rsconstruct 0.9.79

use std::fmt;

/// Exit codes for rsconstruct, allowing CI scripts to distinguish error types.
#[derive(Debug, Clone, Copy, PartialEq, Eq, strum::EnumIter)]
pub enum RsconstructExitCode {
    Success = 0,
    BuildError = 1,
    ConfigError = 2,
    ToolError = 3,
    GraphError = 4,
    IoError = 5,
    Interrupted = 130,
}

/// The exit codes are a public contract: CI scripts branch on these numbers,
/// so a renumbering is a breaking change for every caller. `code()` is `const`,
/// so the check costs nothing at runtime and fails the build rather than a
/// test run — the value is wrong before anything executes.
const _: () = {
    assert!(RsconstructExitCode::Success.code() == 0);
    assert!(RsconstructExitCode::BuildError.code() == 1);
    assert!(RsconstructExitCode::ConfigError.code() == 2);
    assert!(RsconstructExitCode::ToolError.code() == 3);
    assert!(RsconstructExitCode::GraphError.code() == 4);
    assert!(RsconstructExitCode::IoError.code() == 5);
    assert!(RsconstructExitCode::Interrupted.code() == 130);
};

impl RsconstructExitCode {
    pub const fn code(self) -> u8 {
        self as u8
    }

    pub const fn name(self) -> &'static str {
        match self {
            Self::Success => "EXIT_SUCCESS",
            Self::BuildError => "EXIT_BUILD_ERROR",
            Self::ConfigError => "EXIT_CONFIG_ERROR",
            Self::ToolError => "EXIT_TOOL_ERROR",
            Self::GraphError => "EXIT_GRAPH_ERROR",
            Self::IoError => "EXIT_IO_ERROR",
            Self::Interrupted => "EXIT_INTERRUPTED",
        }
    }

    pub const fn description(self) -> &'static str {
        match self {
            Self::Success => "Build completed successfully",
            Self::BuildError => "One or more processors failed",
            Self::ConfigError => "Invalid or missing configuration",
            Self::ToolError => "Required external tool missing or wrong version",
            Self::GraphError => "Dependency cycle or output conflict in build graph",
            Self::IoError => "File system or I/O operation failed",
            Self::Interrupted => "Build interrupted by signal (Ctrl+C)",
        }
    }
}

/// A typed error that carries an exit code for classification.
#[derive(Debug)]
pub struct RsconstructError {
    pub exit_code: RsconstructExitCode,
    pub message: String,
}

impl RsconstructError {
    pub fn new(exit_code: RsconstructExitCode, message: impl Into<String>) -> Self {
        Self {
            exit_code,
            message: message.into(),
        }
    }
}

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

impl std::error::Error for RsconstructError {}

/// Shorthand for a typed `ConfigError`.
pub fn config_error(message: impl Into<String>) -> anyhow::Error {
    RsconstructError::new(RsconstructExitCode::ConfigError, message.into()).into()
}

/// Shorthand for a typed interrupt. Every interruption must be raised
/// through this (never `bail!("Interrupted")` strings): `classify_error`
/// consults only typed information, so an untyped interrupt classifies as
/// exit 1 and a Ctrl+C during `fix`/`clean` reports as a build failure
/// instead of exit 130.
pub fn interrupted() -> anyhow::Error {
    RsconstructError::new(RsconstructExitCode::Interrupted, "Interrupted".to_string()).into()
}

/// Classify an anyhow error into an exit code.
///
/// Only typed information is consulted: a [`RsconstructError`] anywhere in
/// the chain wins, a raw `std::io::Error` in the chain means `IoError`, and
/// everything else is a `BuildError`. There is deliberately no message
/// pattern matching — error chains embed subprocess stderr, so substring
/// matching turns arbitrary tool output into wrong exit codes (a linter
/// printing "unknown field" is not a config error).
pub fn classify_error(err: &anyhow::Error) -> RsconstructExitCode {
    if let Some(rsconstruct_err) = err.downcast_ref::<RsconstructError>() {
        return rsconstruct_err.exit_code;
    }
    if err
        .chain()
        .any(|c| c.downcast_ref::<std::io::Error>().is_some())
    {
        // A raw IO error anywhere in the chain: filesystem-level failure.
        return RsconstructExitCode::IoError;
    }
    RsconstructExitCode::BuildError
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn classify_rsconstruct_error_downcast() {
        let err: anyhow::Error =
            RsconstructError::new(RsconstructExitCode::ConfigError, "bad config").into();
        assert_eq!(classify_error(&err), RsconstructExitCode::ConfigError);

        let err: anyhow::Error =
            RsconstructError::new(RsconstructExitCode::GraphError, "cycle").into();
        assert_eq!(classify_error(&err), RsconstructExitCode::GraphError);
    }

    /// The typed error must win even when wrapped in layers of context —
    /// `downcast_ref` on anyhow searches the whole chain.
    #[test]
    fn classify_typed_error_survives_context_wrapping() {
        let err: anyhow::Error =
            RsconstructError::new(RsconstructExitCode::ToolError, "tool gone").into();
        let wrapped = err.context("while preflighting").context("during build");
        assert_eq!(classify_error(&wrapped), RsconstructExitCode::ToolError);
    }

    /// A raw `io::Error` anywhere in the chain classifies as `IoError` — the
    /// only way exit code 5 is reachable.
    #[test]
    fn classify_io_error_in_chain() {
        let io = std::io::Error::new(std::io::ErrorKind::PermissionDenied, "denied");
        let err = anyhow::Error::new(io).context("Failed to write output");
        assert_eq!(classify_error(&err), RsconstructExitCode::IoError);
    }

    /// Subprocess stderr embedded in an error message must never influence
    /// the exit code — a linter printing "unknown field" is not a config
    /// error, and a tool printing "interrupted" is not exit 130.
    #[test]
    fn classify_never_pattern_matches_messages() {
        for msg in [
            "tool output: unknown field `foo`",
            "tool output: operation interrupted",
            "tool output: cycle detected",
            "tool output: tool version mismatch",
            "something totally unexpected",
        ] {
            assert_eq!(
                classify_error(&anyhow::anyhow!("{msg}")),
                RsconstructExitCode::BuildError,
                "untyped message must default to BuildError: {msg}"
            );
        }
    }

    // The numeric values are asserted at compile time (see the `const _`
    // block at the top of this file), so there is no runtime test for them.
}