//! PAM logging variables and macros.
//!
//! PAM implementations usually include the ability to log to syslog in a way
//! that is associated with the log entry itself. This module defines the enums
//! and macros for logging.
//!
//! For more details, see [`PamShared::log`](crate::PamShared::log).
//!
//! We can't use [the `log` crate](https://docs.rs/log) because that requires
//! that any `Log` implementors be `Sync` and `Send`, and a PAM handle
//! may be neither. Furthermore, PAM handles are passed to PAM modules in
//! dynamic libraries, and `log` doesn't work across dynamic linking boundaries.
//!
//! A `PamShared` implementation may still use the `log` crate on the backend,
//! and may even itself implement `log::Log`, but that interface is not exposed
//! to the generic PAM user.

#[cfg(feature = "link")]
mod levels {
    pub use internal::*;
    #[cfg(pam_impl = "linux-pam")]
    mod internal {
        use crate::libpam::pam_ffi;
        pub const ERROR: u32 = pam_ffi::LOG_ERR;
        pub const WARN: u32 = pam_ffi::LOG_WARNING;
        pub const INFO: u32 = pam_ffi::LOG_INFO;
        pub const DEBUG: u32 = pam_ffi::LOG_DEBUG;
    }
    #[cfg(pam_impl = "openpam")]
    mod internal {
        use crate::libpam::pam_ffi;
        pub const ERROR: u32 = pam_ffi::PAM_LOG_ERROR;
        pub const WARN: u32 = pam_ffi::PAM_LOG_NOTICE;
        pub const INFO: u32 = pam_ffi::PAM_LOG_VERBOSE;
        pub const DEBUG: u32 = pam_ffi::PAM_LOG_DEBUG;
    }
}

#[cfg(not(feature = "link"))]
mod levels {
    pub const ERROR: u32 = 2255887;
    pub const WARN: u32 = 7265000;
    pub const INFO: u32 = 7762323;
    pub const DEBUG: u32 = 8675309;
}

/// An entry to be added to the log.
///
/// The levels are in descending order of importance and correspond roughly
/// to the similarly-named levels in the `log` crate.
///
/// In all implementations, these are ordered such that `Error`, `Warning`,
/// `Info`, and `Debug` are in ascending order.
#[derive(Debug, PartialEq, Ord, PartialOrd, Eq)]
#[repr(u32)]
pub enum Level {
    Error = levels::ERROR,
    Warning = levels::WARN,
    Info = levels::INFO,
    Debug = levels::DEBUG,
}

/// Here's the guts of the logger thingy. You shouldn't be using this!
#[doc(hidden)]
#[macro_export]
macro_rules! __log_internal {
    ($handle:expr, $level:ident, $($arg:tt)+) => {
        $handle.log($crate::logging::Level::$level, &format!($($arg)+));
    }
}

/// Logs a message at error level via the given PAM handle.
///
/// This supports `format!`-style formatting.
///
/// # Example
///
/// ```no_run
/// # fn _test(pam_handle: impl nonstick::PamShared) {
/// # let load_error = "xxx";
/// nonstick::error!(
///     pam_handle,
///     "error loading data from data source: {load_error}"
/// );
/// // Will log a message like "error loading data from data source: timed out"
/// // at ERROR level on syslog.
/// # }
/// ```
#[macro_export]
macro_rules! error { ($handle:expr, $($arg:tt)+) => { $crate::__log_internal!($handle, Error, $($arg)+);}}

/// Logs a message at warning level via the given PAM handle.
///
/// This supports `format!`-style formatting.
///
/// # Example
///
/// ```no_run
/// # fn _test(pam_handle: impl nonstick::PamShared) {
/// # let (start, finish) = (0, 0);
/// nonstick::warn!(
///     pam_handle,
///     "loading took too long: {latency_ms} ms",
///     latency_ms = start - finish
/// );
/// // Will log a message like "loading took too long: 495 ms"
/// // at WARN level on syslog.
/// # }
/// ```
#[macro_export]
macro_rules! warn { ($handle:expr, $($arg:tt)+) => { $crate::__log_internal!($handle, Warning, $($arg)+);}}

/// Logs a message at info level via the given PAM handle.
///
/// This supports `format!`-style formatting.
///
/// # Example
///
/// ```no_run
/// # fn _test(pam_handle: impl nonstick::PamShared) {
/// nonstick::info!(pam_handle, "using remote backend to load user data");
/// // Will log a message like "using remote backend to load user data"
/// // at INFO level on syslog.
/// # }
/// ```
#[macro_export]
macro_rules! info { ($handle:expr, $($arg:tt)+) => { $crate::__log_internal!($handle, Info, $($arg)+);}}

/// Logs a message at debug level via the given PAM handle.
///
/// This level specially includes file/line/column information.
/// This supports `format!`-style formatting.
///
/// # Example
///
/// ```no_run
/// # fn _test(pam_handle: impl nonstick::PamShared) {
/// # let userinfo_url = "https://zombo.com/";
/// nonstick::debug!(pam_handle, "making HTTP GET request to {userinfo_url}");
/// // Will log a message like
/// // "pam_http/lib.rs:39:14: making HTTP GET request to https://zombo.com/"
/// // at DEBUG level on syslog.
/// # }
/// ```
#[macro_export]
macro_rules! debug {($handle:expr, $($arg:tt)+) => {
    $crate::__log_internal!(
        $handle, Debug,
        "{}:{}:{}: {}", file!(), line!(), column!(), format_args!($($arg)+),
    );
}}

#[cfg(test)]
mod tests {
    use super::*;
    use regex::Regex;
    use std::cell::RefCell;

    #[test]
    fn test_order() {
        assert!(Level::Error < Level::Warning);
        assert!(Level::Warning < Level::Info);
        assert!(Level::Info < Level::Debug);
    }

    #[test]
    fn test_logging() {
        struct Logger(RefCell<Vec<(Level, String)>>);

        impl Logger {
            fn log(&self, level: Level, text: &str) {
                self.0.borrow_mut().push((level, text.to_owned()))
            }
        }

        let logger = Logger(Default::default());

        let something = Level::Error;
        error!(logger, "here is another thing: {}", 99);
        warn!(logger, "watch out!");
        info!(logger, "here is some info: {info}", info = "information");
        debug!(logger, "here is something: {something:?}");

        let mut logged = logger.0.into_inner();

        let (last_level, last_string) = logged.pop().unwrap();
        assert_eq!(Level::Debug, last_level);
        let expr = Regex::new(r"^[^:]+:\d+:\d+: here is something: Error$").unwrap();
        assert!(
            expr.is_match(&last_string),
            "{last_string:?} did not match {expr:?}"
        );

        assert_eq!(
            vec![
                (Level::Error, "here is another thing: 99".to_owned()),
                (Level::Warning, "watch out!".to_owned()),
                (Level::Info, "here is some info: information".to_owned()),
            ],
            logged
        );
    }
}