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use std::error::Error;
use std::fmt::{Debug, Display, Formatter};
use crate::processor::ObjectKey;

#[repr(transparent)]
pub struct ProcessingError {
    pub inner: ErrorKind
}

impl ProcessingError {
    pub fn new(inner: ErrorKind) -> ProcessingError {
        ProcessingError { inner }
    }
}

#[derive(Debug)]
pub enum ErrorKind {
    /// Key is invalid for given object. 
    /// This may mean that something is wrong with messages in the topic (or with the processor config).
    InvalidObjectTree {
        invalid_key: Vec<ObjectKey>,
        reason: String,
    },
    
    /// Object key is empty - this should not be allowed.
    /// This means that an empty key was supplied - and there is no way to extract the field from JSON object.
    EmptyKey,
    
    /// Default wrapper for any error.
    OtherError {
        err: Box<dyn Error>
    },

    /// Low priority error - Field not found and thus, cannot use this message processor.
    /// Example: requested to copy $.foo into $.bar, but no $.foo field was present.
    FieldNotFound {
        key: Vec<ObjectKey>,
    },
    
    /// Lowe priority error - processor was skipped for any arbitrary reason.
    /// Example: some processor condition was not met.
    ProcessorSkipped {
        reason: String
    }
}

impl Display for ErrorKind {
    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
        match self {
            ErrorKind::InvalidObjectTree { invalid_key, reason } =>
                write!(f, "Object tree is incompatible with key [{invalid_key:?}], reason: {reason}"),
            ErrorKind::EmptyKey =>
                write!(f, "Illegal object tree key: Key is empty."),
            ErrorKind::FieldNotFound { key } =>
                write!(f, "No key in object: [{key:?}]"),
            ErrorKind::OtherError { err } =>
                write!(f, "Unexpected error while processing: {err}"),
            ErrorKind::ProcessorSkipped { reason } => 
                write!(f, "{reason}"),
        }
    }
}

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

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

impl Error for ProcessingError {}

impl<T: Error + 'static> From<T> for ErrorKind {
    fn from(err: T) -> Self {
        ErrorKind::OtherError { err: Box::new(err) }
    }
}

impl From<ErrorKind> for ProcessingError {
    fn from(e: ErrorKind) -> Self {
        ProcessingError::new(e)
    }
}