let words = [
  "Apple",
  "Pencil",
  "Pen",
  "Chair",
  "Helmet",
  "Grapes",
  "Tub",
  "Trophy",
  "Cookie",
  "Donut",
  "Shirt",
  "Bat",
  "Ash",
  "Bell",
  "Chat",
  "Ball",
  "Eye",
  "Fish",
  "Zip",
  "Game",
  "Juice",
  "Orange",
  "Fan",
  "Ice",
];
words.sort();
let input = document.getElementById("input");
let suggestion = document.getElementById("suggestion");
//Enter key code
const enterKey = 13;

window.onload = () => {
  input.value = "";
  clearSuggestion();
};

const clearSuggestion = () => {
  suggestion.innerHTML = "";
};

const caseCheck = (word) => {
  //Array of characters
  word = word.split("");
  let inp = input.value;
  //loop through every character in ino
  for (let i in inp) {
    //if input character matches with character in word no need to change
    if (inp[i] == word[i]) {
      continue;
    } else if (inp[i].toUpperCase() == word[i]) {
      //if inp[i] when converted to uppercase matches word[i] it means word[i] needs to be lowercase
      word.splice(i, 1, word[i].toLowerCase());
    } else {
      //word[i] needs to be uppercase
      word.splice(i, 1, word[i].toUpperCase());
    }
  }
  //array to string
  return word.join("");
};

//Execute function on input
input.addEventListener("input", (e) => {
  clearSuggestion();
  //Convert input value to regex since string.startsWith() is case sensitive
  let regex = new RegExp("^" + input.value, "i");
  //loop through words array
  for (let i in words) {
    //check if input matches with any word in words array
    if (regex.test(words[i]) && input.value != "") {
      //Change case of word in words array according to user input
      words[i] = caseCheck(words[i]);
      //display suggestion
      suggestion.innerHTML = words[i];
      break;
    }
  }
});

//Complete predictive text on enter key
input.addEventListener("keydown", (e) => {
  //When user presses enter and suggestion exists
  if (e.keyCode == enterKey && suggestion.innerText != "") {
    e.preventDefault();
    input.value = suggestion.innerText;
    //clear the suggestion
    clearSuggestion();
  }
});