#![cfg_attr(target_arch = "wasm32", allow(unused))]
use std::error::Error as StdError;
use std::fmt;
use std::io;

use crate::{StatusCode, Url};

/// A `Result` alias where the `Err` case is `reqwest::Error`.
pub type Result<T> = std::result::Result<T, Error>;

/// The Errors that may occur when processing a `Request`.
pub struct Error {
    inner: Box<Inner>,
}

pub(crate) type BoxError = Box<dyn StdError + Send + Sync>;

struct Inner {
    kind: Kind,
    source: Option<BoxError>,
    url: Option<Url>,
}

impl Error {
    pub(crate) fn new<E>(kind: Kind, source: Option<E>) -> Error
    where
        E: Into<BoxError>,
    {
        Error {
            inner: Box::new(Inner {
                kind,
                source: source.map(Into::into),
                url: None,
            }),
        }
    }

    /// Returns a possible URL related to this error.
    ///
    /// # Examples
    ///
    /// ```
    /// # async fn run() {
    /// // displays last stop of a redirect loop
    /// let response = reqwest::get("http://site.with.redirect.loop").await;
    /// if let Err(e) = response {
    ///     if e.is_redirect() {
    ///         if let Some(final_stop) = e.url() {
    ///             println!("redirect loop at {}", final_stop);
    ///         }
    ///     }
    /// }
    /// # }
    /// ```
    pub fn url(&self) -> Option<&Url> {
        self.inner.url.as_ref()
    }

    /// Returns true if the error is from a type Builder.
    pub fn is_builder(&self) -> bool {
        matches!(self.inner.kind, Kind::Builder)
    }

    /// Returns true if the error is from a `RedirectPolicy`.
    pub fn is_redirect(&self) -> bool {
        matches!(self.inner.kind, Kind::Redirect)
    }

    /// Returns true if the error is from `Response::error_for_status`.
    pub fn is_status(&self) -> bool {
        matches!(self.inner.kind, Kind::Status(_))
    }

    /// Returns true if the error is related to a timeout.
    pub fn is_timeout(&self) -> bool {
        let mut source = self.source();

        while let Some(err) = source {
            if err.is::<TimedOut>() {
                return true;
            }
            source = err.source();
        }

        false
    }

    /// Returns true if the error is related to the request
    pub fn is_request(&self) -> bool {
        matches!(self.inner.kind, Kind::Request)
    }

    #[cfg(not(target_arch = "wasm32"))]
    /// Returns true if the error is related to connect
    pub fn is_connect(&self) -> bool {
        let mut source = self.source();

        while let Some(err) = source {
            if let Some(hyper_err) = err.downcast_ref::<hyper::Error>() {
                if hyper_err.is_connect() {
                    return true;
                }
            }

            source = err.source();
        }

        false
    }

    /// Returns true if the error is related to the request or response body
    pub fn is_body(&self) -> bool {
        matches!(self.inner.kind, Kind::Body)
    }

    /// Returns true if the error is related to decoding the response's body
    pub fn is_decode(&self) -> bool {
        matches!(self.inner.kind, Kind::Decode)
    }

    /// Returns the status code, if the error was generated from a response.
    pub fn status(&self) -> Option<StatusCode> {
        match self.inner.kind {
            Kind::Status(code) => Some(code),
            _ => None,
        }
    }

    // private

    pub(crate) fn with_url(mut self, url: Url) -> Error {
        self.inner.url = Some(url);
        self
    }

    #[allow(unused)]
    pub(crate) fn into_io(self) -> io::Error {
        io::Error::new(io::ErrorKind::Other, self)
    }
}

impl fmt::Debug for Error {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let mut builder = f.debug_struct("reqwest::Error");

        builder.field("kind", &self.inner.kind);

        if let Some(ref url) = self.inner.url {
            builder.field("url", url);
        }
        if let Some(ref source) = self.inner.source {
            builder.field("source", source);
        }

        builder.finish()
    }
}

impl fmt::Display for Error {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        struct ForUrl<'a>(Option<&'a Url>);

        impl fmt::Display for ForUrl<'_> {
            fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
                if let Some(url) = self.0 {
                    write!(f, " for url ({})", url.as_str())
                } else {
                    Ok(())
                }
            }
        }

        match self.inner.kind {
            Kind::Builder => f.write_str("builder error")?,
            Kind::Request => f.write_str("error sending request")?,
            Kind::Body => f.write_str("request or response body error")?,
            Kind::Decode => f.write_str("error decoding response body")?,
            Kind::Redirect => f.write_str("error following redirect")?,
            Kind::Status(ref code) => {
                let prefix = if code.is_client_error() {
                    "HTTP status client error"
                } else {
                    debug_assert!(code.is_server_error());
                    "HTTP status server error"
                };
                write!(f, "{} ({})", prefix, code)?;
            }
        };

        ForUrl(self.inner.url.as_ref()).fmt(f)?;

        if let Some(ref e) = self.inner.source {
            write!(f, ": {}", e)?;
        }

        Ok(())
    }
}

impl StdError for Error {
    fn source(&self) -> Option<&(dyn StdError + 'static)> {
        self.inner.source.as_ref().map(|e| &**e as _)
    }
}

#[cfg(target_arch = "wasm32")]
impl From<crate::error::Error> for wasm_bindgen::JsValue {
    fn from(err: Error) -> wasm_bindgen::JsValue {
        js_sys::Error::from(err).into()
    }
}

#[cfg(target_arch = "wasm32")]
impl From<crate::error::Error> for js_sys::Error {
    fn from(err: Error) -> js_sys::Error {
        js_sys::Error::new(&format!("{}", err))
    }
}

#[derive(Debug)]
pub(crate) enum Kind {
    Builder,
    Request,
    Redirect,
    Status(StatusCode),
    Body,
    Decode,
}

// constructors

pub(crate) fn builder<E: Into<BoxError>>(e: E) -> Error {
    Error::new(Kind::Builder, Some(e))
}

pub(crate) fn body<E: Into<BoxError>>(e: E) -> Error {
    Error::new(Kind::Body, Some(e))
}

pub(crate) fn decode<E: Into<BoxError>>(e: E) -> Error {
    Error::new(Kind::Decode, Some(e))
}

pub(crate) fn request<E: Into<BoxError>>(e: E) -> Error {
    Error::new(Kind::Request, Some(e))
}

pub(crate) fn redirect<E: Into<BoxError>>(e: E, url: Url) -> Error {
    Error::new(Kind::Redirect, Some(e)).with_url(url)
}

pub(crate) fn status_code(url: Url, status: StatusCode) -> Error {
    Error::new(Kind::Status(status), None::<Error>).with_url(url)
}

pub(crate) fn url_bad_scheme(url: Url) -> Error {
    Error::new(Kind::Builder, Some("URL scheme is not allowed")).with_url(url)
}

if_wasm! {
    pub(crate) fn wasm(js_val: wasm_bindgen::JsValue) -> BoxError {
        format!("{:?}", js_val).into()
    }
}

// io::Error helpers

#[allow(unused)]
pub(crate) fn into_io(e: Error) -> io::Error {
    e.into_io()
}

#[allow(unused)]
pub(crate) fn decode_io(e: io::Error) -> Error {
    if e.get_ref().map(|r| r.is::<Error>()).unwrap_or(false) {
        *e.into_inner()
            .expect("io::Error::get_ref was Some(_)")
            .downcast::<Error>()
            .expect("StdError::is() was true")
    } else {
        decode(e)
    }
}

// internal Error "sources"

#[derive(Debug)]
pub(crate) struct TimedOut;

impl fmt::Display for TimedOut {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.write_str("operation timed out")
    }
}

impl StdError for TimedOut {}

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

    fn assert_send<T: Send>() {}
    fn assert_sync<T: Sync>() {}

    #[test]
    fn test_source_chain() {
        let root = Error::new(Kind::Request, None::<Error>);
        assert!(root.source().is_none());

        let link = super::body(root);
        assert!(link.source().is_some());
        assert_send::<Error>();
        assert_sync::<Error>();
    }

    #[test]
    fn mem_size_of() {
        use std::mem::size_of;
        assert_eq!(size_of::<Error>(), size_of::<usize>());
    }

    #[test]
    fn roundtrip_io_error() {
        let orig = super::request("orig");
        // Convert reqwest::Error into an io::Error...
        let io = orig.into_io();
        // Convert that io::Error back into a reqwest::Error...
        let err = super::decode_io(io);
        // It should have pulled out the original, not nested it...
        match err.inner.kind {
            Kind::Request => (),
            _ => panic!("{:?}", err),
        }
    }

    #[test]
    fn from_unknown_io_error() {
        let orig = io::Error::new(io::ErrorKind::Other, "orly");
        let err = super::decode_io(orig);
        match err.inner.kind {
            Kind::Decode => (),
            _ => panic!("{:?}", err),
        }
    }

    #[test]
    fn is_timeout() {
        let err = super::request(super::TimedOut);
        assert!(err.is_timeout());

        let io = io::Error::new(io::ErrorKind::Other, err);
        let nested = super::request(io);
        assert!(nested.is_timeout());
    }
}