use crate::{ast::{ASTType, BinOp, LhsAssign, LhsAssignType, Lit, Name, UnOp, AST}, codegen_binary, codegen_unary, extension::Extension, opcodes::OpCode, vm::{Function, Unit, Value, VM}};

pub struct Codegen {
    pub vm: VM,
    pub scopes: Vec<(ScopeType, usize)>, // number of variables declared in the scope
    break_stack: Vec<Vec<usize>>,
    continue_stack: Vec<Vec<usize>>,
}

impl Codegen {
    pub fn new(text: String) -> Self {
        Codegen {
            vm: VM::new(Vec::new(), Vec::new(),
                Vec::new(), text),
            scopes: vec![(ScopeType::Main, 0)],
            break_stack: Vec::new(),
            continue_stack: Vec::new(),
        }
    }
    pub fn visit(&mut self, ast: AST) {
        use crate::ast::ASTType::*;
        match ast.kind {
            Program(asts) => {
                for ast in asts {
                    self.visit(ast);
                }
            }
            Function(name, args, block) => {
                self.visit_function(name, args, *block);
            }
            Return(ref expr) => {
                self.visit_return(&ast, *expr.clone());
            }
            While(condition, block) => {
                self.visit_while(*condition, *block);
            }
            For(expr1, expr2, expr3, block) => {
                self.visit_for(*expr1, *expr2, *expr3, *block);
            }
            Break => {
                self.visit_break(&ast);
            }
            Continue => {
                self.visit_continue(&ast);
            }
            If(condition, block, else_expr) => {
                self.visit_if(*condition, *block, *else_expr);
            }
            Block(ref stmts) => {
                self.visit_block(&ast, stmts.clone(), ScopeType::Other);
            }
            Decl(ref name, ref expr) => {
                self.visit_decl(&ast, name.clone(), *expr.clone());
            }
            Expr(ref expr) => {
                self.visit_expr_stmt(&ast, *expr.clone());
            }
            // REMOVE LATER
            Print(ref expr) => {
                self.visit_print(&ast, *expr.clone());
            }
            Assign(ref name, ref expr) => {
                self.visit_assign(&ast, name.clone(), *expr.clone());
            }
            Anonymous(params, block) => {
                self.visit_anonymous(params, *block);
            }
            Subscript(ref left, ref right) => {
                self.visit_subscript(&ast, *left.clone(), *right.clone());
            }
            Binary(left, oper, right) => {
                self.visit_binary(*left, oper, *right);
            }
            Unary(oper, right) => {
                self.visit_unary(oper, *right);
            }
            Lit(ref lit) => {
                self.visit_lit(&ast, lit.clone());
            }
            Call(ref name, ref args) => {
                self.visit_call(&ast, *name.clone(), args.clone());
            }
            _ => {}
        }
    }
    pub fn visit_function(&mut self, _name: Name, args: Vec<Name>, block: AST) {
        // create new compilation unit
        self.vm.units.push(Unit::new_empty());

        // add function to constant pool and add a load expression in its place
        let new_unit_ptr = self.vm.units.len()-1;
        self.vm.variables.push(Value::Fun(Function {
            unit_ptr: new_unit_ptr,
            arity: args.len(),
        }));
        self.scopes.last_mut().expect("codegen scopes vec was empty").1 += 1;

        let old_unit_ptr = self.vm.unit_ptr;
        let old_ip = self.vm.ip;
        // set unit to write to
        self.vm.unit_ptr = new_unit_ptr;
        self.vm.ip = 0;
        self.vm.units[self.vm.unit_ptr].pool.push(Value::Fun(Function {
            unit_ptr: new_unit_ptr,
            arity: args.len(),
        }));
        self.scopes.last_mut().expect("codegen scopes vec was empty").1 += args.len();
        
        if let ASTType::Block(ref stmts) = block.kind {
            self.visit_block(&block, stmts.clone(), ScopeType::Function);
        }
        match self.vm.units[self.vm.unit_ptr].code.last() {
            Some(instr) => {
                if *instr != <OpCode as Into<u8>>::into(OpCode::RET) {
                    self.vm.units[self.vm.unit_ptr].pool.push(Value::Null);
                    self.vm.units[self.vm.unit_ptr].code.push(OpCode::LOAD.into());
                    let loc = (self.vm.units[self.vm.unit_ptr].pool.len()-1) as u8;
                    self.vm.units[self.vm.unit_ptr].code.push(loc);
                    self.vm.units[self.vm.unit_ptr].code.push(OpCode::RET.into());
                    if self.vm.units[self.vm.unit_ptr].lines.last().unwrap().0 != block.end_line {
                        self.vm.units[self.vm.unit_ptr].lines.push((block.end_line, 3));
                    } else {
                        self.vm.units[self.vm.unit_ptr].lines.last_mut().unwrap().1 += 3;
                    }
                }
            }
            None => {
                self.vm.units[self.vm.unit_ptr].pool.push(Value::Null);
                self.vm.units[self.vm.unit_ptr].code.push(OpCode::LOAD.into());
                let loc = (self.vm.units[self.vm.unit_ptr].pool.len()-1) as u8;
                self.vm.units[self.vm.unit_ptr].code.push(loc);
                self.vm.units[self.vm.unit_ptr].code.push(OpCode::RET.into());
                if self.vm.units[self.vm.unit_ptr].lines.last().unwrap().0 != block.end_line {
                    self.vm.units[self.vm.unit_ptr].lines.push((block.end_line, 3));
                } else {
                    self.vm.units[self.vm.unit_ptr].lines.last_mut().unwrap().1 += 3;
                }
            }
        };
        self.vm.unit_ptr = old_unit_ptr;
        self.vm.ip = old_ip;
    }
    pub fn visit_return(&mut self, ast: &AST, expr: Option<AST>) {
        if let Some(expr) = expr {
            self.visit(expr);
        } else {
            self.vm.units[self.vm.unit_ptr].pool.push(Value::Null);
            self.vm.units[self.vm.unit_ptr].code.push(OpCode::LOAD.into());
            let loc = (self.vm.units[self.vm.unit_ptr].pool.len()-1) as u8;
            self.vm.units[self.vm.unit_ptr].code.push(loc);
            if self.vm.units[self.vm.unit_ptr].lines.last().unwrap().0 != ast.end_line {
                self.vm.units[self.vm.unit_ptr].lines.push((ast.end_line, 2));
            } else {
                self.vm.units[self.vm.unit_ptr].lines.last_mut().unwrap().1 += 2;
            }
        }
        self.vm.units[self.vm.unit_ptr].code.push(OpCode::RET.into());
        if self.vm.units[self.vm.unit_ptr].lines.last().unwrap().0 != ast.end_line {
            self.vm.units[self.vm.unit_ptr].lines.push((ast.end_line, 1));
        } else {
            self.vm.units[self.vm.unit_ptr].lines.last_mut().unwrap().1 += 1;
        }
    }
    pub fn visit_while(&mut self, condition: AST, block: AST) {
        self.break_stack.push(Vec::new());
        self.continue_stack.push(Vec::new());

        let end_jmp = self.vm.units[self.vm.unit_ptr].code.len();
        self.visit(condition.clone());
        self.vm.units[self.vm.unit_ptr].code.push(OpCode::JNE.into());
        self.vm.units[self.vm.unit_ptr].code.push(0xFF); // placeholder
        self.vm.units[self.vm.unit_ptr].code.push(0xFF); // placeholder
        let start_jmp_loc = self.vm.units[self.vm.unit_ptr].code.len()-2;
        if self.vm.units[self.vm.unit_ptr].lines.last().unwrap().0 != condition.end_line {
            self.vm.units[self.vm.unit_ptr].lines.push((condition.end_line, 3));
        } else {
            self.vm.units[self.vm.unit_ptr].lines.last_mut().unwrap().1 += 3;
        }
        if let ASTType::Block(ref stmts) = block.kind {
            self.visit_block(&block, stmts.clone(), ScopeType::Loop);
        }
        self.vm.units[self.vm.unit_ptr].code.push(OpCode::JMP_UP.into());
        let current = self.vm.units[self.vm.unit_ptr].code.len()+2;
        let current_to_start = current - end_jmp;
        self.vm.units[self.vm.unit_ptr].code.push(((current_to_start >> 8) & 0xFF) as u8);
        self.vm.units[self.vm.unit_ptr].code.push((current_to_start & 0xFF) as u8);
        if self.vm.units[self.vm.unit_ptr].lines.last().unwrap().0 != block.end_line {
            self.vm.units[self.vm.unit_ptr].lines.push((block.end_line, 3));
        } else {
            self.vm.units[self.vm.unit_ptr].lines.last_mut().unwrap().1 += 3;
        }
        self.patch_jump(start_jmp_loc, 0);

        let breaks = self.break_stack.pop().expect("break stack empty on pop");
        for loc in breaks {
            self.patch_jump(loc, 0);
        }
        let continues = self.continue_stack.pop().expect("continue stack empty on pop");
        for loc in continues {
            let jump = loc - end_jmp + 2;
            self.vm.units[self.vm.unit_ptr].code[loc] = ((jump >> 8) & 0xFF) as u8;
            self.vm.units[self.vm.unit_ptr].code[loc + 1] = (jump & 0xFF) as u8;
        }
    }
    pub fn visit_for(&mut self, expr1: Option<AST>, expr2: Option<AST>,
                        expr3: Option<AST>, block: AST) {
        self.scopes.push((ScopeType::Other, 0));

        self.break_stack.push(Vec::new());
        self.continue_stack.push(Vec::new());

        if let Some(expr1) = expr1 {
            self.visit(expr1);
        }
        let end_jmp = self.vm.units[self.vm.unit_ptr].code.len();
        let mut start_jmp_loc = None;
        if let Some(expr2) = expr2 {
            self.visit(expr2.clone());
            self.vm.units[self.vm.unit_ptr].code.push(OpCode::JNE.into());
            self.vm.units[self.vm.unit_ptr].code.push(0xFF); // placeholder
            self.vm.units[self.vm.unit_ptr].code.push(0xFF); // placeholder
            start_jmp_loc = Some(self.vm.units[self.vm.unit_ptr].code.len()-2);
            if self.vm.units[self.vm.unit_ptr].lines.last().unwrap().0 != expr2.end_line {
                self.vm.units[self.vm.unit_ptr].lines.push((expr2.end_line, 3));
            } else {
                self.vm.units[self.vm.unit_ptr].lines.last_mut().unwrap().1 += 3;
            }
        }
        if let ASTType::Block(ref stmts) = block.kind {
            self.visit_block(&block, stmts.clone(), ScopeType::Loop);
        }
        let continues = self.continue_stack.pop().expect("continue stack empty on pop");
        for loc in continues {
            /*let jump = loc - end_jmp + 2;
            self.vm.units[self.vm.unit_ptr].code[loc] = ((jump >> 8) & 0xFF) as u8;
            self.vm.units[self.vm.unit_ptr].code[loc + 1] = (jump & 0xFF) as u8;*/
            self.patch_jump(loc, 0);
        }
        if let Some(expr3) = expr3 {
            self.visit(expr3);
            self.vm.units[self.vm.unit_ptr].code.push(OpCode::POP.into());
            self.vm.units[self.vm.unit_ptr].code.push(0x01);
            if self.vm.units[self.vm.unit_ptr].lines.last().unwrap().0 != block.end_line {
                self.vm.units[self.vm.unit_ptr].lines.push((block.end_line, 2));
            } else {
                self.vm.units[self.vm.unit_ptr].lines.last_mut().unwrap().1 += 2;
            }
        }

        // write instruction to loop
        self.vm.units[self.vm.unit_ptr].code.push(OpCode::JMP_UP.into());
        let current = self.vm.units[self.vm.unit_ptr].code.len()+2;
        let current_to_start = current - end_jmp;
        self.vm.units[self.vm.unit_ptr].code.push(((current_to_start >> 8) & 0xFF) as u8);
        self.vm.units[self.vm.unit_ptr].code.push((current_to_start & 0xFF) as u8);
        if self.vm.units[self.vm.unit_ptr].lines.last().unwrap().0 != block.end_line {
            self.vm.units[self.vm.unit_ptr].lines.push((block.end_line, 3));
        } else {
            self.vm.units[self.vm.unit_ptr].lines.last_mut().unwrap().1 += 3;
        }

        let breaks = self.break_stack.pop().expect("break stack empty on pop");
        for loc in breaks {
            self.patch_jump(loc, 0);
        }


        if let Some(loc) = start_jmp_loc {
            self.patch_jump(loc, 0);
        }

        let (_scope_type, variables) = self.scopes.pop().expect("popped scope in block");
        self.vm.units[self.vm.unit_ptr].code.push(OpCode::POP.into());
        self.vm.units[self.vm.unit_ptr].code.push(variables as u8);
        if self.vm.units[self.vm.unit_ptr].lines.last().unwrap().0 != block.end_line {
            self.vm.units[self.vm.unit_ptr].lines.push((block.end_line, 2));
        } else {
            self.vm.units[self.vm.unit_ptr].lines.last_mut().unwrap().1 += 2;
        }

    }
    pub fn visit_break(&mut self, ast: &AST) {
        let mut scopes = self.scopes.clone();
        let mut pop_count = 0;
        loop {
            let (scope_type, scope) = scopes.pop().expect("scopes empty in break");
            pop_count += scope;
            if scope_type == ScopeType::Loop {
                break;
            }
        }
        self.vm.units[self.vm.unit_ptr].code.push(OpCode::POP.into());
        self.vm.units[self.vm.unit_ptr].code.push(pop_count as u8);

        self.vm.units[self.vm.unit_ptr].code.push(OpCode::JMP.into());
        self.vm.units[self.vm.unit_ptr].code.push(0xFF);
        self.vm.units[self.vm.unit_ptr].code.push(0xFF);
        if self.vm.units[self.vm.unit_ptr].lines.last().unwrap().0 != ast.end_line {
            self.vm.units[self.vm.unit_ptr].lines.push((ast.end_line, 5));
        } else {
            self.vm.units[self.vm.unit_ptr].lines.last_mut().unwrap().1 += 5;
        }
        self.break_stack.last_mut().expect("break not in a loop").push(self.vm.units[self.vm.unit_ptr].code.len()-2);
    }
    pub fn visit_continue(&mut self, ast: &AST) {
        let mut scopes = self.scopes.clone();
        let mut pop_count = 0;
        loop {
            let (scope_type, scope) = scopes.pop().expect("scopes empty in break");
            pop_count += scope;
            if scope_type == ScopeType::Loop {
                break;
            }
        }
        self.vm.units[self.vm.unit_ptr].code.push(OpCode::POP.into());
        self.vm.units[self.vm.unit_ptr].code.push(pop_count as u8);

        self.vm.units[self.vm.unit_ptr].code.push(OpCode::JMP.into());
        self.vm.units[self.vm.unit_ptr].code.push(0xFF);
        self.vm.units[self.vm.unit_ptr].code.push(0xFF);
        if self.vm.units[self.vm.unit_ptr].lines.last().unwrap().0 != ast.end_line {
            self.vm.units[self.vm.unit_ptr].lines.push((ast.end_line, 5));
        } else {
            self.vm.units[self.vm.unit_ptr].lines.last_mut().unwrap().1 += 5;
        }
        self.continue_stack.last_mut().expect("continue not in a loop").push(self.vm.units[self.vm.unit_ptr].code.len()-2);
    }
    pub fn visit_if(&mut self, condition: AST, block: AST, else_expr: Option<AST>) {
        self.visit(condition.clone());
        self.vm.units[self.vm.unit_ptr].code.push(OpCode::JNE.into());
        self.vm.units[self.vm.unit_ptr].code.push(0xFF); // placeholder
        self.vm.units[self.vm.unit_ptr].code.push(0xFF); // placeholder
        let start_jmp_loc = self.vm.units[self.vm.unit_ptr].code.len()-2;
        if self.vm.units[self.vm.unit_ptr].lines.last().unwrap().0 != condition.end_line {
            self.vm.units[self.vm.unit_ptr].lines.push((condition.end_line, 5));
        } else {
            self.vm.units[self.vm.unit_ptr].lines.last_mut().unwrap().1 += 5;
        }
        if let ASTType::Block(ref stmts) = block.kind {
            self.visit_block(&block, stmts.clone(), ScopeType::If);
        }
        if let Some(ast) = else_expr {
            match ast.kind {
                ASTType::If(_, _, _) => {
                    self.vm.units[self.vm.unit_ptr].code.push(OpCode::JMP.into());
                    self.vm.units[self.vm.unit_ptr].code.push(0xFF); // placeholder
                    self.vm.units[self.vm.unit_ptr].code.push(0xFF); // placeholder
                    let end_jmp_loc = self.vm.units[self.vm.unit_ptr].code.len()-2;
                    if self.vm.units[self.vm.unit_ptr].lines.last().unwrap().0 != ast.end_line {
                        self.vm.units[self.vm.unit_ptr].lines.push((ast.end_line, 3));
                    } else {
                        self.vm.units[self.vm.unit_ptr].lines.last_mut().unwrap().1 += 3;
                    }
                    
                    self.patch_jump(start_jmp_loc, 0);
                    self.visit(ast);
                    self.patch_jump(end_jmp_loc, 0);
                }
                ASTType::Block(_) => {

                    self.vm.units[self.vm.unit_ptr].code.push(OpCode::JMP.into());
                    self.vm.units[self.vm.unit_ptr].code.push(0xFF); // placeholder
                    self.vm.units[self.vm.unit_ptr].code.push(0xFF); // placeholder
                    if self.vm.units[self.vm.unit_ptr].lines.last().unwrap().0 != ast.end_line {
                        self.vm.units[self.vm.unit_ptr].lines.push((ast.end_line, 3));
                    } else {
                        self.vm.units[self.vm.unit_ptr].lines.last_mut().unwrap().1 += 3;
                    }
                    
                    let end_jmp_loc = self.vm.units[self.vm.unit_ptr].code.len()-2;
                    self.patch_jump(start_jmp_loc, 0); // jmp to else
                    if let ASTType::Block(ref stmts) = ast.kind {
                        self.visit_block(&ast, stmts.clone(), ScopeType::If);
                    }
                    self.patch_jump(end_jmp_loc, 0); // jmp to after else
                }
                _ => { println!("unimplemented"); }
            }
        } else {
            self.patch_jump(start_jmp_loc, 0);
        }
    }
    pub fn visit_block(&mut self, ast: &AST, stmts: Vec<AST>, scope_type: ScopeType) {
        self.scopes.push((scope_type, 0));
        for stmt in stmts {
            self.visit(stmt);
        }
        let (_scope_type, variables) = self.scopes.pop().expect("popped scope in block");
        self.vm.units[self.vm.unit_ptr].code.push(OpCode::POP.into());
        self.vm.units[self.vm.unit_ptr].code.push(variables as u8);
        match self.vm.units[self.vm.unit_ptr].lines.last() {
            Some(last) => if last.0 != ast.end_line {
                self.vm.units[self.vm.unit_ptr].lines.push((ast.end_line, 2));
            } else {
                self.vm.units[self.vm.unit_ptr].lines.last_mut().unwrap().1 += 2;
            }
            None => self.vm.units[self.vm.unit_ptr].lines.push((ast.end_line, 2))
        }
    }
    pub fn visit_decl(&mut self, ast: &AST, _name: Name, expr: AST) {
        self.visit(expr);
        self.vm.units[self.vm.unit_ptr].code.push(OpCode::DECL.into());
        if self.vm.units[self.vm.unit_ptr].lines.last().unwrap().0 != ast.end_line {
            self.vm.units[self.vm.unit_ptr].lines.push((ast.end_line, 1));
        } else {
            self.vm.units[self.vm.unit_ptr].lines.last_mut().unwrap().1 += 1;
        }
        #[allow(irrefutable_let_patterns)]
        if let Extension::Resolution(_scope, _ptr) = ast.extensions[0] {
            self.scopes.last_mut().expect("codegen scopes vec was empty").1 += 1;
        }
    }
    pub fn visit_expr_stmt(&mut self, ast: &AST, expr: AST) {
        self.visit(expr);
        self.vm.units[self.vm.unit_ptr].code.push(OpCode::POP.into());
        self.vm.units[self.vm.unit_ptr].code.push(0x01);
        if self.vm.units[self.vm.unit_ptr].lines.last().unwrap().0 != ast.end_line {
            self.vm.units[self.vm.unit_ptr].lines.push((ast.end_line, 2));
        } else {
            self.vm.units[self.vm.unit_ptr].lines.last_mut().unwrap().1 += 2;
        }
    }
    // REMOVE LATER
    pub fn visit_print(&mut self, ast: &AST, expr: AST) {
        self.visit(expr);
        self.vm.units[self.vm.unit_ptr].code.push(OpCode::PRINT.into());
        if self.vm.units[self.vm.unit_ptr].lines.last().unwrap().0 != ast.end_line {
            self.vm.units[self.vm.unit_ptr].lines.push((ast.end_line, 1));
        } else {
            self.vm.units[self.vm.unit_ptr].lines.last_mut().unwrap().1 += 1;
        }
    }
    pub fn visit_assign(&mut self, ast: &AST, name: LhsAssign, expr: AST) {
        self.visit(expr);
        // pop stack to get value. then find variable in stack. set variable to value.
        match name.kind {
            LhsAssignType::Ident(_) => {
                #[allow(irrefutable_let_patterns)]
                if let Extension::Resolution(_scope, ptr) = ast.extensions[0] {
                    self.vm.units[self.vm.unit_ptr].code.push(OpCode::ASN.into());
                    self.vm.units[self.vm.unit_ptr].code.push(ptr as u8);
                    if self.vm.units[self.vm.unit_ptr].lines.last().unwrap().0 != ast.end_line {
                        self.vm.units[self.vm.unit_ptr].lines.push((ast.end_line, 2));
                    } else {
                        self.vm.units[self.vm.unit_ptr].lines.last_mut().unwrap().1 += 2;
                    }
                }
            }
            LhsAssignType::Subscript(name, index) => {
                self.visit(*index);

                #[allow(irrefutable_let_patterns)]
                if let Extension::Resolution(_scope, ptr) = name.extensions[0] {
                    self.vm.units[self.vm.unit_ptr].code.push(OpCode::REF.into());
                    self.vm.units[self.vm.unit_ptr].code.push(ptr as u8);
                    if self.vm.units[self.vm.unit_ptr].lines.last().unwrap().0 != ast.end_line {
                        self.vm.units[self.vm.unit_ptr].lines.push((ast.end_line, 2));
                    } else {
                        self.vm.units[self.vm.unit_ptr].lines.last_mut().unwrap().1 += 2;
                    }
                } else {
                    panic!("Subscript assignment should always have a Resolution");
                }

                self.vm.units[self.vm.unit_ptr].code.push(OpCode::ASNARR.into());

                if self.vm.units[self.vm.unit_ptr].lines.last().unwrap().0 != ast.end_line {
                    self.vm.units[self.vm.unit_ptr].lines.push((ast.end_line, 1));
                } else {
                    self.vm.units[self.vm.unit_ptr].lines.last_mut().unwrap().1 += 1;
                }
            }
        }
    }
    pub fn visit_anonymous(&mut self, params: Vec<Name>, block: AST) {
        self.vm.units.push(Unit::new_empty());

        let new_unit_ptr = self.vm.units.len()-1;
        self.vm.units[self.vm.unit_ptr].pool.push(Value::Fun(Function {
            unit_ptr: new_unit_ptr,
            arity: params.len(),
        }));
        // load function to stack
        self.vm.units[self.vm.unit_ptr].code.push(OpCode::LOAD.into());
        let loc = (self.vm.units[self.vm.unit_ptr].pool.len()-1) as u8;
        self.vm.units[self.vm.unit_ptr].code.push(loc);
        if self.vm.units[self.vm.unit_ptr].lines.len() == 0 || self.vm.units[self.vm.unit_ptr].lines.last().unwrap().0 != block.end_line {
            self.vm.units[self.vm.unit_ptr].lines.push((block.end_line, 2));
        } else {
            self.vm.units[self.vm.unit_ptr].lines.last_mut().unwrap().1 += 2;
        }
        self.scopes.last_mut().expect("codegen scopes vec was empty").1 += 1;

        // enter function unit
        let old_unit_ptr = self.vm.unit_ptr;
        let old_ip = self.vm.ip;
        self.vm.unit_ptr = new_unit_ptr;
        self.vm.ip = 0;

        // update scopes with number of parameters
        self.scopes.last_mut().expect("codegen scopes vec was empty").1 += params.len();
        
        if let ASTType::Block(ref stmts) = block.kind {
            self.visit_block(&block, stmts.clone(), ScopeType::Function);
        }
        // add implicit RET
        match self.vm.units[self.vm.unit_ptr].code.last() {
            Some(instr) => {
                if *instr != <OpCode as Into<u8>>::into(OpCode::RET) {
                    self.vm.units[self.vm.unit_ptr].pool.push(Value::Null);
                    self.vm.units[self.vm.unit_ptr].code.push(OpCode::LOAD.into());
                    let loc = (self.vm.units[self.vm.unit_ptr].pool.len()-1) as u8;
                    self.vm.units[self.vm.unit_ptr].code.push(loc);
                    self.vm.units[self.vm.unit_ptr].code.push(OpCode::RET.into());
                    if self.vm.units[self.vm.unit_ptr].lines.last().unwrap().0 != block.end_line {
                        self.vm.units[self.vm.unit_ptr].lines.push((block.end_line, 3));
                    } else {
                        self.vm.units[self.vm.unit_ptr].lines.last_mut().unwrap().1 += 3;
                    }
                }
            }
            None => {
                self.vm.units[self.vm.unit_ptr].pool.push(Value::Null);
                self.vm.units[self.vm.unit_ptr].code.push(OpCode::LOAD.into());
                let loc = (self.vm.units[self.vm.unit_ptr].pool.len()-1) as u8;
                self.vm.units[self.vm.unit_ptr].code.push(loc);
                self.vm.units[self.vm.unit_ptr].code.push(OpCode::RET.into());
                if self.vm.units[self.vm.unit_ptr].lines.last().unwrap().0 != block.end_line {
                    self.vm.units[self.vm.unit_ptr].lines.push((block.end_line, 3));
                } else {
                    self.vm.units[self.vm.unit_ptr].lines.last_mut().unwrap().1 += 3;
                }
            }
        };
        
        self.vm.unit_ptr = old_unit_ptr;
        self.vm.ip = old_ip;
    }
    pub fn visit_subscript(&mut self, ast: &AST, left: AST, right: AST) {
        self.visit(left);
        self.visit(right);
        self.vm.units[self.vm.unit_ptr].code.push(OpCode::SCR.into());
        if self.vm.units[self.vm.unit_ptr].lines.last().unwrap().0 != ast.end_line {
            self.vm.units[self.vm.unit_ptr].lines.push((ast.end_line, 1));
        } else {
            self.vm.units[self.vm.unit_ptr].lines.last_mut().unwrap().1 += 1;
        }
    }
    pub fn visit_binary(&mut self, left: AST, oper: BinOp, right: AST) {
        use crate::ast::BinOp::*;
        codegen_binary!(self, left, right, oper, Add, ADD, Sub, SUB, Mul, MUL,
            Div, DIV, Mod, MOD, BitAnd, BITAND, BitXor, BITXOR, BitOr, BITOR,
            Eq, EQ, Ne, NE, Gr, GR, Ge, GE, Ls, LS, Le, LE, Or, OR, And, AND);
    }
    pub fn visit_unary(&mut self, oper: UnOp, right: AST) {
        use crate::ast::UnOp::*;
        codegen_unary!(self, right, oper, Not, NOT, Neg, NEG);
    }
    pub fn visit_lit(&mut self, ast: &AST, lit: Lit) {
        match lit {
            Lit::Num(value) => {
                self.vm.units[self.vm.unit_ptr].pool.push(Value::Num(value));
                self.vm.units[self.vm.unit_ptr].code.push(OpCode::LOAD.into());
                let loc = (self.vm.units[self.vm.unit_ptr].pool.len()-1) as u8;
                self.vm.units[self.vm.unit_ptr].code.push(loc);
                if self.vm.units[self.vm.unit_ptr].lines.len() == 0 || self.vm.units[self.vm.unit_ptr].lines.last().unwrap().0 != ast.end_line {
                    self.vm.units[self.vm.unit_ptr].lines.push((ast.end_line, 2));
                } else {
                    self.vm.units[self.vm.unit_ptr].lines.last_mut().unwrap().1 += 2;
                }
            }
            Lit::Str(value) => {
                self.vm.units[self.vm.unit_ptr].pool.push(Value::Str(value.into()));
                self.vm.units[self.vm.unit_ptr].code.push(OpCode::LOAD.into());
                let loc = (self.vm.units[self.vm.unit_ptr].pool.len()-1) as u8;
                self.vm.units[self.vm.unit_ptr].code.push(loc);
                if self.vm.units[self.vm.unit_ptr].lines.len() == 0 || self.vm.units[self.vm.unit_ptr].lines.last().unwrap().0 != ast.end_line {
                    self.vm.units[self.vm.unit_ptr].lines.push((ast.end_line, 2));
                } else {
                    self.vm.units[self.vm.unit_ptr].lines.last_mut().unwrap().1 += 2;
                }
            }
            Lit::Bool(value) => {
                self.vm.units[self.vm.unit_ptr].pool.push(Value::Bool(value));
                self.vm.units[self.vm.unit_ptr].code.push(OpCode::LOAD.into());
                let loc = (self.vm.units[self.vm.unit_ptr].pool.len()-1) as u8;
                self.vm.units[self.vm.unit_ptr].code.push(loc);
                if self.vm.units[self.vm.unit_ptr].lines.len() == 0 || self.vm.units[self.vm.unit_ptr].lines.last().unwrap().0 != ast.end_line {
                    self.vm.units[self.vm.unit_ptr].lines.push((ast.end_line, 2));
                } else {
                    self.vm.units[self.vm.unit_ptr].lines.last_mut().unwrap().1 += 2;
                }
            }
            Lit::Array(exprs) => {
                for expr in &exprs {
                    self.visit(expr.clone());
                }
                self.vm.units[self.vm.unit_ptr].code.push(OpCode::LIST.into());
                self.vm.units[self.vm.unit_ptr].code.push(exprs.len() as u8);
                if self.vm.units[self.vm.unit_ptr].lines.len() == 0 || self.vm.units[self.vm.unit_ptr].lines.last().unwrap().0 != ast.end_line {
                    self.vm.units[self.vm.unit_ptr].lines.push((ast.end_line, 2));
                } else {
                    self.vm.units[self.vm.unit_ptr].lines.last_mut().unwrap().1 += 2;
                }
            }
            Lit::Ident(_name) => {
                self.vm.units[self.vm.unit_ptr].code.push(OpCode::VAR.into());
                #[allow(irrefutable_let_patterns)]
                if let Extension::Resolution(_scope, ptr) = ast.extensions[0] {
                    /*println!("line: {} ptr: {} locals: {:?}", ast.end_line, ptr, self.locals);
                    let (_scope, slot) = self.locals.get(ptr).unwrap();
                    println!("slot: {}", *slot);
                    self.vm.units[self.vm.unit_ptr].code.push(*slot);*/
                    self.vm.units[self.vm.unit_ptr].code.push(ptr as u8);
                    if self.vm.units[self.vm.unit_ptr].lines.len() == 0 || self.vm.units[self.vm.unit_ptr].lines.last().unwrap().0 != ast.end_line {
                        self.vm.units[self.vm.unit_ptr].lines.push((ast.end_line, 2));
                    } else {
                        self.vm.units[self.vm.unit_ptr].lines.last_mut().unwrap().1 += 2;
                    }
                }
            }
            _ => {}
        }
    }
    pub fn visit_call(&mut self, ast: &AST, ident: AST, args: Vec<AST>) {
        for arg in args.iter() {
            self.visit(arg.clone());
        }
        self.visit(ident);
        self.vm.units[self.vm.unit_ptr].code.push(OpCode::CALL.into());
        self.vm.units[self.vm.unit_ptr].code.push(args.len() as u8);
        if self.vm.units[self.vm.unit_ptr].lines.len() == 0 || self.vm.units[self.vm.unit_ptr].lines.last().unwrap().0 != ast.end_line {
            self.vm.units[self.vm.unit_ptr].lines.push((ast.end_line, 2));
        } else {
            self.vm.units[self.vm.unit_ptr].lines.last_mut().unwrap().1 += 2;
        }
    }
    pub fn patch_jump(&mut self, loc: usize, offset: i32) {
        let jump = ((self.vm.units[self.vm.unit_ptr].code.len() - loc - 2) as i32) + offset;

        self.vm.units[self.vm.unit_ptr].code[loc] = ((jump >> 8) & 0xFF) as u8;
        self.vm.units[self.vm.unit_ptr].code[loc + 1] = (jump & 0xFF) as u8;
    }
}

#[derive(Debug, Clone, PartialEq, Eq)]
pub enum ScopeType {
    Main, Function, Loop, If, Other,
}