fluffyf 0.2.0

An e621 api wrapper and downloader
Documentation 
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
140
141
142
143
144
145
146
147
148
149

// Copyright 2022 @playfulkittykat, @nasso
//
// Licensed 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
//
//==========================================================================
//
// Changes are stated below:
// 
// 1. Unsplintered `rate limit` and `dummy rate limit`
// 2. Make the true rate limit optional such that the dummy is not replaced per-se
// 3. Make the choice of rate limiter truly optional to the user
// 4. Added a type alias of DefaultRateLimit
// 
// and are copyrighted as follows:
//
// Copyright 2024 Ezra Alvarion
//
// Licensed under the Apache License, Version 2.0 <LICENSE-Apache or
// https://www.apache.org/licenses/LICENSE-2.0> or the BSD 2-Clause 
// License <LICENSE-BSD or https://opensource.org/license/bsd-2-clause/>,
// at Your option. This file may not be copied, modified, or distributed
// except according to those terms.

//! A async block wrapper to limit request
//! 
//! # Rate Limit
//!
//! As per [the official wiki](https://e926.net/wiki_pages/2425#api):
//!
//! > E621/E926 have a hard rate limit of two requests per second.
//! > This is a hard upper limit, and if you are hitting it, you are already going way too fast.
//! > Hitting the rate limit will result in a 503 HTTP response code.
//! >
//! > > **Important!**
//! > >
//! > > You should make a best effort not to make more than one request per second over a sustained period.
//! 
//! And so (if you have enabled the `rate-limiter` feature), fluffyf through [`Client`]
//! will delay each request to 600ms per request
//! 
//! Note: This module is not only directly inspired, but quite literally taken from [rs621].
//! See the top of the source file or [the README] for more details and copyright attribution
//! 
//! [`Client`]: crate::client::Client
//! [rs621]: https://github.com/nasso/rs621
//! [the README]: https://github.com/AntimatterReactor/fluffyf/blob/main/README.md

use {
    std::sync::Arc,

    futures::Future,
};

#[cfg(feature = "rate-limit")]
use tokio::{
    sync::{Mutex, MutexGuard},
    time::{sleep_until, Duration, Instant},
};

const REQ_COOLDOWN_DURATION: Duration = Duration::from_millis(600);

pub trait Limiter {
    async fn check<F, R>(self, fut: F) -> R
    where
        F: Future<Output = R>,
        Self: Sized;
}

#[cfg(feature = "rate-limit")]
#[derive(Debug, Clone, Default)]
pub struct RateLimit {
    // Use a tokio mutex for fairness and because ~500ms is crazy long to block
    // an async task.
    deadline: Arc<Mutex<Option<Instant>>>,
}
 
#[cfg(feature = "rate-limit")]
struct Guard<'a>(MutexGuard<'a, Option<Instant>>);

#[cfg(feature = "rate-limit")]
impl<'a> Drop for Guard<'a> {
    fn drop(&mut self) {
        // Use a `Drop` impl so that updating the deadline is panic-safe.
        *self.0 = Some(Instant::now() + REQ_COOLDOWN_DURATION);
    }
}

#[cfg(feature = "rate-limit")]
impl Limiter for RateLimit {
    async fn check<F, R>(self, fut: F) -> R
    where
        F: Future<Output = R>,
    {
        let guard = self.lock().await;
        let result = fut.await;
        drop(guard);
        result
    }
}

#[cfg(feature = "rate-limit")]
impl RateLimit {
    async fn lock(&self) -> Guard {
        loop {
            let now = Instant::now();

            let deadline = {
                let guard = self.deadline.lock().await;

                match &*guard {
                    None => return Guard(guard),
                    Some(deadline) if now >= *deadline => return Guard(guard),
                    Some(deadline) => *deadline,
                }
            };

            sleep_until(deadline).await;
        }
    }
}

#[derive(Debug, Clone, Default)]
pub struct DummyRateLimit {}

impl Limiter for DummyRateLimit {
    async fn check<F, R>(self, fut: F) -> R
    where
        F: Future<Output = R>,
        Self: Sized
    {
        fut.await
    }
}

#[cfg(feature = "rate-limit")]
pub type DefaultRateLimit = RateLimit;

#[cfg(not(feature = "rate-limit"))]
pub type DefaultRateLimit = DummyRateLimit;