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
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
use quote::{quote, ToTokens};

#[proc_macro_attribute]
pub fn implement(attributes: proc_macro::TokenStream, original_type: proc_macro::TokenStream) -> proc_macro::TokenStream {
    let attributes = syn::parse_macro_input!(attributes as ImplementAttributes);
    let interfaces_len = proc_macro2::Literal::usize_unsuffixed(attributes.implement.len());

    let identity_type = if let Some(first) = attributes.implement.get(0) {
        first.to_ident()
    } else {
        quote! { ::windows::core::IInspectable }
    };

    let original_type2 = original_type.clone();
    let original_type2 = syn::parse_macro_input!(original_type2 as syn::ItemStruct);
    let original_ident = original_type2.ident;
    let mut constraints = quote! {};

    if let Some(where_clause) = original_type2.generics.where_clause {
        where_clause.predicates.to_tokens(&mut constraints);
    }

    let generics = if original_type2.generics.lt_token.is_some() {
        let mut params = quote! {};
        original_type2.generics.params.to_tokens(&mut params);
        quote! { <#params> }
    } else {
        quote! { <> }
    };

    let impl_ident = quote::format_ident!("{}_Impl", original_ident);
    let vtbl_idents = attributes.implement.iter().map(|implement| implement.to_vtbl_ident());
    let vtbl_idents2 = vtbl_idents.clone();

    let vtable_news = attributes.implement.iter().enumerate().map(|(enumerate, implement)| {
        let vtbl_ident = implement.to_vtbl_ident();
        let offset = proc_macro2::Literal::isize_unsuffixed(-1 - enumerate as isize);
        quote! { #vtbl_ident::new::<Self, #original_ident::#generics, #offset>() }
    });

    let offset = attributes.implement.iter().enumerate().map(|(offset, _)| proc_macro2::Literal::usize_unsuffixed(offset));

    let queries = attributes.implement.iter().enumerate().map(|(count, implement)| {
        let vtbl_ident = implement.to_vtbl_ident();
        let offset = proc_macro2::Literal::usize_unsuffixed(count);
        quote! {
            else if #vtbl_ident::matches(iid) {
                &self.vtables.#offset as *const _ as *const _
            }
        }
    });

    let conversions = attributes.implement.iter().enumerate().map(|(enumerate, implement)| {
        let interface_ident = implement.to_ident();
        let offset = proc_macro2::Literal::usize_unsuffixed(enumerate);
        quote! {
            impl #generics ::core::convert::From<#original_ident::#generics> for #interface_ident where #constraints {
                fn from(this: #original_ident::#generics) -> Self {
                    let this = #impl_ident::#generics::new(this);
                    let mut this = ::core::mem::ManuallyDrop::new(::std::boxed::Box::new(this));
                    let vtable_ptr = &this.vtables.#offset;
                    // SAFETY: interfaces are in-memory equivalent to pointers to their vtables.
                    unsafe { ::core::mem::transmute(vtable_ptr) }
                }
            }
            impl #generics ::windows::core::AsImpl<#original_ident::#generics> for #interface_ident where #constraints {
                fn as_impl(&self) -> &#original_ident::#generics {
                    let this = ::windows::core::Interface::as_raw(self);
                    // SAFETY: the offset is guranteed to be in bounds, and the implementation struct
                    // is guaranteed to live at least as long as `self`.
                    unsafe {
                        // Subtract away the vtable offset plus 1, for the `identity` field, to get
                        // to the impl struct which contains that original implementation type.
                        let this = (this as *mut *mut ::core::ffi::c_void).sub(1 + #offset) as *mut #impl_ident::#generics;
                        &(*this).this
                    }
                }
            }
        }
    });

    let tokens = quote! {
        #[repr(C)]
        struct #impl_ident#generics where #constraints {
            identity: *const ::windows::core::IInspectable_Vtbl,
            vtables: (#(*const #vtbl_idents,)*),
             this: #original_ident::#generics,
            count: ::windows::imp::WeakRefCount,
        }
        impl #generics #impl_ident::#generics where #constraints {
            const VTABLES: (#(#vtbl_idents2,)*) = (#(#vtable_news,)*);
            const IDENTITY: ::windows::core::IInspectable_Vtbl = ::windows::core::IInspectable_Vtbl::new::<Self, #identity_type, 0>();
            fn new(this: #original_ident::#generics) -> Self {
                Self {
                    identity: &Self::IDENTITY,
                    vtables:(#(&Self::VTABLES.#offset,)*),
                    this,
                    count: ::windows::imp::WeakRefCount::new(),
                }
            }
        }
         impl #generics ::windows::core::IUnknownImpl for #impl_ident::#generics where #constraints {
            type Impl = #original_ident::#generics;
            fn get_impl(&self) -> &Self::Impl {
                &self.this
            }
            unsafe fn QueryInterface(&self, iid: &::windows::core::GUID, interface: *mut *const ::core::ffi::c_void) -> ::windows::core::HRESULT {
                unsafe {
                    *interface = if iid == &<::windows::core::IUnknown as ::windows::core::ComInterface>::IID
                        || iid == &<::windows::core::IInspectable as ::windows::core::ComInterface>::IID
                        || iid == &<::windows::imp::IAgileObject as ::windows::core::ComInterface>::IID {
                            &self.identity as *const _ as *const _
                    } #(#queries)* else {
                        ::core::ptr::null_mut()
                    };

                    if !(*interface).is_null() {
                        self.count.add_ref();
                        return ::windows::core::HRESULT(0);
                    }

                    *interface = self.count.query(iid, &self.identity as *const _ as *mut _);

                    if (*interface).is_null() {
                        ::windows::core::HRESULT(0x8000_4002) // E_NOINTERFACE
                    } else {
                        ::windows::core::HRESULT(0)
                    }
                }
            }
            fn AddRef(&self) -> u32 {
                self.count.add_ref()
            }
            unsafe fn Release(&self) -> u32 {
                let remaining = self.count.release();
                if remaining == 0 {
                    unsafe {
                        _ = ::std::boxed::Box::from_raw(self as *const Self as *mut Self);
                    }
                }
                remaining
            }
         }
        impl #generics #original_ident::#generics where #constraints {
            /// Try casting as the provided interface
            ///
            /// # Safety
            ///
            /// This function can only be safely called if `self` has been heap allocated and pinned using
            /// the mechanisms provided by `implement` macro.
            unsafe fn cast<I: ::windows::core::ComInterface>(&self) -> ::windows::core::Result<I> {
                let boxed = (self as *const _ as *const *mut ::core::ffi::c_void).sub(1 + #interfaces_len) as *mut #impl_ident::#generics;
                let mut result = None;
                <#impl_ident::#generics as ::windows::core::IUnknownImpl>::QueryInterface(&*boxed, &I::IID, &mut result as *mut _ as _).and_some(result)
            }
        }
        impl #generics ::core::convert::From<#original_ident::#generics> for ::windows::core::IUnknown where #constraints {
            fn from(this: #original_ident::#generics) -> Self {
                let this = #impl_ident::#generics::new(this);
                let boxed = ::core::mem::ManuallyDrop::new(::std::boxed::Box::new(this));
                unsafe {
                    ::core::mem::transmute(&boxed.identity)
                }
            }
        }
        impl #generics ::core::convert::From<#original_ident::#generics> for ::windows::core::IInspectable where #constraints {
            fn from(this: #original_ident::#generics) -> Self {
                let this = #impl_ident::#generics::new(this);
                let boxed = ::core::mem::ManuallyDrop::new(::std::boxed::Box::new(this));
                unsafe {
                    ::core::mem::transmute(&boxed.identity)
                }
            }
        }
        #(#conversions)*
    };

    let mut tokens: proc_macro::TokenStream = tokens.into();
    tokens.extend(core::iter::once(original_type));
    tokens
}

#[derive(Default)]
struct ImplementType {
    type_name: String,
    generics: Vec<ImplementType>,
}

impl ImplementType {
    fn to_ident(&self) -> proc_macro2::TokenStream {
        let type_name = syn::parse_str::<proc_macro2::TokenStream>(&self.type_name).expect("Invalid token stream");
        let generics = self.generics.iter().map(|g| g.to_ident());
        quote! { #type_name<#(#generics,)*> }
    }
    fn to_vtbl_ident(&self) -> proc_macro2::TokenStream {
        let ident = self.to_ident();
        quote! {
            <#ident as ::windows::core::Interface>::Vtable
        }
    }
}

#[derive(Default)]
struct ImplementAttributes {
    pub implement: Vec<ImplementType>,
}

impl syn::parse::Parse for ImplementAttributes {
    fn parse(cursor: syn::parse::ParseStream) -> syn::parse::Result<Self> {
        let mut input = Self::default();

        while !cursor.is_empty() {
            input.parse_implement(cursor)?;
        }

        Ok(input)
    }
}

impl ImplementAttributes {
    fn parse_implement(&mut self, cursor: syn::parse::ParseStream) -> syn::parse::Result<()> {
        let tree = cursor.parse::<UseTree2>()?;
        self.walk_implement(&tree, &mut String::new())?;

        if !cursor.is_empty() {
            cursor.parse::<syn::Token![,]>()?;
        }

        Ok(())
    }

    fn walk_implement(&mut self, tree: &UseTree2, namespace: &mut String) -> syn::parse::Result<()> {
        match tree {
            UseTree2::Path(input) => {
                if !namespace.is_empty() {
                    namespace.push_str("::");
                }

                namespace.push_str(&input.ident.to_string());
                self.walk_implement(&input.tree, namespace)?;
            }
            UseTree2::Name(_) => {
                self.implement.push(tree.to_element_type(namespace)?);
            }
            UseTree2::Group(input) => {
                for tree in &input.items {
                    self.walk_implement(tree, namespace)?;
                }
            }
        }

        Ok(())
    }
}

enum UseTree2 {
    Path(UsePath2),
    Name(UseName2),
    Group(UseGroup2),
}

impl UseTree2 {
    fn to_element_type(&self, namespace: &mut String) -> syn::parse::Result<ImplementType> {
        match self {
            UseTree2::Path(input) => {
                if !namespace.is_empty() {
                    namespace.push_str("::");
                }

                namespace.push_str(&input.ident.to_string());
                input.tree.to_element_type(namespace)
            }
            UseTree2::Name(input) => {
                let mut type_name = input.ident.to_string();

                if !namespace.is_empty() {
                    type_name = format!("{namespace}::{type_name}");
                }

                let mut generics = vec![];

                for g in &input.generics {
                    generics.push(g.to_element_type(&mut String::new())?);
                }

                Ok(ImplementType { type_name, generics })
            }
            UseTree2::Group(input) => Err(syn::parse::Error::new(input.brace_token.span, "Syntax not supported")),
        }
    }
}

struct UsePath2 {
    pub ident: syn::Ident,
    pub tree: Box<UseTree2>,
}

struct UseName2 {
    pub ident: syn::Ident,
    pub generics: Vec<UseTree2>,
}

struct UseGroup2 {
    pub brace_token: syn::token::Brace,
    pub items: syn::punctuated::Punctuated<UseTree2, syn::Token![,]>,
}

impl syn::parse::Parse for UseTree2 {
    fn parse(input: syn::parse::ParseStream) -> syn::parse::Result<UseTree2> {
        let lookahead = input.lookahead1();
        if lookahead.peek(syn::Ident) {
            use syn::ext::IdentExt;
            let ident = input.call(syn::Ident::parse_any)?;
            if input.peek(syn::Token![::]) {
                input.parse::<syn::Token![::]>()?;
                Ok(UseTree2::Path(UsePath2 { ident, tree: Box::new(input.parse()?) }))
            } else {
                let generics = if input.peek(syn::Token![<]) {
                    input.parse::<syn::Token![<]>()?;
                    let mut generics = Vec::new();
                    loop {
                        generics.push(input.parse::<UseTree2>()?);

                        if input.parse::<syn::Token![,]>().is_err() {
                            break;
                        }
                    }
                    input.parse::<syn::Token![>]>()?;
                    generics
                } else {
                    Vec::new()
                };

                Ok(UseTree2::Name(UseName2 { ident, generics }))
            }
        } else if lookahead.peek(syn::token::Brace) {
            let content;
            let brace_token = syn::braced!(content in input);
            let items = content.parse_terminated(UseTree2::parse)?;

            Ok(UseTree2::Group(UseGroup2 { brace_token, items }))
        } else {
            Err(lookahead.error())
        }
    }
}