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

// Take a look at the license at the top of the repository in the LICENSE file.

use proc_macro2::TokenStream;
use quote::{format_ident, quote};
use syn::{Fields, FieldsNamed, FieldsUnnamed, Ident, Type};

use crate::utils::crate_ident_new;

/// Parts needed to derive Downgrade and Upgrade implementation.
pub struct DowngradeStructParts {
    /// Inner part of weak type declaration
    pub weak_fields: TokenStream,
    /// Term needed to finish declaration. It is usually blank but is `;` for tuple structs.
    pub end_of_struct: TokenStream,
    /// Destructuring pattern
    pub destruct: TokenStream,
    /// Downgrade code
    pub downgrade: TokenStream,
    /// Upgrade code
    pub upgrade: TokenStream,
}

/// This function generates parts needed to derive Downgrade and Upgrade
/// implementations.
///
/// # Example
///
/// Let's assume following types are declared.
///
/// ```rust,ignore
/// struct Unnamed(X, Y);
///
/// struct Named {
///     x: X,
///     y: Y,
/// }
///
/// enum Choice {
///     This(X, Y),
///     That { x: X, y: Y },
/// }
/// ```
///
/// ## weak_fields
///
/// For the struct `Unnamed` and for a enum's variant `Choice::This`
/// it will be `(<X as Downgrade>::Weak, <Y as Downgrade>::Weak)`.
/// For the struct `Named` and for a enum's variant `Choice::That`
/// it will be `{ x: <X as Downgrade>::Weak, y: <Y as Downgrade>::Weak, }`.
///
/// ## end_of_struct
///
/// It is a semicolon (`;`) for an `Unnamed` and is blank for the rest.
///
/// ## destruct
///
/// For the struct `Unnamed` and for a enum's variant `Choice::This`
/// it will be `(ref _0, ref _1)`.
/// For the struct `Named` and for a enum's variant `Choice::That`
/// it will be `{ ref x, ref y }`.
/// So it can be used as a destructuring pattern for values of both types,
/// strong and weak.
///
/// ```rust,ignore
/// let Unnamed (ref _0, ref _1) = <expression>;
/// let Named { ref x, ref y } = <expression>;
///
/// match <expression> {
///     Choise::This (ref _0, ref _1) => ... ,
///     Choise::That { ref x, ref y } => ... ,
/// }
/// ```
///
/// # downgrade
///
/// ```rust,ignore
/// (
///     glib::clone::Downgrade::downgrade(_0),
///     glib::clone::Downgrade::downgrade(_1),
/// )
///
/// {
///     x: glib::clone::Downgrade::downgrade(x),
///     y: glib::clone::Downgrade::downgrade(y),
/// }
/// ```
///
/// # upgrade
///
/// ```rust,ignore
/// (
///     glib::clone::Upgrade::upgrade(_0)?,
///     glib::clone::Upgrade::upgrade(_1)?,
/// )
///
/// {
///     x: glib::clone::Upgrade::upgrade(x)?,
///     y: glib::clone::Upgrade::upgrade(y)?,
/// }
/// ```
pub fn derive_downgrade_fields(fields: syn::Fields) -> DowngradeStructParts {
    let glib = crate_ident_new();
    match fields {
        Fields::Unnamed(FieldsUnnamed { unnamed, .. }) => {
            let fields: Vec<Type> = unnamed
                .into_pairs()
                .map(|pair| pair.into_value())
                .map(|field| field.ty)
                .collect();

            let weak_fields: Vec<_> = fields
                .iter()
                .map(|ty| {
                    quote! {
                        <#ty as #glib::clone::Downgrade>::Weak
                    }
                })
                .collect();

            let field_ident: Vec<Ident> =
                (0..fields.len()).map(|i| format_ident!("_{}", i)).collect();

            DowngradeStructParts {
                weak_fields: quote! {
                    (#(
                        #weak_fields
                    ),*)
                },
                end_of_struct: quote!(;),
                destruct: quote! {
                    (#(
                        ref #field_ident
                    ),*)
                },
                downgrade: quote! {
                    (#(
                        #glib::clone::Downgrade::downgrade(#field_ident)
                    ),*)
                },
                upgrade: quote! {
                    (#(
                        #glib::clone::Upgrade::upgrade(#field_ident)?
                    ),*)
                },
            }
        }
        Fields::Named(FieldsNamed { named, .. }) => {
            let fields: Vec<(Ident, Type)> = named
                .into_pairs()
                .map(|pair| pair.into_value())
                .map(|field| (field.ident.expect("Field ident is specified"), field.ty))
                .collect();

            let weak_fields: Vec<_> = fields
                .iter()
                .map(|(ident, ty)| {
                    quote! {
                        #ident: <#ty as #glib::clone::Downgrade>::Weak
                    }
                })
                .collect();

            let field_ident: Vec<_> = fields.iter().map(|(ident, _ty)| ident).collect();

            DowngradeStructParts {
                weak_fields: quote! {
                    {#(
                        #weak_fields
                    ),*}
                },
                end_of_struct: quote!(),
                destruct: quote! {
                    {#(
                        ref #field_ident
                    ),*}
                },
                downgrade: quote! {
                    {#(
                        #field_ident: #glib::clone::Downgrade::downgrade(#field_ident)
                    ),*}
                },
                upgrade: quote! {
                    {#(
                        #field_ident: #glib::clone::Upgrade::upgrade(#field_ident)?
                    ),*}
                },
            }
        }
        Fields::Unit => DowngradeStructParts {
            weak_fields: quote! {},
            end_of_struct: quote! { ; },
            destruct: quote! {},
            downgrade: quote! {},
            upgrade: quote! {},
        },
    }
}