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

use std::marker::PhantomData;

pub trait Query: Copy {
    type Output;
}

pub trait QueryConvert<E>: Query {
    fn convert(e: E) -> Self::Output;
}

pub trait QueryEnrich<A>: Query {
    fn enrich(&self, output: Self::Output, a: A) -> Self::Output;
}

pub trait QueryChain: Query {
    type Original: Query<Output = Self::Output>;

    fn original(&self) -> &Self::Original;
}

pub struct StartQuery<Q, M>(Q, PhantomData<M>);

impl<Q: Clone, M> Clone for StartQuery<Q, M> {
    fn clone(&self) -> Self {
        Self(self.0.clone(), PhantomData)
    }
}

impl<Q: Copy, M> Copy for StartQuery<Q, M> {}

impl<Q: Query, M> Query for StartQuery<Q, M> {
    type Output = Q::Output;
}

impl<Q: Query, M> QueryChain for StartQuery<Q, M> {
    type Original = Q;

    fn original(&self) -> &Self::Original {
        &self.0
    }
}

struct BootQuery;
struct IgnoreQuery;

impl<Q: Query, A> QueryEnrich<A> for StartQuery<Q, BootQuery>
where
    Q: QueryEnrich<A>,
{
    fn enrich(&self, output: Self::Output, a: A) -> Self::Output {
        self.0.enrich(output, a)
    }
}

impl<Q: Query, A> QueryEnrich<A> for StartQuery<Q, IgnoreQuery> {
    fn enrich(&self, output: Self::Output, _a: A) -> Self::Output {
        output
    }
}

impl<Q: Query, E, M> QueryConvert<E> for StartQuery<Q, M>
where
    Q: QueryConvert<E>,
{
    fn convert(e: E) -> Self::Output {
        Q::convert(e)
    }
}

pub struct ChainQuery<Q, A>(Q, PhantomData<A>);

impl<Q: Clone, A> Clone for ChainQuery<Q, A> {
    fn clone(&self) -> Self {
        Self(self.0.clone(), PhantomData)
    }
}

impl<Q: Copy, A> Copy for ChainQuery<Q, A> {}

impl<Q: Query, A> Query for ChainQuery<Q, A> {
    type Output = Q::Output;
}

impl<Q: QueryChain, A> QueryChain for ChainQuery<Q, A> {
    type Original = Q::Original;

    fn original(&self) -> &Self::Original {
        self.0.original()
    }
}

impl<Q: QueryChain, A, Ax: Enriches<A>> QueryEnrich<Ax> for ChainQuery<Q, A>
where
    Q: QueryEnrich<Ax>,
    Q::Original: QueryEnrich<A>,
{
    fn enrich(&self, output: Self::Output, a: Ax) -> Self::Output {
        self.0.enrich(a.enrich(output, self.original()), a)
    }
}

impl<Q: QueryChain, A, E> QueryConvert<E> for ChainQuery<Q, A>
where
    Q::Original: QueryConvert<E>,
{
    fn convert(e: E) -> Self::Output {
        <Q::Original as QueryConvert<E>>::convert(e)
    }
}

pub trait QueryExt: Query {
    fn start<M>(self) -> StartQuery<Self, M> {
        StartQuery(self, PhantomData)
    }

    fn enriching<A>(self) -> ChainQuery<Self, A>
    where
        Self: QueryChain,
        Self::Original: QueryEnrich<A>,
    {
        ChainQuery(self, PhantomData)
    }
}

impl<Q: Query> QueryExt for Q {}

pub trait Enriches<A> {
    fn enrich<Output>(
        &self,
        output: Output,
        query: &impl QueryEnrich<A, Output = Output>,
    ) -> Output;
}

pub trait QueryJoin: QueryEnrich<<Self as Query>::Output> {}

impl<Q: QueryEnrich<<Q as Query>::Output>> QueryJoin for Q {}