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use std::backtrace::Backtrace;
use std::fmt::{self, Debug, Display};
use std::error::Error;
use crate::Exception;
pub trait Context<T, E> {
fn context<C: Display + Send + Sync + 'static>(self, context: C) -> Result<T, Exception>;
fn with_context<C, F>(self, f: F) -> Result<T, Exception> where
C: Display + Send + Sync + 'static,
F: FnOnce(&E) -> C;
}
impl<T, E: Error + Send + Sync + 'static> Context<T, E> for Result<T, E> {
fn context<C: Display + Send + Sync + 'static>(self, context: C) -> Result<T, Exception> {
self.map_err(|error| Exception::from(ContextError { error, context }))
}
fn with_context<C, F>(self, f: F) -> Result<T, Exception> where
C: Display + Send + Sync + 'static,
F: FnOnce(&E) -> C
{
self.map_err(|error| Exception::from(ContextError { context: f(&error), error }))
}
}
impl<T> Context<T, Exception> for Result<T, Exception> {
fn context<C: Display + Send + Sync + 'static>(self, context: C) -> Result<T, Exception> {
self.map_err(|error| Exception::from(ContextError { error, context }))
}
fn with_context<C, F>(self, f: F) -> Result<T, Exception> where
C: Display + Send + Sync + 'static,
F: FnOnce(&Exception) -> C
{
self.map_err(|error| Exception::from(ContextError { context: f(&error), error }))
}
}
struct ContextError<E, C> {
error: E,
context: C,
}
impl<E: Debug, C: Display> Debug for ContextError<E, C> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "{:?}\n\n{}", self.error, self.context)
}
}
impl<E, C: Display> Display for ContextError<E, C> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
Display::fmt(&self.context, f)
}
}
impl<E: Error + 'static, C: Display> Error for ContextError<E, C> {
fn backtrace(&self) -> Option<&Backtrace> {
self.error.backtrace()
}
fn cause(&self) -> Option<&dyn Error> {
Some(&self.error)
}
fn source(&self) -> Option<&(dyn Error + 'static)> {
Some(&self.error)
}
}
impl<C: Display> Error for ContextError<Exception, C> {
fn backtrace(&self) -> Option<&Backtrace> {
Some(self.error.backtrace())
}
fn cause(&self) -> Option<&dyn Error> {
Some(&*self.error)
}
fn source(&self) -> Option<&(dyn Error + 'static)> {
Some(&*self.error)
}
}