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

use std::fmt;
use std::borrow::Cow;

use rocket::{Request, Rocket, Ignite, Sentinel};
use rocket::http::{Status, ContentType};
use rocket::request::{self, FromRequest};
use rocket::serde::Serialize;

use crate::{Template, context::ContextManager};

/// Request guard for dynamically querying template metadata.
///
/// # Usage
///
/// The `Metadata` type implements Rocket's [`FromRequest`] trait, so it can be
/// used as a request guard in any request handler.
///
/// ```rust
/// # #[macro_use] extern crate rocket;
/// # #[macro_use] extern crate rocket_dyn_templates;
/// use rocket_dyn_templates::{Template, Metadata, context};
///
/// #[get("/")]
/// fn homepage(metadata: Metadata) -> Template {
///     // Conditionally render a template if it's available.
///     # let context = ();
///     if metadata.contains_template("some-template") {
///         Template::render("some-template", &context)
///     } else {
///         Template::render("fallback", &context)
///     }
/// }
///
/// fn main() {
///     rocket::build()
///         .attach(Template::fairing())
///         // ...
///     # ;
/// }
/// ```
pub struct Metadata<'a>(&'a ContextManager);

impl Metadata<'_> {
    /// Returns `true` if the template with the given `name` is currently
    /// loaded.  Otherwise, returns `false`.
    ///
    /// # Example
    ///
    /// ```rust
    /// # #[macro_use] extern crate rocket;
    /// # extern crate rocket_dyn_templates;
    /// #
    /// use rocket_dyn_templates::Metadata;
    ///
    /// #[get("/")]
    /// fn handler(metadata: Metadata) {
    ///     // Returns `true` if the template with name `"name"` was loaded.
    ///     let loaded = metadata.contains_template("name");
    /// }
    /// ```
    pub fn contains_template(&self, name: &str) -> bool {
        self.0.context().templates.contains_key(name)
    }

    /// Returns `true` if template reloading is enabled.
    ///
    /// # Example
    ///
    /// ```rust
    /// # #[macro_use] extern crate rocket;
    /// # extern crate rocket_dyn_templates;
    /// #
    /// use rocket_dyn_templates::Metadata;
    ///
    /// #[get("/")]
    /// fn handler(metadata: Metadata) {
    ///     // Returns `true` if template reloading is enabled.
    ///     let reloading = metadata.reloading();
    /// }
    /// ```
    pub fn reloading(&self) -> bool {
        self.0.is_reloading()
    }

    /// Directly render the template named `name` with the context `context`
    /// into a `String`. Also returns the template's detected `ContentType`. See
    /// [`Template::render()`] for more details on rendering.
    ///
    /// # Examples
    ///
    /// ```rust
    /// # #[macro_use] extern crate rocket;
    /// use rocket::http::ContentType;
    /// use rocket_dyn_templates::{Metadata, Template, context};
    ///
    /// #[get("/")]
    /// fn send_email(metadata: Metadata) -> Option<()> {
    ///     let (mime, string) = metadata.render("email", context! {
    ///         field: "Hello, world!"
    ///     })?;
    ///
    ///     # /*
    ///     send_email(mime, string).await?;
    ///     # */
    ///     Some(())
    /// }
    ///
    /// #[get("/")]
    /// fn raw_render(metadata: Metadata) -> Option<(ContentType, String)> {
    ///     metadata.render("index", context! { field: "Hello, world!" })
    /// }
    ///
    /// // Prefer the following, however, which is nearly identical but pithier:
    ///
    /// #[get("/")]
    /// fn render() -> Template {
    ///     Template::render("index", context! { field: "Hello, world!" })
    /// }
    /// ```
    pub fn render<S, C>(&self, name: S, context: C) -> Option<(ContentType, String)>
        where S: Into<Cow<'static, str>>, C: Serialize
    {
        Template::render(name.into(), context).finalize(&self.0.context()).ok()
    }
}

impl fmt::Debug for Metadata<'_> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_map()
            .entries(&self.0.context().templates)
            .finish()
    }
}

impl Sentinel for Metadata<'_> {
    fn abort(rocket: &Rocket<Ignite>) -> bool {
        if rocket.state::<ContextManager>().is_none() {
            error!(
                "uninitialized template context: missing `Template::fairing()`.\n\
                To use templates, you must attach `Template::fairing()`."
            );

            return true;
        }

        false
    }
}

/// Retrieves the template metadata. If a template fairing hasn't been attached,
/// an error is printed and an empty `Err` with status `InternalServerError`
/// (`500`) is returned.
#[rocket::async_trait]
impl<'r> FromRequest<'r> for Metadata<'r> {
    type Error = ();

    async fn from_request(request: &'r Request<'_>) -> request::Outcome<Self, ()> {
        request.rocket().state::<ContextManager>()
            .map(|cm| request::Outcome::Success(Metadata(cm)))
            .unwrap_or_else(|| {
                error!(
                    "uninitialized template context: missing `Template::fairing()`.\n\
                    To use templates, you must attach `Template::fairing()`."
                );

                request::Outcome::Error((Status::InternalServerError, ()))
            })
    }
}