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

use std::any::{Any, TypeId};
use std::sync::{Arc, Mutex};

use crate::*;

/////////////////////////////////////////////////////////////////////////////////////////

/// Builders are responsible for resolving dependencies and creating new
/// instances of a certain type. Builders typically create new instances for
/// every call, delegating the lifetime management to [Scope]s,
pub trait Builder: Send + Sync {
    fn instance_type_id(&self) -> TypeId;
    fn instance_type_name(&self) -> &'static str;
    fn interfaces(&self) -> Vec<InterfaceDesc>; // TODO: Avoid allocating
    fn get(&self, cat: &Catalog) -> Result<Arc<dyn Any + Send + Sync>, InjectionError>;
    fn check(&self, cat: &Catalog) -> Result<(), ValidationError>;
}

pub trait TypedBuilder<T: Send + Sync>: Builder {
    fn get(&self, cat: &Catalog) -> Result<Arc<T>, InjectionError>;
}

/// Allows [CatalogBuilder::add()] to accept types with associated builder
pub trait Component {
    type Builder: Builder;
    fn builder() -> Self::Builder;
    fn register(cat: &mut CatalogBuilder);
}

#[derive(Debug, Copy, Clone)]
pub struct InterfaceDesc {
    pub type_id: TypeId,
    pub type_name: &'static str,
}

/////////////////////////////////////////////////////////////////////////////////////////

/// Arc<T> can infinitely produce clones of itself and therefore is a builder
impl<Impl> Builder for Arc<Impl>
where
    Impl: Send + Sync + 'static,
{
    fn instance_type_id(&self) -> TypeId {
        TypeId::of::<Impl>()
    }

    fn instance_type_name(&self) -> &'static str {
        std::any::type_name::<Impl>()
    }

    fn interfaces(&self) -> Vec<InterfaceDesc> {
        Vec::new()
    }

    fn get(&self, _cat: &Catalog) -> Result<Arc<dyn Any + Send + Sync>, InjectionError> {
        Ok(self.clone())
    }

    fn check(&self, _cat: &Catalog) -> Result<(), ValidationError> {
        Ok(())
    }
}

impl<Impl> TypedBuilder<Impl> for Arc<Impl>
where
    Impl: Send + Sync + 'static,
{
    fn get(&self, _cat: &Catalog) -> Result<Arc<Impl>, InjectionError> {
        Ok(self.clone())
    }
}

/////////////////////////////////////////////////////////////////////////////////////////

/// Fn() -> Arc<T> acts as a builder
impl<Fct, Impl> Builder for Fct
where
    Fct: Fn() -> Arc<Impl> + Send + Sync,
    Impl: Send + Sync + 'static,
{
    fn instance_type_id(&self) -> TypeId {
        TypeId::of::<Impl>()
    }

    fn instance_type_name(&self) -> &'static str {
        std::any::type_name::<Impl>()
    }

    fn interfaces(&self) -> Vec<InterfaceDesc> {
        Vec::new()
    }

    fn get(&self, _cat: &Catalog) -> Result<Arc<dyn Any + Send + Sync>, InjectionError> {
        Ok(self())
    }

    fn check(&self, _cat: &Catalog) -> Result<(), ValidationError> {
        Ok(())
    }
}

impl<Fct, Impl> TypedBuilder<Impl> for Fct
where
    Fct: Fn() -> Arc<Impl> + Send + Sync,
    Impl: Send + Sync + 'static,
{
    fn get(&self, _cat: &Catalog) -> Result<Arc<Impl>, InjectionError> {
        Ok(self())
    }
}

/////////////////////////////////////////////////////////////////////////////////////////

pub(crate) struct Lazy<Fct, Impl>
where
    Fct: FnOnce() -> Impl,
    Impl: 'static + Send + Sync,
{
    state: Mutex<LazyState<Fct, Impl>>,
}

struct LazyState<Fct, Impl> {
    factory: Option<Fct>,
    instance: Option<Arc<Impl>>,
}

impl<Fct, Impl> Lazy<Fct, Impl>
where
    Fct: FnOnce() -> Impl,
    Impl: 'static + Send + Sync,
{
    pub fn new(factory: Fct) -> Self {
        Self {
            state: Mutex::new(LazyState {
                factory: Some(factory),
                instance: None,
            }),
        }
    }
}

impl<Fct, Impl> Builder for Lazy<Fct, Impl>
where
    Fct: FnOnce() -> Impl + Send + Sync,
    Impl: 'static + Send + Sync,
{
    fn instance_type_id(&self) -> TypeId {
        TypeId::of::<Impl>()
    }

    fn instance_type_name(&self) -> &'static str {
        std::any::type_name::<Impl>()
    }

    fn interfaces(&self) -> Vec<InterfaceDesc> {
        Vec::new()
    }

    fn get(&self, cat: &Catalog) -> Result<Arc<dyn Any + Send + Sync>, InjectionError> {
        Ok(TypedBuilder::get(self, cat)?)
    }

    fn check(&self, _cat: &Catalog) -> Result<(), ValidationError> {
        Ok(())
    }
}

impl<Fct, Impl> TypedBuilder<Impl> for Lazy<Fct, Impl>
where
    Fct: FnOnce() -> Impl + Send + Sync,
    Impl: 'static + Send + Sync,
{
    fn get(&self, _cat: &Catalog) -> Result<Arc<Impl>, InjectionError> {
        let mut s = self.state.lock().unwrap();
        if let Some(inst) = s.instance.as_ref() {
            Ok(inst.clone())
        } else {
            let factory = s.factory.take().unwrap();
            let inst = Arc::new(factory());
            s.instance = Some(inst.clone());
            Ok(inst)
        }
    }
}