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use super::errors::{ErrorKind, ParserError};
use super::{core::Parser, core::Result, slice::Slice};
use crate::ast;
#[derive(Debug, PartialEq)]
enum TextElementTermination {
LineFeed,
CRLF,
PlaceableStart,
EOF,
}
// This enum tracks the placement of the text element in the pattern, which is needed for
// dedentation logic.
#[derive(Debug, PartialEq)]
enum TextElementPosition {
InitialLineStart,
LineStart,
Continuation,
}
// This enum allows us to mark pointers in the source which will later become text elements
// but without slicing them out of the source string. This makes the indentation adjustments
// cheaper since they'll happen on the pointers, rather than extracted slices.
#[derive(Debug)]
enum PatternElementPlaceholders<S> {
Placeable(ast::Expression<S>),
// (start, end, indent, position)
TextElement(usize, usize, usize, TextElementPosition),
}
// This enum tracks whether the text element is blank or not.
// This is important to identify text elements which should not be taken into account
// when calculating common indent.
#[derive(Debug, PartialEq)]
enum TextElementType {
Blank,
NonBlank,
}
impl<'s, S> Parser<S>
where
S: Slice<'s>,
{
pub(super) fn get_pattern(&mut self) -> Result<Option<ast::Pattern<S>>> {
let mut elements = vec![];
let mut last_non_blank = None;
let mut common_indent = None;
self.skip_blank_inline();
let mut text_element_role = if self.skip_eol() {
self.skip_blank_block();
TextElementPosition::LineStart
} else {
TextElementPosition::InitialLineStart
};
while self.ptr < self.length {
if self.take_byte_if(b'{') {
if text_element_role == TextElementPosition::LineStart {
common_indent = Some(0);
}
let exp = self.get_placeable()?;
last_non_blank = Some(elements.len());
elements.push(PatternElementPlaceholders::Placeable(exp));
text_element_role = TextElementPosition::Continuation;
} else {
let slice_start = self.ptr;
let mut indent = 0;
if text_element_role == TextElementPosition::LineStart {
indent = self.skip_blank_inline();
if let Some(b) = get_current_byte!(self) {
if indent == 0 {
if b != &b'\r' && b != &b'\n' {
break;
}
} else if !Self::is_byte_pattern_continuation(*b) {
self.ptr = slice_start;
break;
}
} else {
break;
}
}
let (start, end, text_element_type, termination_reason) = self.get_text_slice()?;
if start != end {
if text_element_role == TextElementPosition::LineStart
&& text_element_type == TextElementType::NonBlank
{
if let Some(common) = common_indent {
if indent < common {
common_indent = Some(indent);
}
} else {
common_indent = Some(indent);
}
}
if text_element_role != TextElementPosition::LineStart
|| text_element_type == TextElementType::NonBlank
|| termination_reason == TextElementTermination::LineFeed
{
if text_element_type == TextElementType::NonBlank {
last_non_blank = Some(elements.len());
}
elements.push(PatternElementPlaceholders::TextElement(
slice_start,
end,
indent,
text_element_role,
));
}
}
text_element_role = match termination_reason {
TextElementTermination::LineFeed => TextElementPosition::LineStart,
TextElementTermination::CRLF => TextElementPosition::LineStart,
TextElementTermination::PlaceableStart => TextElementPosition::Continuation,
TextElementTermination::EOF => TextElementPosition::Continuation,
};
}
}
if let Some(last_non_blank) = last_non_blank {
let elements = elements
.into_iter()
.take(last_non_blank + 1)
.enumerate()
.map(|(i, elem)| match elem {
PatternElementPlaceholders::Placeable(expression) => {
ast::PatternElement::Placeable { expression }
}
PatternElementPlaceholders::TextElement(start, end, indent, role) => {
let start = if role == TextElementPosition::LineStart {
common_indent.map_or_else(
|| start + indent,
|common_indent| start + std::cmp::min(indent, common_indent),
)
} else {
start
};
let mut value = self.source.slice(start..end);
if last_non_blank == i {
value.trim();
}
ast::PatternElement::TextElement { value }
}
})
.collect();
return Ok(Some(ast::Pattern { elements }));
}
Ok(None)
}
fn get_text_slice(
&mut self,
) -> Result<(usize, usize, TextElementType, TextElementTermination)> {
let start_pos = self.ptr;
let mut text_element_type = TextElementType::Blank;
while let Some(b) = get_current_byte!(self) {
match b {
b' ' => self.ptr += 1,
b'\n' => {
self.ptr += 1;
return Ok((
start_pos,
self.ptr,
text_element_type,
TextElementTermination::LineFeed,
));
}
b'\r' if self.is_byte_at(b'\n', self.ptr + 1) => {
self.ptr += 1;
return Ok((
start_pos,
self.ptr - 1,
text_element_type,
TextElementTermination::CRLF,
));
}
b'{' => {
return Ok((
start_pos,
self.ptr,
text_element_type,
TextElementTermination::PlaceableStart,
));
}
b'}' => {
return error!(ErrorKind::UnbalancedClosingBrace, self.ptr);
}
_ => {
text_element_type = TextElementType::NonBlank;
self.ptr += 1
}
}
}
Ok((
start_pos,
self.ptr,
text_element_type,
TextElementTermination::EOF,
))
}
}