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#[derive(Clone, Debug)]
pub struct Accumulator<'a> {
content: &'a str,
pos: usize,
peek_pos: usize,
}
impl<'a> Accumulator<'a> {
pub fn new(content: &'a str) -> Self {
Self {
content,
pos: 0,
peek_pos: 0,
}
}
#[inline]
pub fn content(&self) -> &'a str {
&self.content[..]
}
/// Returns the total length of the string being accumulated on.
#[inline]
pub fn len(&self) -> usize {
self.content.len()
}
/// peek_rem_len returns the remaining count of strings
/// left from the current peeks's cursor.
#[inline]
pub fn peek_rem_len(&self) -> usize {
(&self.content[self.peek_pos..]).len()
}
/// rem_len returns the remaining count of strings
/// left from the current position's cursor
/// regardless of where the peek cursor is at.
#[inline]
pub fn rem_len(&self) -> usize {
(&self.content[self.pos..]).len()
}
/// resets resets the location of the cursors for both read and peek to 0.
/// Basically moving them to the start position.
#[inline]
pub fn reset(&mut self) {
self.reset_to(0)
}
/// reset_to lets you reset the position of the cursor for both
/// position and peek to the to value.
#[inline]
pub fn reset_to(&mut self, to: usize) {
self.pos = to;
self.peek_pos = to;
}
/// skip will skip all the contents of the accumulator up to
/// the current position of the peek cursor.
#[inline]
pub fn skip(&mut self) {
self.pos = self.peek_pos
}
/// peek pulls the next token at the current peek position
/// cursor which will
#[inline]
pub fn peek(&mut self, by: usize) -> Option<&'a str> {
self.peek_slice(by)
}
/// peek_next allows you to increment the peek cursor, moving
/// the peek cursor forward by a mount of step and returns the next
/// token string.
#[cfg_attr(feature = "debug_trace", tracing::instrument(level = "trace"))]
#[inline]
pub fn peek_next_by(&mut self, by: usize) -> Option<&'a str> {
if let Some(res) = self.peek_slice(by) {
self.peek_pos = self.ensure_character_boundary_index(self.peek_pos + by);
return Some(res);
}
None
}
/// scan returns the whole string slice currently at the points of where
/// the main pos (position) cursor till the end.
#[cfg_attr(feature = "debug_trace", tracing::instrument(level = "trace"))]
#[inline]
pub fn scan_remaining(&mut self) -> Option<&'a str> {
Some(&self.content[self.pos..])
}
/// scan returns the whole string slice currently at the points of where
/// the main pos (position) cursor and the peek cursor so you can
/// pull the string right at the current range.
#[cfg_attr(feature = "debug_trace", tracing::instrument(level = "trace"))]
#[inline]
pub fn scan(&mut self) -> Option<&'a str> {
Some(&self.content[self.pos..self.peek_pos])
}
/// peek_next allows you to increment the peek cursor, moving
/// the peek cursor forward by a step and returns the next
/// token string.
#[cfg_attr(feature = "debug_trace", tracing::instrument(level = "trace"))]
#[inline]
pub fn peek_next(&mut self) -> Option<&'a str> {
if let Some(res) = self.peek_slice(1) {
self.peek_pos = self.ensure_character_boundary_index(self.peek_pos + 1);
return Some(res);
}
None
}
/// unpeek_next reverses the last forward move of the peek
/// cursor by -1.
#[cfg_attr(feature = "debug_trace", tracing::instrument(level = "trace"))]
#[inline]
pub fn unpeek_next(&mut self) -> Option<&'a str> {
if let Some(res) = self.unpeek_slice(1) {
return Some(res);
}
None
}
/// unpeek_slice lets you reverse the peek cursor position
/// by a certain amount to reverse the forward movement.
#[cfg_attr(feature = "debug_trace", tracing::instrument(level = "trace"))]
#[inline]
fn unpeek_slice(&mut self, by: usize) -> Option<&'a str> {
if self.peek_pos == 0 {
return None;
}
// unpeek only works when we are higher then current pos cursor.
// it should have no effect when have not moved forward
if self.peek_pos > self.pos {
self.peek_pos = self.inverse_ensure_character_boundary_index(self.peek_pos - 1);
}
let new_peek_pos = self.ensure_character_boundary_index(self.peek_pos + by);
Some(&self.content[self.peek_pos..new_peek_pos])
}
/// ppeek_at allows you to do a non-permant position cursor adjustment
/// by taking the current position cursor index with an adjustment
/// where we add the `from` (pos + from) to get the new
/// position to start from and `to` is added (pos + from + to)
/// the position to end at, if the total is more than the length of the string
/// then its adjusted to be the string last index for the slice.
///
/// It's a nice way to get to see whats at a given position without changing
/// the current location of the peek cursor.
#[cfg_attr(feature = "debug_trace", tracing::instrument(level = "trace"))]
#[inline]
pub fn ppeek_at(&mut self, from: usize, to: usize) -> Option<&'a str> {
let new_peek_pos = self.ensure_character_boundary_index(self.pos + from);
let mut until_pos = if new_peek_pos + to > self.content.len() {
self.content.len()
} else {
new_peek_pos + to
};
if new_peek_pos > self.content.len() {
return None;
}
until_pos = self.ensure_character_boundary_index(until_pos);
Some(&self.content[new_peek_pos..until_pos])
}
/// vpeek_at allows you to do a non-permant peek cursor adjustment
/// by taking the current peek cursor position with an adjustment
/// where we add the `from` (peek_cursor + from) to get the new
/// position to start from and `to` is added (peek_cursor + from + to)
/// the position to end at, if the total is more than the length of the string
/// then its adjusted to be the string last index for the slice.
///
/// It's a nice way to get to see whats at a given position without changing
/// the current location of the peek cursor.
#[cfg_attr(feature = "debug_trace", tracing::instrument(level = "trace"))]
#[inline]
pub fn vpeek_at(&mut self, from: usize, to: usize) -> Option<&'a str> {
let mut new_peek_pos = self.peek_pos + from;
let mut until_pos = if new_peek_pos + to > self.content.len() {
self.content.len()
} else {
new_peek_pos + to
};
if new_peek_pos > self.content.len() {
return None;
}
// ensure we are always at the char boundary
new_peek_pos = self.ensure_character_boundary_index(new_peek_pos);
until_pos = self.ensure_character_boundary_index(until_pos);
ewe_trace::debug!(
"Check if we are out of char boundary: start: {}:{}, end: {}:{}",
new_peek_pos,
self.content.is_char_boundary(new_peek_pos),
until_pos,
self.content.is_char_boundary(until_pos)
);
Some(&self.content[new_peek_pos..until_pos])
}
#[inline]
fn inverse_ensure_character_boundary_index(&self, current_index: usize) -> usize {
let mut next_index = current_index;
// ensure we are always at the char boundary
loop {
if !self.content.is_char_boundary(next_index) {
next_index -= 1;
continue;
}
break;
}
return next_index;
}
#[inline]
fn ensure_character_boundary_index(&self, current_index: usize) -> usize {
let mut next_index = current_index;
// ensure we are always at the char boundary
loop {
if !self.content.is_char_boundary(next_index) {
next_index += 1;
continue;
}
break;
}
return next_index;
}
/// peek_slice allows you to peek forward by an amount
/// from the current peek cursor position.
///
/// If we've exhausted the total string slice left or are trying to
/// take more than available text length then we return None
/// which can indicate no more text for processing.
#[cfg_attr(feature = "debug_trace", tracing::instrument(level = "trace"))]
#[inline]
fn peek_slice(&mut self, by: usize) -> Option<&'a str> {
if self.peek_pos + by > self.content.len() {
return None;
}
let from = self.ensure_character_boundary_index(self.peek_pos);
let until_pos = self.ensure_character_boundary_index(self.peek_pos + by);
Some(&self.content[from..until_pos])
}
/// take returns the total string slice from the
/// actual accumulators position cursor til the current
/// peek cursor position with adjustment on `by` amount i.e
/// str[position_cursor..(peek_cursor + by_value)].
///
/// Allow you to collect the whole slice of strings that have been
/// checked and peeked through.
///
/// If we've exhausted the total string slice left or are trying to
/// take more than available text length then we return None
/// which can indicate no more text for processing.
#[cfg_attr(feature = "debug_trace", tracing::instrument(level = "trace"))]
#[inline]
pub fn take_with_amount(&mut self, by: usize) -> Option<(&'a str, (usize, usize))> {
if self.peek_pos + by > self.content.len() {
return None;
}
let mut until_pos = if self.peek_pos + by > self.content.len() {
self.content.len()
} else {
self.peek_pos + by
};
if self.pos >= self.content.len() {
return None;
}
let from = self.ensure_character_boundary_index(self.pos);
until_pos = self.ensure_character_boundary_index(until_pos);
ewe_trace::debug!(
"take_with_amount: possibly shift in positions: org:({}, {}) then end in final:({},{})",
org_positional,
org_until,
from,
until_pos,
);
let position = (from, until_pos);
ewe_trace::debug!(
"take_with_amount: content len: {} with pos: {}, peek_pos: {}, by: {}, until: {}",
self.content.len(),
self.pos,
self.peek_pos,
by,
until_pos,
);
let content_slice = &self.content[from..until_pos];
ewe_trace::debug!(
"take_with_amount: sliced worked from: {}, by: {}, till loc: {} with text: '{}'",
self.pos,
by,
until_pos,
content_slice,
);
let res = Some((content_slice, position));
self.pos = self.peek_pos;
res
}
/// take_positional returns the total string slice from the
/// actual accumulators position cursor til the current
/// peek cursor position i.e str[position_cursor...peek_cursor].
/// Allow you to collect the whole slice of strings that have been
/// checked and peeked through.
#[inline]
pub fn take_positional(&mut self) -> Option<(&'a str, (usize, usize))> {
self.take_with_amount(0)
}
/// take returns the total string slice from the
/// actual accumulators position cursor til the current
/// peek cursor position i.e str[position_cursor...peek_cursor].
/// Allow you to collect the whole slice of strings that have been
/// checked and peeked through.
#[inline]
pub fn take(&mut self) -> Option<&'a str> {
match self.take_with_amount(0) {
Some((text, _)) => Some(text),
None => None,
}
}
}
#[cfg(test)]
mod accumulator_tests {
use super::*;
#[test]
fn test_can_use_accumulator_to_peek_next_character() {
let mut accumulator = Accumulator::new("hello");
assert_eq!("h", accumulator.peek(1).unwrap());
assert_eq!("h", accumulator.peek(1).unwrap());
}
#[test]
fn test_can_use_accumulator_to_peek_two_characters_away() {
let mut accumulator = Accumulator::new("hello");
assert_eq!("he", accumulator.peek(2).unwrap());
}
#[test]
fn test_can_virtual_peek_ahead_without_changing_peek_cursor() {
let mut accumulator = Accumulator::new("hello");
assert_eq!("h", accumulator.peek_next().unwrap());
assert_eq!("e", accumulator.peek_next().unwrap());
assert_eq!("llo", accumulator.vpeek_at(0, 3).unwrap()); // from peek cursor till 3 ahead
assert_eq!("lo", accumulator.vpeek_at(1, 3).unwrap()); // from 1 character ahead of peek cursor
assert_eq!("l", accumulator.peek_next().unwrap());
assert_eq!("l", accumulator.peek_next().unwrap());
assert_eq!("o", accumulator.peek_next().unwrap());
assert_eq!(None, accumulator.peek_next());
}
#[test]
fn test_can_peek_next_to_accumulate_more_seen_text() {
let mut accumulator = Accumulator::new("hello");
assert_eq!("h", accumulator.peek_next().unwrap());
assert_eq!("e", accumulator.peek_next().unwrap());
assert_eq!("l", accumulator.peek_next().unwrap());
assert_eq!("l", accumulator.peek_next().unwrap());
assert_eq!("o", accumulator.peek_next().unwrap());
assert_eq!(None, accumulator.peek_next());
}
#[test]
fn test_can_peek_next_and_take_text_then_continue_peeking() {
let mut accumulator = Accumulator::new("hello");
assert_eq!(5, accumulator.len());
assert_eq!("h", accumulator.peek_next().unwrap());
assert_eq!("e", accumulator.peek_next().unwrap());
assert_eq!("l", accumulator.peek_next().unwrap());
assert_eq!(5, accumulator.len());
assert_eq!(5, accumulator.rem_len());
assert_eq!(2, accumulator.peek_rem_len());
assert_eq!("hel", accumulator.take().unwrap());
assert_eq!(2, accumulator.rem_len());
assert_eq!(2, accumulator.peek_rem_len());
assert_eq!("l", accumulator.peek_next().unwrap());
assert_eq!("o", accumulator.peek_next().unwrap());
assert_eq!(2, accumulator.rem_len());
assert_eq!(0, accumulator.peek_rem_len());
assert_eq!(None, accumulator.peek_next());
assert_eq!(2, accumulator.rem_len());
assert_eq!(0, accumulator.peek_rem_len());
assert_eq!("lo", accumulator.take().unwrap());
assert_eq!(0, accumulator.rem_len());
assert_eq!(None, accumulator.peek_next());
}
}