eventsrc-client 0.0.2

use std::{borrow::Cow, error, fmt};

/// Error categories for event source.
#[non_exhaustive]
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub enum ErrorKind {
    /// Transport error.
    Transport,
    /// Invalid request error.
    InvalidRequest,
    /// Invalid response (status != 200, content-type != text/event-stream or body stream error).
    InvalidResponse,
    /// Event source protocol error.
    Protocol,
}

impl fmt::Display for ErrorKind {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::Transport => write!(f, "Transport")?,
            Self::InvalidRequest => write!(f, "InvalidRequest")?,
            Self::InvalidResponse => write!(f, "InvalidResponse")?,
            Self::Protocol => write!(f, "SseProtocol")?,
        }
        Ok(())
    }
}

/// The lower-level source of [`Error`].
///
/// NOTE: we don't implement `core::error::Error` for `ErrorSource`.
pub struct ErrorSource(anyhow::Error);

impl fmt::Debug for ErrorSource {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt::Debug::fmt(&self.0, f)
    }
}

impl fmt::Display for ErrorSource {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt::Display::fmt(&self.0, f)
    }
}

impl From<String> for ErrorSource {
    fn from(message: String) -> Self {
        ErrorSource(anyhow::Error::msg(message))
    }
}

impl From<&'static str> for ErrorSource {
    fn from(message: &'static str) -> Self {
        ErrorSource(anyhow::Error::msg(message))
    }
}

/// Conversion trait for attaching source errors.
pub trait IntoErrorSource {
    /// Converts the error into an error source.
    fn into_error_source(self) -> ErrorSource;
}

impl IntoErrorSource for ErrorSource {
    fn into_error_source(self) -> ErrorSource {
        self
    }
}

impl<E> IntoErrorSource for E
where
    E: Into<anyhow::Error>,
{
    fn into_error_source(self) -> ErrorSource {
        ErrorSource(self.into())
    }
}

/// Error type for event source.
pub struct Error {
    kind: ErrorKind,
    message: Cow<'static, str>,
    context: Vec<(&'static str, String)>,
    source: Option<ErrorSource>,
}

impl Error {
    /// Creates a new error with the given kind and message.
    pub fn new(kind: ErrorKind, message: impl Into<Cow<'static, str>>) -> Self {
        Self { kind, message: message.into(), context: Vec::new(), source: None }
    }

    /// Returns the error kind.
    pub const fn kind(&self) -> ErrorKind {
        self.kind
    }

    /// Returns the error message.
    pub fn message(&self) -> &str {
        &self.message
    }

    /// Returns the error context entries.
    pub fn context(&self) -> &[(&'static str, String)] {
        &self.context
    }

    /// Adds a context entry to the error.
    pub fn with_context(mut self, key: &'static str, value: impl ToString) -> Self {
        self.context.push((key, value.to_string()));
        self
    }

    /// Attaches a error source.
    pub fn set_source(mut self, source: impl IntoErrorSource) -> Self {
        debug_assert!(self.source.is_none(), "source already set");
        self.source = Some(source.into_error_source());
        self
    }

    /// Returns the source error, if any.
    pub fn source(&self) -> Option<&ErrorSource> {
        self.source.as_ref()
    }
}

impl fmt::Display for Error {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}: {}", self.kind, self.message)?;

        if !self.context.is_empty() {
            f.write_str(" { ")?;
            for (index, (key, value)) in self.context.iter().enumerate() {
                if index > 0 {
                    f.write_str(", ")?;
                }
                write!(f, "{key}={value}")?;
            }
            f.write_str(" }")?;
        }

        Ok(())
    }
}

impl fmt::Debug for Error {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        writeln!(f, "{}: {}", self.kind, self.message)?;
        if !self.context.is_empty() {
            writeln!(f, "Context:")?;
            for (key, value) in &self.context {
                writeln!(f, "    {key}: {value}")?;
            }
        }
        if let Some(source) = &self.source {
            writeln!(f, "Source: {source}")?;
        }
        Ok(())
    }
}

impl error::Error for Error {
    fn source(&self) -> Option<&(dyn error::Error + 'static)> {
        self.source.as_ref().map(|err| err.0.as_ref())
    }
}

impl From<eventsrc::ProtocolError> for Error {
    fn from(err: eventsrc::ProtocolError) -> Self {
        Self {
            kind: ErrorKind::Protocol,
            message: Cow::Owned(err.to_string()),
            context: Vec::new(),
            source: None,
        }
    }
}

impl<E> From<eventsrc::StreamError<E>> for Error
where
    E: error::Error + Send + Sync + 'static,
{
    fn from(err: eventsrc::StreamError<E>) -> Self {
        match err {
            eventsrc::StreamError::Source(e) => Self {
                kind: ErrorKind::InvalidResponse,
                message: "invalid response body stream error".into(),
                context: Vec::new(),
                source: Some(anyhow::Error::new(e).into_error_source()),
            },
            eventsrc::StreamError::Protocol(e) => Self {
                kind: ErrorKind::Protocol,
                message: Cow::Owned(e.to_string()),
                context: Vec::new(),
                source: None,
            },
        }
    }
}