cjk-readings/src/generatePinyin.ts

Web service that generates readings for chinese characters.

/**
 * Parts of this file are based on:
 * - https://github.com/hotoo/pinyin/blob/master/lib/index.js
 * - https://github.com/hotoo/pinyin/blob/master/lib/pinyin.js
 * Copyright 闲耘 <hotoo.cn@gmail.com>
 * Used under MIT License
 */

import jieba from 'nodejieba'
import PINYIN_DICT from 'pinyin/data/dict-zi'
import PHRASES_DICT from 'pinyin/data/phrases-dict'

import { TextPart } from './types'

function segmentIntoPhrases(text: string): string[] {
  return jieba.cutSmall(text, 4)
}

function convertCharacter(char: string): TextPart {
  if (char.length !== 1) {
    return convertCharacter(char.charAt(0))
  }

  const charCode = char.charCodeAt(0)

  if (!PINYIN_DICT[charCode]) {
    return [char, []]
  }

  return [char, PINYIN_DICT[charCode].split(',')]
}

function convertPhrase(phrase: string): TextPart[] {
  let parts: TextPart[] = []
  if (PHRASES_DICT.hasOwnProperty(phrase)) {
    parts = parts.concat(
      PHRASES_DICT[phrase].map((readings, i) => [phrase[i], readings]),
    )
  } else {
    parts = parts.concat(Array.from(phrase).map(convertCharacter))
  }
  return parts
}

function convertText(text: string): TextPart[] {
  const phrases = segmentIntoPhrases(text)

  let parts: TextPart[] = []
  let readingless = ''

  for (let i = 0; i < phrases.length; i++) {
    const phraseOrCharacter = phrases[i]
    const firstCharCode = phraseOrCharacter.charCodeAt(0)

    if (PINYIN_DICT[firstCharCode]) {
      // ends of characters without readings.
      if (readingless.length > 0) {
        parts.push([readingless, []])
        readingless = ''
      }

      if (phraseOrCharacter.length === 1) {
        parts = parts.concat(convertCharacter(phraseOrCharacter))
      } else {
        parts = parts.concat(convertPhrase(phraseOrCharacter))
      }
    } else {
      readingless += phraseOrCharacter
    }
  }

  // finish off with any readingless characters
  if (readingless.length > 0) {
    parts.push([readingless, []])
  }

  return parts
}

export function generatePinyin(text: string): TextPart[] {
  return convertText(text)
}