use std::collections::{HashMap, VecDeque};

use crsn::asm::data::literal::Value;
use crsn::asm::instr::Cond;
use crsn::module::{CrsnExtension, EvalRes, OpTrait};
use crsn::runtime::fault::Fault;
use crsn::runtime::run_thread::{state::RunState, ThreadInfo};

use crate::defs::StackOp;

#[derive(Debug, Default)]
struct Stacks {
    store: HashMap<Value, VecDeque<Value>>,
}

impl OpTrait for StackOp {
    fn execute(&self, info: &ThreadInfo, state: &mut RunState) -> Result<EvalRes, Fault> {
        let eres = EvalRes::default();
        match self {
            StackOp::NewStack { dst } => {
                let id = info.uniq();
                let stacks: &mut Stacks = state.ext_mut();
                stacks.store.insert(id, VecDeque::new());

                state.write(*dst, id)?;
            }
            StackOp::Push { obj, src } => {
                state.clear_status();
                let handle = state.read_obj(*obj)?;
                let val = state.read(*src)?;

                let stacks: &mut Stacks = state.ext_mut();
                stacks.store.get_mut(&handle)
                    .ok_or_else(|| Fault::ObjectNotExist(handle))?
                    .push_back(val);
            }
            StackOp::Pop { dst, obj } => {
                state.clear_status();
                let handle = state.read_obj(*obj)?;

                let stacks: &mut Stacks = state.ext_mut();
                let stack = stacks.store.get_mut(&handle)
                    .ok_or_else(|| Fault::ObjectNotExist(handle))?;

                let val = stack.pop_back();

                if stack.is_empty() {
                    state.set_flag(Cond::Zero, true);
                }

                let val = match val {
                    None => {
                        state.set_flag(Cond::Overflow, true);
                        0
                    }
                    Some(val) => {
                        val
                    }
                };

                state.write(*dst, val)?;
            }
        }

        Ok(eres)
    }
    //
}

pub(crate) fn drop_stack(state: &mut RunState, handle: Value) -> Result<Option<()>, Fault> {
    let stacks: &mut Stacks = state.ext_mut();
    Ok(stacks.store.remove(&handle).map(|_| ()))
}