//! This crate declares only the proc macro attributes, as a crate defining proc macro attributes
//! must not contain any other public items.

#![cfg_attr(docsrs, feature(doc_cfg, doc_auto_cfg))]
use proc_macro::TokenStream;
use proc_macro2::TokenStream as TokenStream2;
use pyo3_macros_backend::{
    build_derive_from_pyobject, build_py_class, build_py_enum, build_py_function, build_py_methods,
    pymodule_function_impl, pymodule_module_impl, PyClassArgs, PyClassMethodsType,
    PyFunctionOptions,
};
use quote::quote;
use syn::{parse::Nothing, parse_macro_input, Item};

/// A proc macro used to implement Python modules.
///
/// The name of the module will be taken from the function name, unless `#[pyo3(name = "my_name")]`
/// is also annotated on the function to override the name. **Important**: the module name should
/// match the `lib.name` setting in `Cargo.toml`, so that Python is able to import the module
/// without needing a custom import loader.
///
/// Functions annotated with `#[pymodule]` can also be annotated with the following:
///
/// |  Annotation  |  Description |
/// | :-  | :- |
/// | `#[pyo3(name = "...")]` | Defines the name of the module in Python. |
///
/// For more on creating Python modules see the [module section of the guide][1].
///
/// Due to technical limitations on how `#[pymodule]` is implemented, a function marked
/// `#[pymodule]` cannot have a module with the same name in the same scope. (The
/// `#[pymodule]` implementation generates a hidden module with the same name containing
/// metadata about the module, which is used by `wrap_pymodule!`).
///
/// [1]: https://pyo3.rs/latest/module.html
#[proc_macro_attribute]
pub fn pymodule(args: TokenStream, input: TokenStream) -> TokenStream {
    parse_macro_input!(args as Nothing);
    match parse_macro_input!(input as Item) {
        Item::Mod(module) => if cfg!(feature = "experimental-declarative-modules") {
            pymodule_module_impl(module)
        } else {
            Err(syn::Error::new_spanned(
                module,
                "#[pymodule] requires the 'experimental-declarative-modules' feature to be used on Rust modules.",
            ))
        },
        Item::Fn(function) => pymodule_function_impl(function),
        unsupported => Err(syn::Error::new_spanned(
            unsupported,
            "#[pymodule] only supports modules and functions.",
        )),
    }
    .unwrap_or_compile_error()
    .into()
}

#[proc_macro_attribute]
pub fn pyclass(attr: TokenStream, input: TokenStream) -> TokenStream {
    let item = parse_macro_input!(input as Item);
    match item {
        Item::Struct(struct_) => pyclass_impl(attr, struct_, methods_type()),
        Item::Enum(enum_) => pyclass_enum_impl(attr, enum_, methods_type()),
        unsupported => {
            syn::Error::new_spanned(unsupported, "#[pyclass] only supports structs and enums.")
                .into_compile_error()
                .into()
        }
    }
}

/// A proc macro used to expose methods to Python.
///
/// Methods within a `#[pymethods]` block can be annotated with  as well as the following:
///
/// |  Annotation  |  Description |
/// | :-  | :- |
/// | [`#[new]`][4]  | Defines the class constructor, like Python's `__new__` method. |
/// | [`#[getter]`][5] and [`#[setter]`][5] | These define getters and setters, similar to Python's `@property` decorator. This is useful for getters/setters that require computation or side effects; if that is not the case consider using [`#[pyo3(get, set)]`][11] on the struct's field(s).|
/// | [`#[staticmethod]`][6]| Defines the method as a staticmethod, like Python's `@staticmethod` decorator.|
/// | [`#[classmethod]`][7]  | Defines the method as a classmethod, like Python's `@classmethod` decorator.|
/// | [`#[classattr]`][9]  | Defines a class variable. |
/// | [`#[args]`][10]  | Deprecated way to define a method's default arguments and allows the function to receive `*args` and `**kwargs`. Use `#[pyo3(signature = (...))]` instead. |
/// | <nobr>[`#[pyo3(<option> = <value>)`][pyo3-method-options]</nobr> | Any of the `#[pyo3]` options supported on [`macro@pyfunction`]. |
///
/// For more on creating class methods,
/// see the [class section of the guide][1].
///
/// If the [`multiple-pymethods`][2] feature is enabled, it is possible to implement
/// multiple `#[pymethods]` blocks for a single `#[pyclass]`.
/// This will add a transitive dependency on the [`inventory`][3] crate.
///
/// [1]: https://pyo3.rs/latest/class.html#instance-methods
/// [2]: https://pyo3.rs/latest/features.html#multiple-pymethods
/// [3]: https://docs.rs/inventory/
/// [4]: https://pyo3.rs/latest/class.html#constructor
/// [5]: https://pyo3.rs/latest/class.html#object-properties-using-getter-and-setter
/// [6]: https://pyo3.rs/latest/class.html#static-methods
/// [7]: https://pyo3.rs/latest/class.html#class-methods
/// [8]: https://pyo3.rs/latest/class.html#callable-objects
/// [9]: https://pyo3.rs/latest/class.html#class-attributes
/// [10]: https://pyo3.rs/latest/class.html#method-arguments
/// [11]: https://pyo3.rs/latest/class.html#object-properties-using-pyo3get-set
#[proc_macro_attribute]
pub fn pymethods(attr: TokenStream, input: TokenStream) -> TokenStream {
    let methods_type = if cfg!(feature = "multiple-pymethods") {
        PyClassMethodsType::Inventory
    } else {
        PyClassMethodsType::Specialization
    };
    pymethods_impl(attr, input, methods_type)
}

/// A proc macro used to expose Rust functions to Python.
///
/// Functions annotated with `#[pyfunction]` can also be annotated with the following `#[pyo3]`
/// options:
///
/// |  Annotation  |  Description |
/// | :-  | :- |
/// | `#[pyo3(name = "...")]` | Defines the name of the function in Python. |
/// | `#[pyo3(text_signature = "...")]` | Defines the `__text_signature__` attribute of the function in Python. |
/// | `#[pyo3(pass_module)]` | Passes the module containing the function as a `&PyModule` first argument to the function. |
///
/// For more on exposing functions see the [function section of the guide][1].
///
/// Due to technical limitations on how `#[pyfunction]` is implemented, a function marked
/// `#[pyfunction]` cannot have a module with the same name in the same scope. (The
/// `#[pyfunction]` implementation generates a hidden module with the same name containing
/// metadata about the function, which is used by `wrap_pyfunction!`).
///
/// [1]: https://pyo3.rs/latest/function.html
#[proc_macro_attribute]
pub fn pyfunction(attr: TokenStream, input: TokenStream) -> TokenStream {
    let mut ast = parse_macro_input!(input as syn::ItemFn);
    let options = parse_macro_input!(attr as PyFunctionOptions);

    let expanded = build_py_function(&mut ast, options).unwrap_or_compile_error();

    quote!(
        #ast
        #expanded
    )
    .into()
}

#[proc_macro_derive(FromPyObject, attributes(pyo3))]
pub fn derive_from_py_object(item: TokenStream) -> TokenStream {
    let ast = parse_macro_input!(item as syn::DeriveInput);
    let expanded = build_derive_from_pyobject(&ast).unwrap_or_compile_error();
    quote!(
        #expanded
    )
    .into()
}

fn pyclass_impl(
    attrs: TokenStream,
    mut ast: syn::ItemStruct,
    methods_type: PyClassMethodsType,
) -> TokenStream {
    let args = parse_macro_input!(attrs with PyClassArgs::parse_stuct_args);
    let expanded = build_py_class(&mut ast, args, methods_type).unwrap_or_compile_error();

    quote!(
        #ast
        #expanded
    )
    .into()
}

fn pyclass_enum_impl(
    attrs: TokenStream,
    mut ast: syn::ItemEnum,
    methods_type: PyClassMethodsType,
) -> TokenStream {
    let args = parse_macro_input!(attrs with PyClassArgs::parse_enum_args);
    let expanded = build_py_enum(&mut ast, args, methods_type).unwrap_or_compile_error();

    quote!(
        #ast
        #expanded
    )
    .into()
}

fn pymethods_impl(
    attr: TokenStream,
    input: TokenStream,
    methods_type: PyClassMethodsType,
) -> TokenStream {
    let mut ast = parse_macro_input!(input as syn::ItemImpl);
    // Apply all options as a #[pyo3] attribute on the ItemImpl
    // e.g. #[pymethods(crate = "crate")] impl Foo { }
    // -> #[pyo3(crate = "crate")] impl Foo { }
    let attr: TokenStream2 = attr.into();
    ast.attrs.push(syn::parse_quote!( #[pyo3(#attr)] ));
    let expanded = build_py_methods(&mut ast, methods_type).unwrap_or_compile_error();

    quote!(
        #ast
        #expanded
    )
    .into()
}

fn methods_type() -> PyClassMethodsType {
    if cfg!(feature = "multiple-pymethods") {
        PyClassMethodsType::Inventory
    } else {
        PyClassMethodsType::Specialization
    }
}

trait UnwrapOrCompileError {
    fn unwrap_or_compile_error(self) -> TokenStream2;
}

impl UnwrapOrCompileError for syn::Result<TokenStream2> {
    fn unwrap_or_compile_error(self) -> TokenStream2 {
        self.unwrap_or_else(|e| e.into_compile_error())
    }
}