//! Macros for Ridicule, a mocking library supporting non-static generics.
#![deny(clippy::all, clippy::pedantic, missing_docs)]
use proc_macro::TokenStream;
use proc_macro_error::{proc_macro_error, ResultExt};
use quote::{format_ident, quote};
use syn::{
    parse,
    FnArg,
    GenericArgument,
    ImplItem,
    Path,
    PathArguments,
    PathSegment,
    ReturnType,
    Type,
    TypeBareFn,
    TypeParamBound,
};

use crate::expectation::Expectation;
use crate::mock::Mock;
use crate::mock_input::MockInput;
use crate::syn_ext::{PathExt, PathSegmentExt, WithLeadingColons};
use crate::util::create_path;

mod expectation;
mod mock;
mod mock_input;
mod syn_ext;
mod util;

/// Creates a mock.
///
/// # Examples
/// ```
/// use ridicule::mock;
///
/// trait Foo
/// {
///     fn bar<A, B>(&self, a: A) -> B;
/// }
///
/// mock! {
///     MockFoo {}
///
///     impl Foo for MockFoo
///     {
///         fn bar<A, B>(&self, a: A) -> B;
///     }
/// }
///
/// fn main()
/// {
///     let mut mock_foo = MockFoo::new();
///
///     mock_foo
///         .expect_bar()
///         .returning(|foo, a: u32| format!("Hello {a}"));
///
///     assert_eq!(mock_foo.bar::<u32, String>(123), "Hello 123");
/// }
/// ```
#[proc_macro]
#[proc_macro_error]
pub fn mock(input_stream: TokenStream) -> TokenStream
{
    let input = parse::<MockInput>(input_stream.clone()).unwrap_or_abort();

    let mock_ident = input.mock;

    let mock_mod_ident = format_ident!("__{mock_ident}");

    let method_items = input
        .item_impl
        .items
        .into_iter()
        .filter_map(|item| match item {
            ImplItem::Method(mut item_method) => {
                item_method.sig.inputs = item_method
                    .sig
                    .inputs
                    .into_iter()
                    .map(|fn_arg| match fn_arg {
                        FnArg::Typed(mut typed_arg) => {
                            typed_arg.ty = Box::new(replace_path_in_type(
                                *typed_arg.ty,
                                &create_path!(Self),
                                &Path::new(
                                    WithLeadingColons::No,
                                    [PathSegment::new(mock_ident.clone(), None)],
                                ),
                            ));

                            FnArg::Typed(typed_arg)
                        }

                        FnArg::Receiver(receiver) => FnArg::Receiver(receiver),
                    })
                    .collect();

                item_method.sig.output = match item_method.sig.output {
                    ReturnType::Type(r_arrow, return_type) => ReturnType::Type(
                        r_arrow,
                        Box::new(replace_path_in_type(
                            *return_type,
                            &create_path!(Self),
                            &Path::new(
                                WithLeadingColons::No,
                                [PathSegment::new(mock_ident.clone(), None)],
                            ),
                        )),
                    ),
                    ReturnType::Default => ReturnType::Default,
                };

                Some(item_method)
            }
            _ => None,
        })
        .collect::<Vec<_>>();

    let mock = Mock::new(
        mock_ident.clone(),
        input.mocked_trait,
        &method_items,
        input.item_impl.generics.clone(),
    );

    let expectations = method_items.iter().map(|item_method| {
        Expectation::new(
            &mock_ident,
            item_method,
            input.item_impl.generics.params.clone(),
        )
    });

    quote! {
        mod #mock_mod_ident {
            use super::*;

            #mock

            #(#expectations)*
        }

        use #mock_mod_ident::#mock_ident;
    }
    .into()
}

fn replace_path_in_type(ty: Type, target_path: &Path, replacement_path: &Path) -> Type
{
    match ty {
        Type::Ptr(mut type_ptr) => {
            type_ptr.elem = Box::new(replace_path_in_type(
                *type_ptr.elem,
                target_path,
                replacement_path,
            ));

            Type::Ptr(type_ptr)
        }
        Type::Path(mut type_path) => {
            if &type_path.path == target_path {
                type_path.path = replacement_path.clone();
            } else {
                type_path.path =
                    replace_path_args(type_path.path, target_path, replacement_path);
            }

            Type::Path(type_path)
        }
        Type::Array(mut type_array) => {
            type_array.elem = Box::new(replace_path_in_type(
                *type_array.elem,
                target_path,
                replacement_path,
            ));

            Type::Array(type_array)
        }
        Type::Group(mut type_group) => {
            type_group.elem = Box::new(replace_path_in_type(
                *type_group.elem,
                target_path,
                replacement_path,
            ));

            Type::Group(type_group)
        }
        Type::BareFn(type_bare_fn) => Type::BareFn(replace_type_bare_fn_type_paths(
            type_bare_fn,
            target_path,
            replacement_path,
        )),
        Type::Paren(mut type_paren) => {
            type_paren.elem = Box::new(replace_path_in_type(
                *type_paren.elem,
                target_path,
                replacement_path,
            ));

            Type::Paren(type_paren)
        }
        Type::Slice(mut type_slice) => {
            type_slice.elem = Box::new(replace_path_in_type(
                *type_slice.elem,
                target_path,
                replacement_path,
            ));

            Type::Slice(type_slice)
        }
        Type::Tuple(mut type_tuple) => {
            type_tuple.elems = type_tuple
                .elems
                .into_iter()
                .map(|elem_type| {
                    replace_path_in_type(elem_type, target_path, replacement_path)
                })
                .collect();

            Type::Tuple(type_tuple)
        }
        Type::Reference(mut type_reference) => {
            type_reference.elem = Box::new(replace_path_in_type(
                *type_reference.elem,
                target_path,
                replacement_path,
            ));

            Type::Reference(type_reference)
        }
        Type::TraitObject(mut type_trait_object) => {
            type_trait_object.bounds = type_trait_object
                .bounds
                .into_iter()
                .map(|bound| match bound {
                    TypeParamBound::Trait(mut trait_bound) => {
                        trait_bound.path = replace_path_args(
                            trait_bound.path,
                            target_path,
                            replacement_path,
                        );

                        TypeParamBound::Trait(trait_bound)
                    }
                    TypeParamBound::Lifetime(lifetime) => {
                        TypeParamBound::Lifetime(lifetime)
                    }
                })
                .collect();

            Type::TraitObject(type_trait_object)
        }
        other_type => other_type,
    }
}

fn replace_path_args(mut path: Path, target_path: &Path, replacement_path: &Path)
    -> Path
{
    path.segments = path
        .segments
        .into_iter()
        .map(|mut segment| {
            segment.arguments = match segment.arguments {
                PathArguments::AngleBracketed(mut generic_args) => {
                    generic_args.args = generic_args
                        .args
                        .into_iter()
                        .map(|generic_arg| match generic_arg {
                            GenericArgument::Type(ty) => GenericArgument::Type(
                                replace_path_in_type(ty, target_path, replacement_path),
                            ),
                            GenericArgument::Binding(mut binding) => {
                                binding.ty = replace_path_in_type(
                                    binding.ty,
                                    target_path,
                                    replacement_path,
                                );

                                GenericArgument::Binding(binding)
                            }
                            generic_arg => generic_arg,
                        })
                        .collect();

                    PathArguments::AngleBracketed(generic_args)
                }
                PathArguments::Parenthesized(mut generic_args) => {
                    generic_args.inputs = generic_args
                        .inputs
                        .into_iter()
                        .map(|input_ty| {
                            replace_path_in_type(input_ty, target_path, replacement_path)
                        })
                        .collect();

                    generic_args.output = match generic_args.output {
                        ReturnType::Type(r_arrow, return_type) => ReturnType::Type(
                            r_arrow,
                            Box::new(replace_path_in_type(
                                *return_type,
                                target_path,
                                replacement_path,
                            )),
                        ),
                        ReturnType::Default => ReturnType::Default,
                    };

                    PathArguments::Parenthesized(generic_args)
                }
                PathArguments::None => PathArguments::None,
            };

            segment
        })
        .collect();

    path
}

fn replace_type_bare_fn_type_paths(
    mut type_bare_fn: TypeBareFn,
    target_path: &Path,
    replacement_path: &Path,
) -> TypeBareFn
{
    type_bare_fn.inputs = type_bare_fn
        .inputs
        .into_iter()
        .map(|mut bare_fn_arg| {
            bare_fn_arg.ty =
                replace_path_in_type(bare_fn_arg.ty, target_path, replacement_path);

            bare_fn_arg
        })
        .collect();

    type_bare_fn.output = match type_bare_fn.output {
        ReturnType::Type(r_arrow, return_type) => ReturnType::Type(
            r_arrow,
            Box::new(replace_path_in_type(
                *return_type,
                target_path,
                replacement_path,
            )),
        ),
        ReturnType::Default => ReturnType::Default,
    };

    type_bare_fn
}