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/*
MIT License

Copyright (c) 2017 David DeSimone

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
*/

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

mod fnargs;

use fnargs::parse_args;

fn generics_to_quote(generics: &syn::Generics) -> quote::Tokens {
    let mut generic_tokens = quote!{ < };

    for life_ty in &generics.lifetimes {
        generic_tokens.append(quote! {  #life_ty, });
    }

    for generic in &generics.ty_params {
        generic_tokens.append(quote! { #generic, });
    }

    generic_tokens.append(quote!{ > });
    generic_tokens
}

fn sig_to_quote(ident: &syn::Ident, sig: &syn::MethodSig) -> quote::Tokens {
    assert!(!sig.decl.variadic, "Impls for variadic functions is not supported");
    let ref unsafety = sig.unsafety;
    let abi = sig.abi.as_ref().map_or(quote!{}, |x| quote!{ #x });
    let ref inputs = sig.decl.inputs;
    let ref generics = sig.generics;

    let ref where_clause = generics.where_clause;
    let qwhere_clause = quote!{ #where_clause };
    let qgenerics = generics_to_quote(generics);

    let outputs = match sig.decl.output {
        syn::FunctionRetTy::Default => quote!{},
        syn::FunctionRetTy::Ty(ref ty) => quote!{ -> #ty }
    };

    let args = parse_args(&inputs);
    let ref args_with_types = args.args_with_types;
    quote!{
        #unsafety #abi fn #ident #qgenerics (#args_with_types) #outputs #qwhere_clause
    }
}

fn parse_methods(items: &Vec<syn::ImplItem>) -> (quote::Tokens, quote::Tokens) {
    let mut decls = quote!{};
    let mut impls = quote!{};
    for x in items.iter() {
        let (decl, imp) = match x.node {
            syn::ImplItemKind::Method(ref sig, ref body) => {
                let qsig = sig_to_quote(&x.ident, sig);
                let qimpl = quote! {
                    #qsig #body
                };

                (quote!{ #qsig; }, qimpl)
            },
            _ => panic!()
        };

        decls.append(decl);
        impls.append(imp);
    }
    
    (decls, impls)
}

pub fn generate_trait(item: &syn::Item, name: Option<String>) -> quote::Tokens {
    match item.node {
        syn::ItemKind::Impl(_unsafety,
                            _impl_pol,
                            ref generics,
                            ref _path,
                            ref ty,
                            ref items) => {
            
            let name = if let Some(name_str) = name {
                syn::Ident::new(name_str)
            } else {
                let name = match **ty {
                    syn::Ty::Path(_, ref path) => {
                        let ref segments = path.segments;
                        let ref last_ident = segments.last().unwrap().ident;
                        quote!{ #last_ident }
                    },
                    _ => panic!()
                };
                concat_idents("Trait", name.as_str())
            };
            
            let (decls, impls) = parse_methods(items);
            let ref where_clause = generics.where_clause;
            let qwhere_clause = quote!{ #where_clause };
            let qgenerics = generics_to_quote(generics);
            quote! {
                trait #name #qgenerics {
                    #decls
                }

                impl #qgenerics #name #qgenerics for #ty #qwhere_clause {
                    #impls
                }
            }
        }
        _ => { panic!() }

    }
}

fn concat_idents(lhs: &str, rhs: &str) -> syn::Ident {
    syn::Ident::new(format!("{}{}", lhs, rhs))
}