use nitrokey_sys;
use std::ffi::CString;
use util::{result_from_string, CommandError, CommandStatus};

/// Modes for one-time password generation.
#[derive(Debug, PartialEq)]
pub enum OtpMode {
    /// Generate one-time passwords with six digits.
    SixDigits,
    /// Generate one-time passwords with eight digits.
    EightDigits,
}

/// Provides methods to configure and erase OTP slots on a Nitrokey device.
pub trait ConfigureOtp {
    /// Configure an HOTP slot with the given data and set the HOTP counter to the given value
    /// (default 0).
    ///
    /// # Errors
    ///
    /// - [`InvalidSlot`][] if there is no slot with the given number
    /// - [`InvalidString`][] if the provided token ID contains a null byte
    /// - [`NoName`][] if the provided name is empty
    ///
    /// # Example
    ///
    /// ```no_run
    /// use nitrokey::{Authenticate, CommandStatus, ConfigureOtp, OtpMode, OtpSlotData};
    /// # use nitrokey::CommandError;
    ///
    /// # fn try_main() -> Result<(), (CommandError)> {
    /// let device = nitrokey::connect()?;
    /// let slot_data = OtpSlotData::new(1, "test", "01234567890123456689", OtpMode::SixDigits);
    /// match device.authenticate_admin("12345678") {
    ///     Ok(admin) => {
    ///         match admin.write_hotp_slot(slot_data, 0) {
    ///             CommandStatus::Success => println!("Successfully wrote slot."),
    ///             CommandStatus::Error(err) => println!("Could not write slot: {:?}", err),
    ///         }
    ///     },
    ///     Err((_, err)) => println!("Could not authenticate as admin: {:?}", err),
    /// }
    /// #     Ok(())
    /// # }
    /// ```
    ///
    /// [`InvalidSlot`]: enum.CommandError.html#variant.InvalidSlot
    /// [`InvalidString`]: enum.CommandError.html#variant.InvalidString
    /// [`NoName`]: enum.CommandError.html#variant.NoName
    fn write_hotp_slot(&self, data: OtpSlotData, counter: u64) -> CommandStatus;

    /// Configure a TOTP slot with the given data and set the TOTP time window to the given value
    /// (default 30).
    ///
    /// # Errors
    ///
    /// - [`InvalidSlot`][] if there is no slot with the given number
    /// - [`InvalidString`][] if the provided token ID contains a null byte
    /// - [`NoName`][] if the provided name is empty
    ///
    /// # Example
    ///
    /// ```no_run
    /// use nitrokey::{Authenticate, CommandStatus, ConfigureOtp, OtpMode, OtpSlotData};
    /// # use nitrokey::CommandError;
    ///
    /// # fn try_main() -> Result<(), (CommandError)> {
    /// let device = nitrokey::connect()?;
    /// let slot_data = OtpSlotData::new(1, "test", "01234567890123456689", OtpMode::EightDigits);
    /// match device.authenticate_admin("12345678") {
    ///     Ok(admin) => {
    ///         match admin.write_totp_slot(slot_data, 30) {
    ///             CommandStatus::Success => println!("Successfully wrote slot."),
    ///             CommandStatus::Error(err) => println!("Could not write slot: {:?}", err),
    ///         }
    ///     },
    ///     Err((_, err)) => println!("Could not authenticate as admin: {:?}", err),
    /// }
    /// #     Ok(())
    /// # }
    /// ```
    ///
    /// [`InvalidSlot`]: enum.CommandError.html#variant.InvalidSlot
    /// [`InvalidString`]: enum.CommandError.html#variant.InvalidString
    /// [`NoName`]: enum.CommandError.html#variant.NoName
    fn write_totp_slot(&self, data: OtpSlotData, time_window: u16) -> CommandStatus;

    /// Erases an HOTP slot.
    ///
    /// # Errors
    ///
    /// - [`InvalidSlot`][] if there is no slot with the given number
    ///
    /// # Example
    ///
    /// ```no_run
    /// use nitrokey::{Authenticate, CommandStatus, ConfigureOtp};
    /// # use nitrokey::CommandError;
    ///
    /// # fn try_main() -> Result<(), (CommandError)> {
    /// let device = nitrokey::connect()?;
    /// match device.authenticate_admin("12345678") {
    ///     Ok(admin) => {
    ///         match admin.erase_hotp_slot(1) {
    ///             CommandStatus::Success => println!("Successfully erased slot."),
    ///             CommandStatus::Error(err) => println!("Could not erase slot: {:?}", err),
    ///         }
    ///     },
    ///     Err((_, err)) => println!("Could not authenticate as admin: {:?}", err),
    /// }
    /// #     Ok(())
    /// # }
    /// ```
    ///
    /// [`InvalidSlot`]: enum.CommandError.html#variant.InvalidSlot
    fn erase_hotp_slot(&self, slot: u8) -> CommandStatus;

    /// Erases a TOTP slot.
    ///
    /// # Errors
    ///
    /// - [`InvalidSlot`][] if there is no slot with the given number
    ///
    /// # Example
    ///
    /// ```no_run
    /// use nitrokey::{Authenticate, CommandStatus, ConfigureOtp};
    /// # use nitrokey::CommandError;
    ///
    /// # fn try_main() -> Result<(), (CommandError)> {
    /// let device = nitrokey::connect()?;
    /// match device.authenticate_admin("12345678") {
    ///     Ok(admin) => {
    ///         match admin.erase_totp_slot(1) {
    ///             CommandStatus::Success => println!("Successfully erased slot."),
    ///             CommandStatus::Error(err) => println!("Could not erase slot: {:?}", err),
    ///         }
    ///     },
    ///     Err((_, err)) => println!("Could not authenticate as admin: {:?}", err),
    /// }
    /// #     Ok(())
    /// # }
    /// ```
    ///
    /// [`InvalidSlot`]: enum.CommandError.html#variant.InvalidSlot
    fn erase_totp_slot(&self, slot: u8) -> CommandStatus;
}

/// Provides methods to generate OTP codes and to query OTP slots on a Nitrokey
/// device.
pub trait GenerateOtp {
    /// Returns the name of the given HOTP slot.
    ///
    /// # Errors
    ///
    /// - [`InvalidSlot`][] if there is no slot with the given number
    /// - [`SlotNotProgrammed`][] if the given slot is not configured
    ///
    /// # Example
    ///
    /// ```no_run
    /// use nitrokey::{CommandError, GenerateOtp};
    ///
    /// # fn try_main() -> Result<(), CommandError> {
    /// let device = nitrokey::connect()?;
    /// match device.get_hotp_slot_name(1) {
    ///     Ok(name) => println!("HOTP slot 1: {:?}", name),
    ///     Err(CommandError::SlotNotProgrammed) => println!("HOTP slot 1 not programmed"),
    ///     Err(err) => println!("Could not get slot name: {:?}", err),
    /// };
    /// #     Ok(())
    /// # }
    /// ```
    ///
    /// [`InvalidSlot`]: enum.CommandError.html#variant.InvalidSlot
    /// [`SlotNotProgrammed`]: enum.CommandError.html#variant.SlotNotProgrammed
    fn get_hotp_slot_name(&self, slot: u8) -> Result<String, CommandError> {
        unsafe { result_from_string(nitrokey_sys::NK_get_hotp_slot_name(slot)) }
    }

    /// Returns the name of the given TOTP slot.
    ///
    /// # Errors
    ///
    /// - [`InvalidSlot`][] if there is no slot with the given number
    /// - [`SlotNotProgrammed`][] if the given slot is not configured
    ///
    /// # Example
    ///
    /// ```no_run
    /// use nitrokey::{CommandError, GenerateOtp};
    ///
    /// # fn try_main() -> Result<(), CommandError> {
    /// let device = nitrokey::connect()?;
    /// match device.get_totp_slot_name(1) {
    ///     Ok(name) => println!("TOTP slot 1: {:?}", name),
    ///     Err(CommandError::SlotNotProgrammed) => println!("TOTP slot 1 not programmed"),
    ///     Err(err) => println!("Could not get slot name: {:?}", err),
    /// };
    /// #     Ok(())
    /// # }
    /// ```
    ///
    /// [`InvalidSlot`]: enum.CommandError.html#variant.InvalidSlot
    /// [`SlotNotProgrammed`]: enum.CommandError.html#variant.SlotNotProgrammed
    fn get_totp_slot_name(&self, slot: u8) -> Result<String, CommandError> {
        unsafe { result_from_string(nitrokey_sys::NK_get_totp_slot_name(slot)) }
    }

    /// Generates an HOTP code on the given slot.  This operation may require user authorization,
    /// depending on the device configuration (see [`get_config`][]).
    ///
    /// # Errors
    ///
    /// - [`InvalidSlot`][] if there is no slot with the given number
    /// - [`NotAuthorized`][] if OTP generation requires user authentication
    /// - [`SlotNotProgrammed`][] if the given slot is not configured
    ///
    /// # Example
    ///
    /// ```no_run
    /// use nitrokey::GenerateOtp;
    /// # use nitrokey::CommandError;
    ///
    /// # fn try_main() -> Result<(), CommandError> {
    /// let device = nitrokey::connect()?;
    /// let code = device.get_hotp_code(1)?;
    /// println!("Generated HOTP code on slot 1: {:?}", code);
    /// #     Ok(())
    /// # }
    /// ```
    ///
    /// [`get_config`]: trait.Device.html#method.get_config
    /// [`InvalidSlot`]: enum.CommandError.html#variant.InvalidSlot
    /// [`NotAuthorized`]: enum.CommandError.html#variant.NotAuthorized
    /// [`SlotNotProgrammed`]: enum.CommandError.html#variant.SlotNotProgrammed
    fn get_hotp_code(&self, slot: u8) -> Result<String, CommandError> {
        unsafe {
            return result_from_string(nitrokey_sys::NK_get_hotp_code(slot));
        }
    }

    /// Generates a TOTP code on the given slot.  This operation may 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
    ///
    /// - [`InvalidSlot`][] if there is no slot with the given number
    /// - [`NotAuthorized`][] if OTP generation requires user authentication
    /// - [`SlotNotProgrammed`][] if the given slot is not configured
    ///
    /// # Example
    ///
    /// ```ignore
    /// extern crate chrono;
    ///
    /// use nitrokey::GenerateOtp;
    /// # use nitrokey::CommandError;
    ///
    /// # fn try_main() -> Result<(), CommandError> {
    /// let device = nitrokey::connect()?;
    /// let time = Utc::now().timestamp();
    /// if time < 0 {
    ///     println!("Timestamps before 1970-01-01 are not supported!");
    /// } else {
    ///     device.set_time(time as u64);
    ///     let code = device.get_totp_code(1)?;
    ///     println!("Generated TOTP code on slot 1: {:?}", code);
    /// }
    /// #     Ok(())
    /// # }
    /// ```
    ///
    /// [`set_time`]: trait.Device.html#method.set_time
    /// [`get_config`]: trait.Device.html#method.get_config
    /// [`InvalidSlot`]: enum.CommandError.html#variant.InvalidSlot
    /// [`NotAuthorized`]: enum.CommandError.html#variant.NotAuthorized
    /// [`SlotNotProgrammed`]: enum.CommandError.html#variant.SlotNotProgrammed
    fn get_totp_code(&self, slot: u8) -> Result<String, CommandError> {
        unsafe {
            return result_from_string(nitrokey_sys::NK_get_totp_code(slot, 0, 0, 0));
        }
    }
}

/// The configuration for an OTP slot.
#[derive(Debug)]
pub struct OtpSlotData {
    /// The number of the slot – must be less than three for HOTP and less than 15 for TOTP.
    pub number: u8,
    /// The name of the slot – must not be empty.
    pub name: String,
    /// The secret for the slot.
    pub secret: String,
    /// The OTP generation mode.
    pub mode: OtpMode,
    /// If true, press the enter key after sending an OTP code using double-pressed
    /// numlock, capslock or scrolllock.
    pub use_enter: bool,
    /// Set the token ID, see [OATH Token Identifier Specification][tokspec], section “Class A”.
    ///
    /// [tokspec]: https://openauthentication.org/token-specs/
    pub token_id: Option<String>,
}

#[derive(Debug)]
pub struct RawOtpSlotData {
    pub number: u8,
    pub name: CString,
    pub secret: CString,
    pub mode: OtpMode,
    pub use_enter: bool,
    pub use_token_id: bool,
    pub token_id: CString,
}

impl OtpSlotData {
    /// Constructs a new instance of this struct.
    pub fn new<S: Into<String>, T: Into<String>>(
        number: u8,
        name: S,
        secret: T,
        mode: OtpMode,
    ) -> OtpSlotData {
        OtpSlotData {
            number,
            name: name.into(),
            secret: secret.into(),
            mode,
            use_enter: false,
            token_id: None,
        }
    }

    /// Enables pressing the enter key after sending an OTP code using double-pressed numlock,
    /// capslock or scrollock.
    pub fn use_enter(mut self) -> OtpSlotData {
        self.use_enter = true;
        self
    }

    /// Sets the token ID, see [OATH Token Identifier Specification][tokspec], section “Class A”.
    ///
    /// [tokspec]: https://openauthentication.org/token-specs/
    pub fn token_id<S: Into<String>>(mut self, id: S) -> OtpSlotData {
        self.token_id = Some(id.into());
        self
    }
}

impl RawOtpSlotData {
    pub fn new(data: OtpSlotData) -> Result<RawOtpSlotData, CommandError> {
        let name = CString::new(data.name);
        let secret = CString::new(data.secret);
        let use_token_id = data.token_id.is_some();
        let token_id = CString::new(data.token_id.unwrap_or_else(String::new));
        if name.is_err() || secret.is_err() || token_id.is_err() {
            return Err(CommandError::InvalidString);
        }

        Ok(RawOtpSlotData {
            number: data.number,
            name: name.unwrap(),
            secret: secret.unwrap(),
            mode: data.mode,
            use_enter: data.use_enter,
            use_token_id,
            token_id: token_id.unwrap(),
        })
    }
}