diff --git a/src/debugger.rs b/src/debugger.rs
deleted file mode 100644
index d413c58..0000000
--- a/src/debugger.rs
+++ /dev/null
@@ -1,270 +0,0 @@
-use rustyline::error::ReadlineError;
-use rustyline::Editor;
-
-use colored::*;
-
-use nom;
-use nom::IResult;
-use nom::bytes::complete::{tag, take_till1, take_till, take_while_m_n, take_while1};
-use nom::combinator::map_res;
-
-use hexdump;
-
-use super::arm7tdmi::cpu;
-use super::sysbus::SysBus;
-
-use crate::disass::Disassembler;
-
-#[derive(Debug)]
-pub struct Debugger {
-    cpu: cpu::Core,
-    sysbus: SysBus,
-    running: bool,
-    breakpoints: Vec<u32>,
-}
-
-
-#[derive(Debug, PartialEq)]
-pub enum DebuggerError {
-    ParsingError(String),
-    CpuError(cpu::CpuError),
-    InvalidCommand(String)
-}
-
-impl From<cpu::CpuError> for DebuggerError {
-    fn from(e: cpu::CpuError) -> DebuggerError {
-        DebuggerError::CpuError(e)
-    }
-}
-
-impl From<nom::Err<(&str, nom::error::ErrorKind)>> for DebuggerError {
-    fn from(e: nom::Err<(&str, nom::error::ErrorKind)>) -> DebuggerError {
-        DebuggerError::ParsingError("parsing of command failed".to_string())
-    }
-}
-
-type DebuggerResult<T> = Result<T, DebuggerError>;
-
-#[derive(Debug, PartialEq)]
-enum DebuggerCommand {
-    Info,
-    SingleStep,
-    Continue,
-    HexDump(u32, usize),
-    Disass { addr: u32, num_opcodes: usize },
-    AddBreakpoint(u32),
-    ListBreakpoints,
-    Reset,
-    Quit,
-    Nop,
-}
-use DebuggerCommand::*;
-
-fn from_hex(input: &str) -> Result<u32, std::num::ParseIntError> {
-  u32::from_str_radix(input, 16)
-}
-
-fn from_dec(input: &str) -> Result<u32, std::num::ParseIntError> {
-  u32::from_str_radix(input, 10)
-}
-
-fn whitespace(input: &str) -> IResult<&str, ()> {
-    let (input, _) = take_while1(char::is_whitespace)(input)?;
-    Ok((input, ()))
-}
-
-fn parse_hex_num(input: &str) -> IResult<&str, u32> {
-    let (input, _) = tag("0x")(input)?;
-    map_res(take_while_m_n(1, 8, |c: char| c.is_digit(16)), from_hex)(input)
-}
-
-fn parse_num(input: &str) -> IResult<&str, u32> {
-    map_res(take_while1(|c: char| c.is_digit(10)), from_dec)(input)
-}
-
-fn parse_word(input: &str) -> IResult<&str, &str> {
-    take_till(char::is_whitespace)(input)
-}
-
-fn parse_debugger_command(input: &str) -> DebuggerResult<DebuggerCommand> {
-    // TODO this code is shit!
-    let (input, command_name) = parse_word(input)?;
-    match command_name {
-        "i" | "info" => Ok(Info),
-        "s" | "step" => Ok(SingleStep),
-        "c" | "continue" => Ok(Continue),
-        "xxd" => {
-            let (input, _) = whitespace(input).map_err(|_| DebuggerError::ParsingError("argument missing".to_string()))?;
-            let (input, addr) = parse_hex_num(input)?;
-            let (input, _) = whitespace(input).map_err(|_| DebuggerError::ParsingError("argument missing".to_string()))?;
-            let (_, nbytes) = parse_num(input)?;
-            let nbytes = nbytes as usize;
-            Ok(HexDump(addr, nbytes))
-        }
-        "d" | "disass" => {
-            let (input, _) = whitespace(input).map_err(|_| DebuggerError::ParsingError("argument missing".to_string()))?;
-            let (input, addr) = parse_hex_num(input)?;
-            let (input, _) = whitespace(input).map_err(|_| DebuggerError::ParsingError("argument missing".to_string()))?;
-            let (_, num_opcodes) = parse_num(input)?;
-            let num_opcodes = num_opcodes as usize;
-            Ok(Disass{ addr, num_opcodes })
-        }
-        "b" | "break" => {
-            let (input, _) = whitespace(input).map_err(|_| DebuggerError::ParsingError("argument missing".to_string()))?;
-            let (_, addr) = parse_hex_num(input)?;
-            Ok(AddBreakpoint(addr))
-        }
-        "bl" => Ok(ListBreakpoints),
-        "q" | "quit" => Ok(Quit),
-        "r" | "reset" => Ok(Reset),
-        "" => Ok(Nop),
-        _ => Err(DebuggerError::InvalidCommand(command_name.to_string()))
-    }
-}
-
-impl Debugger {
-    pub fn new(cpu: cpu::Core, sysbus: SysBus) -> Debugger {
-        Debugger {
-            cpu: cpu,
-            sysbus: sysbus,
-            breakpoints: Vec::new(),
-            running: false,
-        }
-    }
-
-    fn is_breakpoint_reached(&self) -> bool {
-        let pc = self.cpu.pc;
-        for b in &self.breakpoints {
-            if *b == pc {
-                return true;
-            }
-        }
-
-        false
-    }
-
-    fn command(&mut self, cmd: DebuggerCommand) {
-        match cmd {
-                Nop => (),
-                Info => {
-                    println!("cpu info: {:#x?}", self.cpu)
-                }
-                SingleStep => {
-                    ;
-                    match self.cpu.step(&mut self.sysbus) {
-                        Ok(_) => (),
-                        Err(e) => {
-                            println!("{}: {}", "cpu encountered an error".red(), e);
-                            println!("cpu: {:#x?}", self.cpu);
-                        }
-                    };
-                    if self.is_breakpoint_reached() {
-                        println!("breakpoint 0x{:08x} reached!", self.cpu.pc)
-                    }
-                },
-                Continue => {
-                    loop {
-                        match self.cpu.step(&mut self.sysbus) {
-                            Ok(_) => (),
-                            Err(e) => {
-                                println!("{}: {}", "cpu encountered an error".red(), e);
-                                println!("cpu: {:#x?}", self.cpu);
-                                break
-                            }
-                        };
-                        if self.is_breakpoint_reached() {
-                            println!("breakpoint 0x{:08x} reached!", self.cpu.pc)
-                        }
-                    }
-                },
-                HexDump(addr, nbytes) => {
-                    let bytes = match self.sysbus.get_bytes(addr, nbytes) {
-                        Some(bytes) => bytes,
-                        None => {
-                            println!("requested content out of bounds");
-                            return
-                        }
-                    };
-                    hexdump::hexdump(bytes);
-                }
-                Disass{ addr, num_opcodes } => {
-                    let bytes = match self.sysbus.get_bytes(addr, 4*num_opcodes) {
-                        Some(bytes) => bytes,
-                        None => {
-                            println!("requested content out of bounds");
-                            return
-                        }
-                    };
-                    let disass = Disassembler::new(addr, bytes);
-
-                    for line in disass {
-                        println!("{}", line)
-                    }
-                }
-                Quit => {
-                    print!("Quitting!");
-                    self.running = false;
-                },
-                AddBreakpoint(addr) => {
-                    if !self.breakpoints.contains(&addr) {
-                        let new_index = self.breakpoints.len();
-                        self.breakpoints.push(addr);
-                        println!("added breakpoint [{}] 0x{:08x}", new_index, addr);
-                    } else {
-                        println!("breakpoint already exists!")
-                    }
-                }
-                ListBreakpoints => {
-                    println!("breakpoint list:");
-                    for (i, b) in self.breakpoints.iter().enumerate() {
-                        println!("[{}] 0x{:08x}", i, b)
-                    }
-                }
-                Reset => {
-                    println!("resetting cpu...");
-                    self.cpu.reset();
-                    println!("cpu is restarted!")
-                },
-                _ => panic!("command {:?} not implemented", cmd)
-        }
-    }
-    pub fn repl(&mut self) -> DebuggerResult<()> {
-        self.running = true;
-        let mut rl = Editor::<()>::new();
-        while self.running {
-            let readline = rl.readline(&format!("({}) >> ", "rustboyadvance-dbg".cyan()));
-            match readline {
-                Ok(line) => {
-                    let command = parse_debugger_command(&line);
-                    match command {
-                        Ok(cmd) => {
-                            self.command(cmd)
-                        }
-                        Err(DebuggerError::InvalidCommand(command)) => {
-                            println!("invalid command: {}", command)
-                        }
-                        Err(DebuggerError::ParsingError(msg)) => {
-                            println!("Parsing error: {:?}", msg)
-                        }
-                        Err(e) => {
-                            return Err(e);
-                        }
-                    }
-                }
-                Err(ReadlineError::Interrupted) => {
-                    println!("CTRL-C");
-                    break;
-                }
-                Err(ReadlineError::Eof) => {
-                    println!("CTRL-D");
-                    break;
-                }
-                Err(err) => {
-                    println!("Error: {:?}", err);
-                    break;
-                }
-            }
-        }
-        Ok(())
-    }
-}
diff --git a/src/debugger/mod.rs b/src/debugger/mod.rs
new file mode 100644
index 0000000..d31a27e
--- /dev/null
+++ b/src/debugger/mod.rs
@@ -0,0 +1,260 @@
+use std::convert::TryFrom;
+
+use rustyline::error::ReadlineError;
+use rustyline::Editor;
+
+use colored::*;
+
+use hexdump;
+
+use super::arm7tdmi::cpu;
+use super::sysbus::SysBus;
+
+use crate::disass::Disassembler;
+
+mod parser;
+use parser::{parse_command_line, ParsedLine, Argument};
+
+#[derive(Debug)]
+pub struct Debugger {
+    cpu: cpu::Core,
+    sysbus: SysBus,
+    running: bool,
+    breakpoints: Vec<u32>,
+}
+
+#[derive(Debug, PartialEq)]
+pub enum DebuggerError {
+    ParsingError(String),
+    CpuError(cpu::CpuError),
+    InvalidCommand(String),
+    InvalidArgument(String)
+}
+
+impl From<cpu::CpuError> for DebuggerError {
+    fn from(e: cpu::CpuError) -> DebuggerError {
+        DebuggerError::CpuError(e)
+    }
+}
+
+type DebuggerResult<T> = Result<T, DebuggerError>;
+
+#[derive(Debug, PartialEq)]
+pub enum DebuggerCommand {
+    Info,
+    SingleStep,
+    Continue,
+    HexDump(u32, usize),
+    Disass { addr: u32, num_opcodes: usize },
+    AddBreakpoint(u32),
+    ListBreakpoints,
+    Reset,
+    Quit,
+}
+use DebuggerCommand::*;
+
+impl TryFrom<ParsedLine> for DebuggerCommand {
+    type Error = DebuggerError;
+
+    fn try_from(value: ParsedLine) -> Result<Self, Self::Error> {
+        match value.command.as_ref() {
+            "i" | "info" => {
+                Ok(Info)
+                },
+            "s" | "step" => Ok(SingleStep),
+            "c" | "continue" => Ok(Continue),
+            "xxd" => {
+                let mut args = value.args.into_iter();
+                let addr = match args.next() {
+                    Some(Argument::Num(n)) => n,
+                    _ => { 
+                        return Err(DebuggerError::InvalidArgument(format!("expected a number")));
+                    }
+                };
+                let nbytes = match args.next() {
+                    Some(Argument::Num(n)) => n,
+                    _ => { 
+                        return Err(DebuggerError::InvalidArgument(format!("expected a number")));
+                    }
+                };
+                let nbytes = nbytes as usize;
+                Ok(HexDump(addr, nbytes))
+            }
+            "d" | "disass" => {
+                let mut args = value.args.into_iter();
+                let addr = match args.next() {
+                    Some(Argument::Num(n)) => n,
+                    _ => { 
+                        return Err(DebuggerError::InvalidArgument(format!("expected a number")));
+                    }
+                };
+                let num_opcodes = match args.next() {
+                    Some(Argument::Num(n)) => n,
+                    _ => { 
+                        return Err(DebuggerError::InvalidArgument(format!("expected a number")));
+                    }
+                };
+                let num_opcodes = num_opcodes as usize;
+                Ok(Disass { addr, num_opcodes })
+            }
+            "b" | "break" => {
+                let mut args = value.args.into_iter();
+                let addr = match args.next() {
+                    Some(Argument::Num(n)) => n,
+                    _ => { 
+                        return Err(DebuggerError::InvalidArgument(format!("expected a number")));
+                    }
+                };
+                Ok(AddBreakpoint(addr))
+            }
+            "bl" => Ok(ListBreakpoints),
+            "q" | "quit" => Ok(Quit),
+            "r" | "reset" => Ok(Reset),
+            _ => Err(DebuggerError::InvalidCommand(value.command)),
+        }
+    }
+}
+
+impl Debugger {
+    pub fn new(cpu: cpu::Core, sysbus: SysBus) -> Debugger {
+        Debugger {
+            cpu: cpu,
+            sysbus: sysbus,
+            breakpoints: Vec::new(),
+            running: false,
+        }
+    }
+
+    fn is_breakpoint_reached(&self) -> bool {
+        let pc = self.cpu.pc;
+        for b in &self.breakpoints {
+            if *b == pc {
+                return true;
+            }
+        }
+
+        false
+    }
+
+    fn command(&mut self, cmd: DebuggerCommand) {
+        match cmd {
+            Info => println!("cpu info: {:#x?}", self.cpu),
+            SingleStep => {
+                match self.cpu.step(&mut self.sysbus) {
+                    Ok(_) => (),
+                    Err(e) => {
+                        println!("{}: {}", "cpu encountered an error".red(), e);
+                        println!("cpu: {:#x?}", self.cpu);
+                    }
+                };
+                if self.is_breakpoint_reached() {
+                    println!("breakpoint 0x{:08x} reached!", self.cpu.pc)
+                }
+            }
+            Continue => loop {
+                match self.cpu.step(&mut self.sysbus) {
+                    Ok(_) => (),
+                    Err(e) => {
+                        println!("{}: {}", "cpu encountered an error".red(), e);
+                        println!("cpu: {:#x?}", self.cpu);
+                        break;
+                    }
+                };
+                if self.is_breakpoint_reached() {
+                    println!("breakpoint 0x{:08x} reached!", self.cpu.pc)
+                }
+            },
+            HexDump(addr, nbytes) => {
+                let bytes = match self.sysbus.get_bytes(addr, nbytes) {
+                    Some(bytes) => bytes,
+                    None => {
+                        println!("requested content out of bounds");
+                        return;
+                    }
+                };
+                hexdump::hexdump(bytes);
+            }
+            Disass { addr, num_opcodes } => {
+                let bytes = match self.sysbus.get_bytes(addr, 4 * num_opcodes) {
+                    Some(bytes) => bytes,
+                    None => {
+                        println!("requested content out of bounds");
+                        return;
+                    }
+                };
+                let disass = Disassembler::new(addr, bytes);
+
+                for line in disass {
+                    println!("{}", line)
+                }
+            }
+            Quit => {
+                print!("Quitting!");
+                self.running = false;
+            }
+            AddBreakpoint(addr) => {
+                if !self.breakpoints.contains(&addr) {
+                    let new_index = self.breakpoints.len();
+                    self.breakpoints.push(addr);
+                    println!("added breakpoint [{}] 0x{:08x}", new_index, addr);
+                } else {
+                    println!("breakpoint already exists!")
+                }
+            }
+            ListBreakpoints => {
+                println!("breakpoint list:");
+                for (i, b) in self.breakpoints.iter().enumerate() {
+                    println!("[{}] 0x{:08x}", i, b)
+                }
+            }
+            Reset => {
+                println!("resetting cpu...");
+                self.cpu.reset();
+                println!("cpu is restarted!")
+            }
+            _ => panic!("command {:?} not implemented", cmd),
+        }
+    }
+    pub fn repl(&mut self) -> DebuggerResult<()> {
+        self.running = true;
+        let mut rl = Editor::<()>::new();
+        while self.running {
+            let readline = rl.readline(&format!("({}) >> ", "rustboyadvance-dbg".cyan()));
+            match readline {
+                Ok(line) => {
+                    if line.is_empty() {
+                        continue
+                    }
+                    let line = parse_command_line(&line);
+                    match line {
+                        Ok(line) => {
+                            match DebuggerCommand::try_from(line) {
+                                Ok(cmd) => self.command(cmd),
+                                Err(DebuggerError::InvalidCommand(c)) => println!("{}: {:?}", "invalid command".red(), c),
+                                Err(DebuggerError::InvalidArgument(m)) => println!("{}: {}", "invalid argument".red(), m),
+                                _ => ()
+                            }
+                        }
+                        Err(DebuggerError::ParsingError(msg)) => {
+                            println!("Parsing error: {}", msg)
+                        }
+                        _ => ()
+                    }
+                }
+                Err(ReadlineError::Interrupted) => {
+                    println!("CTRL-C");
+                    break;
+                }
+                Err(ReadlineError::Eof) => {
+                    println!("CTRL-D");
+                    break;
+                }
+                Err(err) => {
+                    println!("Error: {:?}", err);
+                    break;
+                }
+            }
+        }
+        Ok(())
+    }
+}
diff --git a/src/debugger/parser.rs b/src/debugger/parser.rs
new file mode 100644
index 0000000..794d3fa
--- /dev/null
+++ b/src/debugger/parser.rs
@@ -0,0 +1,101 @@
+use std::fmt;
+
+use nom;
+use nom::branch::alt;
+use nom::bytes::complete::{tag, take_while_m_n};
+use nom::character::complete::{alphanumeric0, digit1, multispace0, multispace1};
+use nom::combinator::{cut, map, map_res};
+use nom::error::{context, convert_error, ParseError, VerboseError};
+use nom::multi::separated_list;
+use nom::sequence::{preceded, terminated};
+use nom::IResult;
+
+use super::{DebuggerError, DebuggerResult};
+
+#[derive(Debug, PartialEq, Clone)]
+pub enum Argument {
+    Num(u32),
+    Boolean(bool),
+}
+
+impl fmt::Display for Argument {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            Argument::Num(_) => write!(f, "number"),
+            Argument::Boolean(_) => write!(f, "boolean"),
+        }
+    }
+}
+
+#[derive(Debug)]
+pub struct ParsedLine {
+    pub command: String,
+    pub args: Vec<Argument>,
+}
+
+fn parse_u32_hex<'a, E: ParseError<&'a str>>(i: &'a str) -> IResult<&'a str, u32, E> {
+    let (i, _) = context("hex", tag("0x"))(i)?;
+    map_res(take_while_m_n(1, 8, |c: char| c.is_digit(16)), |s| {
+        u32::from_str_radix(s, 16)
+    })(i)
+}
+
+fn parse_u32<'a, E: ParseError<&'a str>>(i: &'a str) -> IResult<&'a str, u32, E> {
+    context("u32", map_res(digit1, |s| u32::from_str_radix(s, 10)))(i)
+}
+
+fn parse_num<'a, E: ParseError<&'a str>>(i: &'a str) -> IResult<&'a str, Argument, E> {
+    map(alt((parse_u32_hex, parse_u32)), |n| Argument::Num(n))(i)
+}
+
+fn parse_boolean<'a, E: ParseError<&'a str>>(i: &'a str) -> IResult<&'a str, Argument, E> {
+    context(
+        "bool",
+        alt((
+            map(tag("true"), |_| Argument::Boolean(true)),
+            map(tag("false"), |_| Argument::Boolean(false)),
+        )),
+    )(i)
+}
+
+fn parse_argument<'a, E: ParseError<&'a str>>(i: &'a str) -> IResult<&'a str, Argument, E> {
+    context("argument", alt((parse_num, parse_boolean)))(i)
+}
+
+fn parse_argument_list<'a, E: ParseError<&'a str>>(
+    i: &'a str,
+) -> IResult<&'a str, Vec<Argument>, E> {
+    context(
+        "argument list",
+        preceded(multispace0, terminated(separated_list(multispace1, parse_argument), multispace0))
+    )(i)
+}
+
+fn parse_command_name<'a, E: ParseError<&'a str>>(i: &'a str) -> IResult<&'a str, &'a str, E> {
+    context("command", preceded(multispace0, cut(alphanumeric0)))(i)
+}
+
+fn parse_line<'a, E: ParseError<&'a str>>(i: &'a str) -> IResult<&str, ParsedLine, E> {
+    let (i, command_name) = parse_command_name(i)?;
+    println!("command name = {:?}, remaining {:?}", command_name, i);
+    let (i, arguments) = parse_argument_list(i)?;
+    println!("command: {} arguments: {:?}", command_name, arguments);
+
+    Ok((
+        i,
+        ParsedLine {
+            command: command_name.to_string(),
+            args: arguments,
+        },
+    ))
+}
+
+pub fn parse_command_line(input: &str) -> DebuggerResult<ParsedLine> {
+    match parse_line::<VerboseError<&str>>(input) {
+        Ok((_, line)) => Ok(line),
+        Err(nom::Err::Failure(e)) | Err(nom::Err::Error(e)) => {
+            Err(DebuggerError::ParsingError(convert_error(input, e)))
+        }
+        _ => panic!("unhandled parser error"),
+    }
+}
\ No newline at end of file