able-script/ablescript/src/parser.rs
2022-04-18 21:43:32 +02:00

822 lines
27 KiB
Rust

//! AbleScript Parser
//!
//! Type of this parser is recursive descent
use crate::ast::*;
use crate::error::{Error, ErrorKind};
use crate::lexer::Token;
use logos::{Lexer, Logos};
/// Parser structure which holds lexer and metadata
///
/// Make one using [`Parser::new`] function
pub struct Parser<'source> {
lexer: Lexer<'source, Token>,
tdark: bool,
}
impl<'source> Parser<'source> {
/// Create a new parser from source code
pub fn new(source: &'source str) -> Self {
Self {
lexer: Token::lexer(source),
tdark: false,
}
}
/// Start parsing tokens
///
/// Loops trough lexer, parses statements, returns AST
pub fn init(&mut self) -> Result<Block, Error> {
let mut ast = vec![];
while let Some(token) = self.lexer.next() {
match token {
// Ignore comments
Token::Comment => continue,
// T-Dark block (replace `lang` with `script`)
Token::TDark => ast.extend(self.tdark_flow()?),
token => ast.push(self.parse(token)?),
}
}
Ok(ast)
}
/// Get next item
///
/// If EOF, return Error instead of None
fn checked_next(&mut self) -> Result<Token, Error> {
loop {
match self
.lexer
.next()
.ok_or_else(|| Error::unexpected_eof(self.lexer.span().start))?
{
Token::Comment => (),
token => break Ok(token),
}
}
}
/// Parse a token
///
/// This function will route to corresponding flow functions
/// which may advance the lexer iterator
fn parse(&mut self, token: Token) -> Result<Spanned<Stmt>, Error> {
let start = self.lexer.span().start;
match token {
Token::Unless => Ok(Spanned::new(
self.unless_flow()?,
start..self.lexer.span().end,
)),
Token::Functio => Ok(Spanned::new(
self.functio_flow()?,
start..self.lexer.span().end,
)),
Token::Bff => Ok(Spanned::new(self.bff_flow()?, start..self.lexer.span().end)),
Token::Dim => Ok(Spanned::new(self.dim_flow()?, start..self.lexer.span().end)),
Token::Melo => Ok(Spanned::new(
self.melo_flow()?,
start..self.lexer.span().end,
)),
Token::Loop => Ok(Spanned::new(
self.loop_flow()?,
start..self.lexer.span().end,
)),
Token::Break => Ok(Spanned::new(
self.semicolon_terminated(Stmt::Break)?,
start..self.lexer.span().end,
)),
Token::HopBack => Ok(Spanned::new(
self.semicolon_terminated(Stmt::HopBack)?,
start..self.lexer.span().end,
)),
Token::Rlyeh => Ok(Spanned::new(
self.semicolon_terminated(Stmt::Rlyeh)?,
start..self.lexer.span().end,
)),
Token::Rickroll => Ok(Spanned::new(
self.semicolon_terminated(Stmt::Rickroll)?,
start..self.lexer.span().end,
)),
Token::Identifier(_)
| Token::String(_)
| Token::Integer(_)
| Token::Char(_)
| Token::Aint
| Token::LeftBracket
| Token::LeftParen => Ok(Spanned::new(
self.value_flow(token)?,
start..self.lexer.span().end,
)),
t => Err(Error {
kind: ErrorKind::UnexpectedToken(t),
span: start..self.lexer.span().end,
}),
}
}
/// Require statement to be semicolon terminated
///
/// Utility function for short statements
fn semicolon_terminated(&mut self, stmt_kind: Stmt) -> Result<Stmt, Error> {
self.require(Token::Semicolon)?;
Ok(stmt_kind)
}
/// Require next item to be equal with expected one
fn require(&mut self, required: Token) -> Result<(), Error> {
match self.checked_next()? {
t if t == required => Ok(()),
t => Err(Error::new(ErrorKind::UnexpectedToken(t), self.lexer.span())),
}
}
/// Get an Identifier
fn get_ident(&mut self) -> Result<Spanned<String>, Error> {
match self.checked_next()? {
Token::Identifier(ident) => Ok(Spanned::new(
if self.tdark {
ident.replace("lang", "script")
} else {
ident
},
self.lexer.span(),
)),
t => Err(Error::new(ErrorKind::UnexpectedToken(t), self.lexer.span())),
}
}
/// Parse an expression
///
/// AbleScript strongly separates expressions from statements.
/// Expressions do not have any side effects and the are
/// only mathematial and logical operations or values.
fn parse_expr(
&mut self,
token: Token,
buf: &mut Option<Spanned<Expr>>,
) -> Result<Spanned<Expr>, Error> {
let start = match buf {
Some(e) => e.span.start,
None => self.lexer.span().start,
};
match token {
// Values
Token::Identifier(i) => Ok(Spanned::new(
Expr::Variable(if self.tdark {
i.replace("lang", "script")
} else {
i
}),
start..self.lexer.span().end,
)),
Token::Integer(i) => Ok(Spanned::new(
Expr::Literal(Literal::Int(i)),
start..self.lexer.span().end,
)),
Token::String(s) => Ok(Spanned::new(
Expr::Literal(Literal::Str(if self.tdark {
s.replace("lang", "script")
} else {
s
})),
start..self.lexer.span().end,
)),
Token::Char(c) => Ok(Spanned::new(
Expr::Literal(Literal::Char(c)),
start..self.lexer.span().end,
)),
Token::LeftBracket => match buf.take() {
Some(buf) => Ok(Spanned::new(
self.index_flow(buf)?,
start..self.lexer.span().end,
)),
None => Ok(Spanned::new(
self.cart_flow()?,
start..self.lexer.span().end,
)),
},
// Operations
Token::Aint if buf.is_none() => Ok(Spanned::new(
{
let next = self.checked_next()?;
Expr::Aint(Box::new(self.parse_expr(next, buf)?))
},
start..self.lexer.span().end,
)),
Token::Plus
| Token::Minus
| Token::Star
| Token::FwdSlash
| Token::Equals
| Token::LessThan
| Token::GreaterThan
| Token::Aint => Ok(Spanned::new(
self.binop_flow(
BinOpKind::from_token(token).map_err(|e| Error::new(e, self.lexer.span()))?,
buf,
)?,
start..self.lexer.span().end,
)),
Token::LeftParen => self.expr_flow(Token::RightParen),
t => Err(Error::new(ErrorKind::UnexpectedToken(t), self.lexer.span())),
}
}
/// Flow for creating carts
fn cart_flow(&mut self) -> Result<Expr, Error> {
let mut cart = vec![];
let mut buf = None;
match self.checked_next()? {
Token::RightBracket => (),
t => {
buf = Some(self.parse_expr(t, &mut buf)?);
'cart: loop {
let value = loop {
match self.checked_next()? {
Token::Arrow => break buf.take(),
t => buf = Some(self.parse_expr(t, &mut buf)?),
}
}
.ok_or_else(|| {
Error::new(ErrorKind::UnexpectedToken(Token::Arrow), self.lexer.span())
})?;
let key = loop {
match self.checked_next()? {
Token::RightBracket => {
cart.push((
value,
buf.take().ok_or_else(|| {
Error::unexpected_eof(self.lexer.span().start)
})?,
));
break 'cart;
}
Token::Comma => break buf.take(),
t => buf = Some(self.parse_expr(t, &mut buf)?),
}
}
.ok_or_else(|| Error::unexpected_eof(self.lexer.span().start))?;
cart.push((value, key));
}
}
}
Ok(Expr::Cart(cart))
}
/// Flow for indexing operations
///
/// Indexing with empty index resolves to length of expression, else it indexes
fn index_flow(&mut self, expr: Spanned<Expr>) -> Result<Expr, Error> {
let mut buf = None;
Ok(loop {
match self.checked_next()? {
Token::RightBracket => match buf {
Some(index) => {
break Expr::Index {
expr: Box::new(expr),
index: Box::new(index),
}
}
None => break Expr::Len(Box::new(expr)),
},
token => buf = Some(self.parse_expr(token, &mut buf)?),
}
})
}
/// Flow for operators
///
/// Generates operation from LHS buffer and next expression as RHS
///
/// This is unaware of precedence, as AbleScript do not have it
fn binop_flow(
&mut self,
kind: BinOpKind,
lhs: &mut Option<Spanned<Expr>>,
) -> Result<Expr, Error> {
Ok(Expr::BinOp {
lhs: Box::new(
lhs.take()
.ok_or_else(|| Error::new(ErrorKind::MissingLhs, self.lexer.span()))?,
),
rhs: {
let next = self
.lexer
.next()
.ok_or_else(|| Error::unexpected_eof(self.lexer.span().start))?;
Box::new(self.parse_expr(next, &mut None)?)
},
kind,
})
}
/// Parse expressions until terminate token
fn expr_flow(&mut self, terminate: Token) -> Result<Spanned<Expr>, Error> {
let mut buf = None;
Ok(loop {
match self.checked_next()? {
t if t == terminate => {
break buf.take().ok_or_else(|| {
Error::new(ErrorKind::UnexpectedToken(t), self.lexer.span())
})?
}
t => buf = Some(self.parse_expr(t, &mut buf)?),
}
})
}
/// Parse a list of statements between curly braces
fn get_block(&mut self) -> Result<Block, Error> {
self.require(Token::LeftCurly)?;
let mut block = vec![];
loop {
match self.checked_next()? {
Token::RightCurly => break,
Token::TDark => block.extend(self.tdark_flow()?),
t => block.push(self.parse(t)?),
}
}
Ok(block)
}
/// Parse T-Dark block
fn tdark_flow(&mut self) -> Result<Block, Error> {
self.tdark = true;
let block = self.get_block();
self.tdark = false;
block
}
/// If Statement parser gets any kind of value (Identifier or Literal)
/// It cannot parse it as it do not parse expressions. Instead of it it
/// will parse it to function call or print statement.
fn value_flow(&mut self, init: Token) -> Result<Stmt, Error> {
let mut buf = Some(self.parse_expr(init, &mut None)?);
let r = loop {
match self.checked_next()? {
// Print to stdout
Token::Print => {
let stmt = Stmt::Print(buf.take().ok_or_else(|| {
Error::new(ErrorKind::UnexpectedToken(Token::Print), self.lexer.span())
})?);
break self.semicolon_terminated(stmt)?;
}
// Functio call
Token::LeftParen => {
break self.functio_call_flow(buf.take().ok_or_else(|| {
Error::new(
ErrorKind::UnexpectedToken(Token::LeftParen),
self.lexer.span(),
)
})?)?;
}
// Variable Assignment
Token::Assign => {
return match buf.take() {
Some(expr) => self.assignment_flow(expr),
None => Err(Error::new(
ErrorKind::UnexpectedToken(Token::Assign),
self.lexer.span(),
)),
}
}
// Read input
Token::Read => {
if let Some(Ok(assignable)) = buf.take().map(Assignable::from_expr) {
self.require(Token::Semicolon)?;
break Stmt::Read(assignable);
} else {
return Err(Error::new(
ErrorKind::UnexpectedToken(Token::Read),
self.lexer.span(),
));
}
}
t => buf = Some(self.parse_expr(t, &mut buf)?),
}
};
Ok(r)
}
/// Parse Unless flow
///
/// Consists of condition and block, there is no else
fn unless_flow(&mut self) -> Result<Stmt, Error> {
self.require(Token::LeftParen)?;
Ok(Stmt::Unless {
cond: self.expr_flow(Token::RightParen)?,
body: self.get_block()?,
})
}
/// Parse functio flow
///
/// functio $ident (a, b, c) { ... }
fn functio_flow(&mut self) -> Result<Stmt, Error> {
let ident = self.get_ident()?;
self.require(Token::LeftParen)?;
let mut params = vec![];
loop {
match self.checked_next()? {
Token::RightParen => break,
Token::Identifier(i) => {
params.push(Spanned::new(i, self.lexer.span()));
// Require comma (next) or right paren (end) after identifier
match self.checked_next()? {
Token::Comma => continue,
Token::RightParen => break,
t => {
return Err(Error::new(
ErrorKind::UnexpectedToken(t),
self.lexer.span(),
))
}
}
}
t => return Err(Error::new(ErrorKind::UnexpectedToken(t), self.lexer.span())),
}
}
let body = self.get_block()?;
Ok(Stmt::Functio {
ident,
params,
body,
})
}
/// Parse BF function declaration
///
/// `bff $ident ([tapelen]) { ... }`
fn bff_flow(&mut self) -> Result<Stmt, Error> {
let ident = self.get_ident()?;
let tape_len = match self.checked_next()? {
Token::LeftParen => {
let len = Some(self.expr_flow(Token::RightParen)?);
self.require(Token::LeftCurly)?;
len
}
Token::LeftCurly => None,
token => {
return Err(Error::new(
ErrorKind::UnexpectedToken(token),
self.lexer.span(),
))
}
};
let mut code: Vec<u8> = vec![];
loop {
match self.checked_next()? {
Token::Plus
| Token::Minus
| Token::Comma
| Token::LeftBracket
| Token::RightBracket
| Token::LessThan
| Token::GreaterThan => code.push(self.lexer.slice().as_bytes()[0]),
Token::RightCurly => break,
_ => (),
}
}
Ok(Stmt::BfFunctio {
ident,
tape_len,
code,
})
}
/// Parse functio call flow
fn functio_call_flow(&mut self, expr: Spanned<Expr>) -> Result<Stmt, Error> {
let mut args = vec![];
let mut buf = None;
loop {
match self.checked_next()? {
// End of argument list
Token::RightParen => {
if let Some(expr) = buf.take() {
args.push(expr)
}
break;
}
// Next argument
Token::Comma => match buf.take() {
Some(expr) => args.push(expr),
// Comma alone
None => {
return Err(Error::new(
ErrorKind::UnexpectedToken(Token::Comma),
self.lexer.span(),
))
}
},
t => buf = Some(self.parse_expr(t, &mut buf)?),
}
}
self.require(Token::Semicolon)?;
Ok(Stmt::Call { expr, args })
}
/// Parse variable declaration
fn dim_flow(&mut self) -> Result<Stmt, Error> {
let ident = self.get_ident()?;
let mut init = None;
loop {
match self.checked_next()? {
Token::Semicolon => break,
t => init = Some(self.parse_expr(t, &mut init)?),
}
}
Ok(Stmt::Dim { ident, init })
}
/// Parse assignment to assignable
fn assignment_flow(&mut self, value: Spanned<Expr>) -> Result<Stmt, Error> {
let ident = self.get_ident()?;
let kind = match self.checked_next()? {
Token::Semicolon => AssignableKind::Variable,
Token::LeftBracket => {
let mut indices = vec![];
loop {
indices.push(self.expr_flow(Token::RightBracket)?);
match self.checked_next()? {
Token::Semicolon => break AssignableKind::Index { indices },
Token::LeftBracket => (),
t => {
return Err(Error::new(
ErrorKind::UnexpectedToken(t),
self.lexer.span(),
))
}
}
}
}
t => return Err(Error::new(ErrorKind::UnexpectedToken(t), self.lexer.span())),
};
Ok(Stmt::Assign {
assignable: Assignable { ident, kind },
value,
})
}
/// Parse Melo flow
fn melo_flow(&mut self) -> Result<Stmt, Error> {
let ident = self.get_ident()?;
self.semicolon_terminated(Stmt::Melo(ident))
}
/// Parse loop flow
///
/// `loop` is an infinite loop, no condition, only body
fn loop_flow(&mut self) -> Result<Stmt, Error> {
Ok(Stmt::Loop {
body: self.get_block()?,
})
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn simple_math() {
let code = "1 * (num + 3) / 666 print;";
let expected = &[Spanned {
item: Stmt::Print(Spanned {
item: Expr::BinOp {
lhs: Box::new(Spanned {
item: Expr::BinOp {
lhs: Box::new(Spanned {
item: Expr::Literal(Literal::Int(1)),
span: 0..1,
}),
rhs: Box::new(Spanned {
item: Expr::BinOp {
lhs: Box::new(Spanned {
item: Expr::Variable("num".to_owned()),
span: 5..6,
}),
rhs: Box::new(Spanned {
item: Expr::Literal(Literal::Int(3)),
span: 9..10,
}),
kind: BinOpKind::Add,
},
span: 5..10,
}),
kind: BinOpKind::Multiply,
},
span: 0..11,
}),
rhs: Box::new(Spanned {
item: Expr::Literal(Literal::Int(666)),
span: 14..17,
}),
kind: BinOpKind::Divide,
},
span: 0..17,
}),
span: 0..24,
}];
let ast = Parser::new(code).init().unwrap();
assert_eq!(ast, expected);
}
#[test]
fn variable_declaration() {
let code = "dim var 42;";
let expected = &[Spanned {
item: Stmt::Dim {
ident: Spanned {
item: "var".to_owned(),
span: 4..5,
},
init: Some(Spanned {
item: Expr::Literal(Literal::Int(42)),
span: 8..10,
}),
},
span: 0..11,
}];
let ast = Parser::new(code).init().unwrap();
assert_eq!(ast, expected);
}
#[test]
fn unless_flow() {
let code = "unless (never + never) { /*Buy Able products!*/ print; }";
let expected = &[Spanned {
item: Stmt::Unless {
cond: Spanned {
item: Expr::BinOp {
lhs: Box::new(Spanned {
item: Expr::Variable("never".to_owned()),
span: 8..13,
}),
rhs: Box::new(Spanned {
item: Expr::Variable("never".to_owned()),
span: 16..21,
}),
kind: BinOpKind::Add,
},
span: 8..21,
},
body: vec![Spanned {
item: Stmt::Print(Spanned {
item: Expr::Literal(Literal::Str("Buy Able products!".to_owned())),
span: 25..47,
}),
span: 25..54,
}],
},
span: 0..56,
}];
let ast = Parser::new(code).init().unwrap();
assert_eq!(ast, expected);
}
#[test]
fn tdark() {
let code = "T-Dark { dim lang /*lang*/ + lang; }";
let expected = &[Spanned {
item: Stmt::Dim {
ident: Spanned {
item: "script".to_owned(),
span: 13..17,
},
init: Some(Spanned {
item: Expr::BinOp {
lhs: Box::new(Spanned {
item: Expr::Literal(Literal::Str("script".to_owned())),
span: 20..26,
}),
rhs: Box::new(Spanned {
item: Expr::Variable("script".to_owned()),
span: 29..33,
}),
kind: BinOpKind::Add,
},
span: 20..33,
}),
},
span: 9..34,
}];
let ast = Parser::new(code).init().unwrap();
assert_eq!(ast, expected);
}
#[test]
fn cart_construction() {
let code = "[/*able*/ <= 1, /*script*/ <= 3 - 1] print;";
let expected = &[Spanned {
item: Stmt::Print(Spanned {
item: Expr::Cart(vec![
(
Spanned {
item: Expr::Literal(Literal::Str("able".to_owned())),
span: 1..7,
},
Spanned {
item: Expr::Literal(Literal::Int(1)),
span: 11..12,
},
),
(
Spanned {
item: Expr::Literal(Literal::Str("script".to_owned())),
span: 14..22,
},
Spanned {
item: Expr::BinOp {
kind: BinOpKind::Subtract,
lhs: Box::new(Spanned {
item: Expr::Literal(Literal::Int(3)),
span: 26..27,
}),
rhs: Box::new(Spanned {
item: Expr::Literal(Literal::Int(1)),
span: 30..31,
}),
},
span: 26..31,
},
),
]),
span: 0..32,
}),
span: 0..39,
}];
let ast = Parser::new(code).init().unwrap();
assert_eq!(ast, expected);
}
#[test]
fn cart_index() {
let code = "[/*able*/ <= /*ablecorp*/][/*ablecorp*/] print;";
let expected = &[Spanned {
item: Stmt::Print(Spanned {
item: Expr::Index {
expr: Box::new(Spanned {
item: Expr::Cart(vec![(
Spanned {
item: Expr::Literal(Literal::Str("able".to_owned())),
span: 1..7,
},
Spanned {
item: Expr::Literal(Literal::Str("ablecorp".to_owned())),
span: 11..21,
},
)]),
span: 0..22,
}),
index: Box::new(Spanned {
item: Expr::Literal(Literal::Str("ablecorp".to_owned())),
span: 23..33,
}),
},
span: 0..34,
}),
span: 0..41,
}];
let ast = Parser::new(code).init().unwrap();
assert_eq!(ast, expected);
}
}