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|
//! Utilities to deal with characters.
use crate::constant::TAB_SIZE;
use crate::tokenizer::{Event, EventType, Point};
/// A range between two places.
#[derive(Debug)]
pub struct Position<'a> {
pub start: &'a Point,
pub end: &'a Point,
}
impl<'a> Position<'a> {
/// Get a position from an exit event.
///
/// Looks backwards for the corresponding `enter` event.
/// This does not support nested events (such as lists in lists).
///
/// ## Panics
///
/// This function panics if an enter event is given.
/// When `micromark` is used, this function never panics.
pub fn from_exit_event(events: &'a [Event], index: usize) -> Position<'a> {
let exit = &events[index];
assert_eq!(
exit.event_type,
EventType::Exit,
"expected `from_exit_event` to be called on `exit` event"
);
let mut enter_index = index - 1;
loop {
let enter = &events[enter_index];
if enter.event_type == EventType::Enter && enter.token_type == exit.token_type {
return Position {
start: &enter.point,
end: &exit.point,
};
}
enter_index -= 1;
}
}
}
/// Chars belonging to a range.
///
/// Includes information on virtual spaces before and after the chars.
#[derive(Debug)]
pub struct Slice<'a> {
pub chars: &'a [char],
pub before: usize,
pub after: usize,
}
impl<'a> Slice<'a> {
/// Get the slice belonging to a position.
pub fn from_point(list: &'a [char], point: &Point) -> Slice<'a> {
let mut before = point.vs;
let mut start = point.index;
let end = if start < list.len() { start + 1 } else { start };
// If we have virtual spaces before, it means we are past the actual
// character at that index, and those virtual spaces.
if before > 0 {
before = TAB_SIZE - before;
start += 1;
};
Slice {
chars: if start < end { &list[start..end] } else { &[] },
before,
after: 0,
}
}
/// Get the slice belonging to a position.
pub fn from_position(list: &'a [char], position: &Position) -> Slice<'a> {
let mut before = position.start.vs;
let mut after = position.end.vs;
let mut start = position.start.index;
let mut end = position.end.index;
// If we have virtual spaces before, it means we are past the actual
// character at that index, and those virtual spaces.
if before > 0 {
before = TAB_SIZE - before;
start += 1;
};
// If we have virtual spaces after, it means that character is included,
// and one less virtual space.
if after > 0 {
after -= 1;
end += 1;
}
Slice {
chars: &list[start..end],
before,
after,
}
}
/// To do.
pub fn size(&self) -> usize {
self.chars.len() + self.before + self.after
}
// To do:
// When we have u8s, we could use: <https://doc.rust-lang.org/std/str/fn.from_utf8.html>
// to implement an `as_str`.
/// To do.
pub fn head(&self) -> Option<char> {
if self.before > 0 {
Some(' ')
} else if self.chars.is_empty() {
None
} else {
Some(self.chars[0])
}
}
/// To do.
pub fn tail(&self) -> Option<char> {
if self.after > 0 {
Some(' ')
} else {
let index = self.chars.len();
if index > 0 {
Some(self.chars[index - 1])
} else {
None
}
}
}
/// To do.
pub fn serialize(&self) -> String {
let mut string = String::with_capacity(self.size());
let mut index = self.before;
while index > 0 {
string.push(' ');
index -= 1;
}
string.push_str(&self.chars.iter().collect::<String>());
index = self.after;
while index > 0 {
string.push(' ');
index -= 1;
}
string
}
}
|
