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

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

/// Generate support code for hardware tasks (`#[exception]`s and `#[interrupt]`s)
pub fn codegen(
    app: &App,
    analysis: &Analysis,
    extra: &Extra,
) -> (
    // const_app_hardware_tasks -- interrupt handlers and `${task}Resources` constructors
    Vec<TokenStream2>,
    // root_hardware_tasks -- items that must be placed in the root of the crate:
    // - `${task}Locals` structs
    // - `${task}Resources` structs
    // - `${task}` modules
    Vec<TokenStream2>,
    // user_hardware_tasks -- the `#[task]` functions written by the user
    Vec<TokenStream2>,
) {
    let mut const_app = vec![];
    let mut root = vec![];
    let mut user_tasks = vec![];

    for (name, task) in &app.hardware_tasks {
        // per: debug
        // println!("// -- name -- {:?}", name);
        // println!("// -- task -- {:?}", task);
        let core = task.args.core;
        let cfg_core = util::cfg_core(core, app.args.cores);

        let (let_instant, instant) = if app.uses_schedule(core) {
            let m = extra.monotonic();

            (
                Some(quote!(let instant = <#m as rtfm::Monotonic>::now();)),
                Some(quote!(, instant)),
            )
        } else {
            (None, None)
        };

        let locals_new = if task.locals.is_empty() {
            quote!()
        } else {
            quote!(#name::Locals::new(),)
        };

        let symbol = if cfg!(feature = "homogeneous") {
            util::suffixed(&task.args.binds.to_string(), core)
        } else {
            task.args.binds.clone()
        };
        let priority = task.args.priority;

        let section = util::link_section("text", core);
        if task.is_generator {
            let gen_static = util::gen_static_ident(&name);
            let gen_type = util::gen_type_ident(&name);
            const_app.push(quote!(
                #[allow(non_snake_case)]
                #[no_mangle]
                #section
                #cfg_core
                unsafe fn #symbol() {
                    const PRIORITY: u8 = #priority;

                    #let_instant

                    rtfm::export::run(PRIORITY, || {
                        // TODO: Remove trace
                        hprintln!("interrupt dispatch").unwrap();
                        // TODO: possible compiler bug
                        // core::pin::Pin::new(#gen_static.as_mut_ptr()).resume();
                        let mut g: &mut dyn Generator<Yield = (), Return = !> = &mut *#gen_static.as_mut_ptr();
                        core::pin::Pin::new_unchecked(&mut *g).resume();
                    });
                }
            ));
        } else {
            const_app.push(quote!(
                #[allow(non_snake_case)]
                #[no_mangle]
                #section
                #cfg_core
                unsafe fn #symbol() {
                    const PRIORITY: u8 = #priority;

                    #let_instant

                    rtfm::export::run(PRIORITY, || {
                        crate::#name(
                            #locals_new
                            #name::Context::new(&rtfm::export::Priority::new(PRIORITY) #instant)
                        )
                    });
                }
            ));
        }

        let mut needs_lt = false;

        // `${task}Resources`
        if !task.args.resources.is_empty() {
            let (item, constructor) = resources_struct::codegen(
                Context::HardwareTask(name),
                priority,
                &mut needs_lt,
                app,
                analysis,
            );

            root.push(item);

            const_app.push(constructor);
        }

        root.push(module::codegen(
            Context::HardwareTask(name),
            needs_lt,
            app,
            extra,
        ));

        // `${task}Locals`
        let mut locals_pat = None;
        if !task.locals.is_empty() {
            let (struct_, pat) = locals::codegen(
                Context::HardwareTask(name),
                &task.locals,
                core,
                app,
            );

            root.push(struct_);
            locals_pat = Some(pat);
        }

        let attrs = &task.attrs;
        let context = &task.context;
        let stmts = &task.stmts;
        let section = util::link_section("text", core);
        // XXX shouldn't this have a cfg_core?
        let locals_pat = locals_pat.iter();

        if task.is_generator {
            // exapmle expansion
            // type GeneratorFoo = impl Generator<Yield = (), Return = !>;
            // static mut GENERATOR_FOO: MaybeUninit<GeneratorFoo> = MaybeUninit::uninit();
            // #[allow(non_snake_case)]
            // fn foo(ctx: foo::Context) -> GeneratorFoo {
            //     use rtfm::Mutex as _;
            //     move || loop  { yield }
            // }

            let gen_type = util::gen_type_ident(&name);
            let gen_static = util::gen_static_ident(&name);

            user_tasks.push(quote!(
                type #gen_type =  impl Generator<Yield = (), Return = !>;
            ));

            user_tasks.push(quote!(
                static mut #gen_static : core::mem::MaybeUninit<#gen_type> = core::mem::MaybeUninit::uninit();
            ));

            user_tasks.push(quote!(
                #(#attrs)*
                #[allow(non_snake_case)]
                #section
                fn #name(#(#locals_pat,)* #context: #name::Context) -> #gen_type {
                    use rtfm::Mutex as _;

                    #(#stmts)*
                }
            ));
        } else {
            // generate ordinary task
            user_tasks.push(quote!(
                #(#attrs)*
                #[allow(non_snake_case)]
                #section
                fn #name(#(#locals_pat,)* #context: #name::Context) {
                    use rtfm::Mutex as _;

                    #(#stmts)*
                }
            ));
        }
    }

    (const_app, root, user_tasks)
}