Basic word position and completion service.

src/services/completion/completion.js

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+import { reduce, find } from 'lodash'
+
+export const replaceWord = (str, toReplace, replacement) => {
+  return str.slice(0, toReplace.start) + replacement + str.slice(toReplace.end)
+}
+
+export const wordAtPosition = (str, pos) => {
+  const words = splitIntoWords(str)
+  const wordsWithPosition = addPositionToWords(words)
+
+  return find(wordsWithPosition, ({start, end}) => start <= pos && end > pos)
+}
+
+export const addPositionToWords = (words) => {
+  return reduce(words, (result, word) => {
+    const data = {
+      word,
+      start: 0,
+      end: word.length
+    }
+
+    if (result.length > 0) {
+      const previous = result.pop()
+
+      data.start += previous.end
+      data.end += previous.end
+
+      result.push(previous)
+    }
+
+    result.push(data)
+
+    return result
+  }, [])
+}
+
+export const splitIntoWords = (str) => {
+  // Split at word boundaries
+  const regex = /\b/
+  const triggers = /[@#]+$/
+
+  let split = str.split(regex)
+
+  // Add trailing @ and # to the following word.
+  const words = reduce(split, (result, word) => {
+    if (result.length > 0) {
+      let previous = result.pop()
+      const matches = previous.match(triggers)
+      if (matches) {
+        previous = previous.replace(triggers, '')
+        word = matches[0] + word
+      }
+      result.push(previous)
+    }
+    result.push(word)
+
+    return result
+  }, [])
+
+  return words
+}
+
+const completion = {
+  wordAtPosition,
+  addPositionToWords,
+  splitIntoWords,
+  replaceWord
+}
+
+export default completion

test/unit/specs/services/completion/completion.spec.js

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+import { replaceWord, addPositionToWords, wordAtPosition, splitIntoWords } from '../../../../../src/services/completion/completion.js'
+
+describe('addPositiontoWords', () => {
+  it('adds the position to a word list', () => {
+    const words = ['hey', 'this', 'is', 'fun']
+
+    const expected = [
+      {
+        word: 'hey',
+        start: 0,
+        end: 3
+      },
+      {
+        word: 'this',
+        start: 3,
+        end: 7
+      },
+      {
+        word: 'is',
+        start: 7,
+        end: 9
+      },
+      {
+        word: 'fun',
+        start: 9,
+        end: 12
+      }
+    ]
+
+    const res = addPositionToWords(words)
+
+    expect(res).to.eql(expected)
+  })
+})
+
+describe('splitIntoWords', () => {
+  it('splits at whitespace boundaries', () => {
+    const str = 'This is a #nice @test for you, @idiot.'
+    const expected = ['This', ' ', 'is', ' ', 'a', ' ', '#nice', ' ', '@test', ' ', 'for', ' ', 'you', ', ', '@idiot', '.']
+    const res = splitIntoWords(str)
+
+    expect(res).to.eql(expected)
+  })
+})
+
+describe('wordAtPosition', () => {
+  it('returns the word for a given string and postion, plus the start and end position of that word', () => {
+    const str = 'Hey this is fun'
+
+    const { word, start, end } = wordAtPosition(str, 4)
+
+    expect(word).to.eql('this')
+    expect(start).to.eql(4)
+    expect(end).to.eql(8)
+  })
+})
+
+describe('replaceWord', () => {
+  it('replaces a word (with start and end) with another word in a given string', () => {
+    const str = 'hey @take, how are you'
+    const wordsWithPosition = addPositionToWords(splitIntoWords(str))
+    const toReplace = wordsWithPosition[2]
+
+    expect(toReplace.word).to.eql('@take')
+
+    const expected = 'hey @takeshitakenji, how are you'
+    const res = replaceWord(str, toReplace, '@takeshitakenji')
+    expect(res).to.eql(expected)
+  })
+})