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

use std::{
    char::ParseCharError,
    convert::Infallible,
    fmt::Display,
    num::{ParseFloatError, ParseIntError},
    ops::{Deref, DerefMut},
    str::ParseBoolError,
};

use serde::{de::DeserializeOwned, Serialize};

use crate::ID;

/// Cursor type
///
/// A custom scalar that serializes as a string.
/// <https://relay.dev/graphql/connections.htm#sec-Cursor>
pub trait CursorType: Sized {
    /// Error type for `decode_cursor`.
    type Error: Display;

    /// Decode cursor from string.
    fn decode_cursor(s: &str) -> Result<Self, Self::Error>;

    /// Encode cursor to string.
    fn encode_cursor(&self) -> String;
}

macro_rules! cursor_type_int_impl {
    ($($t:ty)*) => {$(
        impl CursorType for $t {
            type Error = ParseIntError;

            fn decode_cursor(s: &str) -> Result<Self, Self::Error> {
                s.parse()
            }

            fn encode_cursor(&self) -> String {
                self.to_string()
            }
        }
    )*}
}

cursor_type_int_impl! { isize i8 i16 i32 i64 i128 usize u8 u16 u32 u64 u128 }

impl CursorType for f32 {
    type Error = ParseFloatError;

    fn decode_cursor(s: &str) -> Result<Self, Self::Error> {
        s.parse()
    }

    fn encode_cursor(&self) -> String {
        self.to_string()
    }
}

impl CursorType for f64 {
    type Error = ParseFloatError;

    fn decode_cursor(s: &str) -> Result<Self, Self::Error> {
        s.parse()
    }

    fn encode_cursor(&self) -> String {
        self.to_string()
    }
}

impl CursorType for char {
    type Error = ParseCharError;

    fn decode_cursor(s: &str) -> Result<Self, Self::Error> {
        s.parse()
    }

    fn encode_cursor(&self) -> String {
        self.to_string()
    }
}

impl CursorType for bool {
    type Error = ParseBoolError;

    fn decode_cursor(s: &str) -> Result<Self, Self::Error> {
        s.parse()
    }

    fn encode_cursor(&self) -> String {
        self.to_string()
    }
}

impl CursorType for String {
    type Error = Infallible;

    fn decode_cursor(s: &str) -> Result<Self, Self::Error> {
        Ok(s.to_string())
    }

    fn encode_cursor(&self) -> String {
        self.clone()
    }
}

impl CursorType for ID {
    type Error = Infallible;

    fn decode_cursor(s: &str) -> Result<Self, Self::Error> {
        Ok(s.to_string().into())
    }

    fn encode_cursor(&self) -> String {
        self.to_string()
    }
}

/// A opaque cursor that encode/decode the value to base64
pub struct OpaqueCursor<T>(pub T);

impl<T> Deref for OpaqueCursor<T> {
    type Target = T;

    #[inline]
    fn deref(&self) -> &Self::Target {
        &self.0
    }
}

impl<T> DerefMut for OpaqueCursor<T> {
    #[inline]
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.0
    }
}

impl<T> CursorType for OpaqueCursor<T>
where
    T: Serialize + DeserializeOwned,
{
    type Error = Box<dyn std::error::Error + Send + Sync>;

    fn decode_cursor(s: &str) -> Result<Self, Self::Error> {
        let data = base64::decode_config(s, base64::URL_SAFE_NO_PAD)?;
        Ok(Self(serde_json::from_slice(&data)?))
    }

    fn encode_cursor(&self) -> String {
        let value = serde_json::to_vec(&self.0).unwrap_or_default();
        base64::encode_config(value, base64::URL_SAFE_NO_PAD)
    }
}