use config::{Config, RawConfig};
use libc;
use nitrokey_sys;
use std::ffi::CString;
use std::os::raw::c_int;
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)]
pub enum Model {
    /// The Nitrokey Storage.
    Storage,
    /// The Nitrokey Pro.
    Pro,
}

/// A Nitrokey device without user or admin authentication.
///
/// Use [`connect`][] or [`connect_model`][] to 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::{UnauthenticatedDevice, UserAuthenticatedDevice};
/// # use nitrokey::CommandError;
///
/// fn perform_user_task(device: &UserAuthenticatedDevice) {}
/// fn perform_other_task(device: &UnauthenticatedDevice) {}
///
/// # 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(())
/// # }
/// ```
///
/// [`authenticate_admin`]: #method.authenticate_admin
/// [`authenticate_user`]: #method.authenticate_user
/// [`connect`]: fn.connect.html
/// [`connect_model`]: fn.connect_model.html
#[derive(Debug)]
pub struct UnauthenticatedDevice {}

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

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

/// A Nitrokey device.
///
/// This trait provides the commands that can be executed without
/// authentication.
pub trait Device {
    /// Sets the time on the Nitrokey.  This command may set the time to
    /// arbitrary values.  `time` is the number of seconds since January 1st,
    /// 1970 (Unix timestamp).
    ///
    /// The time is used for TOTP generation (see [`get_totp_code`][]).
    ///
    /// # Errors
    ///
    /// - [`Timestamp`][] if the time could not be set
    ///
    /// [`get_totp_code`]: trait.ProvideOtp.html#method.get_totp_code
    /// [`Timestamp`]: enum.CommandError.html#variant.Timestamp
    // TODO: example
    fn set_time(&self, time: u64) -> CommandStatus {
        unsafe { CommandStatus::from(nitrokey_sys::NK_totp_set_time(time)) }
    }

    /// 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 {
    fn new(device: UnauthenticatedDevice, temp_password: Vec<u8>) -> Self;
}

impl UnauthenticatedDevice {
    fn authenticate<D, T>(
        self,
        password: &str,
        callback: T,
    ) -> Result<D, (UnauthenticatedDevice, CommandError)>
    where
        D: AuthenticatedDevice,
        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))),
        };
    }

    /// Performs user authentication.  This method consumes the device.  If
    /// successful, an authenticated device is returned.  Otherwise, the
    /// current unauthenticated device and the error are returned.
    ///
    /// This method generates a random temporary password that is used for all
    /// operations that require user access.
    ///
    /// # Errors
    ///
    /// - [`InvalidString`][] if the provided user password contains a null byte
    /// - [`RngError`][] if the generation of the temporary password failed
    /// - [`WrongPassword`][] if the provided user password is wrong
    ///
    /// # Example
    ///
    /// ```no_run
    /// use nitrokey::{UnauthenticatedDevice, UserAuthenticatedDevice};
    /// # use nitrokey::CommandError;
    ///
    /// fn perform_user_task(device: &UserAuthenticatedDevice) {}
    /// fn perform_other_task(device: &UnauthenticatedDevice) {}
    ///
    /// # 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(())
    /// # }
    /// ```
    ///
    /// [`InvalidString`]: enum.CommandError.html#variant.InvalidString
    /// [`RngError`]: enum.CommandError.html#variant.RngError
    /// [`WrongPassword`]: enum.CommandError.html#variant.WrongPassword
    pub fn authenticate_user(
        self,
        password: &str,
    ) -> Result<UserAuthenticatedDevice, (UnauthenticatedDevice, CommandError)> {
        return self.authenticate(password, |password_ptr, temp_password_ptr| unsafe {
            nitrokey_sys::NK_user_authenticate(password_ptr, temp_password_ptr)
        });
    }

    /// Performs admin authentication.  This method consumes the device.  If
    /// successful, an authenticated device is returned.  Otherwise, the
    /// current unauthenticated device and the error are returned.
    ///
    /// This method generates a random temporary password that is used for all
    /// operations that require admin access.
    ///
    /// # Errors
    ///
    /// - [`InvalidString`][] if the provided admin password contains a null byte
    /// - [`RngError`][] if the generation of the temporary password failed
    /// - [`WrongPassword`][] if the provided admin password is wrong
    ///
    /// # Example
    ///
    /// ```no_run
    /// use nitrokey::{AdminAuthenticatedDevice, UnauthenticatedDevice};
    /// # use nitrokey::CommandError;
    ///
    /// fn perform_admin_task(device: &AdminAuthenticatedDevice) {}
    /// fn perform_other_task(device: &UnauthenticatedDevice) {}
    ///
    /// # fn try_main() -> Result<(), CommandError> {
    /// let device = nitrokey::connect()?;
    /// let device = match device.authenticate_admin("123456") {
    ///     Ok(admin) => {
    ///         perform_admin_task(&admin);
    ///         admin.device()
    ///     },
    ///     Err((device, err)) => {
    ///         println!("Could not authenticate as admin: {:?}", err);
    ///         device
    ///     },
    /// };
    /// perform_other_task(&device);
    /// #     Ok(())
    /// # }
    /// ```
    ///
    /// [`InvalidString`]: enum.CommandError.html#variant.InvalidString
    /// [`RngError`]: enum.CommandError.html#variant.RngError
    /// [`WrongPassword`]: enum.CommandError.html#variant.WrongPassword
    pub fn authenticate_admin(
        self,
        password: &str,
    ) -> Result<AdminAuthenticatedDevice, (UnauthenticatedDevice, CommandError)> {
        return self.authenticate(password, |password_ptr, temp_password_ptr| unsafe {
            nitrokey_sys::NK_first_authenticate(password_ptr, temp_password_ptr)
        });
    }
}

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

impl Device for UnauthenticatedDevice {}

impl GenerateOtp for UnauthenticatedDevice {}

impl UserAuthenticatedDevice {
    /// 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) -> UnauthenticatedDevice {
        self.device
    }
}

impl Device for UserAuthenticatedDevice {}

impl GenerateOtp for UserAuthenticatedDevice {
    /// Generates an HOTP code on the given slot.  This operation may not
    /// require user authorization, depending on the device configuration (see
    /// [`get_config`][]).
    ///
    /// # Errors
    ///
    /// - [`SlotNotProgrammed`][] if the given slot is not configured
    /// - [`WrongSlot`][] if there is no slot with the given number
    ///
    /// # Example
    ///
    /// ```no_run
    /// use nitrokey::{Device, GenerateOtp};
    /// # use nitrokey::CommandError;
    ///
    /// # fn try_main() -> Result<(), CommandError> {
    /// let device = nitrokey::connect()?;
    /// match device.authenticate_user("123456") {
    ///     Ok(user) => {
    ///         let code = user.get_hotp_code(1)?;
    ///         println!("Generated HOTP code on slot 1: {:?}", code);
    ///     },
    ///     Err(err) => println!("Could not authenticate: {:?}", err),
    /// };
    /// #     Ok(())
    /// # }
    /// ```
    ///
    /// [`get_config`]: #method.get_config
    /// [`SlotNotProgrammed`]: enum.CommandError.html#variant.SlotNotProgrammed
    /// [`WrongSlot`]: enum.CommandError.html#variant.WrongSlot
    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));
        }
    }

    /// Generates a TOTP code on the given slot.  This operation may not
    /// require user authorization, depending on the device configuration (see
    /// [`get_config`][]).
    ///
    /// To make sure that the Nitrokey’s time is in sync, consider calling
    /// [`set_time`][] before calling this method.
    ///
    /// # Errors
    ///
    /// - [`SlotNotProgrammed`][] if the given slot is not configured
    /// - [`WrongSlot`][] if there is no slot with the given number
    ///
    /// # Example
    ///
    /// ```no_run
    /// use nitrokey::{Device, GenerateOtp};
    /// # use nitrokey::CommandError;
    ///
    /// # fn try_main() -> Result<(), CommandError> {
    /// let device = nitrokey::connect()?;
    /// match device.authenticate_user("123456") {
    ///     Ok(user) => {
    ///         let code = user.get_totp_code(1)?;
    ///         println!("Generated TOTP code on slot 1: {:?}", code);
    ///     },
    ///     Err(err) => println!("Could not authenticate: {:?}", err),
    /// };
    /// #     Ok(())
    /// # }
    /// ```
    ///
    /// [`get_config`]: #method.get_config
    /// [`set_time`]: trait.Device.html#method.set_time
    /// [`SlotNotProgrammed`]: enum.CommandError.html#variant.SlotNotProgrammed
    /// [`WrongSlot`]: enum.CommandError.html#variant.WrongSlot
    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 AuthenticatedDevice for UserAuthenticatedDevice {
    fn new(device: UnauthenticatedDevice, temp_password: Vec<u8>) -> Self {
        UserAuthenticatedDevice {
            device,
            temp_password,
        }
    }
}

impl AdminAuthenticatedDevice {
    /// 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) -> UnauthenticatedDevice {
        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::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<T>(&self, data: OtpSlotData, callback: T) -> CommandStatus
    where
        T: 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 Device for AdminAuthenticatedDevice {}

impl ConfigureOtp for AdminAuthenticatedDevice {
    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 GenerateOtp for AdminAuthenticatedDevice {}

impl AuthenticatedDevice for AdminAuthenticatedDevice {
    fn new(device: UnauthenticatedDevice, temp_password: Vec<u8>) -> Self {
        AdminAuthenticatedDevice {
            device,
            temp_password,
        }
    }
}