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use crate::error::RadError;
use crate::consts::*;
pub struct Lexor {
previous_char : Option<char>,
pub cursor: Cursor,
pub escape_next : bool,
pub lit_count: usize,
pub paren_count : usize,
pub escape_nl : bool,
}
impl Lexor {
pub fn new() -> Self {
Lexor {
previous_char : None,
cursor: Cursor::None,
escape_next : false,
escape_nl : false,
lit_count : 0,
paren_count : 0,
}
}
pub fn reset(&mut self) {
self.previous_char = None;
self.cursor= Cursor::None;
self.escape_next = false;
self.escape_nl = false;
self.paren_count = 0;
// CHECK TODO is it necessary?
// Don't reset literal
}
pub fn lex(&mut self, ch: char) -> Result<LexResult, RadError> {
let result: LexResult;
if self.start_literal(ch) {
self.previous_char.replace('0');
return Ok(LexResult::Literal(self.cursor));
} else if self.end_literal(ch){
self.previous_char.replace('0');
return Ok(LexResult::Literal(self.cursor));
} else if self.lit_count >0 {
self.previous_char.replace(ch);
return Ok(LexResult::Literal(self.cursor));
}
match self.cursor {
Cursor::None => {
result = self.branch_none(ch);
},
Cursor::Name => {
result = self.branch_name(ch);
}
Cursor::NameToArg => {
result = self.branch_name_to_arg(ch);
}
Cursor::Arg => {
result = self.branch_arg(ch);
} // end arg match
}
let replace = ch;
// Reserved for later usage
// Don't set previous as it is when double ESCAPE_CHAR is used.
//if ch == ESCAPE_CHAR && self.previous_char.unwrap_or('0') == ESCAPE_CHAR {
//replace = '0';
//}
self.previous_char.replace(replace);
Ok(result)
}
fn branch_none(&mut self, ch: char) -> LexResult {
let result: LexResult;
if ch == MACRO_START_CHAR
&& self.previous_char.unwrap_or('0') != ESCAPE_CHAR
{
self.cursor = Cursor::Name;
result = LexResult::Ignore;
self.escape_nl = false;
}
// This applies to cases where new lines comes after invocation
// e.g. $define(..) \n
// in this case last \n is ignored and deleted
// escape_nl is only set after define
else if self.escape_nl && (ch as i32 == 13 || ch as i32 == 10) {
result = LexResult::Ignore;
}
// Characters other than newline means other characters has been introduced
// after definition thus, escape_nl is now false
else {
self.escape_nl = false;
result = LexResult::AddToRemainder;
}
result
}
fn branch_name(&mut self, ch: char) -> LexResult {
let mut result: LexResult;
// Start arg if parenthesis was given,
// whitespaces are ignored and don't trigger exit
if ch == ' ' {
self.cursor = Cursor::NameToArg;
result = LexResult::Ignore;
}
// Left parenthesis trigger macro invocation
else if ch == '(' {
self.cursor = Cursor::Arg;
self.paren_count = 1;
result = LexResult::StartFrag;
// Empty name
if self.previous_char.unwrap_or('0') == '$' {
result = LexResult::EmptyName;
}
}
// Put any character in name
// It is ok not to validate macro name
// because invalid name cannot be registered anyway
else {
result = LexResult::AddToFrag(Cursor::Name);
}
result
}
/// Space between name and args
/// e.g.
/// $define ()
/// |-> This is the name to args characters
fn branch_name_to_arg(&mut self, ch: char) -> LexResult {
let result: LexResult;
// White space or tab character is ignored
if ch == ' ' || ch == '\t' {
result = LexResult::Ignore;
}
// Parenthesis start arguments
else if ch == '(' {
self.cursor = Cursor::Arg;
self.paren_count = 1;
result = LexResult::StartFrag;
}
// Other characters are invalid
else {
self.cursor = Cursor::None;
result = LexResult::ExitFrag;
}
result
}
// Double quote rule is somewhat suspicious?
fn branch_arg(&mut self, ch: char) -> LexResult {
let mut result: LexResult = LexResult::AddToFrag(Cursor::Arg);
// Right paren decreases paren_count
if ch == ')' && self.previous_char.unwrap_or('0') != ESCAPE_CHAR {
self.paren_count = self.paren_count - 1;
if self.paren_count == 0 {
self.cursor = Cursor::None;
result = LexResult::EndFrag;
}
}
// Left paren increases paren_count
else if ch == '(' && self.previous_char.unwrap_or('0') != ESCAPE_CHAR {
self.paren_count = self.paren_count + 1;
}
// Other characters are added normally
result
}
fn start_literal(&mut self, ch: char) -> bool {
// if given value is literal character and preceding character is escape
if ch == LIT_CHAR && self.previous_char.unwrap_or('0') == ESCAPE_CHAR {
self.lit_count = self.lit_count + 1;
true
} else {
false
}
}
fn end_literal(&mut self, ch: char) -> bool {
// if given value is literal character and preceding character is escape
if ch == ESCAPE_CHAR && self.previous_char.unwrap_or('0') == LIT_CHAR {
self.lit_count = self.lit_count - 1;
true
} else {
false
}
}
}
#[derive(Debug)]
pub enum LexResult {
Ignore,
AddToRemainder,
StartFrag,
EmptyName,
AddToFrag(Cursor),
EndFrag,
ExitFrag,
Literal(Cursor),
}
#[derive(Clone, Copy, Debug)]
pub enum Cursor {
None,
Name,
NameToArg,
Arg,
}