// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License..

#[cfg(feature = "backtrace")]
use crate::backtrace::Backtrace;
use core::alloc::{AllocError, LayoutErr};
use core::array;
use core::any::TypeId;
use core::cell;
use core::char;
use core::fmt::{self, Debug, Display};
use core::mem::transmute;
use core::num;
use alloc_crate::str;
use alloc_crate::string::{self, String};
use alloc_crate::boxed::Box;
use alloc_crate::borrow::Cow;
use alloc_crate::collections;

/// `Error` is a trait representing the basic expectations for error values,
/// i.e., values of type `E` in [`Result<T, E>`]. Errors must describe
/// themselves through the [`Display`] and [`Debug`] traits, and may provide
/// cause chain information:
///
/// The [`source`] method is generally used when errors cross "abstraction
/// boundaries". If one module must report an error that is caused by an error
/// from a lower-level module, it can allow access to that error via the
/// [`source`] method. This makes it possible for the high-level module to
/// provide its own errors while also revealing some of the implementation for
/// debugging via [`source`] chains.
///
/// [`Result<T, E>`]: ../result/enum.Result.html
/// [`Display`]: ../fmt/trait.Display.html
/// [`Debug`]: ../fmt/trait.Debug.html
/// [`source`]: trait.Error.html#method.source
pub trait Error: Debug + Display {
    /// The lower-level source of this error, if any.
    ///
    fn source(&self) -> Option<&(dyn Error + 'static)> {
        None
    }

    /// Gets the `TypeId` of `self`.
    fn type_id(&self, _: private::Internal) -> TypeId
    where
        Self: 'static,
    {
        TypeId::of::<Self>()
    }

    /// Returns a stack backtrace, if available, of where this error occurred.
    ///
    /// This function allows inspecting the location, in code, of where an error
    /// happened. The returned `Backtrace` contains information about the stack
    /// trace of the OS thread of execution of where the error originated from.
    ///
    /// Note that not all errors contain a `Backtrace`. Also note that a
    /// `Backtrace` may actually be empty. For more information consult the
    /// `Backtrace` type itself.
    #[cfg(feature = "backtrace")]
    fn backtrace(&self) -> Option<&Backtrace> {
        None
    }

    /// ```
    /// if let Err(e) = "xc".parse::<u32>() {
    ///     // Print `e` itself, no need for description().
    ///     eprintln!("Error: {}", e);
    /// }
    /// ```
    fn description(&self) -> &str {
        "description() is deprecated; use Display"
    }

    fn cause(&self) -> Option<&dyn Error> {
        self.source()
    }
}

mod private {
    // This is a hack to prevent `type_id` from being overridden by `Error`
    // implementations, since that can enable unsound downcasting.
    #[derive(Debug)]
    pub struct Internal;
}

impl<'a, E: Error + 'a> From<E> for Box<dyn Error + 'a> {
    /// Converts a type of [`Error`] into a box of dyn [`Error`].
    ///
    /// [`Error`]: ../error/trait.Error.html
    ///
    fn from(err: E) -> Box<dyn Error + 'a> {
        Box::new(err)
    }
}

impl<'a, E: Error + Send + Sync + 'a> From<E> for Box<dyn Error + Send + Sync + 'a> {
    /// Converts a type of [`Error`] + [`Send`] + [`Sync`] into a box of
    /// dyn [`Error`] + [`Send`] + [`Sync`].
    ///
    /// [`Error`]: ../error/trait.Error.html
    ///
    fn from(err: E) -> Box<dyn Error + Send + Sync + 'a> {
        Box::new(err)
    }
}

impl From<String> for Box<dyn Error + Send + Sync> {
    /// Converts a [`String`] into a box of dyn [`Error`] + [`Send`] + [`Sync`].
    ///
    fn from(err: String) -> Box<dyn Error + Send + Sync> {
        struct StringError(String);

        impl Error for StringError {
            fn description(&self) -> &str {
                &self.0
            }
        }

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

        // Purposefully skip printing "StringError(..)"
        impl Debug for StringError {
            fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
                Debug::fmt(&self.0, f)
            }
        }

        Box::new(StringError(err))
    }
}

impl From<String> for Box<dyn Error> {
    /// Converts a [`String`] into a box of dyn [`Error`].
    ///
    fn from(str_err: String) -> Box<dyn Error> {
        let err1: Box<dyn Error + Send + Sync> = From::from(str_err);
        let err2: Box<dyn Error> = err1;
        err2
    }
}

impl<'a> From<&str> for Box<dyn Error + Send + Sync + 'a> {
    /// Converts a [`str`] into a box of dyn [`Error`] + [`Send`] + [`Sync`].
    ///
    #[inline]
    fn from(err: &str) -> Box<dyn Error + Send + Sync + 'a> {
        From::from(String::from(err))
    }
}

impl From<&str> for Box<dyn Error> {
    /// Converts a [`str`] into a box of dyn [`Error`].
    ///
    fn from(err: &str) -> Box<dyn Error> {
        From::from(String::from(err))
    }
}

impl<'a, 'b> From<Cow<'b, str>> for Box<dyn Error + Send + Sync + 'a> {
    /// Converts a [`Cow`] into a box of dyn [`Error`] + [`Send`] + [`Sync`].
    ///
    /// [`Cow`]: ../borrow/enum.Cow.html
    /// [`Error`]: ../error/trait.Error.html
    ///
    fn from(err: Cow<'b, str>) -> Box<dyn Error + Send + Sync + 'a> {
        From::from(String::from(err))
    }
}

impl<'a> From<Cow<'a, str>> for Box<dyn Error> {
    /// Converts a [`Cow`] into a box of dyn [`Error`].
    ///
    /// [`Cow`]: ../borrow/enum.Cow.html
    /// [`Error`]: ../error/trait.Error.html
    ///
    fn from(err: Cow<'a, str>) -> Box<dyn Error> {
        From::from(String::from(err))
    }
}

impl Error for ! {
    fn description(&self) -> &str {
        *self
    }
}

impl Error for AllocError {
    fn description(&self) -> &str {
        "memory allocation failed"
    }
}

impl Error for LayoutErr {
    fn description(&self) -> &str {
        "invalid parameters to Layout::from_size_align"
    }
}

impl Error for str::ParseBoolError {
    fn description(&self) -> &str {
        "failed to parse bool"
    }
}

impl Error for str::Utf8Error {
    fn description(&self) -> &str {
        "invalid utf-8: corrupt contents"
    }
}

impl Error for num::ParseIntError {
    fn description(&self) -> &str {
        self.__description()
    }
}

impl Error for num::TryFromIntError {
    fn description(&self) -> &str {
        self.__description()
    }
}

impl Error for array::TryFromSliceError {
    fn description(&self) -> &str {
        self.__description()
    }
}

impl Error for num::ParseFloatError {
    fn description(&self) -> &str {
        self.__description()
    }
}

impl Error for string::FromUtf8Error {
    fn description(&self) -> &str {
        "invalid utf-8"
    }
}

impl Error for string::FromUtf16Error {
    fn description(&self) -> &str {
        "invalid utf-16"
    }
}

impl Error for string::ParseError {
    fn description(&self) -> &str {
        match *self {}
    }
}

impl Error for char::DecodeUtf16Error {
    fn description(&self) -> &str {
        "unpaired surrogate found"
    }
}

impl<T: Error> Error for Box<T> {
    fn description(&self) -> &str {
        Error::description(&**self)
    }

    #[allow(deprecated)]
    fn cause(&self) -> Option<&dyn Error> {
        Error::cause(&**self)
    }

    fn source(&self) -> Option<&(dyn Error + 'static)> {
        Error::source(&**self)
    }
}

impl Error for fmt::Error {
    fn description(&self) -> &str {
        "an error occurred when formatting an argument"
    }
}

impl Error for cell::BorrowError {
    fn description(&self) -> &str {
        "already mutably borrowed"
    }
}

impl Error for cell::BorrowMutError {
    fn description(&self) -> &str {
        "already borrowed"
    }
}

impl Error for char::CharTryFromError {
    fn description(&self) -> &str {
        "converted integer out of range for `char`"
    }
}

impl Error for char::ParseCharError {
    fn description(&self) -> &str {
        self.__description()
    }
}

impl Error for collections::TryReserveError {}

// Copied from `any.rs`.
impl dyn Error + 'static {
    /// Returns `true` if the boxed type is the same as `T`
    #[inline]
    pub fn is<T: Error + 'static>(&self) -> bool {
        // Get `TypeId` of the type this function is instantiated with.
        let t = TypeId::of::<T>();

        // Get `TypeId` of the type in the trait object.
        let boxed = self.type_id(private::Internal);

        // Compare both `TypeId`s on equality.
        t == boxed
    }

    /// Returns some reference to the boxed value if it is of type `T`, or
    /// `None` if it isn't.
    #[inline]
    pub fn downcast_ref<T: Error + 'static>(&self) -> Option<&T> {
        if self.is::<T>() {
            unsafe { Some(&*(self as *const dyn Error as *const T)) }
        } else {
            None
        }
    }

    /// Returns some mutable reference to the boxed value if it is of type `T`, or
    /// `None` if it isn't.
    #[inline]
    pub fn downcast_mut<T: Error + 'static>(&mut self) -> Option<&mut T> {
        if self.is::<T>() {
            unsafe { Some(&mut *(self as *mut dyn Error as *mut T)) }
        } else {
            None
        }
    }
}

impl dyn Error + 'static + Send {
    /// Forwards to the method defined on the type `dyn Error`.
    #[inline]
    pub fn is<T: Error + 'static>(&self) -> bool {
        <dyn Error + 'static>::is::<T>(self)
    }

    /// Forwards to the method defined on the type `dyn Error`.
    #[inline]
    pub fn downcast_ref<T: Error + 'static>(&self) -> Option<&T> {
        <dyn Error + 'static>::downcast_ref::<T>(self)
    }

    /// Forwards to the method defined on the type `dyn Error`.
    #[inline]
    pub fn downcast_mut<T: Error + 'static>(&mut self) -> Option<&mut T> {
        <dyn Error + 'static>::downcast_mut::<T>(self)
    }
}

impl dyn Error + 'static + Send + Sync {
    /// Forwards to the method defined on the type `dyn Error`.
    #[inline]
    pub fn is<T: Error + 'static>(&self) -> bool {
        <dyn Error + 'static>::is::<T>(self)
    }

    /// Forwards to the method defined on the type `dyn Error`.
    #[inline]
    pub fn downcast_ref<T: Error + 'static>(&self) -> Option<&T> {
        <dyn Error + 'static>::downcast_ref::<T>(self)
    }

    /// Forwards to the method defined on the type `dyn Error`.
    #[inline]
    pub fn downcast_mut<T: Error + 'static>(&mut self) -> Option<&mut T> {
        <dyn Error + 'static>::downcast_mut::<T>(self)
    }
}

impl dyn Error {
    #[inline]
    /// Attempts to downcast the box to a concrete type.
    pub fn downcast<T: Error + 'static>(self: Box<Self>) -> Result<Box<T>, Box<dyn Error>> {
        if self.is::<T>() {
            unsafe {
                let raw: *mut dyn Error = Box::into_raw(self);
                Ok(Box::from_raw(raw as *mut T))
            }
        } else {
            Err(self)
        }
    }

    /// Returns an iterator starting with the current error and continuing with
    /// recursively calling [`source`].
    ///
    /// If you want to omit the current error and only use its sources,
    /// use `skip(1)`.
    ///
    #[inline]
    pub fn chain(&self) -> Chain<'_> {
        Chain { current: Some(self) }
    }

    /// Returns an iterator starting with the current error and continuing with
    /// recursively calling [`source`].
    ///
    #[inline]
    pub fn iter_chain(&self) -> ErrorIter<'_> {
        ErrorIter {
            current: Some(self),
        }
    }

    /// Returns an iterator starting with the [`source`] of this error
    /// and continuing with recursively calling [`source`].
    ///
    #[inline]
    pub fn iter_sources(&self) -> ErrorIter<'_> {
        ErrorIter {
            current: self.source(),
        }
    }
}

/// An iterator over an [`Error`] and its sources.
///
/// If you want to omit the initial error and only process
/// its sources, use `skip(1)`.
///
/// [`Error`]: trait.Error.html
#[derive(Clone, Debug)]
pub struct Chain<'a> {
    current: Option<&'a (dyn Error + 'static)>,
}

impl<'a> Iterator for Chain<'a> {
    type Item = &'a (dyn Error + 'static);

    fn next(&mut self) -> Option<Self::Item> {
        let current = self.current;
        self.current = self.current.and_then(Error::source);
        current
    }
}

/// An iterator over an [`Error`] and its sources.
///
/// [`Error`]: trait.Error.html
#[derive(Copy, Clone, Debug)]
pub struct ErrorIter<'a> {
    current: Option<&'a (dyn Error + 'static)>,
}

impl<'a> Iterator for ErrorIter<'a> {
    type Item = &'a (dyn Error + 'static);

    fn next(&mut self) -> Option<Self::Item> {
        let current = self.current;
        self.current = self.current.and_then(Error::source);
        current
    }
}

impl dyn Error + Send {
    #[inline]
    /// Attempts to downcast the box to a concrete type.
    pub fn downcast<T: Error + 'static>(self: Box<Self>) -> Result<Box<T>, Box<dyn Error + Send>> {
        let err: Box<dyn Error> = self;
        <dyn Error>::downcast(err).map_err(|s| unsafe {
            // Reapply the `Send` marker.
            transmute::<Box<dyn Error>, Box<dyn Error + Send>>(s)
        })
    }
}

impl dyn Error + Send + Sync {
    #[inline]
    /// Attempts to downcast the box to a concrete type.
    pub fn downcast<T: Error + 'static>(self: Box<Self>) -> Result<Box<T>, Box<Self>> {
        let err: Box<dyn Error> = self;
        <dyn Error>::downcast(err).map_err(|s| unsafe {
            // Reapply the `Send + Sync` marker.
            transmute::<Box<dyn Error>, Box<dyn Error + Send + Sync>>(s)
        })
    }
}