//! The wrapper types and traits for handles into the PAM library.

use crate::constants::{Flags, Result};
use crate::conv::Conversation;
use crate::environ::{EnvironMap, EnvironMapMut};
use crate::logging::{Level, Location};
use crate::{guide, linklist, man7, manbsd, stdlinks};

macro_rules! trait_item {
    ($(#[$md:meta])* get = $getter:ident, item = $item:literal $(, see = $see:path)?) => {
        $(#[$md])*
        #[doc = ""]
        #[doc = concat!("Gets the `", $item, "` of the PAM handle.")]
        $(
            #[doc = concat!("See [`", stringify!($see), "`].")]
        )?
        ///
        /// Returns a reference to the item's value, owned by PAM.
        /// The item is assumed to be valid UTF-8 text.
        /// If it is not, `ConversationError` is returned.
        ///
        /// # References
        ///
        #[doc = linklist!(pam_get_item: mwg, adg, _std)]
        ///
        #[doc = guide!(adg: "adg-interface-by-app-expected.html#adg-pam_get_item")]
        #[doc = guide!(mwg: "mwg-expected-by-module-item.html#mwg-pam_get_item")]
        #[doc = stdlinks!(3 pam_get_item)]
        fn $getter(&self) -> Result<Option<String>>;
    };
    ($(#[$md:meta])* set = $setter:ident, item = $item:literal $(, see = $see:path)?) => {
        $(#[$md])*
        #[doc = ""]
        #[doc = concat!("Sets the `", $item, "` from the PAM handle.")]
        $(
            #[doc = concat!("See [`", stringify!($see), "`].")]
        )?
        ///
        /// Sets the item's value. PAM copies the string's contents.
        /// If the string contains a null byte, this will return
        /// a `ConversationError`.
        ///
        /// # References
        ///
        #[doc = linklist!(pam_set_item: mwg, adg, _std)]
        ///
        #[doc = guide!(adg: "adg-interface-by-app-expected.html#adg-pam_set_item")]
        #[doc = guide!(mwg: "mwg-expected-by-module-item.html#mwg-pam_set_item")]
        #[doc = stdlinks!(3 pam_set_item)]
        fn $setter(&mut self, value: Option<&str>) -> Result<()>;
    };
}

/// Functionality for both PAM applications and PAM modules.
///
/// This base trait includes features of a PAM handle that are available
/// to both applications and modules.
///
/// You probably want [`LibPamHandle`](crate::libpam::OwnedLibPamHandle).
/// This trait is intended to allow creating mock PAM handle types
/// to test PAM modules and applications.
pub trait PamShared {
    /// Logs something via this PAM handle.
    ///
    /// You probably want to use one of the logging macros,
    /// like [`error!`](crate::error!),
    /// [`warn!`](crate::warn!),
    /// [`info!`](crate::info!),
    /// or [`debug!`](crate::debug!).
    ///
    /// In most PAM implementations, this will go to syslog.
    /// See [Linux-PAM's `pam_syslog`][man7] or
    /// [OpenPAM's `openpam_log`][manbsd] for more details.
    ///
    /// # Example
    ///
    /// ```no_run
    /// # use nonstick::PamShared;
    /// use nonstick::logging::Level;
    /// use nonstick::location;
    /// # fn _test(pam_hdl: impl PamShared) {
    /// # let delay_ms = 100;
    /// # let url = "https://zombo.com";
    /// // Usually, instead of calling this manually, just use the macros.
    /// nonstick::error!(pam_hdl, "something bad happened!");
    /// nonstick::warn!(pam_hdl, "loading information took {delay_ms} ms");
    /// nonstick::info!(pam_hdl, "using network backend");
    /// nonstick::debug!(pam_hdl, "sending GET request to {url}");
    /// // But if you really want to, you can call this yourself:
    /// pam_hdl.log(Level::Warning, location!(), "this is unnecessarily verbose");
    /// # }
    /// ```
    #[doc = man7!(3 pam_syslog)]
    #[doc = manbsd!(3 openpam_log)]
    fn log(&self, level: Level, loc: Location<'_>, entry: &str);

    /// Retrieves the name of the user who is authenticating or logging in.
    ///
    /// If the username has previously been obtained, this uses that username;
    /// otherwise it prompts the user with the first of these that is present:
    ///
    ///  1. The prompt string passed to this function.
    ///  2. The string returned by `get_user_prompt_item`.
    ///  3. The default prompt, `login: `.
    ///
    /// # References
    #[doc = linklist!(pam_get_user: mwg, _std)]
    ///
    /// # Example
    ///
    /// ```no_run
    /// # use nonstick::PamShared;
    /// # fn _doc(handle: &mut impl PamShared) -> Result<(), Box<dyn std::error::Error>> {
    /// // Get the username using the default prompt.
    /// let user = handle.username(None)?;
    /// // Get the username using a custom prompt.
    /// // If this were actually called right after the above,
    /// // both user and user_2 would have the same value.
    /// let user_2 = handle.username(Some("who ARE you even???"))?;
    /// # Ok(())
    /// # }
    /// ```
    #[doc = stdlinks!(3 pam_get_user)]
    #[doc = guide!(mwg: "mwg-expected-by-module-item.html#mwg-pam_get_user")]
    fn username(&mut self, prompt: Option<&str>) -> Result<String>;

    /// The contents of the environment to set, read-only.
    fn environ(&self) -> impl EnvironMap;

    /// A writable version of the environment.
    fn environ_mut(&mut self) -> impl EnvironMapMut;

    trait_item!(
        /// The identity of the user for whom service is being requested.
        ///
        /// Unlike [`username`](Self::username), this will simply get
        /// the current state of the user item, and not request the username.
        /// While PAM usually sets this automatically in the `username` call,
        /// it may be changed by a module during the PAM transaction.
        /// Applications should check it after each step of the PAM process.
        get = user_item,
        item = "PAM_USER",
        see = Self::username
    );
    trait_item!(
        /// Sets the identity of the logging-in user.
        ///
        /// Usually this will be set during the course of
        /// a [`username`](Self::username) call, but you may set it manually
        /// or change it during the PAM process.
        set = set_user_item,
        item = "PAM_USER",
        see = Self::user_item
    );

    trait_item!(
        /// The service name, which identifies the PAM stack which is used
        /// to perform authentication.
        get = service,
        item = "PAM_SERVICE"
    );
    trait_item!(
        /// Sets the service name. It's probably a bad idea to change this.
        set = set_service,
        item = "PAM_SERVICE",
        see = Self::service
    );

    trait_item!(
        /// The string used to prompt for a user's name.
        /// By default, this is a localized version of `login: `.
        get = user_prompt,
        item = "PAM_USER_PROMPT"
    );
    trait_item!(
        /// Sets the string used to prompt for a user's name.
        set = set_user_prompt,
        item = "PAM_USER_PROMPT",
        see = Self::user_prompt
    );

    trait_item!(
        /// The device path of the TTY being used to log in.
        ///
        /// This is the terminal the user is logging in on,
        /// specified as the full device path (e.g. `/dev/tty0`).
        /// Very old applications may use this instead of `PAM_XDISPLAY`.
        get = tty_name,
        item = "PAM_TTY"
    );
    trait_item!(
        /// Sets the path to the terminal where the user is logging on.
        set = set_tty_name,
        item = "PAM_TTY",
        see = Self::tty_name
    );

    trait_item!(
        /// If set, the identity of the remote user logging in.
        ///
        /// This is only as trustworthy as the application calling PAM.
        get = remote_user,
        item = "PAM_RUSER",
        see = Self::remote_host
    );
    trait_item!(
        /// Sets the identity of the remote user logging in.
        ///
        /// This may be set by the application before making calls
        /// into a PAM transaction.
        set = set_remote_user,
        item = "PAM_RUSER",
        see = Self::remote_user
    );

    trait_item!(
        /// If set, the remote location where the user is coming from.
        ///
        /// This is only as trustworthy as the application calling PAM.
        /// This can be combined with [`Self::remote_user`] to identify
        /// the account the user is attempting to log in from,
        /// with `remote_user@remote_host`.
        ///
        /// If unset, "it is unclear where the authentication request
        /// is originating from."
        get = remote_host,
        item = "PAM_RHOST",
        see = Self::remote_user
    );
    trait_item!(
        /// Sets the location where the user is coming from.
        ///
        /// This may be set by the application before making calls
        /// into a PAM transaction.
        set = set_remote_host,
        item = "PAM_RHOST",
        see = Self::remote_host
    );

    trait_item!(
        /// Gets the user's authentication token (e.g., password).
        ///
        /// This is usually set automatically when
        /// [`authtok`](PamHandleModule::authtok) is called,
        /// but can be manually set.
        set = set_authtok_item,
        item = "PAM_AUTHTOK",
        see = PamHandleModule::authtok_item
    );

    trait_item!(
        /// Sets the user's "old authentication token" when changing passwords.
        ///
        /// This is usually set automatically by PAM.
        set = set_old_authtok_item,
        item = "PAM_OLDAUTHTOK",
        see = PamHandleModule::old_authtok_item
    );
}

/// Functionality of a PAM handle that can be expected by a PAM application.
///
/// If you are not writing a PAM client application (e.g., you are writing
/// a module), you should not use the functionality exposed by this trait.
///
/// Like [`PamShared`], this is intended to allow creating mock implementations
/// of PAM for testing PAM applications.
pub trait PamHandleApplication: PamShared {
    /// Starts the authentication process for the user.
    ///
    /// The application calls this to find out who the user is, and verify that
    /// they are really that person. If authentication is successful,
    /// this will return an `Ok(())` [`Result`].
    ///
    /// A PAM module may change the caller's [username](PamShared::username)
    /// as part of the login process, so be sure to check it after making
    /// any PAM application call.
    ///
    /// # References
    #[doc = linklist!(pam_authenticate: adg, _std)]
    ///
    #[doc = guide!(adg: "adg-interface-by-app-expected.html#adg-pam_authenticate")]
    #[doc = stdlinks!(3 pam_authenticate)]
    fn authenticate(&mut self, flags: Flags) -> Result<()>;

    /// Verifies the validity of the user's account (and other stuff).
    ///
    /// After [authentication](Self::authenticate), an application should call
    /// this to ensure that the user's account is still valid. This may check
    /// for token expiration or that the user's account is not locked.
    ///
    /// # References
    #[doc = linklist!(pam_acct_mgmt: adg, _std)]
    ///
    #[doc = guide!(adg: "adg-interface-by-app-expected.html#adg-pam_acct_mgmt")]
    #[doc = stdlinks!(3 pam_acct_mgmt)]
    fn account_management(&mut self, flags: Flags) -> Result<()>;

    /// Changes the authentication token.
    ///
    /// # References
    #[doc = linklist!(pam_chauthtok: adg, _std)]
    ///
    #[doc = guide!(adg: "adg-interface-by-app-expected.html#adg-pam_chauthtok")]
    #[doc = stdlinks!(3 pam_chauthtok)]
    fn change_authtok(&mut self, flags: Flags) -> Result<()>;
}

/// Functionality of a PAM handle that can be expected by a PAM module.
///
/// If you are not writing a PAM module (e.g., you are writing an application),
/// you should not use any of the functionality exposed by this trait.
///
/// Like [`PamShared`], this is intended to allow creating mock implementations
/// of PAM for testing PAM modules.
pub trait PamHandleModule: Conversation + PamShared {
    /// Retrieves the authentication token from the user.
    ///
    /// This should only be used by *authentication* and *password-change*
    /// PAM modules.
    ///
    /// # References
    ///
    #[doc = linklist!(pam_get_authtok: man7, manbsd)]
    ///
    /// # Example
    ///
    /// ```no_run
    /// # use nonstick::handle::PamHandleModule;
    /// # fn _doc(handle: &mut impl PamHandleModule) -> Result<(), Box<dyn std::error::Error>> {
    /// // Get the user's password using the default prompt.
    /// let pass = handle.authtok(None)?;
    /// // Get the user's password using a custom prompt.
    /// let pass = handle.authtok(Some("Reveal your secrets!"))?;
    /// Ok(())
    /// # }
    /// ```
    #[doc = man7!(3 pam_get_authtok)]
    #[doc = manbsd!(3 pam_get_authtok)]
    fn authtok(&mut self, prompt: Option<&str>) -> Result<String>;

    /// Retrieves the user's old authentication token when changing passwords.
    ///
    ///
    fn old_authtok(&mut self, prompt: Option<&str>) -> Result<String>;

    trait_item!(
        /// Gets the user's authentication token (e.g., password).
        ///
        /// This is normally set automatically by PAM when calling
        /// [`authtok`](Self::authtok), but can be set explicitly.
        ///
        /// Like `authtok`, this should only ever be called
        /// by *authentication* and *password-change* PAM modules.
        get = authtok_item,
        item = "PAM_AUTHTOK",
        see = Self::authtok
    );

    trait_item!(
        /// Gets the user's old authentication token when changing passwords.
        ///
        /// This is normally set automatically by PAM when calling
        /// [`old_authtok`](Self::old_authtok), but can be set explicitly.
        ///
        /// This should only ever be called by *password-change* PAM modules.
        get = old_authtok_item,
        item = "PAM_OLDAUTHTOK",
        see = PamShared::set_old_authtok_item
    );
}