asm.rs

use std::fmt;
use std::convert::{TryFrom};
use std::collections::HashMap;
use std::collections::HashSet;
use std::mem::transmute;
use crate::vm::{VM, MemBlock, Op};

#[derive(Debug)]
pub struct ParseError
{
    msg: String,
    line_no: usize,
    col_no: usize,
}

impl ParseError
{
    fn new(input: &Input, msg: &str) -> Self
    {
        ParseError {
            msg: msg.to_string(),
            line_no: input.line_no,
            col_no: input.col_no
        }
    }

    pub fn msg_only<T>(msg: &str) -> Result<T, ParseError>
    {
        Err(ParseError {
            msg: msg.to_string(),
            line_no: 0,
            col_no: 0,
        })
    }
}

impl fmt::Display for ParseError
{
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        if self.line_no != 0 {
            write!(f, "@{}:{}: {}", self.line_no, self.col_no, self.msg)
        } else {
            write!(f, "{}", self.msg)
        }
    }
}

#[derive(Debug)]
struct Input
{
    input: Vec<char>,

    idx: usize,

    line_no: usize,

    col_no: usize,
}

impl Input
{
    fn new(input: String) -> Self
    {
        Self {
            input: input.chars().collect(),
            idx: 0,
            line_no: 1,
            col_no: 1,
        }
    }

    /// Shortcut for yielding a parse error wrapped in a result type
    fn parse_error<T>(&self, msg: &str) -> Result<T, ParseError>
    {
        Err(ParseError::new(self, msg))
    }

    /// Check if we have reached the end of the input
    fn eof(&self) -> bool
    {
        self.idx >= self.input.len()
    }

    /// Peek at the next character in the input
    fn peek_ch(&self) -> char
    {
        if self.idx < self.input.len() {
            return self.input[self.idx]
        }

        '\0'
    }

    /// Consume one character from the input
    fn eat_ch(&mut self) -> char
    {
        if self.idx >= self.input.len() {
            panic!("unexpected end of input");
        }

        let ch = self.input[self.idx];
        self.idx += 1;

        if ch == '\n' {
            self.line_no += 1;
            self.col_no = 1;
        }
        else
        {
            self.col_no += 1;
        }

        ch
    }

    /// Consume whitespace characters (excluding newlines)
    fn eat_ws(&mut self) -> Result<(), ParseError>
    {
        loop
        {
            let ch = self.peek_ch();

            match ch {
                '\r' |
                '\n' |
                '\t' |
                ' ' => {
                    self.eat_ch();
                }

                // Single-line comment
                '#' => {
                    self.eat_line_comment();
                }

                '/' => {
                    if self.match_str("//") {
                        self.eat_line_comment();
                    }
                    else if self.match_str("/*") {
                        self.eat_multi_comment()?;
                    }
                }

                _ => break
            }
        }

        Ok(())
    }

    /// Check that a separator character is present
    fn expect_sep(&mut self) -> Result<(), ParseError>
    {
        match self.peek_ch() {
            '\r' |
            '\n' |
            '\t' |
            ' ' |
            '\0' |
            '#' |
            ';' |
            ':' => {
                Ok(())
            }

            _ => {
                self.parse_error(&format!("expected separator after token"))
            }
        }
    }

    /// Consume characters until the end of a single-line comment
    fn eat_line_comment(&mut self)
    {
        loop
        {
            let ch = self.peek_ch();

            if ch == '\0' {
                break;
            }

            if ch == '\n' {
                self.eat_ch();
                break;
            }

            self.eat_ch();
        }
    }

    /// Consume characters until the end of a multi-line comment
    fn eat_multi_comment(&mut self) -> Result<(), ParseError>
    {
        let mut depth = 1;

        loop
        {
            if self.eof() {
                return self.parse_error(&format!("unexpected end of input inside multi-line comment"));
            }
            else if self.match_str("/*") {
                depth += 1;
            }
            else if self.match_str("*/") {
                depth -= 1;

                if depth == 0 {
                    break
                }
            }
            else
            {
                self.eat_ch();
            }
        }

        Ok(())
    }

    /// Match a single character in the input, no preceding whitespace allowed
    pub fn match_char(&mut self, ch: char) -> bool
    {
        if self.peek_ch() == ch {
            self.eat_ch();
            return true;
        }

        return false;
    }

    /// Check if the input matches a given string
    fn match_str(&mut self, token: &str) -> bool
    {
        let tok_chars: Vec<char> = token.chars().collect();
        let tok_end_idx = self.idx + tok_chars.len();

        if tok_end_idx > self.input.len() {
            return false;
        }

        // If the token matches the input
        if self.input[self.idx .. tok_end_idx] == tok_chars {
            for i in 0..tok_chars.len() {
                self.eat_ch();
            }

            return true;
        }

        false
    }

    /// Expect a token to be present, which can be preceded by whitespace
    fn expect_token(&mut self, token: &str) -> Result<(), ParseError>
    {
        self.eat_ws()?;

        if !self.match_str(token) {
            return self.parse_error(&format!("expected {}", token));
        }

        Ok(())
    }

    /// Parse a decimal integer
    fn parse_int(&mut self) -> Result<i128, ParseError>
    {
        let mut val: i128 = 0;

        let sign = if self.match_str("-") { -1 } else { 1 };

        let mut base = 10;
        if self.match_str("0x") { base = 16 };
        if self.match_str("0b") { base = 2 };

        loop
        {
            let ch = self.eat_ch();

            // There must be at least one digit
            if !ch.is_digit(base) {
                return self.parse_error("expected digit");
            }

            val = (base as i128) * val + (ch.to_digit(base).unwrap() as i128);

            let ch = self.peek_ch();

            // Allow underscores as separators
            if ch == '_' {
                self.eat_ch();
                continue;
            }

            if ch == '\0' {
                break;
            }

            if !ch.is_digit(base) {
                break;
            }
        }

        return Ok(sign * val);
    }

    /// Parse a floating-point number
    fn parse_float<FloatType: std::str::FromStr>(&mut self) -> Result<FloatType, ParseError>
    {
        fn read_digits(input: &mut Input)
        {
            loop
            {
                let ch = input.peek_ch();
                if !ch.is_ascii_digit() {
                    break;
                }
                input.eat_ch();
            }
        }

        fn read_sign(input: &mut Input)
        {
            let _ = input.match_char('+') || input.match_char('-');
        }

        let start_idx = self.idx;

        // Read optional sign
        read_sign(self);

        // Read decimal part
        read_digits(self);

        // Fractional part
        if self.match_char('.') {
            read_digits(self);
        }

        // Exponent
        if self.match_char('e') || self.match_char('E') {
            read_sign(self);
            read_digits(self);
        }

        let end_idx = self.idx;
        let number_str: String = self.input[start_idx..end_idx].iter().collect();

        match number_str.parse::<FloatType>() {
            Ok(float_val) => Ok(float_val),
            Err(_) => self.parse_error("invalid floating-point value")
        }
    }

    /// Parse a string literal
    fn parse_str(&mut self) -> Result<String, ParseError>
    {
        let open_ch = self.eat_ch();
        assert!(open_ch == '"');

        let mut out = String::new();

        loop
        {
            if self.eof() {
                return self.parse_error("unexpected end of input while parsing string literal");
            }

            let ch = self.eat_ch();

            if ch == open_ch {
                break;
            }

            if ch == '\\' {
                match self.eat_ch() {
                    '\\' => out.push('\\'),
                    '\'' => out.push('\''),
                    '\"' => out.push('\"'),
                    't' => out.push('\t'),
                    'r' => out.push('\r'),
                    'n' => out.push('\n'),
                    '0' => out.push('\0'),

                    // Hexadecimal escape sequence
                    'x' => {
                        let digit0 = self.eat_ch().to_digit(16);
                        let digit1 = self.eat_ch().to_digit(16);

                        match (digit0, digit1) {
                            (Some(d0), Some(d1)) => {
                                let byte_val = ((d0 << 4) + d1) as u8;
                                out.push(byte_val as char);
                            }
                            _ => return self.parse_error("invalid hexadecimal escape sequence")
                        }
                    }

                    _ => return self.parse_error("unknown escape sequence")
                }

                continue;
            }

            out.push(ch);
        }

        return Ok(out);
    }

    /// Parse an identifier
    fn parse_ident(&mut self) -> Result<String, ParseError>
    {
        let mut ident = "".to_string();

        loop
        {
            let ch = self.peek_ch();

            if ch == '\0' {
                break;
            }

            if !ch.is_ascii_alphanumeric() && ch != '_' {
                break;
            }

            ident.push(ch);
            self.eat_ch();
        }

        if ident.len() == 0 {
            return self.parse_error("expected identifier");
        }

        Ok(ident)
    }
}

#[derive(Copy, Clone, PartialEq, Debug)]
enum Section
{
    Code,
    Data,
}

#[derive(Copy, Clone)]
struct LabelDef
{
    section: Section,
    pos: usize,
    line_no: usize,
    col_no: usize,
}

#[derive(Copy, Clone)]
enum LabelRefKind
{
    Address32,
    Address64,
    Offset32(usize),
}

struct LabelRef
{
    section: Section,
    name: String,
    pos: usize,
    line_no: usize,
    col_no: usize,
    kind: LabelRefKind
}

pub struct Assembler
{
    /// Map of available special constants
    const_map: HashMap<String, i128>,

    /// Map of available syscalls
    syscall_map: HashMap<String, u16>,

    /// Set of syscalls referenced by this program
    syscall_set: HashSet<u16>,

    // Generated code
    code: MemBlock,

    // Data section
    data: MemBlock,

    /// Label definitions (name, position)
    label_defs: HashMap<String, LabelDef>,

    /// References to labels (name, position)
    label_refs: Vec<LabelRef>,

    /// Current section
    section: Section,
}

impl Assembler
{
    pub fn new() -> Self
    {
        /*
        // Populate the available constants
        use crate::sys::constants::SYSCALL_DESCS;
        let mut const_map = HashMap::new();
        for syscall in SYSCALL_DESCS {
            const_map.insert(
                syscall.name.to_uppercase(),
                syscall.const_idx as i128
            );
        }
        */

        /// Populate the available syscalls
        use crate::sys::constants::SYSCALL_DESCS;
        let mut syscall_map = HashMap::new();
        for syscall in SYSCALL_DESCS {
            if let Some(syscall) = syscall {
                syscall_map.insert(syscall.name.to_string(), syscall.const_idx);
            }
        }

        Self {
            const_map: HashMap::new(),
            syscall_map: syscall_map,
            syscall_set: HashSet::new(),
            code: MemBlock::new(),
            data: MemBlock::new(),
            label_defs: HashMap::default(),
            label_refs: Vec::default(),
            section: Section::Code,
        }
    }

    fn parse_input(mut self, input: &mut Input) -> Result<VM, ParseError>
    {
        // Until we've reached the end of the input
        loop
        {
            input.eat_ws()?;

            if input.eof() {
                break
            }

            self.parse_line(input)?;
        }

        // Link the labels
        for label_ref in self.label_refs {
            let def = self.label_defs.get(&label_ref.name);

            if def.is_none() {
                return Err(ParseError {
                    msg: format!("label not found {}", label_ref.name),
                    line_no: label_ref.line_no,
                    col_no: label_ref.col_no,
                });
            }

            let def = *def.unwrap();

            match label_ref.kind {
                LabelRefKind::Address32 => {
                    let ptr32 = u32::try_from(def.pos);

                    if ptr32.is_err() {
                        return Err(ParseError {
                            msg: format!("address doesn't fit in u32 {}", label_ref.name),
                            line_no: label_ref.line_no,
                            col_no: label_ref.col_no,
                        });
                    }

                    match label_ref.section {
                        Section::Code => self.code.write(label_ref.pos, ptr32.unwrap()),
                        Section::Data => self.data.write(label_ref.pos, ptr32.unwrap()),
                    }
                }

                LabelRefKind::Address64 => {
                    let ptr64 = def.pos as u64;

                    match label_ref.section {
                        Section::Code => self.code.write(label_ref.pos, ptr64),
                        Section::Data => self.data.write(label_ref.pos, ptr64),
                    }
                }

                LabelRefKind::Offset32(end_offset) => {
                    assert!(def.section == Section::Code);
                    assert!(def.section == label_ref.section);
                    let offs32 = (def.pos as i32) - ((label_ref.pos + end_offset) as i32 + 4);

                    match label_ref.section {
                        Section::Code => self.code.write(label_ref.pos, offs32),
                        Section::Data => self.data.write(label_ref.pos, offs32),
                    }
                }
            }
        }

        Ok(VM::new(self.code, self.data, self.syscall_set))
    }

    pub fn parse_file(mut self, file_name: &str) -> Result<VM, ParseError>
    {
        match std::fs::read_to_string(file_name) {
            Err(_) => {
                ParseError::msg_only(&format!("could not open asm file \"{}\"", file_name))
            }
            Ok(input_str) => {
                let mut input = Input::new(input_str);
                self.parse_input(&mut input)
            }
        }
    }

    /// Parse a string of source code
    pub fn parse_str(mut self, src: &str) -> Result<VM, ParseError>
    {
        let mut input = Input::new(src.to_string());
        return self.parse_input(&mut input);
    }

    /// Parse an integer argument
    fn parse_int_arg<T>(&self, input: &mut Input) -> Result<T, ParseError> where T: TryFrom<i128>
    {
        input.eat_ws()?;

        let ch = input.peek_ch();

        // If this is a special constant
        if ch == '$' {
            input.eat_ch();
            let const_name = input.parse_ident()?;

            if let Some(int_val) = self.const_map.get(&const_name) {
                return match (*int_val).try_into() {
                    Ok(out_val) => Ok(out_val),
                    Err(_) => input.parse_error("special constant did not fit required size")
                }
            }
            else
            {
                return input.parse_error(&format!("unknown special constant ${}", const_name));
            }
        }

        // If this is an integer literal
        if ch.is_digit(10) || ch == '-' {
            let int_val = input.parse_int()?;

            return match int_val.try_into() {
                Ok(out_val) => Ok(out_val),
                Err(_) => input.parse_error("integer literal did not fit required size")
            }
        }

        input.parse_error("expected integer argument")
    }

    /// Get the memory block for the current section
    fn mem(&mut self) -> &mut MemBlock
    {
        match self.section {
            Section::Code => &mut self.code,
            Section::Data => &mut self.data,
        }
    }

    /// Add a new label reference at the current position
    fn add_label_ref(&mut self, input: &Input, name: String, kind: LabelRefKind)
    {
        let label_ref_pos = self.mem().len();

        self.label_refs.push(
            LabelRef {
                section: self.section,
                name: name,
                pos: label_ref_pos,
                line_no: input.line_no,
                col_no: input.line_no,
                kind: kind
            }
        );

        match kind {
            LabelRefKind::Address32 => self.mem().push_u32(0),
            LabelRefKind::Address64 => self.mem().push_u64(0),
            LabelRefKind::Offset32(_) => self.mem().push_u32(0),
        }
    }

    /// Parse the current line of the input
    fn parse_line(&mut self, input: &mut Input) -> Result<(), ParseError>
    {
        let ch = input.peek_ch();

        // If this line is empty
        if ch == '\n' {
            input.eat_ch();
            return Ok(());
        }

        // If this is an assembler command
        if ch == '.' {
            input.eat_ch();
            let cmd = input.parse_ident()?;

            input.expect_sep()?;
            input.eat_ws()?;

            self.parse_cmd(input, cmd)?;

            return Ok(());
        }

        // If this is the start of an identifier
        if ch.is_ascii_alphabetic() || ch == '_' {
            let ident = input.parse_ident()?;

            input.expect_sep()?;
            input.eat_ws()?;

            if input.match_str(":") {
                if self.label_defs.get(&ident).is_some() {
                    return input.parse_error(&format!("label already defined {}", ident));
                }

                let label_pos = self.mem().len();
                self.label_defs.insert(
                    ident,
                    LabelDef {
                        section: self.section,
                        pos: label_pos,
                        line_no: input.line_no,
                        col_no: input.col_no,
                    }
                );
            }
            else if self.section == Section::Code
            {
                self.parse_insn(input, ident)?;
            }

            return Ok(());
        }

        input.parse_error("invalid input")
    }

    /// Parse an assembler command
    fn parse_cmd(&mut self, input: &mut Input, cmd: String) -> Result<(), ParseError>
    {
        match cmd.as_str() {
            "code" => self.section = Section::Code,
            "data" => self.section = Section::Data,

            "align" => {
                let align_bytes = self.parse_int_arg::<u32>(input)? as usize;
                let mem = self.mem();
                let cur_pos = mem.len();
                let pos_rem = cur_pos % align_bytes;

                if pos_rem != 0 {
                    let delta = align_bytes - pos_rem;
                    for i in 0..delta {
                        mem.push_u8(0);
                    }
                }
            }

            "zero" => {
                let num_bytes: u32 = self.parse_int_arg(input)?;
                let mem = self.mem();
                for i in 0..num_bytes {
                    mem.push_u8(0);
                }
            }

            "fill" => {
                let num_bytes: u32 = self.parse_int_arg(input)?;

                input.expect_token(",")?;

                let val: u8 = self.parse_int_arg(input)?;
                let mem = self.mem();
                for i in 0..num_bytes {
                    mem.push_u8(val);
                }
            }

            // Unsigned 8-bit integer constant
            "u8" => {
                let val: u8 = self.parse_int_arg(input)?;
                self.mem().push_u8(val);
            }

            // Unsigned 16-bit integer constant
            "u16" => {
                let val: u16 = self.parse_int_arg(input)?;
                self.mem().push_u16(val);
            }

            // Unsigned 32-bit integer constant
            "u32" => {
                let val: u32 = self.parse_int_arg(input)?;
                self.mem().push_u32(val);
            }

            // Unsigned 64-bit integer constant
            "u64" => {
                let val: u64 = self.parse_int_arg(input)?;
                self.mem().push_u64(val);
            }

            // Signed 8-bit integer constant
            "i8" => {
                let val: i8 = self.parse_int_arg(input)?;
                self.mem().push_u8(val as u8);
            }

            // Signed 16-bit integer constant
            "i16" => {
                let val: i16 = self.parse_int_arg(input)?;
                self.mem().push_u16(val as u16);
            }

            // Signed 32-bit integer constant
            "i32" => {
                let val: i32 = self.parse_int_arg(input)?;
                self.mem().push_u32(val as u32);
            }

            // Signed 64-bit integer constant
            "i64" => {
                let val: i64 = self.parse_int_arg(input)?;
                self.mem().push_u64(val as u64);
            }

            // 32-bit floating-point value
            "f32" => {
                let val: f32 = input.parse_float()?;
                let val_u32: u32 = unsafe { transmute(val) };
                self.mem().push_u32(val_u32);
            }

            // Command to read an arbitrary number of bytes
            // with optional whitespace between bytes
            "hex" => {
                loop {
                    let ch0 = input.peek_ch();
                    let digit0 = ch0.to_digit(16);

                    if digit0.is_none() {
                        break;
                    }

                    let digit0 = digit0.unwrap();
                    input.eat_ch();

                    let ch1 = input.peek_ch();
                    let digit1 = ch1.to_digit(16);

                    if digit1.is_none() {
                        return input.parse_error("expected hex digit");
                    }

                    let digit1 = digit1.unwrap();
                    input.eat_ch();

                    let byte_val = ((digit0 << 4) + digit1) as u8;
                    self.mem().push_u8(byte_val);

                    // Allow whitespace between bytes
                    input.eat_ws()?;
                }
            }

            // Null-terminated UTF-8 string
            "stringz" => {
                let val = input.parse_str()?;

                let mem = self.mem();
                for byte in val.bytes() {
                    mem.push_u8(byte);
                }

                // Write a null terminator byte
                mem.push_u8(0);
            }

            // Absolute 64-bit address of a label
            "addr64" => {
                let label_name = input.parse_ident()?;
                self.add_label_ref(input, label_name, LabelRefKind::Address64);
            }

            _ => {
                return input.parse_error(&format!("unknown assembler command \"{}\"", cmd))
            }
        }

        input.expect_token(";")?;

        Ok(())
    }

    /// Parse an instruction and its arguments
    fn parse_insn(&mut self, input: &mut Input, op_name: String) -> Result<(), ParseError>
    {
        match op_name.as_str() {
            "panic" => self.code.push_op(Op::panic),
            "nop" => self.code.push_op(Op::nop),

            "pop" => self.code.push_op(Op::pop),
            "dup" => self.code.push_op(Op::dup),
            "swap" => self.code.push_op(Op::swap),

            "getn" => {
                let n: u8 = self.parse_int_arg(input)?;
                self.code.push_op(Op::getn);
                self.code.push_u8(n);
            }

            "setn" => {
                let n: u8 = self.parse_int_arg(input)?;
                self.code.push_op(Op::setn);
                self.code.push_u8(n);
            }

            "get_arg" => {
                let idx: u8 = self.parse_int_arg(input)?;
                self.code.push_op(Op::get_arg);
                self.code.push_u8(idx);
            }

            "get_var_arg" => {
                self.code.push_op(Op::get_var_arg);
            }

            "set_arg" => {
                let idx: u8 = self.parse_int_arg(input)?;
                self.code.push_op(Op::set_arg);
                self.code.push_u8(idx);
            }

            "get_local" => {
                let idx: u8 = self.parse_int_arg(input)?;
                self.code.push_op(Op::get_local);
                self.code.push_u8(idx);
            }

            "set_local" => {
                let idx: u8 = self.parse_int_arg(input)?;
                self.code.push_op(Op::set_local);
                self.code.push_u8(idx);
            }

            "push_0" => {
                self.code.push_op(Op::push_0);
            }
            "push_1" => {
                self.code.push_op(Op::push_1);
            }
            "push_2" => {
                self.code.push_op(Op::push_2);
            }

            "push_0n" => {
                let n: u8 = self.parse_int_arg(input)?;
                self.code.push_op(Op::push_0n);
                self.code.push_u8(n);
            }

            "push_i8" => {
                let val: i8 = self.parse_int_arg(input)?;
                self.code.push_op(Op::push_i8);
                self.code.push_i8(val);
            }

            "push_u32" => {
                let val: u32 = self.parse_int_arg(input)?;
                self.code.push_op(Op::push_u32);
                self.code.push_u32(val);
            }

            "push_u64" => {
                let val: u64 = self.parse_int_arg(input)?;
                self.code.push_op(Op::push_u64);
                self.code.push_u64(val);
            }

            // Push a pointer to a label
            "push_p32" => {
                let label_name = input.parse_ident()?;
                self.code.push_op(Op::push_u32);
                self.add_label_ref(input, label_name, LabelRefKind::Address32);
            }

            // Push a 32-bit floating-point value
            "push_f32" => {
                let val: f32 = input.parse_float()?;
                let val_u32: u32 = unsafe { transmute(val) };
                self.code.push_op(Op::push_u32);
                self.code.push_u32(val_u32);
            }

            // Variable-size push
            "push" => {
                self.gen_push(input)?;
            }

            "and_u32" => self.code.push_op(Op::and_u32),
            "or_u32" => self.code.push_op(Op::or_u32),
            "xor_u32" => self.code.push_op(Op::xor_u32),
            "not_u32" => self.code.push_op(Op::not_u32),
            "lshift_u32" => self.code.push_op(Op::lshift_u32),
            "rshift_u32" => self.code.push_op(Op::rshift_u32),
            "rshift_i32" => self.code.push_op(Op::rshift_i32),

            "add_u32" => self.code.push_op(Op::add_u32),
            "sub_u32" => self.code.push_op(Op::sub_u32),
            "mul_u32" => self.code.push_op(Op::mul_u32),
            "div_u32" => self.code.push_op(Op::div_u32),
            "mod_u32" => self.code.push_op(Op::mod_u32),
            "div_i32" => self.code.push_op(Op::div_i32),
            "mod_i32" => self.code.push_op(Op::mod_i32),

            "eq_u32" => self.code.push_op(Op::eq_u32),
            "ne_u32" => self.code.push_op(Op::ne_u32),
            "lt_u32" => self.code.push_op(Op::lt_u32),
            "le_u32" => self.code.push_op(Op::le_u32),
            "gt_u32" => self.code.push_op(Op::gt_u32),
            "ge_u32" => self.code.push_op(Op::ge_u32),
            "lt_i32" => self.code.push_op(Op::lt_i32),
            "le_i32" => self.code.push_op(Op::le_i32),
            "gt_i32" => self.code.push_op(Op::gt_i32),
            "ge_i32" => self.code.push_op(Op::ge_i32),

            "and_u64" => self.code.push_op(Op::and_u64),
            "or_u64" => self.code.push_op(Op::or_u64),
            "xor_u64" => self.code.push_op(Op::xor_u64),
            "not_u64" => self.code.push_op(Op::not_u64),
            "lshift_u64" => self.code.push_op(Op::lshift_u64),
            "rshift_u64" => self.code.push_op(Op::rshift_u64),
            "rshift_i64" => self.code.push_op(Op::rshift_i64),

            "add_u64" => self.code.push_op(Op::add_u64),
            "sub_u64" => self.code.push_op(Op::sub_u64),
            "mul_u64" => self.code.push_op(Op::mul_u64),
            "div_u64" => self.code.push_op(Op::div_u64),
            "mod_u64" => self.code.push_op(Op::mod_u64),
            "div_i64" => self.code.push_op(Op::div_i64),
            "mod_i64" => self.code.push_op(Op::mod_i64),

            "eq_u64" => self.code.push_op(Op::eq_u64),
            "ne_u64" => self.code.push_op(Op::ne_u64),
            "lt_u64" => self.code.push_op(Op::lt_u64),
            "le_u64" => self.code.push_op(Op::le_u64),
            "gt_u64" => self.code.push_op(Op::gt_u64),
            "ge_u64" => self.code.push_op(Op::ge_u64),
            "lt_i64" => self.code.push_op(Op::lt_i64),
            "le_i64" => self.code.push_op(Op::le_i64),
            "gt_i64" => self.code.push_op(Op::gt_i64),
            "ge_i64" => self.code.push_op(Op::ge_i64),

            "sx_i8_i32" => self.code.push_op(Op::sx_i8_i32),
            "sx_i8_i64" => self.code.push_op(Op::sx_i8_i64),
            "sx_i16_i32" => self.code.push_op(Op::sx_i16_i32),
            "sx_i16_i64" => self.code.push_op(Op::sx_i16_i64),
            "sx_i32_i64" => self.code.push_op(Op::sx_i32_i64),

            "trunc_u8" => self.code.push_op(Op::trunc_u8),
            "trunc_u16" => self.code.push_op(Op::trunc_u16),
            "trunc_u32" => self.code.push_op(Op::trunc_u32),

            "add_f32" => self.code.push_op(Op::add_f32),
            "sub_f32" => self.code.push_op(Op::sub_f32),
            "mul_f32" => self.code.push_op(Op::mul_f32),
            "div_f32" => self.code.push_op(Op::div_f32),

            "sin_f32" => self.code.push_op(Op::sin_f32),
            "cos_f32" => self.code.push_op(Op::cos_f32),
            "tan_f32" => self.code.push_op(Op::tan_f32),
            "asin_f32" => self.code.push_op(Op::asin_f32),
            "acos_f32" => self.code.push_op(Op::acos_f32),
            "atan_f32" => self.code.push_op(Op::atan_f32),
            "pow_f32" => self.code.push_op(Op::pow_f32),
            "sqrt_f32" => self.code.push_op(Op::sqrt_f32),

            "eq_f32" => self.code.push_op(Op::eq_f32),
            "ne_f32" => self.code.push_op(Op::ne_f32),
            "lt_f32" => self.code.push_op(Op::lt_f32),
            "le_f32" => self.code.push_op(Op::le_f32),
            "gt_f32" => self.code.push_op(Op::gt_f32),
            "ge_f32" => self.code.push_op(Op::ge_f32),

            "i32_to_f32" => self.code.push_op(Op::i32_to_f32),
            "i64_to_f32" => self.code.push_op(Op::i64_to_f32),
            "f32_to_i32" => self.code.push_op(Op::f32_to_i32),

            "load_u8" => self.code.push_op(Op::load_u8),
            "load_u16" => self.code.push_op(Op::load_u16),
            "load_u32" => self.code.push_op(Op::load_u32),
            "load_u64" => self.code.push_op(Op::load_u64),
            "store_u8" => self.code.push_op(Op::store_u8),
            "store_u16" => self.code.push_op(Op::store_u16),
            "store_u32" => self.code.push_op(Op::store_u32),
            "store_u64" => self.code.push_op(Op::store_u64),

            "jmp" => {
                self.code.push_op(Op::jmp);
                let label_name = input.parse_ident()?;
                self.add_label_ref(input, label_name, LabelRefKind::Offset32(0));
            }

            "jz" => {
                self.code.push_op(Op::jz);
                let label_name = input.parse_ident()?;
                self.add_label_ref(input, label_name, LabelRefKind::Offset32(0));
            }

            "jnz" => {
                self.code.push_op(Op::jnz);
                let label_name = input.parse_ident()?;
                self.add_label_ref(input, label_name, LabelRefKind::Offset32(0));
            }

            "syscall" => {
                // Get the index for this syscall
                let syscall_idx: u16 = if input.peek_ch().is_ascii_alphabetic() {
                    let name = input.parse_ident()?;
                    match self.syscall_map.get(&name) {
                        Some(syscall_idx) => *syscall_idx,
                        None => return input.parse_error(
                            &format!("unknown syscall \"{}\"", name)
                        )
                    }
                }
                else
                {
                    self.parse_int_arg(input)?
                };

                self.syscall_set.insert(syscall_idx);
                self.code.push_op(Op::syscall);
                self.code.push_u16(syscall_idx);
            }

            // Call label
            "call" => {
                let label_name = input.parse_ident()?;
                input.expect_token(",")?;
                let argc: u8 = self.parse_int_arg(input)?;

                self.code.push_op(Op::call);
                self.add_label_ref(input, label_name, LabelRefKind::Offset32(1));
                self.code.push_u8(argc);
            }

            // Call function pointer
            "call_fp" => {
                let argc: u8 = self.parse_int_arg(input)?;
                self.code.push_op(Op::call_fp);
                self.code.push_u8(argc);
            }

            "ret" => self.code.push_op(Op::ret),
            "exit" => self.code.push_op(Op::exit),

            _ => {
                return input.parse_error(&format!("unknown instruction opcode \"{}\"", op_name))
            }
        }

        input.expect_token(";")?;

        Ok(())
    }

    // Convenient push mnemonic that automatically infers
    // the right push instruction to use based on the operand
    fn gen_push(&mut self, input: &mut Input) -> Result<(), ParseError>
    {
        let ch = input.peek_ch();

        // If this is a decimal integer
        if ch.is_digit(10) || ch == '-' {
            let int_val = input.parse_int()?;

            if int_val == 0 {
                self.code.push_op(Op::push_0);
            }
            else if int_val == 1 {
                self.code.push_op(Op::push_1);
            }
            else if int_val == 2 {
                self.code.push_op(Op::push_2);
            }
            else if let Ok(val) = i8::try_from(int_val) {
                self.code.push_op(Op::push_i8);
                self.code.push_i8(val);
            }
            else if let Ok(val) = u32::try_from(int_val) {
                self.code.push_op(Op::push_u32);
                self.code.push_u32(val);
            }
            else if let Ok(val) = u64::try_from(int_val) {
                self.code.push_op(Op::push_u64);
                self.code.push_u64(val);
            }
            else if let Ok(val) = i64::try_from(int_val) {
                self.code.push_op(Op::push_u64);
                self.code.push_u64(val as u64);
            }
            else
            {
                return input.parse_error("integer literal did not fit required size");
            }

            return Ok(());
        }

        // Assume that this must be a label reference
        let label_name = input.parse_ident()?;
        self.code.push_op(Op::push_u32);
        self.add_label_ref(input, label_name, LabelRefKind::Address32);

        Ok(())
    }
}

#[cfg(test)]
mod tests
{
    use super::*;

    fn parse_ok(src: &str)
    {
        dbg!(src);
        let asm = Assembler::new();
        asm.parse_str(src).unwrap();
    }

    fn parse_fails(src: &str)
    {
        dbg!(src);
        let asm = Assembler::new();
        assert!(asm.parse_str(src).is_err());
    }

    fn parse_file(file_name: &str)
    {
        dbg!(file_name);
        let asm = Assembler::new();
        assert!(asm.parse_file(file_name).is_ok());
    }

    #[test]
    fn test_basics()
    {
        // Basics
        parse_ok("");
        parse_ok("#!/usr/bin/uvm\nret;");
        parse_ok("# comment");
        parse_ok("// comment");
        parse_ok("/* comment */");
        parse_ok("/* nested /* little */ comment */");
        parse_ok("push_i8  0 ; # comment");
        parse_ok("push_i8 /*comment!*/ 0; // comment");
        parse_ok(".code;\npush_u32 0xFFFFFFFF;");
        parse_ok(".code; push_u32 1_000_000;");
        parse_ok(".code; push_i8 55; push_i8 -1;");
    }

    #[test]
    fn test_floats()
    {
        parse_ok(".f32 123;");
        parse_ok(".f32 +123;");
        parse_ok(".f32 -123;");
        parse_ok(".f32 -123.456;");
        parse_ok(".f32 123e10;");
        parse_ok(".f32 1E+10;");
        parse_ok(".f32 123.456e10;");
        parse_ok(".f32 123.456e+10;");
        parse_ok(".f32 123.456e-10;");
        parse_ok(".code; push_f32 3.5;");

        parse_fails(".f32 123e10.5;");
        parse_fails(".f32 123 e10.5;");
        parse_fails(".f32 123e;");
        parse_fails(".f32 ++123;");
        parse_fails(".f32 123..456;");
    }

    #[test]
    fn test_hex()
    {
        parse_ok(".hex FF;");
        parse_ok(".hex ffaabbcc;");
        parse_ok(".hex FF AA BB CC 09;");
        parse_ok(".hex FFAABBCC09;");
        parse_ok(".hex\nFF AA\nBB CC\n09;");

        parse_fails(".hex F;");
        parse_fails(".hex FAB;");
    }

    #[test]
    fn test_labels()
    {
        // Labels
        parse_ok("FOO:");
        parse_ok("_FOO_:");
        parse_ok("FOO: BAR:");
        parse_ok("FOO: #Label\n BAR:");
        parse_ok("FOO: push_i8 55; push_i8 55; eq_u64; jnz FOO;");
        parse_ok("FOO: push_i8 55; push_i8 55; eq_u64; jz FOO;");
        parse_ok(" FOO_BAR:   jmp  FOO_BAR; ");

        // Callback label
        parse_ok("CB: ret; push_p32 CB; exit;");
    }

    #[test]
    fn test_strings()
    {
        parse_ok(".data; .stringz \"foo\";");
        parse_ok(".data; .stringz \"foo\\nbar\";");
        parse_ok(".data; .stringz \"foo\\nbar\\xAA\";");
    }

    #[test]
    fn test_data()
    {
        // Data section
        parse_ok(".code;");
        parse_ok(".code; .data;");
        parse_ok(".data; .u8 255;");
        parse_ok(".data; .u64 7777;");
        parse_ok(".data; .align 64; .u64 255;");
        parse_ok(".data; DATA_LABEL: .zero 256;");
        parse_ok(" .data;   .fill 256   ,   0xFF ;   #comment");
        parse_ok(" .data; .fill 256,0xFF;");
        parse_ok(".data; .zero 512; .code; push_u32 0xFFFF; push_i8 7; add_u64;");
        parse_ok(" .data; #comment .fill 256, 0xFF; .code; push_u64 777; #comment");
        parse_ok(".data; DATA_LABEL: .fill 256, 0xFF; .code; push_p32 DATA_LABEL;");
        parse_ok(".data; STR_LABEL: .stringz \"hi!\"; .code; push_p32 STR_LABEL;");
    }

    #[test]
    fn test_invalid()
    {
        // Failing parses
        parse_fails("/*");
        parse_fails("1");
        parse_fails(";");
        parse_fails("_?:");
        parse_fails(".fill 256 ,, 0xFF;");
        parse_fails(".code.zero 512");
        parse_fails(".data .u640");
        parse_fails(". code");
        parse_fails("FOO: FOO: jmp FOO;");
        parse_fails("FOO: jmp BAR;");
        parse_fails("push_i8 555");
        parse_fails("push_i855;");
        parse_fails("push_i8 55; comment without hash");
    }

    #[test]
    fn parse_files()
    {
        parse_file("examples/empty.asm");
        parse_file("examples/factorial.asm");
        parse_file("examples/fib.asm");
        parse_file("examples/fizzbuzz.asm");
        parse_file("examples/loop.asm");
        parse_file("examples/memcpy.asm");
        parse_file("examples/gradient.asm");
        parse_file("examples/circle.asm");
    }
}