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//! Generate command framgents from String command.
use std::{fmt, iter::Peekable, str::CharIndices};
use super::{CommandToken, RawStringPattern};
/// An error that can appear while lexing a command.
#[derive(Debug, PartialEq, Eq)]
pub enum CommandLexError<'a> {
/// There is a unclosed quote.
UnclosedQuote(usize, &'a str),
/// There is a whitespace before/after equal sign.
NamedProhibitsWhitespace(usize, &'a str),
/// There is a nam assignment syntax after equal sign
NamedCannotContainNamed(usize, &'a str),
}
impl fmt::Display for CommandLexError<'_> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
CommandLexError::UnclosedQuote(pos, src_part) => {
write!(
f,
"Unclosed quote at position {} in command: {}",
pos, src_part
)
}
CommandLexError::NamedProhibitsWhitespace(pos, src_part) => write!(
f,
"Named argument prohibits whitespace at position {} in command: {}",
pos, src_part
),
CommandLexError::NamedCannotContainNamed(pos, src_part) => write!(
f,
"Named argument cannot contain named argument at position {} in command: {}",
pos, src_part
),
}
}
}
impl std::error::Error for CommandLexError<'_> {}
/// A lexer transforming command string into sequence of [`CommandToken`]/
pub struct CommandLexer<'a> {
source: &'a str,
iter: Peekable<CharIndices<'a>>,
in_named: bool,
failed: bool,
}
impl<'a> CommandLexer<'a> {
/// Create a new `CommandLexer` instance from a command string.
pub fn new(source: &'a str) -> Self {
CommandLexer {
source,
iter: source.char_indices().peekable(),
in_named: false,
failed: false,
}
}
}
impl<'a> CommandLexer<'a> {
fn next_whitespace(&mut self) -> Option<Result<CommandToken<'a>, CommandLexError<'a>>> {
let (first, _) = self.iter.peek()?;
let first = *first;
let last = loop {
match self.iter.peek() {
Some((_, ch)) if ch.is_whitespace() => {
self.iter.next();
}
Some((i, _)) => break *i,
None => break self.source.len(),
}
};
Some(Ok(CommandToken::Whitespace(&self.source[first..last])))
}
fn next_quote(&mut self) -> Option<Result<CommandToken<'a>, CommandLexError<'a>>> {
let (first, ch) = self.iter.next()?;
let mut src = String::new();
let src_first = match self.iter.next() {
None => {
return Some(Err(CommandLexError::UnclosedQuote(
first,
&self.source[first..],
)))
}
Some((last, c)) if c == ch => {
return Some(Ok(CommandToken::QuotedString(
&self.source[first..=last],
"".to_string(),
&self.source[last..=self
.iter
.peek()
.map(|(next_i, _)| *next_i)
.unwrap_or(self.source.len())],
)))
}
Some((src_first, ch)) => {
src.push(ch);
src_first
}
};
let mut previous_backslash = false;
let src_last = loop {
match self.iter.next() {
Some((src_last, c)) if c == ch => {
if previous_backslash {
src.push(c);
previous_backslash = false;
} else {
break src_last;
}
}
Some((_, '\\')) => {
if previous_backslash {
src.push('\\');
previous_backslash = false;
} else {
previous_backslash = true;
}
}
Some((_, ch)) => {
src.push(ch);
if previous_backslash {
previous_backslash = false;
}
}
None => {
return Some(Err(CommandLexError::UnclosedQuote(
first,
&self.source[first..],
)))
}
}
};
Some(Ok(CommandToken::QuotedString(
&self.source[first..src_first],
src,
&self.source[src_last
..self
.iter
.peek()
.map(|(next_i, _)| *next_i)
.unwrap_or(self.source.len())],
)))
}
fn next_raw_string_or_named(
&mut self,
) -> Option<Result<CommandToken<'a>, CommandLexError<'a>>> {
let (first, _) = self.iter.peek()?;
let first = *first;
let mut is_numeric = true;
let mut met_float_dot = false;
let last = loop {
match self.iter.peek() {
Some((i, ch)) if ch.is_whitespace() => break *i,
Some((i, ch)) => {
let i = *i;
match ch {
'=' => {
let name = &self.source[first..i];
if self.in_named {
return Some(Ok(CommandToken::Named(
name,
Box::new(CommandToken::Whitespace("")),
)));
}
if name.is_empty() {
return Some(Err(CommandLexError::NamedProhibitsWhitespace(
first,
&self.source[first..],
)));
}
self.iter.next();
self.in_named = true;
let token = match self.next() {
Some(Ok(CommandToken::Whitespace(_))) | None => {
return Some(Err(CommandLexError::NamedProhibitsWhitespace(
first,
&self.source[first..],
)))
}
Some(Ok(CommandToken::Named(..))) => {
return Some(Err(CommandLexError::NamedCannotContainNamed(
first,
&self.source[first..],
)))
}
Some(Ok(expr)) => expr,
otherwise => return otherwise,
};
self.in_named = false;
return Some(Ok(CommandToken::Named(name, Box::new(token))));
}
'0'..='9' => {
self.iter.next();
}
'.' => {
if met_float_dot {
is_numeric = false;
} else {
met_float_dot = true;
}
self.iter.next();
}
'-' | '+' => {
if first != i {
is_numeric = false;
met_float_dot = false;
}
self.iter.next();
}
_ => {
is_numeric = false;
met_float_dot = false;
self.iter.next();
}
}
}
None => break self.source.len(),
}
};
let pattern = match (is_numeric, met_float_dot) {
(false, _) => RawStringPattern::Unrecognized,
(true, true) => RawStringPattern::Float,
(true, false) => RawStringPattern::Integer,
};
Some(Ok(CommandToken::RawString(
&self.source[first..last],
pattern,
)))
}
}
impl<'a> Iterator for CommandLexer<'a> {
type Item = Result<CommandToken<'a>, CommandLexError<'a>>;
fn next(&mut self) -> Option<Self::Item> {
if self.failed {
return None;
}
let (_, ch) = self.iter.peek()?;
let res = match ch {
ch if ch.is_whitespace() => self.next_whitespace(),
'"' | '\'' => self.next_quote(),
_ => self.next_raw_string_or_named(),
};
if res.as_ref().map(|res| res.is_err()).unwrap_or(false) {
self.failed = true;
}
res
}
}