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