typingfreaks/src/kana.ts

/**
 * This module is mainly for handling romaji input to match the provided kana
 * input. While most kana map one-to-one with romaji, some kana have multiple
 * ways to be inputted. In addition, we also have to handle っ which causes the
 * next consonant to be repeated.
 *
 * The state management is done by having a state machine for each kana and it
 * should handle all possible variations of the romaji to be inputted.
 * Additionally, it also keeps track of what is left to be input, and adjusts
 * itself accordingly if an alternative romaji was used.
 *
 * One of the key considerations is handling っ. It doesn't have a spelling in
 * and of itself, but just modifies the state machine that will come after it.
 * Intermediate states need to be created and care should be given in what shows
 * up in the display.
 */

import * as state from './state';
import {
  State,
  StateMachine,
  makeTransition as t,
} from './state';

  function literal(source: string, ...extraBoundaries: number[]): StateMachine {
    let transitions: state.Transition[] = [];
    for (let i = 0; i < source.length; ++i) {
      let from = source.substring(i);
      let input = source.charAt(i);
      let to = source.substring(i+1);
      let boundary = i === (source.length - 1) || extraBoundaries.indexOf(i) >= 0;
      transitions.push(t(from, input, to, boundary));
    }
    return state.buildFromTransitions(source, transitions);
  }

  function shi(): StateMachine {
    return state.buildFromTransitions('shi', [
      t('shi', 's', 'hi'),
      t('hi', 'h', 'i'),
      t('hi', 'i', '', true),
      t('i', 'i', '', true)
    ]);
  }

  function chi(): StateMachine {
    return state.buildFromTransitions('chi', [
      t('chi', 'c', 'hi'),
      t('chi', 't', 'i'),
      t('hi', 'h', 'i'),
      t('i', 'i', '', true)
    ]);
  }

  function tsu(): StateMachine {
    return state.buildFromTransitions('tsu', [
      t('tsu', 't', 'su'),
      t('su', 's', 'u'),
      t('su', 'u', '', true),
      t('u', 'u', '', true)
    ]);
  }

  function fu(): StateMachine {
    return state.buildFromTransitions('fu', [
      t('fu', 'f', 'u'),
      t('fu', 'h', 'u'),
      t('u', 'u', '', true)
    ]);
  }

  function ji(): StateMachine {
    return state.buildFromTransitions('ji', [
      t('ji', 'j', 'i'),
      t('ji', 'z', 'i'),
      t('i', 'i', '', true)
    ]);
  }

  function sh(end: string): StateMachine {
    let source = 'sh' + end;
    let middle = 'h' + end;
    return state.buildFromTransitions(source, [
      t(source, 's', middle, true),
      t(middle, 'h', end),
      t(middle, 'y', end),
      t(end, end, '', true)
    ]);
  }

  function ch(end: string): StateMachine {
    let source = 'ch' + end;
    let middle = 'h' + end;
    let altMiddle = 'y' + end;

    return state.buildFromTransitions(source, [
      t(source, 'c', middle),
      t(middle, 'h', end, true),
      t(source, 't', altMiddle, true),
      t(altMiddle, 'y', end),
      t(end, end, '', true)
    ]);
  }

  function j(end: string): StateMachine {
    let source = 'j' + end;
    let altMiddle = 'y' + end;

    return state.buildFromTransitions(source, [
      t(source, 'j', end, true),
      t(source, 'z', altMiddle),
      t(end, 'y', end),
      t(altMiddle, 'y', end, true),
      t(end, end, '', true)
    ]);
  }

  function smallTsu(base: StateMachine): StateMachine {
    let { display, transitions } = base.initialState;

    let newState = new State(display.charAt(0) + display);
    Object.keys(transitions).forEach(k => {
      let [nextState, _] = transitions[k];
      let intermediateDisplay = k + nextState.display;
      let intermediateState = new State(intermediateDisplay);
      intermediateState.addTransition(k, nextState);
      newState.addTransition(k, intermediateState, true);
    })

    return new StateMachine(newState, base.finalState);
  }

  function smallKana(base: StateMachine): StateMachine {
    let newState = base.initialState.clone();
    newState.addTransition('l', base.initialState);
    newState.addTransition('x', base.initialState);
    return new StateMachine(newState, base.finalState);
  }

  interface KanaMapping {
    [index: string]: StateMachine
  }

  interface StringMapping {
    [index: string]: string
  }

  const WHITESPACE = state.buildFromTransitions('_', [
    t('_', '_', ''),
    t('_', ' ', '')
  ]);

  const KATAKANA_MAPPING: StringMapping = {
    "ア": "あ",
    "イ": "い",
    "ウ": "う",
    "エ": "え",
    "オ": "お",
    "カ": "か",
    "キ": "き",
    "ク": "く",
    "ケ": "け",
    "コ": "こ",
    "サ": "さ",
    "シ": "し",
    "ス": "す",
    "セ": "せ",
    "ソ": "そ",
    "タ": "た",
    "チ": "ち",
    "ツ": "つ",
    "テ": "て",
    "ト": "と",
    "ナ": "な",
    "ニ": "に",
    "ヌ": "ぬ",
    "ネ": "ね",
    "ノ": "の",
    "ハ": "は",
    "ヒ": "ひ",
    "フ": "ふ",
    "ヘ": "へ",
    "ホ": "ほ",
    "マ": "ま",
    "ミ": "み",
    "ム": "む",
    "メ": "め",
    "モ": "も",
    "ヤ": "や",
    "ユ": "ゆ",
    "ヨ": "よ",
    "ラ": "ら",
    "リ": "り",
    "ル": "る",
    "レ": "れ",
    "ロ": "ろ",
    "ワ": "わ",
    "ヰ": "ゐ",
    "ヱ": "ゑ",
    "ヲ": "を",
    "ン": "ん",
    "ガ": "が",
    "ギ": "ぎ",
    "グ": "ぐ",
    "ゲ": "げ",
    "ゴ": "ご",
    "ザ": "ざ",
    "ジ": "じ",
    "ズ": "ず",
    "ゼ": "ぜ",
    "ゾ": "ぞ",
    "ダ": "だ",
    "ヂ": "ぢ",
    "ヅ": "づ",
    "デ": "で",
    "ド": "ど",
    "バ": "ば",
    "ビ": "び",
    "ブ": "ぶ",
    "ベ": "べ",
    "ボ": "ぼ",
    "パ": "ぱ",
    "ピ": "ぴ",
    "プ": "ぷ",
    "ペ": "ぺ",
    "ポ": "ぽ",
    "ヴ": "ゔ",
    "ァ": "ぁ",
    "ィ": "ぃ",
    "ゥ": "ぅ",
    "ェ": "ぇ",
    "ォ": "ぉ",
    "ャ": "ゃ",
    "ュ": "ゅ",
    "ョ": "ょ",
    "ッ": "っ"
  }

  const SINGLE_KANA_MAPPING: KanaMapping = {
    "あ": literal('a'),
    "い": literal('i'),
    "う": literal('u'),
    "え": literal('e'),
    "お": literal('o'),
    "か": literal('ka'),
    "き": literal('ki'),
    "く": literal('ku'),
    "け": literal('ke'),
    "こ": literal('ko'),
    "さ": literal('sa'),
    "し": shi(),
    "す": literal('su'),
    "せ": literal('se'),
    "そ": literal('so'),
    "た": literal('ta'),
    "ち": chi(),
    "つ": tsu(),
    "て": literal('te'),
    "と": literal('to'),
    "な": literal('na'),
    "に": literal('ni'),
    "ぬ": literal('nu'),
    "ね": literal('ne'),
    "の": literal('no'),
    "は": literal('ha'),
    "ひ": literal('hi'),
    "ふ": fu(),
    "へ": literal('he'),
    "ほ": literal('ho'),
    "ま": literal('ma'),
    "み": literal('mi'),
    "む": literal('mu'),
    "め": literal('me'),
    "も": literal('mo'),
    "や": literal('ya'),
    "ゆ": literal('yu'),
    "よ": literal('yo'),
    "ら": literal('ra'),
    "り": literal('ri'),
    "る": literal('ru'),
    "れ": literal('re'),
    "ろ": literal('ro'),
    "わ": literal('wa'),
    "ゐ": literal('i'),
    "ゑ": literal('e'),
    "を": literal('wo'),
    "ん": literal('n'),
    "が": literal('ga'),
    "ぎ": literal('gi'),
    "ぐ": literal('gu'),
    "げ": literal('ge'),
    "ご": literal('go'),
    "ざ": literal('za'),
    "じ": ji(),
    "ず": literal('zu'),
    "ぜ": literal('ze'),
    "ぞ": literal('zo'),
    "だ": literal('da'),
    "ぢ": literal('di'),
    "づ": literal('du'),
    "で": literal('de'),
    "ど": literal('do'),
    "ば": literal('ba'),
    "び": literal('bi'),
    "ぶ": literal('bu'),
    "べ": literal('be'),
    "ぼ": literal('bo'),
    "ぱ": literal('pa'),
    "ぴ": literal('pi'),
    "ぷ": literal('pu'),
    "ぺ": literal('pe'),
    "ぽ": literal('po'),
    "ゔ": literal('vu'),
    "ー": literal('-'),
    " ": WHITESPACE
  };

  'abcdefghijklmnopqrstuvwxyz'.split('').forEach(letter => {
    SINGLE_KANA_MAPPING[letter] = literal(letter);
  });

  [
    ['ぁ', 'あ'],
    ['ぃ', 'い'],
    ['ぅ', 'う'],
    ['ぇ', 'え'],
    ['ぉ', 'お'],
    ['ヵ', 'か']
  ].forEach(pair => {
    let [ small, big ] = pair;
    SINGLE_KANA_MAPPING[small] = smallKana(SINGLE_KANA_MAPPING[big]);
  });

  const DOUBLE_KANA_MAPPING: KanaMapping = {
    "きゃ": literal('kya', 0),
    "きゅ": literal('kyu', 0),
    "きょ": literal('kyo', 0),
    "しゃ": sh('a'),
    "しゅ": sh('u'),
    "しょ": sh('o'),
    "ちゃ": ch('a'),
    "ちゅ": ch('u'),
    "ちょ": ch('o'),
    "にゃ": literal('nya', 0),
    "にゅ": literal('nyu', 0),
    "にょ": literal('nyo', 0),
    "ひゃ": literal('hya', 0),
    "ひゅ": literal('hyu', 0),
    "ひょ": literal('hyo', 0),
    "みゃ": literal('mya', 0),
    "みゅ": literal('myu', 0),
    "みょ": literal('myo', 0),
    "りゃ": literal('rya', 0),
    "りゅ": literal('ryu', 0),
    "りょ": literal('ryo', 0),
    "ぎゃ": literal('gya', 0),
    "ぎゅ": literal('gyu', 0),
    "ぎょ": literal('gyo', 0),
    "じゃ": j('a'),
    "じゅ": j('u'),
    "じょ": j('o'),
    "ぢゃ": literal('dya', 0),
    "ぢゅ": literal('dyu', 0),
    "ぢょ": literal('dyo', 0),
    "びゃ": literal('bya', 0),
    "びゅ": literal('byu', 0),
    "びょ": literal('byo', 0),
    "ぴゃ": literal('pya', 0),
    "ぴゅ": literal('pyu', 0),
    "ぴょ": literal('pyo', 0),
    "ふぁ": literal('fa', 0),
    "ふぃ": literal('fi', 0),
    "ふぇ": literal('fe', 0),
    "ふぉ": literal('fo', 0),
    "ゔぁ": literal('va', 0),
    "ゔぃ": literal('vi', 0),
    "ゔぇ": literal('ve', 0),
    "ゔぉ": literal('vo', 0)
  }

  const TRIPLE_KANA_MAPPING: KanaMapping = {};

  [
    "か", "き", "く", "け", "こ",
    "さ", "し", "す", "せ", "そ",
    "た", "ち", "つ", "て", "と",
    "は", "ひ", "ふ", "へ", "ほ",
    "が", "ぎ", "ぐ", "げ", "ご",
    "ざ", "じ", "ず", "ぜ", "ぞ",
    "だ", "ぢ", "づ", "で", "ど",
    "ば", "び", "ぶ", "べ", "ぼ",
    "ぱ", "ぴ", "ぷ", "ぺ", "ぽ",
    "ゔ"
  ].forEach(kana => {
    DOUBLE_KANA_MAPPING['っ' + kana] = smallTsu(SINGLE_KANA_MAPPING[kana]);
  });
  [
    "きゃ", "きゅ", "きょ",
    "しゃ", "しゅ", "しょ",
    "ちゃ", "ちゅ", "ちょ",
    "ぎゃ", "ぎゅ", "ぎょ",
    "じゃ", "じゅ", "じょ",
    "ぢゃ", "ぢゅ", "ぢょ",
    "びゃ", "びゅ", "びょ",
    "ぴゃ", "ぴゅ", "ぴょ",
    "ふぁ", "ふぃ", "ふぇ", "ふぉ",
    "ゔぁ", "ゔぃ", "ゔぇ", "ゔぉ"
  ].forEach(kana => {
    TRIPLE_KANA_MAPPING['っ' + kana] = smallTsu(DOUBLE_KANA_MAPPING[kana]);
  });

  /**
   * This normalizes input for matching. All alphabet is lower-cased, katakana
   * is transformed to hiragana. All whitespace is now just a space. We take
   * care to not change the length of the string as we have to match it
   * one-for-one so we can display the original source kana.
   */
  export function normalizeInput(input: string): string {
    return input.toLowerCase().split('').map(letter => {
      let transform = KATAKANA_MAPPING[letter];
      if (transform !== undefined) {
        return transform;
      } else if (/\s/.test(letter)) {
        return ' ';
      } else {
        return letter;
      }
    }).join('');
  }

  export class KanaInputState {
    kana: string[];
    stateMachines: StateMachine[];
    currentIndex: number;

    constructor(input: string) {
      let kana: string[] = [];
      let machines: StateMachine[] = [];
      let position = 0;

      let mappings = [
        SINGLE_KANA_MAPPING,
        DOUBLE_KANA_MAPPING,
        TRIPLE_KANA_MAPPING
      ]

      // we pad the input so checking 3 at a time is simpler
      let normalized = normalizeInput(input) + '  ';
      while (position < input.length) {
        // we check substrings of length 3, 2, then 1
        for (let i = 3; i > 0; --i) {
          let original = input.substr(position, i);
          let segment = normalized.substr(position, i);
          let machine = mappings[i - 1][segment];
          if (machine != undefined) {
            kana.push(original);
            let nextMachine = machine.clone();
            if (machines.length > 0) {
              let prevMachine = machines[machines.length - 1];
              prevMachine.nextMachine = nextMachine;
            }
            machines.push(nextMachine);
            position += i - 1;
            break;
          }
        }
        // even if we don't find a match, keep progressing
        // unmapped characters will be ignored
        position += 1;
      }

      this.kana = kana;
      this.stateMachines = machines;
      this.currentIndex = 0;
    }

    map<T>(func: (s: string, m: StateMachine) => T): T[] {
      let result: T[] = [];
      for (let i = 0; i < this.kana.length; ++i) {
        result.push(func(this.kana[i], this.stateMachines[i]));
      }
      return result;
    }

    handleInput(input: string): boolean {
      if (this.currentIndex >= this.stateMachines.length) return false;

      let currentMachine = this.stateMachines[this.currentIndex];
      currentMachine.transition(input);
      while (currentMachine.isFinished()) {
        this.currentIndex += 1;
        currentMachine = this.stateMachines[this.currentIndex];
        if (currentMachine == null) {
          return true;
        }
      }
      return this.currentIndex >= this.stateMachines.length;
    }

    getRemainingInput(): string {
      let remaining = '';
      for (let i = this.currentIndex; i < this.stateMachines.length; ++i) {
        remaining += this.stateMachines[i].getDisplay();
      }
      return remaining;
    }
  }