/*
 * Copyright (C) 2017, David PHAM-VAN <dev.nfet.net@gmail.com>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/// Arabic shape substitutions: char code => (isolated, final, initial, medial).
/// Arabic Substition A
const Map<int, dynamic> _arabicSubstitionA = <int, dynamic>{
  0x0640: <int>[0x0640, 0x0640, 0x0640, 0x0640], // ARABIC TATWEEL

  0x0621: <int>[1569], // ARABIC LETTER HAMZA
  0x0622: <int>[1570, 0xFE82], // ARABIC LETTER ALEF WITH MADDA ABOVE
  0x0623: <int>[1571, 0xFE84], // ARABIC LETTER ALEF WITH HAMZA ABOVE
  0x0624: <int>[1572, 0xFE86], // ARABIC LETTER WAW WITH HAMZA ABOVE
  0x0625: <int>[1573, 0xFE88], // ARABIC LETTER ALEF WITH HAMZA BELOW
  0x0626: <int>[
    1574,
    0xFE8A,
    0xFE8B,
    0xFE8C
  ], // ARABIC LETTER YEH WITH HAMZA ABOVE
  0x0627: <int>[1575, 0xFE8E], // ARABIC LETTER ALEF
  0x0628: <int>[1576, 0xFE90, 0xFE91, 0xFE92], // ARABIC LETTER BEH
  0x0629: <int>[1577, 0xFE94], // ARABIC LETTER TEH MARBUTA
  0x062A: <int>[1578, 0xFE96, 0xFE97, 0xFE98], // ARABIC LETTER TEH
  0x062B: <int>[1579, 0xFE9A, 0xFE9B, 0xFE9C], // ARABIC LETTER THEH
  0x062C: <int>[1580, 0xFE9E, 0xFE9F, 0xFEA0], // ARABIC LETTER JEEM
  0x062D: <int>[1581, 0xFEA2, 0xFEA3, 0xFEA4], // ARABIC LETTER HAH
  0x062E: <int>[1582, 0xFEA6, 0xFEA7, 0xFEA8], // ARABIC LETTER KHAH
  0x062F: <int>[1583, 0xFEAA], // ARABIC LETTER DAL
  0x0630: <int>[1584, 0xFEAC], // ARABIC LETTER THAL
  0x0631: <int>[1585, 0xFEAE], // ARABIC LETTER REH
  0x0632: <int>[1586, 0xFEB0], // ARABIC LETTER ZAIN
  0x0633: <int>[1587, 0xFEB2, 0xFEB3, 0xFEB4], // ARABIC LETTER SEEN
  0x0634: <int>[1588, 0xFEB6, 0xFEB7, 0xFEB8], // ARABIC LETTER SHEEN
  0x0635: <int>[1589, 0xFEBA, 0xFEBB, 0xFEBC], // ARABIC LETTER SAD
  0x0636: <int>[1590, 0xFEBE, 0xFEBF, 0xFEC0], // ARABIC LETTER DAD
  0x0637: <int>[1591, 0xFEC2, 0xFEC3, 0xFEC4], // ARABIC LETTER TAH
  0x0638: <int>[1592, 0xFEC6, 0xFEC7, 0xFEC8], // ARABIC LETTER ZAH
  0x0639: <int>[1593, 0xFECA, 0xFECB, 0xFECC], // ARABIC LETTER AIN
  0x063A: <int>[1594, 0xFECE, 0xFECF, 0xFED0], // ARABIC LETTER GHAIN
  0x0641: <int>[1601, 0xFED2, 0xFED3, 0xFED4], // ARABIC LETTER FEH
  0x0642: <int>[1602, 0xFED6, 0xFED7, 0xFED8], // ARABIC LETTER QAF
  0x0643: <int>[1603, 0xFEDA, 0xFEDB, 0xFEDC], // ARABIC LETTER KAF
  0x0644: <int>[1604, 0xFEDE, 0xFEDF, 0xFEE0], // ARABIC LETTER LAM
  0x0645: <int>[1605, 0xFEE2, 0xFEE3, 0xFEE4], // ARABIC LETTER MEEM
  0x0646: <int>[1606, 0xFEE6, 0xFEE7, 0xFEE8], // ARABIC LETTER NOON
  0x0647: <int>[1607, 0xFEEA, 0xFEEB, 0xFEEC], // ARABIC LETTER HEH
  0x0648: <int>[1608, 0xFEEE], // ARABIC LETTER WAW
  0x0649: <int>[1609, 0xFEF0, 64488, 64489], // ARABIC LETTER ALEF MAKSURA
  0x064A: <int>[1610, 0xFEF2, 0xFEF3, 0xFEF4], // ARABIC LETTER YEH
  0x0671: <int>[0xFB50, 0xFB51], // ARABIC LETTER ALEF WASLA
  0x0677: <int>[0xFBDD], // ARABIC LETTER U WITH HAMZA ABOVE
  0x0679: <int>[0xFB66, 0xFB67, 0xFB68, 0xFB69], // ARABIC LETTER TTEH
  0x067A: <int>[0xFB5E, 0xFB5F, 0xFB60, 0xFB61], // ARABIC LETTER TTEHEH
  0x067B: <int>[0xFB52, 0xFB53, 0xFB54, 0xFB55], // ARABIC LETTER BEEH
  0x067E: <int>[0xFB56, 0xFB57, 0xFB58, 0xFB59], // ARABIC LETTER PEH
  0x067F: <int>[0xFB62, 0xFB63, 0xFB64, 0xFB65], // ARABIC LETTER TEHEH
  0x0680: <int>[0xFB5A, 0xFB5B, 0xFB5C, 0xFB5D], // ARABIC LETTER BEHEH
  0x0683: <int>[0xFB76, 0xFB77, 0xFB78, 0xFB79], // ARABIC LETTER NYEH
  0x0684: <int>[0xFB72, 0xFB73, 0xFB74, 0xFB75], // ARABIC LETTER DYEH
  0x0686: <int>[0xFB7A, 0xFB7B, 0xFB7C, 0xFB7D], // ARABIC LETTER TCHEH
  0x0687: <int>[0xFB7E, 0xFB7F, 0xFB80, 0xFB81], // ARABIC LETTER TCHEHEH
  0x0688: <int>[0xFB88, 0xFB89], // ARABIC LETTER DDAL
  0x068C: <int>[0xFB84, 0xFB85], // ARABIC LETTER DAHAL
  0x068D: <int>[0xFB82, 0xFB83], // ARABIC LETTER DDAHAL
  0x068E: <int>[0xFB86, 0xFB87], // ARABIC LETTER DUL
  0x0691: <int>[0xFB8C, 0xFB8D], // ARABIC LETTER RREH
  0x0698: <int>[0xFB8A, 0xFB8B], // ARABIC LETTER JEH
  0x06A4: <int>[0xFB6A, 0xFB6B, 0xFB6C, 0xFB6D], // ARABIC LETTER VEH
  0x06A6: <int>[0xFB6E, 0xFB6F, 0xFB70, 0xFB71], // ARABIC LETTER PEHEH
  0x06A9: <int>[0xFB8E, 0xFB8F, 0xFB90, 0xFB91], // ARABIC LETTER KEHEH
  0x06AD: <int>[0xFBD3, 0xFBD4, 0xFBD5, 0xFBD6], // ARABIC LETTER NG
  0x06AF: <int>[0xFB92, 0xFB93, 0xFB94, 0xFB95], // ARABIC LETTER GAF
  0x06B1: <int>[0xFB9A, 0xFB9B, 0xFB9C, 0xFB9D], // ARABIC LETTER NGOEH
  0x06B3: <int>[0xFB96, 0xFB97, 0xFB98, 0xFB99], // ARABIC LETTER GUEH
  0x06BA: <int>[0xFB9E, 0xFB9F], // ARABIC LETTER NOON GHUNNA
  0x06BB: <int>[0xFBA0, 0xFBA1, 0xFBA2, 0xFBA3], // ARABIC LETTER RNOON
  0x06BE: <int>[
    0xFBAA,
    0xFBAB,
    0xFBAC,
    0xFBAD
  ], // ARABIC LETTER HEH DOACHASHMEE
  0x06C0: <int>[0xFBA4, 0xFBA5], // ARABIC LETTER HEH WITH YEH ABOVE
  0x06C1: <int>[0xFBA6, 0xFBA7, 0xFBA8, 0xFBA9], // ARABIC LETTER HEH GOAL
  0x06C5: <int>[0xFBE0, 0xFBE1], // ARABIC LETTER KIRGHIZ OE
  0x06C6: <int>[0xFBD9, 0xFBDA], // ARABIC LETTER OE
  0x06C7: <int>[0xFBD7, 0xFBD8], // ARABIC LETTER U
  0x06C8: <int>[0xFBDB, 0xFBDC], // ARABIC LETTER YU
  0x06C9: <int>[0xFBE2, 0xFBE3], // ARABIC LETTER KIRGHIZ YU
  0x06CB: <int>[0xFBDE, 0xFBDF], // ARABIC LETTER VE
  0x06CC: <int>[0xFBFC, 0xFBFD, 0xFBFE, 0xFBFF], // ARABIC LETTER FARSI YEH
  0x06D0: <int>[0xFBE4, 0xFBE5, 0xFBE6, 0xFBE7], //ARABIC LETTER E
  0x06D2: <int>[0xFBAE, 0xFBAF], // ARABIC LETTER YEH BARREE
  0x06D3: <int>[0xFBB0, 0xFBB1], // ARABIC LETTER YEH BARREE WITH HAMZA ABOVE
};

/*
    var ligaturesSubstitutionA = {
        0xFBEA: []// ARABIC LIGATURE YEH WITH HAMZA ABOVE WITH ALEF ISOLATED FORM
    };
    */

const Map<int, dynamic> _diacriticLigatures = <int, dynamic>{
  0x0651: <int, int>{
    0x064C: 0xFC5E, // Shadda + Dammatan
    0x064D: 0xFC5F, // Shadda + Kasratan
    0x064E: 0xFC60, // Shadda + Fatha
    0x064F: 0xFC61, // Shadda + Damma
    0x0650: 0xFC62, // Shadda + Kasra
    0x0670: 0xFC63, // Shadda + Dagger alif
  },
};

const Map<int, dynamic> _ligatures = <int, dynamic>{
  0xFEDF: <int, int>{
    0xFE82:
        0xFEF5, // ARABIC LIGATURE LAM WITH ALEF WITH MADDA ABOVE ISOLATED FORM
    0xFE84:
        0xFEF7, // ARABIC LIGATURE LAM WITH ALEF WITH HAMZA ABOVE ISOLATED FORM
    0xFE88:
        0xFEF9, // ARABIC LIGATURE LAM WITH ALEF WITH HAMZA BELOW ISOLATED FORM
    0xFE8E: 0xFEFB // ARABIC LIGATURE LAM WITH ALEF ISOLATED FORM
  },
  0xFEE0: <int, int>{
    0xFE82: 0xFEF6, // ARABIC LIGATURE LAM WITH ALEF WITH MADDA ABOVE FINAL FORM
    0xFE84: 0xFEF8, // ARABIC LIGATURE LAM WITH ALEF WITH HAMZA ABOVE FINAL FORM
    0xFE88: 0xFEFA, // ARABIC LIGATURE LAM WITH ALEF WITH HAMZA BELOW FINAL FORM
    0xFE8E: 0xFEFC // ARABIC LIGATURE LAM WITH ALEF FINAL FORM
  },
  0xFE8D: <int, dynamic>{
    0xFEDF: <int, dynamic>{
      0xFEE0: <int, int>{0xFEEA: 0xFDF2}
    }
  }, // ALLAH
};

const List<int> _alfletter = <int>[1570, 1571, 1573, 1575];

const Map<int, int> _arabicDiacritics = <int, int>{
  0x064B: 0x064B, // Fathatan
  0x064C: 0x064C, // Dammatan
  0x064D: 0x064D, // Kasratan
  0x064E: 0x064E, // Fatha
  0x064F: 0x064F, // Damma
  0x0650: 0x0650, // Kasra
  0x0651: 0x0651, // Shadda
  0x0652: 0x0652, // Sukun

  0x0670: 0x0670, // Dagger alif

  0xFC5E: 0xFC5E, // Shadda + Dammatan
  0xFC5F: 0xFC5F, // Shadda + Kasratan
  0xFC60: 0xFC60, // Shadda + Fatha
  0xFC61: 0xFC61, // Shadda + Damma
  0xFC62: 0xFC62, // Shadda + Kasra
  0xFC63: 0xFC63, // Shadda + Dagger alif
  // 1548: 1548,
};

const int _noChangeInForm = -1;
const int _isolatedForm = 0;
const int _finalForm = 1;
const int _initialForm = 2;
const int _medialForm = 3;

bool _isInArabicSubstitutionA(int letter) {
  return _arabicSubstitionA.containsKey(letter);
}

bool _isArabicLetter(int letter) {
  return (letter >= 0x0600 && letter <= 0x06FF) ||
      (letter >= 0x0750 && letter <= 0x077F) ||
      (letter >= 0x0870 && letter <= 0x089F) ||
      (letter >= 0x08A0 && letter <= 0x08FF) ||
      (letter >= 0xFB50 && letter <= 0xFDFF) ||
      (letter >= 0xFE70 && letter <= 0xFEFF) ||
      (letter >= 0x10E60 && letter <= 0x10E7F) ||
      (letter >= 0x1EC70 && letter <= 0x1ECBF) ||
      (letter >= 0x1ED00 && letter <= 0x1ED4F) ||
      (letter >= 0x1EE00 && letter <= 0x1EEFF);
}

bool _isArabicEndLetter(int letter) {
  return _isArabicLetter(letter) &&
      _isInArabicSubstitutionA(letter) &&
      _arabicSubstitionA[letter].length <= 2;
}

bool _isArabicAlfLetter(int letter) {
  return _isArabicLetter(letter) && _alfletter.contains(letter);
}

bool _arabicLetterHasFinalForm(int letter) {
  return _isArabicLetter(letter) &&
      _isInArabicSubstitutionA(letter) &&
      (_arabicSubstitionA[letter].length >= 2);
}

bool _arabicLetterHasMedialForm(int letter) {
  return _isArabicLetter(letter) &&
      _isInArabicSubstitutionA(letter) &&
      _arabicSubstitionA[letter].length == 4;
}

bool _isArabicDiacritic(int letter) {
  return _arabicDiacritics.containsKey(letter);
}

bool isArabicDiacriticValue(int letter) {
  return _arabicDiacritics.containsValue(letter);
}

List<int> _resolveLigatures(List<int> lettersq) {
  final result = <int>[];
  dynamic tmpLigatures = _ligatures;
  dynamic tmpDiacritic = _diacriticLigatures;
  final letters = lettersq.reversed.toList();

  final effectedLetters = <int>[];
  final effectedDiacritics = <int>[];

  final finalDiacritics = <int>[];

  for (var i = 0; i < letters.length; i++) {
    if (isArabicDiacriticValue(letters[i])) {
      effectedDiacritics.insert(0, letters[i]);
      if (tmpDiacritic.containsKey(letters[i])) {
        tmpDiacritic = tmpDiacritic[letters[i]];

        if (tmpDiacritic is int) {
          finalDiacritics.insert(0, tmpDiacritic);
          tmpDiacritic = _diacriticLigatures;
          effectedDiacritics.clear();
        }
      } else {
        tmpDiacritic = _diacriticLigatures;

        // add all Diacritics if there is no letter Ligatures.
        if (effectedLetters.isEmpty) {
          result.insertAll(0, finalDiacritics);
          result.insertAll(0, effectedDiacritics);
          finalDiacritics.clear();
          effectedDiacritics.clear();
        }
      }
    } else if (tmpLigatures.containsKey(letters[i])) {
      effectedLetters.insert(0, letters[i]);
      tmpLigatures = tmpLigatures[letters[i]];

      if (tmpLigatures is int) {
        result.insert(0, tmpLigatures);
        tmpLigatures = _ligatures;
        effectedLetters.clear();
      }
    } else {
      tmpLigatures = _ligatures;

      // add effected letters if they aren't ligature.
      if (effectedLetters.isNotEmpty) {
        result.insertAll(0, effectedLetters);
        effectedLetters.clear();
      }

      // add Diacritics after or before letter ligature.
      if (effectedLetters.isEmpty && effectedDiacritics.isNotEmpty) {
        result.insertAll(0, effectedDiacritics);
        effectedDiacritics.clear();
      }

      result.insert(0, letters[i]);
    }

    // add Diacritic ligatures.
    if (effectedLetters.isEmpty && finalDiacritics.isNotEmpty) {
      result.insertAll(0, finalDiacritics);
      finalDiacritics.clear();
    }
  }

  return result;
}

int _getCorrectForm(int currentChar, int beforeChar, int nextChar) {
  if (_isInArabicSubstitutionA(currentChar) == false) {
    return _noChangeInForm;
  }
  if (!_arabicLetterHasFinalForm(currentChar) ||
      (!_isArabicLetter(beforeChar) && !_isArabicLetter(nextChar)) ||
      (!_isArabicLetter(nextChar) && _isArabicEndLetter(beforeChar)) ||
      (_isArabicEndLetter(currentChar) && !_isArabicLetter(beforeChar)) ||
      (_isArabicEndLetter(currentChar) && _isArabicAlfLetter(beforeChar)) ||
      (_isArabicEndLetter(currentChar) && _isArabicEndLetter(beforeChar))) {
    return _isolatedForm;
  }

  if (_arabicLetterHasMedialForm(currentChar) &&
      _isArabicLetter(beforeChar) &&
      !_isArabicEndLetter(beforeChar) &&
      _isArabicLetter(nextChar) &&
      _arabicLetterHasFinalForm(nextChar)) {
    return _medialForm;
  }

  if (_isArabicEndLetter(currentChar) || (!_isArabicLetter(nextChar))) {
    return _finalForm;
  }
  return _initialForm;
}

Iterable<String> _parse(String text) sync* {
  final words = text.split(' ');

  final notArabicWords = <List<int>>[];

  var first = true;
  for (var word in words) {
    final newWord = <int>[];
    var isNewWordArabic = false;

    var prevLetter = 0;

    for (var j = 0; j < word.length; j += 1) {
      final currentLetter = word.codeUnitAt(j);

      if (_isArabicDiacritic(currentLetter)) {
        newWord.insert(0, _arabicDiacritics[currentLetter]!);
        continue;
      }
      final nextLetter = word
          .split('')
          .skip(j + 1)
          .map((String e) => e.codeUnitAt(0))
          .firstWhere(
            (int element) => !_isArabicDiacritic(element),
            orElse: () => 0,
          );

      if (_isArabicLetter(currentLetter)) {
        isNewWordArabic = true;

        final position = _getCorrectForm(currentLetter, prevLetter, nextLetter);
        prevLetter = currentLetter;
        if (position != -1) {
          newWord.insert(0, _arabicSubstitionA[currentLetter][position]);
        } else {
          newWord.add(currentLetter);
        }
      } else {
        prevLetter = 0;
        if (isNewWordArabic && currentLetter > 32) {
          newWord.insert(0, currentLetter);
        } else {
          newWord.add(currentLetter);
        }
      }
    }

    if (!first && isNewWordArabic) {
      yield ' ';
    }
    first = false;

    if (isNewWordArabic) {
      isNewWordArabic = false;
      for (var notArabicNewWord in notArabicWords) {
        yield '${String.fromCharCodes(notArabicNewWord)} ';
      }
      notArabicWords.clear();
      yield String.fromCharCodes(_resolveLigatures(newWord));
    } else {
      notArabicWords.insert(0, newWord);
    }
  }
  // if notArabicWords.length != 0, that means all sentence doesn't contain Arabic.
  for (var i = 0; i < notArabicWords.length; i++) {
    yield String.fromCharCodes(notArabicWords[i]);
    if (i != notArabicWords.length - 1) {
      yield ' ';
    }
  }
}

/// Apply Arabic shape substitutions
String convert(String input) {
  return List<String>.from(_parse(input)).join('');
}