_ptr() as *const i8;
        return match callback(password_ptr, temp_password_ptr) {
            0 => Ok(D::new(self, temp_password)),
            rv => Err((self, CommandError::from(rv))),
        };
    }
}

impl Authenticate for Pro {
    fn authenticate_user(self, password: &str) -> Result<User<Self>, (Self, CommandError)> {
        return self.authenticate(password, |password_ptr, temp_password_ptr| unsafe {
            nitrokey_sys::NK_user_authenticate(password_ptr, temp_password_ptr)
        });
    }

    fn authenticate_admin(self, password: &str) -> Result<Admin<Self>, (Self, CommandError)> {
        return self.authenticate(password, |password_ptr, temp_password_ptr| unsafe {
            nitrokey_sys::NK_first_authenticate(password_ptr, temp_password_ptr)
        });
    }
}

impl Drop for Pro {
    fn drop(&mut self) {
        unsafe {
            nitrokey_sys::NK_logout();
        }
    }
}

impl Device for Pro {}

impl GenerateOtp for Pro {}

impl<T: Device> User<T> {
    /// Forgets the user authentication and returns an unauthenticated device.  This method
    /// consumes the authenticated device.  It does not perform any actual commands on the
    /// Nitrokey.
    pub fn device(self) -> T {
        self.device
    }
}

impl<T: Device> Deref for User<T> {
    type Target = T;

    fn deref(&self) -> &Self::Target {
        &self.device
    }
}

impl<T: Device> GenerateOtp for User<T> {
    fn get_hotp_code(&self, slot: u8) -> Result<String, CommandError> {
        unsafe {
            let temp_password_ptr = self.temp_password.as_ptr() as *const i8;
            return result_from_string(nitrokey_sys::NK_get_hotp_code_PIN(slot, temp_password_ptr));
        }
    }

    fn get_totp_code(&self, slot: u8) -> Result<String, CommandError> {
        unsafe {
            let temp_password_ptr = self.temp_password.as_ptr() as *const i8;
            return result_from_string(nitrokey_sys::NK_get_totp_code_PIN(
                slot,
                0,
                0,
                0,
                temp_password_ptr,
            ));
        }
    }
}

impl<T: Device> AuthenticatedDevice<T> for User<T> {
    fn new(device: T, temp_password: Vec<u8>) -> Self {
        User {
            device,
            temp_password,
        }
    }
}

impl<T: Device> Deref for Admin<T> {
    type Target = T;

    fn deref(&self) -> &Self::Target {
        &self.device
    }
}

impl<T: Device> Admin<T> {
    /// Forgets the user authentication and returns an unauthenticated device.  This method
    /// consumes the authenticated device.  It does not perform any actual commands on the
    /// Nitrokey.
    pub fn device(self) -> T {
        self.device
    }

    /// Writes the given configuration to the Nitrokey device.
    ///
    /// # Errors
    ///
    /// - [`InvalidSlot`][] if the provided numlock, capslock or scrolllock slot is larger than two
    ///
    /// # Example
    ///
    /// ```no_run
    /// use nitrokey::{Authenticate, Config};
    /// # use nitrokey::CommandError;
    ///
    /// # fn try_main() -> Result<(), CommandError> {
    /// let device = nitrokey::connect()?;
    /// let config = Config::new(None, None, None, false);
    /// match device.authenticate_admin("12345678") {
    ///     Ok(admin) => {
    ///         admin.write_config(config);
    ///         ()
    ///     },
    ///     Err((_, err)) => println!("Could not authenticate as admin: {:?}", err),
    /// };
    /// #     Ok(())
    /// # }
    /// ```
    ///
    /// [`InvalidSlot`]: enum.CommandError.html#variant.InvalidSlot
    pub fn write_config(&self, config: Config) -> CommandStatus {
        let raw_config = match RawConfig::try_from(config) {
            Ok(raw_config) => raw_config,
            Err(err) => return CommandStatus::Error(err),
        };
        unsafe {
            let rv = nitrokey_sys::NK_write_config(
                raw_config.numlock,
                raw_config.capslock,
                raw_config.scrollock,
                raw_config.user_password,
                false,
                self.temp_password.as_ptr() as *const i8,
            );
            return CommandStatus::from(rv);
        }
    }

    fn write_otp_slot<C>(&self, data: OtpSlotData, callback: C) -> CommandStatus
    where
        C: Fn(RawOtpSlotData, *const i8) -> c_int,
    {
        let raw_data = match RawOtpSlotData::new(data) {
            Ok(raw_data) => raw_data,
            Err(err) => return CommandStatus::Error(err),
        };
        let temp_password_ptr = self.temp_password.as_ptr() as *const i8;
        let rv = callback(raw_data, temp_password_ptr);
        return CommandStatus::from(rv);
    }
}

impl<T: Device> ConfigureOtp for Admin<T> {
    fn write_hotp_slot(&self, data: OtpSlotData, counter: u64) -> CommandStatus {
        return self.write_otp_slot(data, |raw_data: RawOtpSlotData, temp_password_ptr| unsafe {
            nitrokey_sys::NK_write_hotp_slot(
                raw_data.number,
                raw_data.name.as_ptr(),
                raw_data.secret.as_ptr(),
                counter,
                raw_data.mode == OtpMode::EightDigits,
                raw_data.use_enter,
                raw_data.use_token_id,
                raw_data.token_id.as_ptr(),
                temp_password_ptr,
            )
        });
    }

    fn write_totp_slot(&self, data: OtpSlotData, time_window: u16) -> CommandStatus {
        return self.write_otp_slot(data, |raw_data: RawOtpSlotData, temp_password_ptr| unsafe {
            nitrokey_sys::NK_write_totp_slot(
                raw_data.number,
                raw_data.name.as_ptr(),
                raw_data.secret.as_ptr(),
                time_window,
                raw_data.mode == OtpMode::EightDigits,
                raw_data.use_enter,
                raw_data.use_token_id,
                raw_data.token_id.as_ptr(),
                temp_password_ptr,
            )
        });
    }

    fn erase_hotp_slot(&self, slot: u8) -> CommandStatus {
        let temp_password_ptr = self.temp_password.as_ptr() as *const i8;
        unsafe { CommandStatus::from(nitrokey_sys::NK_erase_hotp_slot(slot, temp_password_ptr)) }
    }

    fn erase_totp_slot(&self, slot: u8) -> CommandStatus {
        let temp_password_ptr = self.temp_password.as_ptr() as *const i8;
        unsafe { CommandStatus::from(nitrokey_sys::NK_erase_totp_slot(slot, temp_password_ptr)) }
    }
}

impl<T: Device> AuthenticatedDevice<T> for Admin<T> {
    fn new(device: T, temp_password: Vec<u8>) -> Self {
        Admin {
            device,
            temp_password,
        }
    }
}