use crate::constants_table::ConstantsTable;
use crate::ir::assemble::{Assemble, InstructionsBuilder};
use crate::ir::ir_operation::IrOperation;
use crate::ir::ir_variable::{IrVariable, IrVariableDescriptor, IrVrVariableDescriptor};
use crate::ir::register_allocation::{OffsetCounter, VrUser};
use dvm_lib::instruction::{Instruction, Location};
use std::cell::RefCell;
use std::collections::{HashMap, HashSet};
use std::fmt::{Display, Formatter};
use std::rc::Rc;

pub struct IrAssign {
    destination: Rc<RefCell<IrVariable>>,
    initializer: Box<IrOperation>,
}

impl IrAssign {
    pub fn new(destination: Rc<RefCell<IrVariable>>, initializer: IrOperation) -> Self {
        Self {
            destination,
            initializer: initializer.into(),
        }
    }
}

impl VrUser for IrAssign {
    fn vr_definitions(&self) -> HashSet<IrVrVariableDescriptor> {
        match self.destination.borrow().descriptor() {
            IrVariableDescriptor::VirtualRegister(vr_descriptor) => {
                HashSet::from([vr_descriptor.clone()])
            }
            IrVariableDescriptor::Stack(_) => HashSet::new(),
        }
    }

    fn vr_uses(&self) -> HashSet<IrVrVariableDescriptor> {
        self.initializer.vr_uses()
    }

    fn propagate_spills(&mut self, spills: &HashSet<IrVrVariableDescriptor>) {
        let borrowed_destination = self.destination.borrow();
        if let IrVariableDescriptor::VirtualRegister(vr_variable) =
            borrowed_destination.descriptor()
        {
            if spills.contains(vr_variable) {
                let replacement = IrVariable::new_stack(
                    vr_variable.name().into(),
                    vr_variable.block_id(),
                    borrowed_destination.type_info().clone(),
                );
                drop(borrowed_destination);
                self.destination.replace(replacement);
            }
        }
    }

    fn propagate_register_assignments(
        &mut self,
        assignments: &HashMap<IrVrVariableDescriptor, usize>,
    ) {
        let mut borrowed_destination = self.destination.borrow_mut();
        if let IrVariableDescriptor::VirtualRegister(vr_variable) =
            borrowed_destination.descriptor_mut()
        {
            if assignments.contains_key(vr_variable) {
                vr_variable.set_assigned_register(assignments[vr_variable]);
            }
        }
        self.initializer.propagate_register_assignments(assignments);
    }

    fn propagate_stack_offsets(&mut self, counter: &mut OffsetCounter) {
        let mut borrowed_destination = self.destination.borrow_mut();
        if let IrVariableDescriptor::Stack(stack_variable) = borrowed_destination.descriptor_mut() {
            stack_variable.set_offset(counter.next());
        }
    }
}

impl Assemble for IrAssign {
    fn assemble(&self, builder: &mut InstructionsBuilder, constants_table: &mut ConstantsTable) {
        let destination = match self.destination.borrow().descriptor() {
            IrVariableDescriptor::VirtualRegister(vr_variable) => {
                Location::Register(vr_variable.assigned_register())
            }
            IrVariableDescriptor::Stack(stack_variable) => {
                Location::StackFrameOffset(stack_variable.offset())
            }
        };

        match self.initializer.as_ref() {
            IrOperation::Load(ir_expression) => {
                let move_operand = ir_expression.move_operand(constants_table);
                builder.push(Instruction::Move(move_operand, destination));
            }
            IrOperation::Add(ir_add) => {
                let (left, right) = ir_add.operand_pair(constants_table);
                builder.push(Instruction::Add(left, right, destination));
            }
            IrOperation::Subtract(ir_subtract) => {
                let (left, right) = ir_subtract.operand_pair();
                builder.push(Instruction::Subtract(left, right, destination));
            }
            IrOperation::Multiply(ir_multiply) => {
                let (left, right) = ir_multiply.operand_pair();
                builder.push(Instruction::Multiply(left, right, destination));
            }
            IrOperation::Call(ir_call) => {
                ir_call.assemble(builder, constants_table);
                builder.push(Instruction::Pop(Some(destination)));
            }
        }
    }
}

impl Display for IrAssign {
    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
        write!(
            f,
            "{}: {} = {}",
            self.destination.borrow(),
            self.destination.borrow().type_info(),
            self.initializer
        )
    }
}