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use core::fmt;
pub fn escape(string: &str, quote: char) -> EscapeQuotedString<'_> {
EscapeQuotedString { string, quote }
}
pub struct EscapeQuotedString<'a> {
string: &'a str,
quote: char,
}
impl fmt::Display for EscapeQuotedString<'_> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
// EscapeQuotedString doesn't know which mode of escape was
// chosen by the user. So this code must to correctly display
// strings without knowing if the strings are already escaped
// or not.
//
// If the quote symbol in the string is repeated twice, OR, if
// the quote symbol is after backslash, display all the chars
// without any escape. However, if the quote symbol is used
// just between usual chars, `fmt()` should display it twice."
//
// The following table has examples
//
// | original query | mode | AST Node | serialized |
// | ------------- | --------- | -------------------------------------------------- | ------------ |
// | `"A""B""A"` | no-escape | `DoubleQuotedString(String::from("A\"\"B\"\"A"))` | `"A""B""A"` |
// | `"A""B""A"` | default | `DoubleQuotedString(String::from("A\"B\"A"))` | `"A""B""A"` |
// | `"A\"B\"A"` | no-escape | `DoubleQuotedString(String::from("A\\\"B\\\"A"))` | `"A\"B\"A"` |
// | `"A\"B\"A"` | default | `DoubleQuotedString(String::from("A\"B\"A"))` | `"A""B""A"` |
let quote = self.quote;
let mut previous_char = char::default();
let mut start_idx = 0;
let mut peekable_chars = self.string.char_indices().peekable();
while let Some(&(idx, ch)) = peekable_chars.peek() {
match ch {
char if char == quote => {
if previous_char == '\\' {
// the quote is already escaped with a backslash, skip
peekable_chars.next();
continue;
}
peekable_chars.next();
match peekable_chars.peek() {
Some((_, c)) if *c == quote => {
// the quote is already escaped with another quote, skip
peekable_chars.next();
}
_ => {
// The quote is not escaped.
// Including idx in the range, so the quote at idx will be printed twice:
// in this call to write_str() and in the next one.
f.write_str(&self.string[start_idx..=idx])?;
start_idx = idx;
}
}
}
_ => {
peekable_chars.next();
}
}
previous_char = ch;
}
f.write_str(&self.string[start_idx..])?;
Ok(())
}
}