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
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
//! Useful compositors for update handlers.
//!
//! Let's start with a simple example. You're writing a bot, and its main
//! functionality is searching through something. In private chats, it's enough
//! to send a text message to start searching; but in groups, it's better to
//! search only when someone sent the `/search` command. Since you already
//! expected to have the same logic in different handlers, you wrote a generic
//! handler, `search`, and then registered it like this:
//!
//! ```no_run
//! use std::sync::Arc;
//! use tbot::{Bot, contexts::fields::Text, prelude::*};
//! async fn search(context: Arc<impl Text>) {
//!     // ..
//! }
//!
//! let mut bot = Bot::from_env("BOT_TOKEN").event_loop();
//!
//! bot.text(|context| async move {
//!     if context.chat.kind.is_private() {
//!         search(context).await;
//!     }
//! });
//!
//! bot.command("search", search);
//! ```
//!
//! The `text` handler seems a bit too long just to filter out messages from
//! channels and groups. That's where we can make use of our first compositor,
//! [`filter`]! It takes a predicate and a handler and returns its own handler.
//! If the predicate returns `true`, [`filter`]'s handler executes yours.
//! Here's an example:
//!
//! ```no_run
//! # use std::sync::Arc;
//! # use tbot::{Bot, contexts::fields, prelude::*};
//! # async fn search(context: Arc<impl fields::Text>) {}
//! # let mut bot = Bot::from_env("BOT_TOKEN").event_loop();
//! use tbot::{contexts::Text, compositors::filter};
//!
//! bot.text(filter(
//!     |context: Arc<Text>| async move { context.chat.kind.is_private() },
//!     search,
//! ));
//! ```
//!
//! That looks better! But `tbot` already provides the predicate we just wrote
//! ourselves, so let's use that:
//!
//! ```no_run
//! # use std::sync::Arc;
//! # use tbot::{Bot, contexts::fields::Text, prelude::*};
//! # async fn search(context: Arc<impl Text>) {}
//! # let mut bot = Bot::from_env("BOT_TOKEN").event_loop();
//! use tbot::{compositors::filter, predicates::chat::is_private};
//!
//! bot.text(filter(is_private, search));
//! ```
//!
//! Great! Now you see how compositors make registering handlers easier.
//! [`filter`] isn't the only compositor, you'll find all of them in this
//! module.
//!
//! Remember one thing though. Compositors add layers between the handler
//! and handler registers. If you're going to use a closure for your handler,
//! type inference will fail and you'll have to explicitly define `context`'s
//! type, as seen in the example with an inlined predicate above. That only
//! affects closures: using plain functions is fine even with generics, as seen
//! in the last example.

use crate::contexts::fields::Context;
use futures::future::BoxFuture;
use std::{future::Future, sync::Arc};

pub mod state;

/// Filters updates: executes `handler` only if `predicate` returns `true`.
///
/// # Example
///
/// ```no_run
/// use tbot::{Bot, contexts::Text, compositors::filter, predicates::chat::is_group};
/// use std::sync::Arc;
///
/// let mut bot = Bot::from_env("BOT_TOKEN").event_loop();
/// bot.text(filter(is_group, |context: Arc<Text>| async move {
///     // Do something assuming we're in a group
/// }));
/// ```
pub fn filter<C, P, PF, H, HF>(
    predicate: P,
    handler: H,
) -> impl Fn(Arc<C>) -> BoxFuture<'static, ()>
where
    C: Context,
    P: Fn(Arc<C>) -> PF + Send + Sync + 'static,
    PF: Future<Output = bool> + Send + 'static,
    H: Fn(Arc<C>) -> HF + Send + Sync + 'static,
    HF: Future<Output = ()> + Send + 'static,
{
    let shared = Arc::new((predicate, handler));

    move |context| {
        let shared = Arc::clone(&shared);

        Box::pin(async move {
            let (predicate, handler) = &*shared;

            if predicate(Arc::clone(&context)).await {
                handler(context).await;
            }
        })
    }
}

/// Maps updates: calls `mapper`, and then passes its return value to `handler`.
///
/// # Example
///
/// ```no_run
/// use tbot::{Bot, contexts::Text, compositors::map};
/// use std::sync::Arc;
///
/// let mut bot = Bot::from_env("BOT_TOKEN").event_loop();
/// bot.text(map(
///     |context: Arc<Text>| async move { context.text.clone() },
///     |text| async move {
///         dbg!(text);
///     },
/// ));
/// ```
pub fn map<C, T, M, MF, H, HF>(
    mapper: M,
    handler: H,
) -> impl Fn(Arc<C>) -> BoxFuture<'static, ()>
where
    C: Context,
    T: Send + 'static,
    M: Fn(Arc<C>) -> MF + Send + Sync + 'static,
    MF: Future<Output = T> + Send + 'static,
    H: Fn(T) -> HF + Send + Sync + 'static,
    HF: Future<Output = ()> + Send + 'static,
{
    let shared = Arc::new((mapper, handler));

    move |context| {
        let shared = Arc::clone(&shared);

        Box::pin(async move {
            let (mapper, handler) = &*shared;
            handler(mapper(context).await).await;
        })
    }
}

/// Filters and maps updates: calls `predicate`, and if it returned `Some`,
/// calls `handler` with that value.
///
/// # Example
///
/// ```no_run
/// use tbot::{Bot, contexts::Text, compositors::filter_map};
/// use std::sync::Arc;
///
/// let mut bot = Bot::from_env("BOT_TOKEN").event_loop();
/// bot.text(filter_map(
///     |context: Arc<Text>| async move { context.reply_to.clone() },
///     |reply_to| async move {
///         println!("Recevied a message in reply to {}", reply_to.id);
///     },
/// ));
/// ```
pub fn filter_map<C, T, M, MF, H, HF>(
    mapper: M,
    handler: H,
) -> impl Fn(Arc<C>) -> BoxFuture<'static, ()>
where
    C: Context,
    T: Send + 'static,
    M: Fn(Arc<C>) -> MF + Send + Sync + 'static,
    MF: Future<Output = Option<T>> + Send + 'static,
    H: Fn(T) -> HF + Send + Sync + 'static,
    HF: Future<Output = ()> + Send + 'static,
{
    let shared = Arc::new((mapper, handler));

    move |context| {
        let shared = Arc::clone(&shared);

        Box::pin(async move {
            let (mapper, handler) = &*shared;
            if let Some(mapped) = mapper(context).await {
                handler(mapped).await;
            }
        })
    }
}