use super::*;

impl MirInterpreter {
    pub(super) fn reg_load(&self, id: ValueId) -> Result<VMValue, VMError> {
        self.regs
            .get(&id)
            .cloned()
            .ok_or_else(|| VMError::InvalidValue(format!("use of undefined value {:?}", id)))
    }

    pub(super) fn eval_binop(
        &self,
        op: BinaryOp,
        a: VMValue,
        b: VMValue,
    ) -> Result<VMValue, VMError> {
        use BinaryOp::*;
        use VMValue::*;
        Ok(match (op, a, b) {
            (Add, Integer(x), Integer(y)) => Integer(x + y),
            (Add, String(s), Integer(y)) => String(format!("{}{}", s, y)),
            (Add, String(s), Float(y)) => String(format!("{}{}", s, y)),
            (Add, String(s), Bool(y)) => String(format!("{}{}", s, y)),
            (Add, String(s), String(t)) => String(format!("{}{}", s, t)),
            (Add, Integer(x), String(t)) => String(format!("{}{}", x, t)),
            (Add, Float(x), String(t)) => String(format!("{}{}", x, t)),
            (Add, Bool(x), String(t)) => String(format!("{}{}", x, t)),
            (Sub, Integer(x), Integer(y)) => Integer(x - y),
            (Mul, Integer(x), Integer(y)) => Integer(x * y),
            (Div, Integer(_), Integer(0)) => return Err(VMError::DivisionByZero),
            (Div, Integer(x), Integer(y)) => Integer(x / y),
            (Mod, Integer(_), Integer(0)) => return Err(VMError::DivisionByZero),
            (Mod, Integer(x), Integer(y)) => Integer(x % y),
            (Add, Float(x), Float(y)) => Float(x + y),
            (Sub, Float(x), Float(y)) => Float(x - y),
            (Mul, Float(x), Float(y)) => Float(x * y),
            (Div, Float(_), Float(y)) if y == 0.0 => return Err(VMError::DivisionByZero),
            (Div, Float(x), Float(y)) => Float(x / y),
            (Mod, Float(x), Float(y)) => Float(x % y),
            (BitAnd, Integer(x), Integer(y)) => Integer(x & y),
            (BitOr, Integer(x), Integer(y)) => Integer(x | y),
            (BitXor, Integer(x), Integer(y)) => Integer(x ^ y),
            (Shl, Integer(x), Integer(y)) => Integer(x.wrapping_shl(y as u32)),
            (Shr, Integer(x), Integer(y)) => Integer(x.wrapping_shr(y as u32)),
            (opk, va, vb) => {
                return Err(VMError::TypeError(format!(
                    "unsupported binop {:?} on {:?} and {:?}",
                    opk, va, vb
                )))
            }
        })
    }

    pub(super) fn eval_cmp(&self, op: CompareOp, a: VMValue, b: VMValue) -> Result<bool, VMError> {
        use CompareOp::*;
        use VMValue::*;
        Ok(match (op, &a, &b) {
            (Eq, _, _) => eq_vm(&a, &b),
            (Ne, _, _) => !eq_vm(&a, &b),
            (Lt, Integer(x), Integer(y)) => x < y,
            (Le, Integer(x), Integer(y)) => x <= y,
            (Gt, Integer(x), Integer(y)) => x > y,
            (Ge, Integer(x), Integer(y)) => x >= y,
            (Lt, Float(x), Float(y)) => x < y,
            (Le, Float(x), Float(y)) => x <= y,
            (Gt, Float(x), Float(y)) => x > y,
            (Ge, Float(x), Float(y)) => x >= y,
            (opk, va, vb) => {
                return Err(VMError::TypeError(format!(
                    "unsupported compare {:?} on {:?} and {:?}",
                    opk, va, vb
                )))
            }
        })
    }
}