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//! Paranoid text spacing for good readability, to automatically insert
//! whitespace between CJK (Chinese, Japanese, Korean) and half-width
//! characters (alphabetical letters, numerical digits and symbols).

#[macro_use]
extern crate lazy_static;
extern crate regex;

use regex::Regex;
use std::borrow::Cow;

// Chinese, Japanese, Korean
// See <http://unicode-table.com>
const CJK: &str = "\u{2e80}-\u{2eff}\u{2f00}-\u{2fdf}\u{3040}-\u{309f}\u{30a0}-\u{30ff}\u{3100}-\u{312f}\u{3200}-\u{32ff}\u{3400}-\u{4dbf}\u{4e00}-\u{9fff}\u{f900}-\u{faff}";

// Alphabets, Numbers, Symbols
const ANS: &str = "A-Za-z0-9`\\$%\\^&\\*\\-=\\+\\\\|/\u{00a1}-\u{00ff}\u{2022}\u{2027}\u{2150}-\u{218f}";

/// Insert whitespace between CJK and half-width characters.
pub fn spacing(text: &str) -> Cow<str> {
  lazy_static! {
    // <https://github.com/vinta/pangu/blob/master/pangu.go>
    static ref CJK_QUOTE: Regex = Regex::new(&format!("([{CJK}])([\"'])", CJK = CJK)).unwrap();
    static ref QUOTE_CJK: Regex = Regex::new(&format!("([\"'])([{CJK}])", CJK = CJK)).unwrap();
    static ref FIX_QUOTE: Regex = Regex::new("([\"'\\(\\[\\{{<\u{201c}])(\\s*)(.+?)(\\s*)([\"'\\)\\]\\}}>\u{201d}])").unwrap();
    static ref FIX_SINGLE_QUOTE: Regex = Regex::new(&format!("([{CJK}])( )(')([A-Za-z])", CJK = CJK)).unwrap();
    // -----
    static ref CJK_HASH: Regex = Regex::new(&format!("([{CJK}])(#(\\S+))", CJK = CJK)).unwrap();
    static ref HASH_CJK: Regex = Regex::new(&format!("((\\S+)#)([{CJK}])", CJK = CJK)).unwrap();
    // -----
    static ref CJK_OPERATOR_ANS: Regex = Regex::new(&format!("([{CJK}])([\\+\\-\\*/=&\\|<>])([A-Za-z0-9])", CJK = CJK)).unwrap();
    static ref ANS_OPERATOR_CJK: Regex = Regex::new(&format!("([A-Za-z0-9])([\\+\\-\\*/=&\\|<>])([{CJK}])", CJK = CJK)).unwrap();
    // -----
    static ref CJK_BRACKET_CJK: Regex = Regex::new(&format!("([{CJK}])([\\(\\[\\{{<\u{201c}]+(.*?)[\\)\\]\\}}>\u{201d}]+)([{CJK}])", CJK = CJK)).unwrap();
    static ref CJK_BRACKET: Regex = Regex::new(&format!("([{CJK}])([\\(\\[\\{{<\u{201c}>])", CJK = CJK)).unwrap();
    static ref BRACKET_CJK: Regex = Regex::new(&format!("([\\)\\]\\}}>\u{201d}<])([{CJK}])", CJK = CJK)).unwrap();
    static ref FIX_BRACKET: Regex = Regex::new("([\\(\\[\\{{<\u{201c}]+)(\\s*)(.+?)(\\s*)([\\)\\]\\}}>\u{201d}]+)").unwrap();
    // -----
    static ref FIX_SYMBOL: Regex = Regex::new(&format!("([{CJK}])([~!;:,\\.\\?\u{2026}])([A-Za-z0-9])", CJK = CJK)).unwrap();
    // -----
    static ref CJK_ANS: Regex = Regex::new(&format!("([{CJK}])([{ANS}@])", CJK = CJK, ANS = ANS)).unwrap();
    static ref ANS_CJK: Regex = Regex::new(&format!("([{ANS}~!;:,\\.\\?\u{2026}])([{CJK}])", CJK = CJK, ANS = ANS)).unwrap();
  }

  let text_1 = CJK_QUOTE.replace_all(text, "$1 $2");
  let text_2 = QUOTE_CJK.replace_all(&text_1, "$1 $2");
  let text_3 = FIX_QUOTE.replace_all(&text_2, "$1$3$5");
  let text_4 = FIX_SINGLE_QUOTE.replace_all(&text_3, "$1$3$4");

  let text_5 = CJK_HASH.replace_all(&text_4, "$1 $2");
  let text_6 = HASH_CJK.replace_all(&text_5, "$1 $3");

  let text_7 = CJK_OPERATOR_ANS.replace_all(&text_6, "$1 $2 $3");
  let text_8 = ANS_OPERATOR_CJK.replace_all(&text_7, "$1 $2 $3");

  let old_text = text_8;
  let new_text = CJK_BRACKET_CJK.replace_all(&old_text, "$1 $2 $4");
  let text_ir;
  let text_11 = if *new_text == *old_text {
    text_ir = CJK_BRACKET.replace_all(&new_text, "$1 $2");
    BRACKET_CJK.replace_all(&text_ir, "$1 $2")
  } else {
    new_text
  };
  let text_12 = FIX_BRACKET.replace_all(&text_11, "$1$3$5");

  let text_13 = FIX_SYMBOL.replace_all(&text_12, "$1$2 $3");

  let text_14 = CJK_ANS.replace_all(&text_13, "$1 $2");
  let text_15 = ANS_CJK.replace_all(&text_14, "$1 $2");

  let eq = |x: &str, y: &str| x.as_ptr() == y.as_ptr() && x.len() == y.len();

  match text_15 {
    Cow::Borrowed(t) if eq(t, text) => Cow::Borrowed(text),
    spaced => Cow::Owned(spaced.into_owned()),
  }
}