1 files changed, 227 insertions, 0 deletions
diff --git a/ecs/src/error.rs b/ecs/src/error.rs
new file mode 100644
index 0000000..f70524d
--- /dev/null
+++ b/ecs/src/error.rs
@@ -0,0 +1,227 @@
+use std::fmt::{Debug, Display, Write as _};
+
+use backtrace::Backtrace;
+
+#[macro_export]
+macro_rules! error {
+    ($lit: literal) => {
+        $crate::error::Error::from($lit)
+    };
+
+    ($lit: literal, $($tt: tt)*) => {
+        $crate::error::Error::from(std::format!($lit, $($tt)*))
+    };
+
+    ($err: expr) => {
+        $crate::error::Error::from($err)
+    };
+}
+
+pub struct Error
+{
+    inner: Box<dyn std::error::Error + Send + Sync>,
+    backtrace: Backtrace,
+}
+
+impl Debug for Error
+{
+    fn fmt(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result
+    {
+        let error = &*self.inner;
+
+        write!(formatter, "{error}")?;
+
+        if let Some(cause) = error.source() {
+            write!(formatter, "\n\nCaused by:")?;
+            let multiple = cause.source().is_some();
+            for (n, error) in anyhow::Chain::new(cause).enumerate() {
+                writeln!(formatter)?;
+
+                let mut indented = Indented {
+                    inner: formatter,
+                    number: if multiple { Some(n) } else { None },
+                    started: false,
+                };
+                write!(indented, "{error}")?;
+            }
+        }
+
+        write!(
+            formatter,
+            "\n\nStack backtrace:\n{:?}",
+            std::fmt::from_fn(|backtrace_formatter| fmt_backtrace(
+                &self.backtrace,
+                backtrace_formatter
+            ))
+        )?;
+
+        Ok(())
+    }
+}
+
+impl Display for Error
+{
+    fn fmt(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result
+    {
+        let error = &*self.inner;
+
+        write!(formatter, "{error}")?;
+
+        if formatter.alternate() {
+            let chain = anyhow::Chain::new(error);
+            for cause in chain.skip(1) {
+                write!(formatter, ": {}", cause)?;
+            }
+        }
+
+        Ok(())
+    }
+}
+
+impl<Err: Send + Sync + 'static> From<Err> for Error
+where
+    Box<dyn std::error::Error + Send + Sync>: From<Err>,
+{
+    fn from(err: Err) -> Self
+    {
+        Self {
+            inner: err.into(),
+            backtrace: Backtrace::new(),
+        }
+    }
+}
+
+pub type ErrorHandler = fn(Error, Metadata);
+
+/// Error metadata.
+#[derive(Debug)]
+pub struct Metadata
+{
+    pub source_name: &'static str,
+    pub source_kind: SourceKind,
+}
+
+/// Error source kind.
+#[derive(Debug)]
+#[non_exhaustive]
+pub enum SourceKind
+{
+    System,
+    Observer,
+}
+
+impl Display for SourceKind
+{
+    fn fmt(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result
+    {
+        match self {
+            SourceKind::System => formatter.write_str("system"),
+            SourceKind::Observer => formatter.write_str("observer"),
+        }
+    }
+}
+
+pub fn err_handler_panic(err: Error, err_metadata: Metadata)
+{
+    panic!(
+        "Error occurred in {} '{}': {err:?}",
+        err_metadata.source_kind, err_metadata.source_name
+    );
+}
+
+pub fn err_handler_log_error(err: Error, err_metadata: Metadata)
+{
+    tracing::error!(
+        "Error occurred in {} '{}': {err:#}",
+        err_metadata.source_kind,
+        err_metadata.source_name
+    );
+}
+
+fn fmt_backtrace(
+    backtrace: &Backtrace,
+    fmt: &mut std::fmt::Formatter<'_>,
+) -> std::fmt::Result
+{
+    let style = if fmt.alternate() {
+        backtrace::PrintFmt::Full
+    } else {
+        backtrace::PrintFmt::Short
+    };
+
+    // When printing paths we try to strip the cwd if it exists, otherwise
+    // we just print the path as-is. Note that we also only do this for the
+    // short format, because if it's full we presumably want to print
+    // everything.
+    let cwd = std::env::current_dir();
+    let mut print_path =
+        move |fmt: &mut std::fmt::Formatter<'_>,
+              path: backtrace::BytesOrWideString<'_>| {
+            let path = path.into_path_buf();
+            if style != backtrace::PrintFmt::Full {
+                if let Ok(cwd) = &cwd {
+                    if let Ok(suffix) = path.strip_prefix(cwd) {
+                        return std::fmt::Display::fmt(&suffix.display(), fmt);
+                    }
+                }
+            }
+            std::fmt::Display::fmt(&path.display(), fmt)
+        };
+
+    let mut f = backtrace::BacktraceFmt::new(fmt, style, &mut print_path);
+
+    f.add_context()?;
+
+    for frame in backtrace.frames() {
+        if frame.symbols().iter().all(|symbol| {
+            symbol.name().is_some_and(|symbol_name| {
+                let symbol_name = symbol_name.to_string();
+
+                symbol_name
+                    .contains("<ecs::error::Error as core::convert::From<Err>>::from")
+            })
+        }) {
+            continue;
+        }
+
+        f.frame().backtrace_frame(frame)?;
+    }
+    f.finish()?;
+    Ok(())
+}
+
+struct Indented<'a, D>
+{
+    inner: &'a mut D,
+    number: Option<usize>,
+    started: bool,
+}
+
+impl<T> std::fmt::Write for Indented<'_, T>
+where
+    T: std::fmt::Write,
+{
+    fn write_str(&mut self, s: &str) -> std::fmt::Result
+    {
+        for (i, line) in s.split('\n').enumerate() {
+            if !self.started {
+                self.started = true;
+                match self.number {
+                    Some(number) => write!(self.inner, "{: >5}: ", number)?,
+                    None => self.inner.write_str("    ")?,
+                }
+            } else if i > 0 {
+                self.inner.write_char('\n')?;
+                if self.number.is_some() {
+                    self.inner.write_str("       ")?;
+                } else {
+                    self.inner.write_str("    ")?;
+                }
+            }
+
+            self.inner.write_str(line)?;
+        }
+
+        Ok(())
+    }
+}