use proc_macro2::TokenStream as TokenStream2;
use quote::quote;
use rtic_syntax::{ast::App, Context};

use crate::{
    analyze::Analysis,
    check::Extra,
    codegen::{locals, module, resources_struct},
};

type CodegenResult = (
    // mod_app_idle -- the `${init}Resources` constructor
    Option<TokenStream2>,
    // root_init -- items that must be placed in the root of the crate:
    // - the `${init}Locals` struct
    // - the `${init}Resources` struct
    // - the `${init}LateResources` struct
    // - the `${init}` module, which contains types like `${init}::Context`
    Vec<TokenStream2>,
    // user_init -- the `#[init]` function written by the user
    Option<TokenStream2>,
    // call_init -- the call to the user `#[init]` if there's one
    Option<TokenStream2>,
);

/// Generates support code for `#[init]` functions
pub fn codegen(app: &App, analysis: &Analysis, extra: &Extra) -> CodegenResult {
    if !app.inits.is_empty() {
        let init = &app.inits.first().unwrap();
        let mut needs_lt = false;
        let name = &init.name;

        let mut root_init = vec![];

        let mut locals_pat = None;
        let mut locals_new = None;
        if !init.locals.is_empty() {
            let (struct_, pat) = locals::codegen(Context::Init, &init.locals, app);

            locals_new = Some(quote!(#name::Locals::new()));
            locals_pat = Some(pat);
            root_init.push(struct_);
        }

        let context = &init.context;
        let attrs = &init.attrs;
        let stmts = &init.stmts;
        let locals_pat = locals_pat.iter();

        let user_init_return = quote! {#name::LateResources, #name::Monotonics};

        let user_init = Some(quote!(
            #(#attrs)*
            #[allow(non_snake_case)]
            fn #name(#(#locals_pat,)* #context: #name::Context) -> (#user_init_return) {
                #(#stmts)*
            }
        ));

        let mut mod_app = None;
        if !init.args.resources.is_empty() {
            let (item, constructor) = resources_struct::codegen(Context::Init, &mut needs_lt, app);

            root_init.push(item);
            mod_app = Some(constructor);
        }

        let locals_new = locals_new.iter();
        let call_init = Some(
            quote!(let (late, mut monotonics) = #name(#(#locals_new,)* #name::Context::new(core.into()));),
        );

        root_init.push(module::codegen(
            Context::Init,
            needs_lt,
            app,
            analysis,
            extra,
        ));

        (mod_app, root_init, user_init, call_init)
    } else {
        (None, vec![], None, None)
    }
}