transcribe-cpp 0.4.1

//! Error type mapped from `transcribe_status`.
//!
//! The C API reports failures as a `transcribe_status` int; this module maps
//! each one to a distinct [`Error`] variant (requirements §3: "distinct
//! failures stay distinct"). The grouping mirrors the Python binding's
//! exception hierarchy — the conformance precedent — and the raw status is
//! preserved via [`Error::raw_status`].

use crate::result::Transcript;
use transcribe_cpp_sys as sys;

/// Convenience alias for results from this crate.
pub type Result<T> = std::result::Result<T, Error>;

/// Everything that can go wrong talking to the native library.
///
/// Match on the variant for typed handling; [`Error::raw_status`] recovers the
/// underlying `transcribe_status` code (0 for errors raised purely on the Rust
/// side, e.g. the load-time version gate or a `NUL` in a caller string).
#[derive(Debug, thiserror::Error)]
#[non_exhaustive]
pub enum Error {
    /// `TRANSCRIBE_ERR_INVALID_ARG` (or `_SAMPLE_RATE`).
    #[error("invalid argument: {0}")]
    InvalidArgument(String),
    /// `TRANSCRIBE_ERR_NOT_IMPLEMENTED` — the model has no path for this call.
    #[error("not implemented by this model: {0}")]
    NotImplemented(String),
    /// `TRANSCRIBE_ERR_FILE_NOT_FOUND` — the GGUF path does not exist.
    #[error("model file not found: {0}")]
    ModelFileNotFound(String),
    /// `TRANSCRIBE_ERR_GGUF` / `_UNSUPPORTED_ARCH` / `_UNSUPPORTED_VARIANT`.
    #[error("model load failed: {0}")]
    ModelLoad(String),
    /// `TRANSCRIBE_ERR_OOM`.
    #[error("out of memory: {0}")]
    OutOfMemory(String),
    /// `TRANSCRIBE_ERR_BACKEND` — the requested backend could not be satisfied.
    #[error("backend error: {0}")]
    Backend(String),
    /// `TRANSCRIBE_ERR_UNSUPPORTED_{TASK,LANGUAGE,TIMESTAMPS,PNC,ITN}` — the
    /// model cannot satisfy this request shape.
    #[error("unsupported request: {0}")]
    Unsupported(String),
    /// `TRANSCRIBE_ERR_BAD_STRUCT_SIZE` — an ABI/struct-size fault. With the
    /// generated FFI this indicates a header/library skew, not caller error.
    #[error("ABI struct-size mismatch: {0}")]
    BadStructSize(String),
    /// `TRANSCRIBE_ERR_INPUT_TOO_LONG` — audio longer than the model can decode.
    #[error("input too long: {0}")]
    InputTooLong(String),
    /// `TRANSCRIBE_ERR_ABORTED` — the abort callback returned true. The
    /// transcript of chunks that completed before the abort is preserved.
    #[error("operation aborted: {message}")]
    Aborted {
        message: String,
        /// Partial transcript from chunks that completed before the abort.
        partial: Option<Box<Transcript>>,
    },
    /// `TRANSCRIBE_ERR_OUTPUT_TRUNCATED` — the decode hit the generation budget
    /// before end-of-stream; the transcript is incomplete by contract. The
    /// partial transcript is always preserved.
    #[error("output truncated before end-of-stream: {message}")]
    OutputTruncated {
        message: String,
        /// The (incomplete) transcript produced before truncation.
        partial: Option<Box<Transcript>>,
    },
    /// `TRANSCRIBE_ERR_OUTPUT_REPETITION` — the decode was stopped because the
    /// output began repeating itself; the transcript is incomplete by contract.
    /// The partial transcript, with the repeats dropped, is always preserved.
    #[error("output began repeating before end-of-stream: {message}")]
    OutputRepetition {
        message: String,
        /// The (incomplete) transcript produced before the loop, one copy kept.
        partial: Option<Box<Transcript>>,
    },
    /// `TRANSCRIBE_ERR_UNSUPPORTED_ROLE` — see [`Model::roles`](crate::Model::roles).
    #[error("unsupported role: {0}")]
    UnsupportedRole(String),
    /// `TRANSCRIBE_ERR_INPUT_TOO_SHORT` — the audio is shorter than the role's
    /// minimum (e.g. [`LangIdInfo::min_audio_ms`](crate::LangIdInfo)).
    #[error("input too short: {0}")]
    InputTooShort(String),
    /// The loaded library's base version disagrees with the headers this crate
    /// was generated against (the pre-1.0 version lock). Raised on first use.
    #[error("native library version mismatch: {0}")]
    VersionMismatch(String),
    /// A caller-supplied string contained an interior NUL byte.
    #[error("string contains an interior NUL byte: {0}")]
    Nul(#[from] std::ffi::NulError),
    /// Another session of the same model already has a compute operation in
    /// flight. The C library serializes compute per model (the 0.x limitation):
    /// at most one run / batch / active stream across ALL of a model's sessions
    /// at a time. Finish or drop the in-flight stream (one-shot runs/batches
    /// just queue) before starting another, or give each concurrent worker its
    /// own model. Raised purely on the Rust side, so [`Error::raw_status`] is 0.
    #[error("model busy: {0}")]
    Busy(String),
    /// A non-OK status with no more specific mapping.
    #[error("{0}")]
    Other(String),
}

/// The category of an [`Error`], without its payload. One kind per variant.
///
/// Stable for matching and, under the `serde` feature, serialized as a
/// snake_case string (`"aborted"`, `"model_file_not_found"`, ...). A kind
/// this version does not know deserializes as [`ErrorKind::Other`].
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
#[non_exhaustive]
#[cfg_attr(
    feature = "serde",
    derive(serde::Serialize, serde::Deserialize),
    serde(rename_all = "snake_case")
)]
pub enum ErrorKind {
    InvalidArgument,
    NotImplemented,
    ModelFileNotFound,
    ModelLoad,
    OutOfMemory,
    Backend,
    Unsupported,
    BadStructSize,
    InputTooLong,
    Aborted,
    OutputTruncated,
    OutputRepetition,
    UnsupportedRole,
    VersionMismatch,
    Nul,
    Busy,
    InputTooShort,
    #[cfg_attr(feature = "serde", serde(other))]
    Other,
}

/// An owned, plain-data snapshot of an [`Error`]: what crosses a process or
/// IPC boundary (e.g. a Tauri command's error).
///
/// [`Error`] itself serializes to exactly this shape under the `serde`
/// feature; deserialize into `ErrorReport` on the receiving side (an
/// [`Error`] cannot be rebuilt from it). JSON looks like:
///
/// ```json
/// { "kind": "aborted", "message": "operation aborted: ...", "status": 13, "partial": { "text": "..." } }
/// ```
///
/// `partial` is `null` unless the error carried a partial transcript. It is
/// always written (never skipped) so non-self-describing formats such as
/// postcard round-trip.
#[derive(Debug, Clone, PartialEq)]
#[non_exhaustive]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct ErrorReport {
    /// The error category.
    pub kind: ErrorKind,
    /// The error's `Display` text.
    pub message: String,
    /// [`Error::raw_status`]: the `transcribe_status`, or 0 for Rust-side errors.
    #[cfg_attr(feature = "serde", serde(default))]
    pub status: i32,
    /// [`Error::partial`], if any.
    #[cfg_attr(feature = "serde", serde(default))]
    pub partial: Option<Transcript>,
}

impl From<&Error> for ErrorReport {
    fn from(err: &Error) -> Self {
        ErrorReport {
            kind: err.kind(),
            message: err.to_string(),
            status: err.raw_status(),
            partial: err.partial().cloned(),
        }
    }
}

/// Moves the partial transcript out instead of cloning it.
impl From<Error> for ErrorReport {
    fn from(err: Error) -> Self {
        let (kind, message, status) = (err.kind(), err.to_string(), err.raw_status());
        let partial = match err {
            Error::Aborted { partial, .. }
            | Error::OutputTruncated { partial, .. }
            | Error::OutputRepetition { partial, .. } => partial.map(|p| *p),
            _ => None,
        };
        ErrorReport {
            kind,
            message,
            status,
            partial,
        }
    }
}

/// Serializes as an [`ErrorReport`] (see there for the shape), without
/// cloning the partial transcript.
#[cfg(feature = "serde")]
impl serde::Serialize for Error {
    fn serialize<S: serde::Serializer>(&self, s: S) -> std::result::Result<S::Ok, S::Error> {
        #[derive(serde::Serialize)]
        struct Report<'a> {
            kind: ErrorKind,
            message: String,
            status: i32,
            partial: Option<&'a Transcript>,
        }
        Report {
            kind: self.kind(),
            message: self.to_string(),
            status: self.raw_status(),
            partial: self.partial(),
        }
        .serialize(s)
    }
}

impl Error {
    /// This error's [`ErrorKind`].
    pub fn kind(&self) -> ErrorKind {
        // Exhaustive on purpose: a new variant must pick a kind to compile.
        match self {
            Error::InvalidArgument(_) => ErrorKind::InvalidArgument,
            Error::NotImplemented(_) => ErrorKind::NotImplemented,
            Error::ModelFileNotFound(_) => ErrorKind::ModelFileNotFound,
            Error::ModelLoad(_) => ErrorKind::ModelLoad,
            Error::OutOfMemory(_) => ErrorKind::OutOfMemory,
            Error::Backend(_) => ErrorKind::Backend,
            Error::Unsupported(_) => ErrorKind::Unsupported,
            Error::BadStructSize(_) => ErrorKind::BadStructSize,
            Error::InputTooLong(_) => ErrorKind::InputTooLong,
            Error::Aborted { .. } => ErrorKind::Aborted,
            Error::OutputTruncated { .. } => ErrorKind::OutputTruncated,
            Error::OutputRepetition { .. } => ErrorKind::OutputRepetition,
            Error::UnsupportedRole(_) => ErrorKind::UnsupportedRole,
            Error::InputTooShort(_) => ErrorKind::InputTooShort,
            Error::VersionMismatch(_) => ErrorKind::VersionMismatch,
            Error::Nul(_) => ErrorKind::Nul,
            Error::Busy(_) => ErrorKind::Busy,
            Error::Other(_) => ErrorKind::Other,
        }
    }

    /// The `transcribe_status` this error was mapped from, or `0` for errors
    /// raised on the Rust side (version gate, NUL in a string, …).
    pub fn raw_status(&self) -> i32 {
        use sys::transcribe_status as S;
        let s = match self {
            Error::InvalidArgument(_) => S::TRANSCRIBE_ERR_INVALID_ARG,
            Error::NotImplemented(_) => S::TRANSCRIBE_ERR_NOT_IMPLEMENTED,
            Error::ModelFileNotFound(_) => S::TRANSCRIBE_ERR_FILE_NOT_FOUND,
            Error::ModelLoad(_) => S::TRANSCRIBE_ERR_GGUF,
            Error::OutOfMemory(_) => S::TRANSCRIBE_ERR_OOM,
            Error::Backend(_) => S::TRANSCRIBE_ERR_BACKEND,
            Error::Unsupported(_) => S::TRANSCRIBE_ERR_UNSUPPORTED_TASK,
            Error::BadStructSize(_) => S::TRANSCRIBE_ERR_BAD_STRUCT_SIZE,
            Error::InputTooLong(_) => S::TRANSCRIBE_ERR_INPUT_TOO_LONG,
            Error::Aborted { .. } => S::TRANSCRIBE_ERR_ABORTED,
            Error::OutputTruncated { .. } => S::TRANSCRIBE_ERR_OUTPUT_TRUNCATED,
            Error::OutputRepetition { .. } => S::TRANSCRIBE_ERR_OUTPUT_REPETITION,
            Error::UnsupportedRole(_) => S::TRANSCRIBE_ERR_UNSUPPORTED_ROLE,
            Error::InputTooShort(_) => S::TRANSCRIBE_ERR_INPUT_TOO_SHORT,
            _ => S::TRANSCRIBE_OK,
        };
        s.0 as i32
    }

    /// The partial transcript carried by [`Error::Aborted`] /
    /// [`Error::OutputTruncated`] / [`Error::OutputRepetition`], if any. `None`
    /// for every other variant.
    pub fn partial(&self) -> Option<&Transcript> {
        match self {
            Error::Aborted { partial, .. }
            | Error::OutputTruncated { partial, .. }
            | Error::OutputRepetition { partial, .. } => partial.as_deref(),
            _ => None,
        }
    }
}

/// Human-readable text for a `transcribe_status` (from the C side).
pub(crate) fn status_string(status: i32) -> String {
    // Borrowed pointer into static storage; copy at the boundary.
    let ptr = unsafe { sys::transcribe_status_string(status) };
    if ptr.is_null() {
        return format!("status {status}");
    }
    unsafe { std::ffi::CStr::from_ptr(ptr) }
        .to_string_lossy()
        .into_owned()
}

/// Build the mapped error for a non-OK status (without a partial transcript).
/// The run path re-attaches partials for the two result-bearing statuses.
pub(crate) fn error_for_status(status: sys::transcribe_status, context: &str) -> Error {
    use sys::transcribe_status as S;
    let code = status.0 as i32;
    let msg = {
        let s = status_string(code);
        if context.is_empty() {
            format!("{s} (status {code})")
        } else {
            format!("{context}: {s} (status {code})")
        }
    };
    match status {
        S::TRANSCRIBE_ERR_INVALID_ARG | S::TRANSCRIBE_ERR_SAMPLE_RATE => {
            Error::InvalidArgument(msg)
        }
        S::TRANSCRIBE_ERR_NOT_IMPLEMENTED => Error::NotImplemented(msg),
        S::TRANSCRIBE_ERR_FILE_NOT_FOUND => Error::ModelFileNotFound(msg),
        S::TRANSCRIBE_ERR_GGUF
        | S::TRANSCRIBE_ERR_UNSUPPORTED_ARCH
        | S::TRANSCRIBE_ERR_UNSUPPORTED_VARIANT => Error::ModelLoad(msg),
        S::TRANSCRIBE_ERR_OOM => Error::OutOfMemory(msg),
        S::TRANSCRIBE_ERR_BACKEND => Error::Backend(msg),
        S::TRANSCRIBE_ERR_UNSUPPORTED_LANGUAGE
        | S::TRANSCRIBE_ERR_UNSUPPORTED_TASK
        | S::TRANSCRIBE_ERR_UNSUPPORTED_TIMESTAMPS
        | S::TRANSCRIBE_ERR_UNSUPPORTED_PNC
        | S::TRANSCRIBE_ERR_UNSUPPORTED_ITN => Error::Unsupported(msg),
        S::TRANSCRIBE_ERR_BAD_STRUCT_SIZE => Error::BadStructSize(msg),
        S::TRANSCRIBE_ERR_INPUT_TOO_LONG => Error::InputTooLong(msg),
        S::TRANSCRIBE_ERR_ABORTED => Error::Aborted {
            message: msg,
            partial: None,
        },
        S::TRANSCRIBE_ERR_OUTPUT_TRUNCATED => Error::OutputTruncated {
            message: msg,
            partial: None,
        },
        S::TRANSCRIBE_ERR_OUTPUT_REPETITION => Error::OutputRepetition {
            message: msg,
            partial: None,
        },
        S::TRANSCRIBE_ERR_UNSUPPORTED_ROLE => Error::UnsupportedRole(msg),
        S::TRANSCRIBE_ERR_INPUT_TOO_SHORT => Error::InputTooShort(msg),
        _ => Error::Other(msg),
    }
}

/// `Ok(())` for `TRANSCRIBE_OK`, otherwise the mapped error.
pub(crate) fn check(status: sys::transcribe_status, context: &str) -> Result<()> {
    if status == sys::transcribe_status::TRANSCRIBE_OK {
        Ok(())
    } else {
        Err(error_for_status(status, context))
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::mem::discriminant;
    use sys::transcribe_status as S;

    #[test]
    fn every_status_maps_to_a_typed_variant() {
        // Every non-OK status the linked library knows, found by walking codes
        // upward until `transcribe_status_string` falls back to its "unknown"
        // text, so a status appended to the header without a mapping fails here.
        let unknown = status_string(-1);
        let codes: Vec<S> = (1..256u32)
            .take_while(|&c| status_string(c as i32) != unknown)
            .map(S)
            .collect();
        assert!(
            codes.len() >= S::TRANSCRIBE_ERR_UNSUPPORTED_ROLE.0 as usize,
            "status walk stopped early at {} codes",
            codes.len()
        );
        for status in codes {
            let code = status.0;
            let err = error_for_status(status, "ctx");
            assert!(
                !matches!(err, Error::Other(_)),
                "status {code} falls through to Error::Other: {err:?}"
            );
            // raw_status must name a status that maps back to the same
            // variant (grouped codes like SAMPLE_RATE report their group's
            // primary status, never 0).
            let raw = err.raw_status();
            assert_ne!(raw, 0, "status {code} reports raw_status 0: {err:?}");
            let back = error_for_status(S(raw as u32), "ctx");
            assert_eq!(
                discriminant(&back),
                discriminant(&err),
                "status {code} -> {err:?} -> raw {raw} -> {back:?}"
            );
            assert_eq!(back.kind(), err.kind(), "status {code}");
            assert_ne!(err.kind(), ErrorKind::Other, "status {code}");
        }
        let role = error_for_status(S::TRANSCRIBE_ERR_UNSUPPORTED_ROLE, "ctx");
        assert!(matches!(role, Error::UnsupportedRole(_)), "{role:?}");
    }
}