//! Errors for the shared crate.
//!
//! `shared` is `#![no_std]` and is compiled for SPIR-V and CUDA, so it must not
//! depend on `anyhow` -- whose default features enable `std`. These variants are
//! `Copy` and allocation-free; the CPU-side caller holds the offending string and
//! the `FileLoc`, so it supplies those when reporting.

use core::fmt;

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Error {
    UnknownWrapMode,
    UnknownFilterFunction,
    UnknownColorEncoding,
    /// `look_at` received an up vector parallel to the viewing direction.
    DegenerateLookAt,
    /// A transform matrix could not be inverted (pbrt's `InverseOrDie`).
    SingularMatrix,
}

impl fmt::Display for Error {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str(match self {
            Self::UnknownWrapMode => "unknown wrap mode",
            Self::UnknownFilterFunction => "unknown filter function",
            Self::UnknownColorEncoding => "unknown color encoding",
            Self::DegenerateLookAt => {
                "LookAt: \"up\" vector and viewing direction are parallel"
            }
            Self::SingularMatrix => "matrix is not invertible",
        })
    }
}

// Stable in core since 1.81, and the same trait `std::error::Error` re-exports --
// so `?` and `anyhow::Context` keep working unchanged on the CPU side.
impl core::error::Error for Error {}

pub type Result<T> = core::result::Result<T, Error>;