cas-error 0.2.0

#![doc = include_str!("../README.md")]

use ariadne::{Color, Report, Source};
use std::{fmt::Debug, io::Write, ops::Range};

/// The color to use to highlight expressions.
pub const EXPR: Color = Color::RGB(52, 235, 152);

/// Represents any kind of error that can occur during some operation.
pub trait ErrorKind: Debug + Send {
    /// Builds the report for this error.
    fn build_report<'a>(
        &self,
        src_id: &'a str,
        spans: &[Range<usize>],
    ) -> Report<(&'a str, Range<usize>)>;
}

/// An error associated with regions of source code that can be highlighted.
#[derive(Debug)]
pub struct Error {
    /// The regions of the source code that this error originated from.
    pub spans: Vec<Range<usize>>,

    /// The kind of error that occurred.
    pub kind: Box<dyn ErrorKind>,
}

impl Error {
    /// Creates a new error with the given spans and kind.
    pub fn new(spans: Vec<Range<usize>>, kind: impl ErrorKind + 'static) -> Self {
        Self { spans, kind: Box::new(kind) }
    }

    /// Build a report from this error kind.
    pub fn build_report<'a>(&self, src_id: &'a str) -> Report<(&'a str, Range<usize>)> {
        self.kind.build_report(src_id, &self.spans)
    }

    /// Writes the error to stderr.
    ///
    /// The `ariadne` crate's [`Report`] type does not have a `Display` implementation, so we can
    /// only use its `eprint` method to print to stderr.
    ///
    /// [`Report`]: ariadne::Report
    pub fn report_to_stderr(&self, src_id: &str, input: &str) -> std::io::Result<()> {
        self.report_to(std::io::stderr(), src_id, input)
    }

    /// Writes the error to an output stream.
    pub fn report_to<W: Write>(
        &self,
        writer: W,
        src_id: &str,
        input: &str,
    ) -> std::io::Result<()> {
        let report = self.build_report(src_id);
        report.write((src_id, Source::from(input)), writer)
    }
}