use quote::quote;

use crate::function::ExportedFn;

pub(crate) type ExportedConst = (String, syn::Expr);

pub(crate) fn generate_body(
    fns: &Vec<ExportedFn>,
    consts: &Vec<ExportedConst>
) -> proc_macro2::TokenStream {
    let mut set_fn_stmts: Vec<syn::Stmt> = Vec::new();
    let mut set_const_stmts: Vec<syn::Stmt> = Vec::new();
    let str_type_path = syn::parse2::<syn::Path>(quote! { str }).unwrap();

    for (const_name, const_expr) in consts {
        let const_literal = syn::LitStr::new(&const_name, proc_macro2::Span::call_site());
        set_const_stmts.push(syn::parse2::<syn::Stmt>(quote! {
            m.set_var(#const_literal, #const_expr);
        }).unwrap());
    }

    // NB: these are token streams, because reparsing messes up "> >" vs ">>"
    let mut gen_fn_tokens: Vec<proc_macro2::TokenStream> = Vec::new();
    for function in fns {
        let fn_token_name = syn::Ident::new(&format!("{}__Token", function.name().to_string()),
                                            function.name().span());
        let fn_literal = syn::LitStr::new(&function.name().to_string(),
                                          proc_macro2::Span::call_site());
        let fn_input_types: Vec<syn::Expr> = function.arg_list()
            .map(|fnarg| match fnarg {
                syn::FnArg::Receiver(_) => panic!("internal error: receiver fn outside impl!?"),
                syn::FnArg::Typed(syn::PatType { ref ty, .. }) => {
                    let arg_type = match ty.as_ref() {
                        &syn::Type::Reference(syn::TypeReference { mutability: None,
                                                                   ref elem, .. }) => {
                            match elem.as_ref() {
                                &syn::Type::Path(ref p) if p.path == str_type_path =>
                                    syn::parse2::<syn::Type>(quote! {
                                        rhai::ImmutableString }).unwrap(),
                                _ => panic!("internal error: non-string shared reference!?"),
                            }
                        },
                        &syn::Type::Reference(syn::TypeReference { mutability: Some(_),
                                                                   ref elem, .. }) => {
                            match elem.as_ref() {
                                &syn::Type::Path(ref p) => syn::parse2::<syn::Type>(quote! {
                                    #p }).unwrap(),
                                _ => panic!("internal error: non-string shared reference!?"),
                            }
                        },
                        t => t.clone(),
                    };
                    syn::parse2::<syn::Expr>(quote! {
                        core::any::TypeId::of::<#arg_type>()}).unwrap()
                },
            }).collect();

        set_fn_stmts.push(syn::parse2::<syn::Stmt>(quote! {
            m.set_fn(#fn_literal, FnAccess::Public, &[#(#fn_input_types),*],
                     rhai::plugin::CallableFunction::from_plugin(#fn_token_name()));
        }).unwrap());

        gen_fn_tokens.push(quote! {
            #[allow(non_camel_case_types)]
            pub struct #fn_token_name();
        });
        gen_fn_tokens.push(function.generate_impl(&fn_token_name.to_string()));
    }

    let mut generate_fncall = syn::parse2::<syn::ItemMod>(quote! {
        pub mod generate_info {
            #[allow(unused_imports)]
            use rhai::{Module, FnAccess};
            #[allow(unused_mut)]
            pub fn rhai_module__generate() -> Module {
                let mut m = Module::new();
                #(#set_fn_stmts)*
                #(#set_const_stmts)*
                m
            }
        }
    }).unwrap();

    let (_, generate_call_content) = generate_fncall.content.take().unwrap();

    quote! {
        #(#generate_call_content)*
        #(#gen_fn_tokens)*
    }
}