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pub use to_offset::*;
/// Trait with extension methods to manipulate substrings by character indices
/// behaving like similar methods in other languages
pub trait SubstringReplace where Self:ToString {
/// Return a substring by start and end character index
/// With multibyte characters this will not be the same as the byte indices
/// used by str slices
fn substring<T: ToOffset>(&self, start: usize, end: T) -> &str;
/// Return a substring from the start and to a specified end character index
fn substring_start(&self, end: i64) -> &str {
let end_index = if end < 0 { self.char_len().checked_sub(end.abs() as usize).unwrap_or(0) } else { end as usize };
self.substring(0, end_index)
}
/// Return a substring from a specified start character index to a specified end
/// A negative offset represents character index from the end, e.g. if character length is 15, -5 translates to 10
/// If start index is greater than the max character index, the function will yield an empty string
fn substring_end(&self, start: i64) -> &str {
let max_index = self.char_len();
let start_index = if start < 0 { max_index.checked_sub(start.abs() as usize).unwrap_or(0) } else { start as usize };
self.substring(start_index, max_index)
}
/// Return a substring by start and end character index
/// Unlike the default substring() method, the end index may be negative,
/// in which case it counts backwards from the end, e.g. if character length is 15, -5 translates to 10
#[deprecated(since = "0.2.1", note = "Use `substring` instead")]
fn substring_range(&self, start: usize, end: i64) -> &str {
self.substring(start, end)
}
// Replace substring delimited by start and end character index
// with any string (&str)
// To inject a string use substring_insert()
fn substring_replace<T: ToOffset>(&self, replacement: &str, start: usize, end: T) -> String;
/// Replace substring delimited by start and end character index
/// Unlike the default substring_replace() method, the end index may be negative,
/// in which case it counts backwards from the end, e.g. if character length is 15, -5 translates to 10
#[deprecated(since = "0.2.1", note = "Use `substring` instead")]
fn substring_replace_range(&self, replacement: &str, start: usize, end: i64) -> String {
self.substring_replace(replacement, start, end)
}
/// Replace the start of a string to specified end character index
/// e.g. "brown".substring_replace_start("d", 2);
/// will replace the first two characters with "d", yield "down"
/// A negative offset represents character index from the end, e.g. if character length is 15, -5 translates to 10
fn substring_replace_start(&self, replacement: &str, end: i64) -> String {
let end_index = if end < 0 { self.char_len().saturating_sub(end.abs() as usize) } else { end as usize };
self.substring_replace(replacement, 0, end_index)
}
/// Replace the remainder of string from a specified start character index
/// e.g. "blue".substring_replace_last("ack", 2);
/// will replace the last 2 characters with "ack", yielding "black"
/// A negative offset represents character index from the end, e.g. if character length is 15, -5 translates to 10
fn substring_replace_end(&self, replacement: &str, start: i64) -> String {
let end = self.char_len();
let start_index = if start < 0 { end.saturating_sub(start.abs() as usize) } else { start as usize };
self.substring_replace(replacement, start_index, end)
}
/// Remove a string delimited by a start and end character index
/// e.g. "abcde".substring_remove(2, 4);
/// will remove characters with indices of 2 and 3 (3rd and 4th or c and d)
/// resulting in "abe", i.e. the opposite behaviour to substring()
fn substring_remove(&self, start: usize, end: usize) -> String {
self.substring_replace("", start, end)
}
/// Extract a substring from a start index for n characters to the right
/// A negative length in the second parameter will start at the start index
fn substring_offset(&self, position: usize, length: i32) -> &str {
let (start, end) = position_and_offset_to_start_end(position, length);
self.substring(start, end)
}
/// Remove a string from a start position to given length
/// negative lengths will remove characters to the left
/// e.g. "abcde".substring_remove(3, -3);
/// will remove characters with indices of 1 and 2 (2nd and 3rd or b and c)
/// resulting in "ade", i.e. the opposite behaviour to substring_offset()
fn substring_pull(&self, position: usize, length: i32) -> String {
let (start, end) = position_and_offset_to_start_end(position, length);
self.substring_replace("", start, end)
}
/// Insert a string at a given character index
/// This differs from String::insert by using character rather than byte indices
/// to work better with multibyte characters
/// It's also implemented for &str, while returning a new owned string
fn substring_insert(&self, replacement: &str, start: usize) -> String {
self.substring_replace(replacement, start, start)
}
/// Convert character index to start byte index
fn to_start_byte_index(&self, start: usize) -> usize;
/// Convert character index to end byte index
fn to_end_byte_index(&self, start: usize) -> usize;
/// Return the character length rather than the byte length
fn char_len(&self) -> usize;
/// Return the character index rather than the byte index of the first match of a pattern
fn char_find(&self, pat: &str) -> Option<usize>;
/// Return the character index rather than the byte index of the last match of a pattern
/// this will be first index of the match
fn char_rfind(&self, pat: &str) -> Option<usize>;
/// Insert before or after the first or last occurrence
fn insert_adjacent(&self, insert: &str, pat: &str, before: bool, first: bool) -> String;
/// Insert before the first occurrence of a string
fn insert_before_first(&self, insert: &str, pat: &str) -> String {
self.insert_adjacent(insert, pat, true, true)
}
/// Insert before the first occurrence of a string
fn insert_before_last(&self, insert: &str, pat: &str) -> String {
self.insert_adjacent(insert, pat, true, false)
}
/// Insert after the last occurrence of a string
fn insert_after_first(&self, insert: &str, pat: &str) -> String {
self.insert_adjacent(insert, pat, false, true)
}
/// Insert after the last occurrence of a string
fn insert_after_last(&self, insert: &str, pat: &str) -> String {
self.insert_adjacent(insert, pat, false, false)
}
/// Insert between the first occurrence of a one string and the last occurrence of another
fn insert_between(&self, insert: &str, start_pat: &str, end_pat: &str) -> String {
if let Some(start_index) = self.char_find(start_pat) {
if let Some(end_index) = self.char_rfind(end_pat) {
return self.substring_replace(insert, start_index + 1, end_index);
}
}
self.to_string()
}
/// Insert between the first occurrence of a one string and the last occurrence of another
fn prepend(&self, insert: &str) -> String {
[insert.to_string(), self.to_string()].concat()
}
fn append(&self, insert: &str) -> String {
[self.to_string(), insert.to_string()].concat()
}
}
impl SubstringReplace for str {
/// Extract substring by character indices and hand overflow gracefully
/// if the end index is equal or greater than start index, the function will yield an empty string
fn substring<T: ToOffset>(&self, start: usize, end: T) -> &str {
let end_index = end.to_offset(self.char_len());
if end_index > start {
&self[self.to_start_byte_index(start)..self.to_end_byte_index(end_index)]
} else {
""
}
}
/// Replace a segment delimited by start and end characters indices with a string pattern (&str)
fn substring_replace<T: ToOffset>(&self, replacement: &str, start: usize, end: T) -> String {
let end_index = end.to_offset(self.char_len());
[&self[0..self.to_start_byte_index(start)], replacement, &self[self.to_end_byte_index(end_index)..]].concat()
}
/// Translate the character start index to the start byte index
/// to avoid boundary collisions with multibyte characters
fn to_start_byte_index(&self, start: usize) -> usize {
char_index_to_byte_index(self, start, false)
}
/// Translate the character end index to the end byte index
/// to avoid boundary collisions with multibyte characters
fn to_end_byte_index(&self, end: usize) -> usize {
char_index_to_byte_index(self, end, true)
}
/// Return the character length as opposed to the byte length
/// This will differ from len() only multibyte characters
fn char_len(&self) -> usize {
self.char_indices().count()
}
/// Return the character index of the first match of a given pattern
fn char_find(&self, pat: &str) -> Option<usize>{
extract_char_index(self, pat, false)
}
/// Return the character index rather than the byte index of the last match of a pattern
/// this will be first index of the match
fn char_rfind(&self, pat: &str) -> Option<usize>{
extract_char_index(self, pat, true)
}
/// Insert before or after the first or last occurrence
fn insert_adjacent(&self, insert: &str, pat: &str, before: bool, first: bool) -> String {
if let Some(index) = extract_char_index(self, pat, !first) {
let rel_index = if before {
index
} else {
index + 1
};
self.substring_insert(insert, rel_index)
} else {
self.to_string()
}
}
}
/*
* private function to convert a character index to byte index requied by &str slices
*/
fn char_index_to_byte_index(text: &str, char_index: usize, to_end: bool) -> usize {
let default_index = if to_end { text.len() } else { 0 };
text.char_indices().nth(char_index).map(|(i, _)| i).unwrap_or(default_index)
}
/*
* private function to convert an index position and i32 position or negative offset length
* to valid start and end indices
* where the start must be positive and the end may not be before the start
*/
fn position_and_offset_to_start_end(position: usize, length: i32) -> (usize, usize) {
let reverse = length < 0;
let start = if reverse {
position.checked_sub(length.abs() as usize).unwrap_or(0)
} else {
position
};
let start_i32 = if start > i32::MAX as usize { i32::MAX } else { start as i32 };
let end_i32 = start_i32 + length.abs();
let end = if end_i32 < 0 {
0
} else {
end_i32 as usize
};
(start, end)
}
/// private function to extract the character index of pattenr (char sequence)
fn extract_char_index(text: &str, pat: &str, reverse: bool) -> Option<usize> {
let mut start_index: Option<usize> = None;
let pat_chars = pat.chars().collect::<Vec<_>>();
let pat_len = pat.char_len();
let text_chars = text.chars().collect::<Vec<_>>();
let num_text_chars = text_chars.len();
let range = 0..num_text_chars;
let mut next_pat_char_index = if reverse { pat_len - 1 } else { 0 };
let mut temp_pat_len = 0;
for tc_index in range {
let rel_index = if reverse { num_text_chars - 1 - tc_index } else { tc_index };
let tc = text_chars[rel_index];
if tc == pat_chars[next_pat_char_index] {
if !reverse && next_pat_char_index == 0 {
start_index = Some(rel_index);
}
if pat_len > 1 {
if reverse {
if next_pat_char_index > 0 {
next_pat_char_index -= 1;
}
} else {
next_pat_char_index += 1;
}
}
temp_pat_len += 1;
} else {
next_pat_char_index = if reverse { pat_len - 1 } else { 0 };
temp_pat_len = 0;
}
if temp_pat_len == pat_len {
if reverse {
start_index = Some(rel_index);
}
break;
}
}
start_index
}