1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139

//! HTTP Redirect middleware.
//!
//! # Examples
//!
//! ```no_run
//! # enum Event { ReceiveResponse(crux_http::Result<crux_http::Response<Vec<u8>>>) }
//! # struct Capabilities { http: crux_http::Http<Event> }
//! # fn update(caps: &Capabilities) {
//!
//! caps.http
//!     .get("https://httpbin.org/redirect/2")
//!     .middleware(crux_http::middleware::Redirect::default())
//!     .send(Event::ReceiveResponse)
//! # }
//! ```

use crate::http::{self, headers, StatusCode, Url};
use crate::middleware::{Middleware, Next, Request};
use crate::{Client, ResponseAsync, Result};

// List of acceptable 300-series redirect codes.
const REDIRECT_CODES: &[StatusCode] = &[
    StatusCode::MovedPermanently,
    StatusCode::Found,
    StatusCode::SeeOther,
    StatusCode::TemporaryRedirect,
    StatusCode::PermanentRedirect,
];

/// A middleware which attempts to follow HTTP redirects.
#[derive(Debug)]
pub struct Redirect {
    attempts: u8,
}

impl Redirect {
    /// Create a new instance of the Redirect middleware, which attempts to follow redirects
    /// up to as many times as specified.
    ///
    /// Consider using `Redirect::default()` for the default number of redirect attempts.
    ///
    /// This middleware will follow redirects from the `Location` header if the server returns
    /// any of the following http response codes:
    /// - 301 Moved Permanently
    /// - 302 Found
    /// - 303 See other
    /// - 307 Temporary Redirect
    /// - 308 Permanent Redirect
    ///
    /// # Errors
    ///
    /// An error will be passed through the middleware stack if the value of the `Location`
    /// header is not a validly parsing url.
    ///
    /// # Caveats
    ///
    /// This will presently make at least one additional HTTP request before the actual request to
    /// determine if there is a redirect that should be followed, so as to preserve any request body.
    ///
    /// # Examples
    ///
    /// ```no_run
    /// # enum Event { ReceiveResponse(crux_http::Result<crux_http::Response<Vec<u8>>>) }
    /// # struct Capabilities { http: crux_http::Http<Event> }
    /// # fn update(caps: &Capabilities) {
    ///
    /// caps.http
    ///     .get("https://httpbin.org/redirect/2")
    ///     .middleware(crux_http::middleware::Redirect::default())
    ///     .send(Event::ReceiveResponse)
    /// # }
    /// ```
    pub fn new(attempts: u8) -> Self {
        Redirect { attempts }
    }
}

#[async_trait::async_trait]
impl Middleware for Redirect {
    async fn handle(
        &self,
        mut req: Request,
        client: Client,
        next: Next<'_>,
    ) -> Result<ResponseAsync> {
        let mut redirect_count: u8 = 0;

        // Note(Jeremiah): This is not ideal.
        //
        // HttpClient is currently too limiting for efficient redirects.
        // We do not want to make unnecessary full requests, but it is
        // presently required due to how Body streams work.
        //
        // Ideally we'd have methods to send a partial request stream,
        // without sending the body, that would potnetially be able to
        // get a server status before we attempt to send the body.
        //
        // As a work around we clone the request first (without the body),
        // and try sending it until we get some status back that is not a
        // redirect.

        let mut base_url = req.url().clone();

        while redirect_count < self.attempts {
            redirect_count += 1;
            let r: Request = req.clone();
            let res: ResponseAsync = client.send(r).await?;
            if REDIRECT_CODES.contains(&res.status()) {
                if let Some(location) = res.header(headers::LOCATION) {
                    let http_req: &mut http::Request = req.as_mut();
                    *http_req.url_mut() = match Url::parse(location.last().as_str()) {
                        Ok(valid_url) => {
                            base_url = valid_url;
                            base_url.clone()
                        }
                        Err(e) => match e {
                            http::url::ParseError::RelativeUrlWithoutBase => {
                                base_url.join(location.last().as_str())?
                            }
                            e => return Err(e.into()),
                        },
                    };
                }
            } else {
                break;
            }
        }

        Ok(next.run(req, client).await?)
    }
}

impl Default for Redirect {
    /// Create a new instance of the Redirect middleware, which attempts to follow up to
    /// 3 redirects (not including the actual request).
    fn default() -> Self {
        Self { attempts: 3 }
    }
}