export type Casing =
  //camelCase
  | "camel"
  //PascalCase
  | "pascal"
  //snake_case
  | "snake"
  //kebab-case
  | "kebab"
  //CAPITAL_CASE
  | "capital"
  //Human case
  | "human";

/**
 * this function does the same as kebabCase but it also does some more transformation on top
 *
 * useful for making simple URLs and filenames. Kebacase is not enough
 *
 * NB: this is no two way transformation. When slugifying something, information is lost and it cannot be converted back in the original name.
 *
 * TODO: make the tranformations that are done here into smaller util functions and make a clean function that can be ran before running every casing conversion (maybe in a config)
 */
export function slugify(string: string) {
  const a =
    "àáâäæãåāăąçćčđďèéêëēėęěğǵḧîïíīįìıİłḿñńǹňôöòóœøōõőṕŕřßśšşșťțûüùúūǘůűųẃẍÿýžźż·/_,:;";
  const b =
    "aaaaaaaaaacccddeeeeeeeegghiiiiiiiilmnnnnoooooooooprrsssssttuuuuuuuuuwxyyzzz------";
  const p = new RegExp(a.split("").join("|"), "g");

  return string
    .toString()
    .toLowerCase()
    .replace(/\s+/g, "-") // Replace spaces with -
    .replace(p, (c) => b.charAt(a.indexOf(c))) // Replace special characters
    .replace(/&/g, "-and-") // Replace & with 'and'
    .replace(/[^\w\-]+/g, "") // Remove all non-word characters
    .replace(/\-\-+/g, "-") // Replace multiple - with single -
    .replace(/^-+/, "") // Trim - from start of text
    .replace(/-+$/, ""); // Trim - from end of text
}

/**
 * Slugification for filepaths in specific
 */
export function fileSlugify(string: string) {
  const a =
    "àáâäæãåāăąçćčđďèéêëēėęěğǵḧîïíīįìıİłḿñńǹňôöòóœøōõőṕŕřßśšşșťțûüùúūǘůűųẃẍÿýžźż·,:;";
  const b =
    "aaaaaaaaaacccddeeeeeeeegghiiiiiiiilmnnnnoooooooooprrsssssttuuuuuuuuuwxyyzzz----";
  const p = new RegExp(a.split("").join("|"), "g");

  return (
    string
      .toString()
      .replace(/\s+/g, "-") // Replace spaces with -
      .replace(p, (c) => b.charAt(a.indexOf(c))) // Replace special characters
      .replace(/&/g, "-and-") // Replace & with 'and'
      // .replace(/[^\w\-]+/g, "") // Remove all non-word characters
      .replace(/\-\-+/g, "-") // Replace multiple - with single -
      .replace(/^-+/, "") // Trim - from start of text
      .replace(/-+$/, "")
  ); // Trim - from end of text
}

/**
 * Besides normal delimiters, every capital letter also marks the start of a new word
 */
const splitCasingDelimiters = (word: string): string[] => {
  const letters = word.split("");
  const allWords = letters.reduce(
    (words, letter) => {
      //get the last word, we know it's always defined because of the initial value of the reduce
      const lastWord: string = words.pop()!;
      //let's also get the last letter
      const lastLetter = lastWord.substring(-1);
      const lastLetterIsLowercase = lastLetter.toUpperCase() !== lastLetter;
      // NB: numbers or special characters are not uppercase in this logic, only letters change.
      const letterIsUppercase = letter.toLowerCase() !== letter;

      /**
       * If the last letter was lowercase and the next one is uppercase
       */
      const shouldCreateNewWord = lastLetterIsLowercase && letterIsUppercase;

      const newSequence = shouldCreateNewWord
        ? [lastWord, letter]
        : [`${lastWord}${letter}`];
      const newWords = words.concat(newSequence);
      return newWords;
    },
    [""],
  );

  return allWords;
  // if it was lowercase but it became upper, it's a new word
};

const nonCasingDelimiters = /[\s,._-]+/; //space, comma, dot, underscore, dash

export const getDelimiter = (target: Casing) => {
  if (target === "capital") return "_";
  if (target === "human") return " ";
  if (target === "kebab") return "-";
  if (target === "snake") return "_";
  return "";
};

export const capitaliseFirstLetter = (word: string) => {
  return word.charAt(0).toUpperCase().concat(word.substring(1));
};

const convertToTargetCasing = (word: string, index: number, target: Casing) => {
  if (target === "capital") return word.toUpperCase();
  if (target === "kebab" || target === "snake") return word.toLowerCase();
  if (target === "pascal") return capitaliseFirstLetter(word);
  if (target === "camel")
    return index === 0 ? word.toLowerCase() : capitaliseFirstLetter(word);

  //human case
  return index === 0 ? capitaliseFirstLetter(word) : word.toLowerCase();
};

/**
 *
 */
export const convertCase = (
  /**
   * NB: texts of more than a sentence are not supported
   */
  text: string,
  target: Casing,
) =>
  text
    .split(nonCasingDelimiters)
    .reduce(
      (all, word) => all.concat(splitCasingDelimiters(word)),
      [] as string[],
    )
    .map((word, index) => convertToTargetCasing(word, index, target))
    .join(getDelimiter(target));

export const camelCase = (text: string) => convertCase(text, "camel");
export const pascalCase = (text: string) => convertCase(text, "pascal");
export const snakeCase = (text: string) => convertCase(text, "snake");
export const kebabCase = (text: string) => convertCase(text, "kebab");
export const capitalCase = (text: string) => convertCase(text, "capital");
export const humanCase = (text: string) => convertCase(text, "human");

/**
 * converts any string to an array of lowercase words
 *
 * format ["word1","word2","word3"] from a string of any casing.
 */
export const lowerCaseArray = (text: string) => {
  return kebabCase(text).split("-");
};