//! The Report type which reports errors nicely

use std::error::Error as StdError;

use std::fmt::{self, Debug, Display};

use crate::sealed::Sealed;

/// Wraps any Error, providing a nicely-reporting Display impl

#[derive(Debug, Copy, Clone)]

#[allow(clippy::exhaustive_structs)] // this is a transparent wrapper

pub struct Report<E>(pub E)

where

    E: AsRef<dyn StdError>;

impl<E> Display for Report<E>

where

    E: AsRef<dyn StdError>,

{

        /// Non-generic inner function avoids code bloat

}

/// Report the error E to stderr, and exit the program

///

/// Does not return.  Return type is any type R, for convenience with eg `unwrap_or_else`.

#[allow(clippy::print_stderr)] // this is the point of this function

{

    /// Non-generic inner function avoids code bloat

}

/// Helper type for reporting errors that are concrete implementors of `StdError`

///

/// This is an opaque type, only constructable via the [`ErrorReport`] helper trait

/// and only usable via its `AsRef` implementation.

//

// We need this because Rust's trait object handling rules, and provided AsRef impls,

// are rather anaemic.  We cannot simply put a &dyn Error into Report, because

// &dyn Error doesn't impl AsRef<dyn Error> even though the implementation is trivial.

// We can't provide that AsRef impl ourselves due to trait coherency rules.

// So instead, we wrap up the &dyn Error in a newtype, for which we *can* provide the AsRef.

pub struct ReportHelper<'e>(&'e (dyn StdError + 'static));

impl<'e> AsRef<dyn StdError + 'static> for ReportHelper<'e> {

}

/// Extension trait providing `.report()` method on concrete errors

///

/// This is implemented for types that directly implement [`std::error::Error`]` + 'static`.

///

/// For types like `anyhow::Error` that `impl Deref<Target = dyn Error...>`,

/// you can use `tor_error::Report(err)` directly,

/// but you can also call `.report()` via the impl of this trait for `dyn Error`.

pub trait ErrorReport: Sealed + StdError + 'static {

    /// Return an object that displays the error and its causes

    //

    // We would ideally have returned `Report<impl AsRef<...>>` but that's TAIT.

    fn report(&self) -> Report<ReportHelper>;

}

impl<E: StdError + Sized + 'static> Sealed for E {}

impl<E: StdError + Sized + 'static> ErrorReport for E {

}

impl Sealed for dyn StdError + Send + Sync {}

/// Implementation for `anyhow::Error`, which derefs to `dyn StdError`.

impl ErrorReport for dyn StdError + Send + Sync {

}

impl Sealed for dyn StdError + 'static {}

impl ErrorReport for dyn StdError + 'static {

}

/// Defines `AsRef<dyn StdError + 'static>` for a type implementing [`StdError`]

///

/// This trivial `AsRef` impl enables use of `tor_error::Report`.

// Rust don't do this automatically, sadly, even though

// it's basically `impl AsRef<dyn Trait> for T where T: Trait`.

#[macro_export]

macro_rules! define_asref_dyn_std_error { { $ty:ty } => {

// TODO: It would nice if this could be generated more automatically;

// TODO wouldn't it be nice if this was a `derive` (eg using derive-deftly)

    impl AsRef<dyn std::error::Error + 'static> for $ty {

    }

} }

#[cfg(test)]

mod test {

    // @@ begin test lint list maintained by maint/add_warning @@

    #![allow(clippy::bool_assert_comparison)]

    #![allow(clippy::clone_on_copy)]

    #![allow(clippy::dbg_macro)]

    #![allow(clippy::mixed_attributes_style)]

    #![allow(clippy::print_stderr)]

    #![allow(clippy::print_stdout)]

    #![allow(clippy::single_char_pattern)]

    #![allow(clippy::unwrap_used)]

    #![allow(clippy::unchecked_time_subtraction)]

    #![allow(clippy::useless_vec)]

    #![allow(clippy::needless_pass_by_value)]

    #![allow(clippy::string_slice)] // See arti#2571

    //! <!-- @@ end test lint list maintained by maint/add_warning @@ -->

    use super::*;

    use std::io;

    use thiserror::Error;

    #[derive(Error, Debug)]

    #[error("terse")]

    struct TerseError {

        #[from]

        source: Box<dyn StdError>,

    }

    #[derive(Error, Debug)]

    #[error("verbose - {source}")]

    struct VerboseError {

        #[from]

        source: Box<dyn StdError>,

    }

    #[derive(Error, Debug)]

    #[error("shallow")]

    struct ShallowError;

    fn chk<E: StdError + 'static>(e: E, expected: &str) {

        let e: Box<dyn StdError> = Box::new(e);

        let got = Report(&e).to_string();

        assert_eq!(got, expected, "\nmismatch: {:?}", &e);

    }

    #[test]

    #[rustfmt::skip] // preserve layout of chk calls

    fn test() {

        chk(ShallowError,

            "error: shallow");

        let terse_1 = || TerseError { source: ShallowError.into() };

        chk(terse_1(),

            "error: terse: shallow");

        let verbose_1 = || VerboseError { source: ShallowError.into() };

        chk(verbose_1(),

            "error: verbose - shallow");

        chk(VerboseError { source: terse_1().into() },

            "error: verbose - terse: shallow");

        chk(TerseError { source: verbose_1().into() },

            "error: terse: verbose - shallow");

        chk(io::Error::other(ShallowError),

            "error: shallow");

    }

}