extern crate proc_macro;
extern crate proc_macro2;
#[macro_use]
extern crate syn;
#[macro_use]
extern crate quote;

use proc_macro::TokenStream;
use proc_macro2::TokenStream as TokenStream2;
use quote::ToTokens;
use syn::{parse::Parser, AttributeArgs, DeriveInput, ItemFn, ItemImpl, ItemType};

mod methods;
mod native_script;
mod profiled;
mod utils;
mod varargs;
mod variant;

/// Collects method signatures of all functions in a `NativeClass` that have the `#[method]`
/// attribute and registers them with Godot.
///
/// The `#[methods]` attribute can be used with both `impl Type` and `impl Trait for Type`
/// blocks. The semantics change depending on whether a mix-in name is provided for the block.
///
/// ## Universal `impl` blocks: `#[methods]`
///
/// An `impl` block that doesn't have a `mixin` parameter is universal. Universal `#[methods]`
/// blocks **must not overlap**. Usually, this means that **only one** `impl` block per struct
/// may be universal.
///
/// When applied to a generic `impl`, the `impl` block must apply to **all** monomorphizations
/// of the type, i.e. be *universal*.
///
/// One applicable universal block must be present for each type one wishes to use as a
/// `NativeClass`. Universal blocks are always registered automatically.
///
/// ## Mix-ins: `#[methods(mixin = "Name")]`
///
/// When given a name with the `mixin` argument, a block behaves instead as a mix-in block.
/// `#[method(mixin = "Name")]` creates an opaque type called `Name` under the current scope,
/// that can be manually registered to any type the `impl` block covers. This can be done in
/// a `register_with` callback with `builder.mixin::<MyMixin>()`.
///
/// Unlike universal blocks, mix-in blocks have a **many-to-many** relationship with the types
/// they are registered to. Any number of mix-ins can be applied to any number of compatible
/// types. This can be useful for reusing generics `impl`s, or organizing code for big interfaces.
///
/// Additionally, the attribute accepts the following arguments:
///
/// - `#[methods(pub)]`<br>
/// Mix-in types are private by default. The `pub` argument makes them public instead.
///
/// ## Example
///
/// ### Universal
///
/// ```
/// use gdnative::prelude::*;
///
/// #[derive(NativeClass)]
/// #[inherit(Reference)]
/// #[no_constructor]
/// struct Foo {}
///
/// #[methods]
/// impl Foo {
///     #[method]
///     fn foo(&self, #[base] _base: &Reference, bar: i64) -> i64 {
///         bar
///     }
/// }
///
/// ```
///
/// ### Mix-in
///
/// ```
/// use gdnative::prelude::*;
///
/// #[derive(NativeClass)]
/// #[inherit(Reference)]
/// #[register_with(register_foo)]
/// #[no_constructor]
/// struct Foo {}
///
/// fn register_foo(builder: &ClassBuilder<Foo>) {
///     builder.mixin::<FooMixin>();
/// }
///
/// #[methods(mixin = "FooMixin")]
/// impl Foo {
///     #[method]
///     fn foo(&self, #[base] _base: &Reference, bar: i64) -> i64 {
///         bar
///     }
/// }
/// ```
#[proc_macro_attribute]
pub fn methods(meta: TokenStream, input: TokenStream) -> TokenStream {
    let args =
        match syn::punctuated::Punctuated::<syn::NestedMeta, syn::Token![,]>::parse_terminated
            .parse(meta)
        {
            Ok(args) => args.into_iter().collect::<Vec<_>>(),
            Err(err) => return error_with_input(input, err),
        };

    let impl_block = match syn::parse::<ItemImpl>(input.clone()) {
        Ok(impl_block) => impl_block,
        Err(err) => return error_with_input(input, err),
    };

    fn error_with_input(input: TokenStream, err: syn::Error) -> TokenStream {
        let mut err = TokenStream::from(err.to_compile_error());
        err.extend(std::iter::once(input));
        err
    }

    match methods::derive_methods(args, impl_block) {
        Ok(ts) => ts.into(),
        Err(err) => error_with_input(input, err),
    }
}

/// Makes a function profiled in Godot's built-in profiler. This macro automatically
/// creates a tag using the name of the current module and the function by default.
///
/// This attribute may also be used on non-exported functions. If the GDNative API isn't
/// initialized when the function is called, the data will be ignored silently.
///
/// A custom tag can also be provided using the `tag` option.
///
/// See the `gdnative::export::profiler` for a lower-level API to the profiler with
/// more control.
///
/// # Examples
///
/// ```ignore
/// mod foo {
///     // This function will show up as `foo/bar` under Script Functions.
///     #[profiled]
///     fn bar() {
///         std::thread::sleep(std::time::Duration::from_millis(1));
///     }
/// }
/// ```
///
/// ```ignore
/// // This function will show up as `my_custom_tag` under Script Functions.
/// #[profiled(tag = "my_custom_tag")]
/// fn baz() {
///     std::thread::sleep(std::time::Duration::from_millis(1));
/// }
/// ```
#[proc_macro_attribute]
pub fn profiled(meta: TokenStream, input: TokenStream) -> TokenStream {
    let args = parse_macro_input!(meta as AttributeArgs);
    let item_fn = parse_macro_input!(input as ItemFn);

    match profiled::derive_profiled(args, item_fn) {
        Ok(tokens) => tokens.into(),
        Err(err) => err.to_compile_error().into(),
    }
}

/// Makes it possible to use a type as a NativeScript. Automatically registers the type
/// if the `inventory` feature is enabled on supported platforms.
///
/// ## Type attributes
///
/// The behavior of the derive macro can be customized using attributes on the type
/// deriving `NativeClass`. All type attributes are optional.
///
/// ### `#[inherit(gdnative::api::BaseClass)]`
///
/// Sets `gdnative::api::BaseClass` as the base class for the script. This *must* be
/// a type from the generated Godot API (that implements `GodotObject`). All `owner`
/// arguments of exported methods must be references (`TRef`, `Ref`, or `&`) to this
/// type.
///
/// Inheritance from other scripts, either in Rust or other languages, is
/// not supported.
///
/// If no `#[inherit(...)]` is provided, [`gdnative::api::Reference`](../gdnative/api/struct.Reference.html)
/// is used as a base class. This behavior is consistent with GDScript: omitting the
/// `extends` keyword will inherit `Reference`.
///
///
/// ### `#[user_data(gdnative::user_data::SomeWrapper<Self>)]`
///
/// Use the given type as the user-data wrapper. See the module-level docs on
/// `gdnative::user_data` for more information.
///
/// ### `#[register_with(path::to::function)]`
///
/// Use a custom function to register signals, properties or methods, in addition
/// to the one generated by `#[methods]`:
///
/// ```
/// use gdnative::prelude::*;
/// use gdnative::export::hint::{RangeHint, FloatHint};
///
/// #[derive(NativeClass)]
/// #[inherit(Reference)]
/// #[register_with(Self::my_register_function)]
/// struct Foo;
///
/// #[methods]
/// impl Foo {
///     fn new(_: &Reference) -> Self {
///         Self {}
///     }
///     fn my_register_function(builder: &ClassBuilder<Foo>) {
///         builder.signal("my_sig").done();
///         builder.property::<f32>("my_prop")
///             .with_getter(|_, _| 42.0)
///             .with_hint(FloatHint::Range(RangeHint::new(0.0, 100.0)))
///             .done();
///     }
/// }
/// ```
///
/// ### `#[no_constructor]`
///
/// Indicates that this type has no zero-argument constructor. Instances of such
/// scripts can only be created from Rust using `Instance::emplace`. `Instance::new`
/// or `ScriptName.new` from GDScript will result in panics at runtime.
///
/// See documentation on `Instance::emplace` for an example on how this can be used.
///
///
/// ## Field attributes
///
/// All field attributes are optional.
///
/// ### `#[property]`
///
/// Convenience attribute to register a field as a property. Possible arguments for
/// the attribute are:
///
/// - `path = "my_category/my_property_name"`
///
///   Puts the property under the `my_category` category and renames it to
///   `my_property_name` in the inspector and for GDScript.
///
/// - `default = 42.0`
///
///   Sets the default value *in the inspector* for this property. The setter is *not*
///   guaranteed to be called by the engine with the value.
///
/// - `get` / `get_ref` / `set`
///
///   Configure getter/setter for property. All of them can accept a path to specify a custom
///   property accessor. For example, `#[property(get = "Self::my_getter")]` will use
///   `Self::my_getter` as the getter.
///
///   The difference of `get` and `get_ref` is that `get` will register the getter with
///   `with_getter` function, which means your getter should return an owned value `T`, but
///   `get_ref` use `with_ref_getter` to register getter. In this case, your custom getter
///   should return a shared reference `&T`.
///
///   Situations with custom getters/setters and no backing fields require the use of the
///   type [`Property<T>`][gdnative::export::Property]. Consult its documentation for
///   a deeper elaboration of property exporting.
///
/// - `no_editor`
///
///   Hides the property from the editor. Does not prevent it from being sent over network or saved in storage.
///
/// ### `#[methods]`
/// Adds the necessary information to a an `impl` block to register the properties and methods with Godot.
///
/// One and only one universal `impl` block must be available for each `NativeClass`
/// monomorphization, along with any number of additional mix-ins. See [`methods`](attr.methods.html)
/// for more information.
///
/// ### `#[method]`
/// Registers the attributed function signature to be used by Godot.
///
/// This attribute was formerly called `#[export]`, but is not directly related to the concept of
/// [exporting](https://docs.godotengine.org/en/stable/tutorials/export/exporting_basics.html) in GDScript.
///
/// A valid function signature must have:
/// - `self`, `&self` or `&mut self` as its first parameter, if applicable.
/// - Up of one of each of the following special arguments, in any order, denoted by the attributes:
///     - `#[base]` - A reference to the base/owner object. This may be `&T` or `TRef<T>`m where `T` refers to
///       the type declared in `#[inherit(T)]` attribute for the `NativeClass` type.
///     - `#[async_ctx]` - The [async context](gdnative::tasks::Context), for async methods. See the `async` argument
///       below.
/// - Any number of required parameters, which must have the type `Variant` or must implement the `FromVariant` trait.
///  `FromVariant` is implemented for most common types.
/// - Any number of optional parameters annotated with `#[opt]`. Same rules as for required parameters apply.
///   Optional parameters must appear at the end of the parameter list.
/// - Return values must implement the `OwnedToVariant` trait (automatically implemented by `ToVariant`)
///   or be a `Variant` type.
///
/// ```ignore
/// // Associated function
/// #[method]
/// fn foo();
///
/// // No access to base parameter
/// #[method]
/// fn foo(&self);
///
/// // Access base parameter as &T
/// #[method]
/// fn foo(&self, #[base] base: &Reference);
///
/// // Access base parameter as TRef<T>
/// #[method]
/// fn foo(&self, #[base] base: TRef<Reference>);
///
/// // Access only the async context. Both variations are valid.
/// #[method]
/// async fn foo(#[async_ctx] ctx: Arc<Context>);
/// #[method(async)]
/// fn foo(#[async_ctx] ctx: Arc<Context>) -> impl Future<Output = ()> + 'static;
///
/// // Access the base parameter as TRef<T>, and the async context. Both variations are valid.
/// // Note the absence of `async fn`s here: this is due to a current limitation in Rust's lifetime elision rules.
/// // See the `async` attribute argument down below for more details.
/// #[method(async)]
/// fn foo(&self, #[base] base: TRef<Reference>, #[async_ctx] ctx: Arc<Context>) -> impl Future<Output = ()> + 'static;
/// #[method(async)]
/// fn foo(&self, #[async_ctx] ctx: Arc<Context>, #[base] base: TRef<Reference>) -> impl Future<Output = ()> + 'static;
/// ```
///
/// **Note**: Marking a function with `#[method]` does not have any effect unless inside an `impl` block that has the `#[methods]` attribute.
///
/// Possible arguments for this attribute are:
///
/// - `name = "overridden_function_name"`
///
///   Overrides the function name as the method name to be registered in Godot.
///
/// - `rpc = "selected_rpc"`
///
///   `"selected_rpc"` must be one of the following values, which refer to the associated [Multiplayer API RPC Mode](https://docs.godotengine.org/en/stable/classes/class_multiplayerapi.html?highlight=RPC#enumerations).
///   See also the Rust type [`export::RpcMode`].
///     - `"disabled"`
///     - `"remote"`
///     - `"remote_sync"`
///     - `"master"`
///     - `"master_sync"`
///     - `"puppet"`
///     - `"puppet_sync"`
///
///   This enables you to set the [Multiplayer API RPC Mode](https://docs.godotengine.org/en/stable/classes/class_multiplayerapi.html?highlight=RPC#enumerations) for the function.
///   Refer to [Godot's Remote Procedure documentation](https://docs.godotengine.org/en/stable/tutorials/networking/high_level_multiplayer.html#rpc) for more details.
///
/// - `deref_return`
///
///   Allows you to return a type using its `Deref` representation. This can avoid extra intermediate copies for larger objects, by explicitly
///   returning a reference (or in general, a type that dereferences to something that can be exported).
///
///   For example:
///   ```ignore
///   #[method(deref_return)]
///   fn get_numbers(&self) -> std::cell::Ref<Vec<i32>> {
///      // Assume self.cell is std::cell::RefCell<Vec<i32>>
///      self.cell.borrow()
///   }
///   ```
///
/// - `async`
///
///   Marks the function as async. This is used for functions that aren't `async` themselves, but return `Future`s instead.
///   This is especially useful for working around Rust's lifetime elision rules, which put the lifetime of `&self` into the
///   return value for `async fn`s. The `impl Future` syntax instead allows one to explicitly specify a `'static` lifetime,
///   as required by the async runtime:
///
///   ```ignore
///   // This will NOT compile: Rust assumes that any futures returned by an `async fn` may only live as long as each of its
///   // arguments, and there is no way to tell it otherwise. As a result, it will emit some cryptic complaints about lifetime.
///   #[method]
///   async fn answer(&self) -> i32 {
///      42
///   }
///
///   // This, however, compiles, thanks to the explicit `'static` lifetime in the return signature.
///   #[method(async)]
///   fn answer(&self) -> impl Future<Output = i32> + 'static {
///      async { 42 }
///   }
///
///   ```
///
///
/// #### `Node` virtual functions
///
/// This is a list of common Godot virtual functions that are automatically called via [notifications](https://docs.godotengine.org/en/stable/classes/class_object.html#class-object-method-notification).
///
/// It is assumed that every method is exported via `#[method]` attribute. The parameter `#[base] base: &Node` can be omitted if you don't need it.
///
/// ```ignore
/// fn _ready(&self, #[base] base: &Node);
/// ```
/// Called when both the node and its children have entered the scene tree.  
/// _See [Godot docs](https://docs.godotengine.org/en/stable/classes/class_node.html#class-node-method-ready) for more information._
/// <br><br>
///
/// ```ignore
/// fn _enter_tree(&self, #[base] base: &Node);
/// ```
/// Called when the node enters the scene tree.  
/// _See [Godot docs](https://docs.godotengine.org/en/stable/classes/class_node.html#class-node-method-enter-tree) for more information._
/// <br><br>
///
/// ```ignore
/// fn _exit_tree(&self, #[base] base: &Node);
/// ```
/// Called when the node is removed from the scene tree.  
/// _See [Godot docs](https://docs.godotengine.org/en/stable/classes/class_node.html#class-node-method-exit-tree) for more information._
/// <br><br>
///
/// ```ignore
/// fn _get_configuration_warning(&self, #[base] base: &Node) -> GodotString;
/// ```
/// The string returned from this method is displayed as a warning in the Scene Dock if the script that overrides it is a tool script.  
/// _See [Godot docs](https://docs.godotengine.org/en/stable/classes/class_node.html#class-node-method-get-configuration-warning) for more information._
/// <br><br>
///
/// ```ignore
/// fn _process(&mut self, #[base] base: &Node, delta: f64);
/// ```
/// Called during processing step of the main loop.  
/// _See [Godot docs](https://docs.godotengine.org/en/stable/classes/class_node.html#class-node-method-process) for more information._
/// <br><br>
///
/// ```ignore
/// fn _physics_process(&self, #[base] base: &Node, delta: f64);
/// ```
/// Called during physics update, with a fixed timestamp.  
/// _See [Godot docs](https://docs.godotengine.org/en/stable/classes/class_node.html#class-node-method-physics-process) for more information._
/// <br><br>
///
/// ```ignore
/// fn _input(&self, #[base] base: &Node, event: Ref<InputEvent>);
/// ```
/// Called when there is an input event.  
/// _See [Godot docs](https://docs.godotengine.org/en/stable/classes/class_node.html#class-node-method-input) for more information._
/// <br><br>
///
/// ```ignore
/// fn _unhandled_input(&self, #[base] base: &Node, event: Ref<InputEvent>);
/// ```
/// Called when an `InputEvent` hasn't been consumed by `_input()` or any GUI.  
/// _See [Godot docs](https://docs.godotengine.org/en/stable/classes/class_node.html#class-node-method-unhandled-input) for more information._
/// <br><br>
///
/// ```ignore
/// fn _unhandled_key_input (&self, #[base] base: &Node, event: Ref<InputKeyEvent>);
/// ```
/// Called when an `InputEventKey` hasn't been consumed by `_input()` or any GUI.  
/// _See [Godot docs](https://docs.godotengine.org/en/stable/classes/class_node.html#class-node-method-unhandled-key-input) for more information._
/// <br><br>
///
/// #### `Control` virtual functions
///
/// This is a list of common Godot virtual functions that are automatically called via [notifications](https://docs.godotengine.org/en/stable/classes/class_object.html#class-object-method-notification).
///
/// ```ignore
/// fn _clips_input(&self, #[base] base: &Control) -> bool;
/// ```
/// Returns whether `_gui_input()` should not be called for children controls outside this control's rectangle.  
/// _See [Godot docs](https://docs.godotengine.org/en/stable/classes/class_control.html#class-control-method-clips-input) for more information._
/// <br><br>
///
/// ```ignore
/// fn _get_minimum_size(&self, #[base] base: &Control) -> Vector2;
/// ```
/// Returns the minimum size for this control.  
/// _See [Godot docs](https://docs.godotengine.org/en/stable/classes/class_control.html#class-control-method-get-minimum-size) for more information._
/// <br><br>
///
/// ```ignore
/// fn _gui_input(&self, #[base] base: &Control, event: Ref<InputEvent>);
/// ```
/// Use this method to process and accept inputs on UI elements.  
/// _See [Godot docs](https://docs.godotengine.org/en/stable/classes/class_control.html#class-control-method-gui-input) for more information._
/// <br><br>
///
/// ```ignore
/// fn _make_custom_tooltip(&self, #[base] base: &Control, for_text: String) -> Ref<Control>;
/// ```
/// Returns a `Control` node that should be used as a tooltip instead of the default one.  
/// _See [Godot docs](https://docs.godotengine.org/en/stable/classes/class_control.html#class-control-method-make-custom-tooltip) for more information._
/// <br><br>
#[proc_macro_derive(
    NativeClass,
    attributes(inherit, register_with, no_constructor, user_data, property)
)]
pub fn derive_native_class(input: TokenStream) -> TokenStream {
    // Converting the proc_macro::TokenStream into non proc_macro types so that tests
    // can be written against the inner functions.
    let derive_input = syn::parse_macro_input!(input as DeriveInput);

    // Implement NativeClass for the input
    let derived = native_script::derive_native_class(&derive_input).map_or_else(
        |err| {
            // Silence the other errors that happen because NativeClass is not implemented
            let empty_nativeclass = native_script::impl_empty_nativeclass(&derive_input);
            let err = err.to_compile_error();

            quote! {
                #empty_nativeclass
                #err
            }
        },
        std::convert::identity,
    );

    TokenStream::from(derived)
}

/// Wires up necessary internals for a concrete monomorphization of a generic `NativeClass`,
/// represented as a type alias, so it can be registered.
///
/// The monomorphized type will be available to Godot under the name of the type alias,
/// once registered.  Automatically registers the type if the `inventory` feature is enabled on
/// supported platforms.
///
/// For more context, please refer to [gdnative::derive::NativeClass](NativeClass).
///
/// ## Type attributes
///
/// The behavior of the attribute can be customized using additional attributes on the type
/// alias. All type attributes are optional.
///
/// ### `#[register_with(path::to::function)]`
///
/// Use a custom function to register signals, properties or methods, in addition
/// to the one generated by a universal `#[methods]` block on the generic type.
/// This can be used to register extra mix-ins that apply to the specific monomorphization.
#[proc_macro_attribute]
pub fn monomorphize(meta: TokenStream, input: TokenStream) -> TokenStream {
    let args = parse_macro_input!(meta as AttributeArgs);
    let item_type = parse_macro_input!(input as ItemType);

    match native_script::derive_monomorphize(args, item_type) {
        Ok(tokens) => tokens.into(),
        Err(err) => err.to_compile_error().into(),
    }
}

#[proc_macro_derive(ToVariant, attributes(variant))]
pub fn derive_to_variant(input: TokenStream) -> TokenStream {
    match variant::derive_to_variant(variant::ToVariantTrait::ToVariant, input) {
        Ok(stream) => stream.into(),
        Err(err) => err.to_compile_error().into(),
    }
}

#[proc_macro_derive(OwnedToVariant, attributes(variant))]
pub fn derive_owned_to_variant(input: TokenStream) -> TokenStream {
    match variant::derive_to_variant(variant::ToVariantTrait::OwnedToVariant, input) {
        Ok(stream) => stream.into(),
        Err(err) => err.to_compile_error().into(),
    }
}

#[proc_macro_derive(FromVariant, attributes(variant))]
pub fn derive_from_variant(input: TokenStream) -> TokenStream {
    let derive_input = syn::parse_macro_input!(input as syn::DeriveInput);
    match variant::derive_from_variant(derive_input) {
        Ok(stream) => stream.into(),
        Err(err) => err.to_compile_error().into(),
    }
}

/// Enable struct types to be parsed as argument lists.
///
/// The `FromVarargs` trait can be derived for structure types where each type implements
/// `FromVariant`. The order of fields matter for this purpose:
///
/// ```ignore
/// #[derive(FromVarargs)]
/// struct MyArgs {
///     foo: i32,
///     bar: String,
///     #[opt] baz: Option<Ref<Node>>,
/// }
/// ```
///
/// ## Field attributes
///
/// Attributes can be used to customize behavior of certain fields. All attributes are optional.
///
/// ### `#[opt]`
///
/// Marks an argument as optional. Required arguments must precede all optional arguments.
/// Default values are obtained through `Default::default`.
///
/// ### `#[skip]`
///
/// Instructs the macro to skip a field. Skipped fields do not affect the signature of the
/// argument list. They may be located anywhere. Values are obtained through `Default::default`.
#[proc_macro_derive(FromVarargs, attributes(opt, skip))]
pub fn derive_from_varargs(input: TokenStream) -> TokenStream {
    let derive_input = syn::parse_macro_input!(input as syn::DeriveInput);
    match varargs::derive_from_varargs(derive_input) {
        Ok(stream) => stream.into(),
        Err(err) => err.to_compile_error().into(),
    }
}

/// Convenience macro to wrap an object's method into a `Method` implementor
/// that can be passed to the engine when registering a class.
#[proc_macro]
#[deprecated = "The legacy manual export macro is deprecated and will be removed in a future godot-rust version. \
Either use the `#[methods]` attribute macro, or implement the `Method` trait manually instead."]
pub fn godot_wrap_method(input: TokenStream) -> TokenStream {
    match methods::expand_godot_wrap_method(input.into()) {
        Ok(stream) => stream.into(),
        Err(xs) => {
            let mut tokens = TokenStream2::new();
            for err in xs {
                tokens.extend(err.to_compile_error());
            }
            tokens.into()
        }
    }
}

/// Returns a standard header for derived implementations.
///
/// Adds the `automatically_derived` attribute and prevents common lints from triggering
/// in user code. See:
///
/// - https://doc.rust-lang.org/reference/attributes/derive.html
/// - https://doc.rust-lang.org/rustc/lints/groups.html
/// - https://github.com/rust-lang/rust-clippy#clippy
fn automatically_derived() -> proc_macro2::TokenStream {
    quote! {
        #[automatically_derived]
        #[allow(nonstandard_style, unused, clippy::style, clippy::complexity, clippy::perf, clippy::pedantic)]
    }
}

/// Returns the (possibly renamed or imported as `gdnative`) identifier of the `gdnative_core` crate.
fn crate_gdnative_core() -> proc_macro2::TokenStream {
    let found_crate = proc_macro_crate::crate_name("gdnative-core")
        .or_else(|_| proc_macro_crate::crate_name("gdnative"))
        .expect("crate not found");

    match found_crate {
        proc_macro_crate::FoundCrate::Itself => {
            // Workaround: `proc-macro-crate` returns `Itself` in doc-tests, and refuses to use unstable env
            // variables for detection.
            // See https://github.com/bkchr/proc-macro-crate/issues/11
            if std::env::var_os("UNSTABLE_RUSTDOC_TEST_PATH").is_some() {
                quote!(gdnative_core)
            } else {
                quote!(crate)
            }
        }
        proc_macro_crate::FoundCrate::Name(name) => {
            let ident = proc_macro2::Ident::new(&name, proc_macro2::Span::call_site());
            ident.to_token_stream()
        }
    }
}

/// Returns the (possibly renamed or imported as `gdnative`) identifier of the `gdnative_async` crate,
/// if found.
fn crate_gdnative_async() -> proc_macro2::TokenStream {
    if let Ok(found_crate) = proc_macro_crate::crate_name("gdnative-async") {
        return match found_crate {
            proc_macro_crate::FoundCrate::Itself => quote!(crate),
            proc_macro_crate::FoundCrate::Name(name) => {
                let ident = proc_macro2::Ident::new(&name, proc_macro2::Span::call_site());
                ident.to_token_stream()
            }
        };
    }

    let found_crate = proc_macro_crate::crate_name("gdnative").expect("crate not found");

    match found_crate {
        proc_macro_crate::FoundCrate::Itself => quote!(crate::tasks),
        proc_macro_crate::FoundCrate::Name(name) => {
            let ident = proc_macro2::Ident::new(&name, proc_macro2::Span::call_site());
            quote!( #ident::tasks )
        }
    }
}

/// Returns the (possibly renamed or imported as `gdnative`) identifier of the `gdnative_bindings` crate.
fn crate_gdnative_bindings() -> proc_macro2::TokenStream {
    if let Ok(found_crate) = proc_macro_crate::crate_name("gdnative-bindings") {
        return match found_crate {
            proc_macro_crate::FoundCrate::Itself => quote!(crate),
            proc_macro_crate::FoundCrate::Name(name) => {
                let ident = proc_macro2::Ident::new(&name, proc_macro2::Span::call_site());
                ident.to_token_stream()
            }
        };
    }

    let found_crate = proc_macro_crate::crate_name("gdnative").expect("crate not found");

    match found_crate {
        proc_macro_crate::FoundCrate::Itself => quote!(crate::api),
        proc_macro_crate::FoundCrate::Name(name) => {
            let ident = proc_macro2::Ident::new(&name, proc_macro2::Span::call_site());
            quote!( #ident::api )
        }
    }
}

/// Hack to emit a warning in expression position through `deprecated`.
/// This is because there is no way to emit warnings from macros in stable Rust.
fn emit_warning<S: std::fmt::Display>(
    span: proc_macro2::Span,
    warning_name: &str,
    message: S,
) -> proc_macro2::TokenStream {
    let warning_name = proc_macro2::Ident::new(warning_name, span);
    let message = message.to_string();

    quote_spanned! { span =>
        {
            #[deprecated = #message]
            fn #warning_name() {}
            #warning_name()
        }
    }
}