use std::fmt::Debug;

use async_trait::async_trait;
use bytes::Bytes;
use http::{Request, Response};
use opentelemetry::{
    propagation::{Extractor, Injector},
    trace::TraceError,
};

pub struct HeaderInjector<'a>(pub &'a mut http::HeaderMap);

impl<'a> Injector for HeaderInjector<'a> {
    /// Set a key and value in the HeaderMap.  Does nothing if the key or value are not valid inputs.
    fn set(&mut self, key: &str, value: String) {
        if let Ok(name) = http::header::HeaderName::from_bytes(key.as_bytes()) {
            if let Ok(val) = http::header::HeaderValue::from_str(&value) {
                self.0.insert(name, val);
            }
        }
    }
}

pub struct HeaderExtractor<'a>(pub &'a http::HeaderMap);

impl<'a> Extractor for HeaderExtractor<'a> {
    /// Get a value for a key from the HeaderMap.  If the value is not valid ASCII, returns None.
    fn get(&self, key: &str) -> Option<&str> {
        self.0.get(key).and_then(|value| value.to_str().ok())
    }

    /// Collect all the keys from the HeaderMap.
    fn keys(&self) -> Vec<&str> {
        self.0
            .keys()
            .map(|value| value.as_str())
            .collect::<Vec<_>>()
    }
}

pub type HttpError = Box<dyn std::error::Error + Send + Sync + 'static>;

/// A minimal interface necessary for export spans over HTTP.
///
/// Users sometime choose HTTP clients that relay on a certain async runtime. This trait allows
/// users to bring their choice of HTTP client.
#[async_trait]
pub trait HttpClient: Debug + Send + Sync {
    /// Send the specified HTTP request
    ///
    /// Returns the HTTP response including the status code and body.
    ///
    /// Returns an error if it can't connect to the server or the request could not be completed,
    /// e.g. because of a timeout, infinite redirects, or a loss of connection.
    async fn send(&self, request: Request<Vec<u8>>) -> Result<Response<Bytes>, HttpError>;
}

#[cfg(feature = "reqwest")]
mod reqwest {
    use super::{async_trait, Bytes, HttpClient, HttpError, Request, Response};
    use std::convert::TryInto;

    #[async_trait]
    impl HttpClient for reqwest::Client {
        async fn send(&self, request: Request<Vec<u8>>) -> Result<Response<Bytes>, HttpError> {
            let request = request.try_into()?;
            let response = self.execute(request).await?;
            Ok(Response::builder()
                .status(response.status())
                .body(response.bytes().await?)?)
        }
    }

    #[async_trait]
    impl HttpClient for reqwest::blocking::Client {
        async fn send(&self, request: Request<Vec<u8>>) -> Result<Response<Bytes>, HttpError> {
            let request = request.try_into()?;
            let response = self.execute(request)?;
            Ok(Response::builder()
                .status(response.status())
                .body(response.bytes()?)?)
        }
    }
}

#[cfg(feature = "surf")]
mod surf {
    use super::{async_trait, Bytes, HttpClient, HttpError, Request, Response};

    #[async_trait]
    impl HttpClient for surf::Client {
        async fn send(&self, request: Request<Vec<u8>>) -> Result<Response<Bytes>, HttpError> {
            let (parts, body) = request.into_parts();
            let method = parts.method.as_str().parse()?;
            let uri = parts.uri.to_string().parse()?;

            let mut request_builder = surf::Request::builder(method, uri).body(body);
            let mut prev_name = None;
            for (new_name, value) in parts.headers.into_iter() {
                let name = new_name.or(prev_name).expect("the first time new_name should be set and from then on we always have a prev_name");
                request_builder = request_builder.header(name.as_str(), value.to_str()?);
                prev_name = Some(name);
            }

            let mut response = self.send(request_builder).await?;
            Ok(Response::builder()
                .status(response.status() as u16)
                .body(response.body_bytes().await?.into())?)
        }
    }
}

#[cfg(feature = "isahc")]
mod isahc {
    use super::{async_trait, Bytes, HttpClient, HttpError, Request, Response};
    use futures_util::io::AsyncReadExt as _;
    use std::convert::TryInto as _;

    #[async_trait]
    impl HttpClient for isahc::HttpClient {
        async fn send(&self, request: Request<Vec<u8>>) -> Result<Response<Bytes>, HttpError> {
            let response = self.send_async(request).await?;
            Ok(Response::builder()
                .status(response.status())
                .body(body_to_bytes(response.into_body()).await?)?)
        }
    }

    async fn body_to_bytes(mut body: isahc::Body) -> Result<Bytes, HttpError> {
        let mut bytes = Vec::with_capacity(body.len().unwrap_or(0).try_into()?);
        let _ = body.read_to_end(&mut bytes).await?;
        Ok(bytes.into())
    }
}

/// Methods to make working with responses from the [`HttpClient`] trait easier.
pub trait ResponseExt: Sized {
    /// Turn a response into an error if the HTTP status does not indicate success (200 - 299).
    fn error_for_status(self) -> Result<Self, TraceError>;
}

impl<T> ResponseExt for Response<T> {
    fn error_for_status(self) -> Result<Self, TraceError> {
        if self.status().is_success() {
            Ok(self)
        } else {
            Err(format!("request failed with status {}", self.status()).into())
        }
    }
}

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

    #[test]
    fn http_headers_get() {
        let mut carrier = http::HeaderMap::new();
        HeaderInjector(&mut carrier).set("headerName", "value".to_string());

        assert_eq!(
            HeaderExtractor(&carrier).get("HEADERNAME"),
            Some("value"),
            "case insensitive extraction"
        )
    }

    #[test]
    fn http_headers_keys() {
        let mut carrier = http::HeaderMap::new();
        HeaderInjector(&mut carrier).set("headerName1", "value1".to_string());
        HeaderInjector(&mut carrier).set("headerName2", "value2".to_string());

        let extractor = HeaderExtractor(&carrier);
        let got = extractor.keys();
        assert_eq!(got.len(), 2);
        assert!(got.contains(&"headername1"));
        assert!(got.contains(&"headername2"));
    }
}