// Copyright (c) Microsoft. All rights reserved.

// This code is a copy of the code made available by https://www.npmjs.com/package/camelcase
// Since the original module isn't supported by create-react-app we are using the code manually here
// as a workaround.

const preserveCamelCase = input => {
  let isLastCharLower = false;
  let isLastCharUpper = false;
  let isLastLastCharUpper = false;

  for (let i = 0; i < input.length; i++) {
    const c = input[i];

    if (isLastCharLower && /[a-zA-Z]/.test(c) && c.toUpperCase() === c) {
      input = input.slice(0, i) + '-' + input.slice(i);
      isLastCharLower = false;
      isLastLastCharUpper = isLastCharUpper;
      isLastCharUpper = true;
      i++;
    } else if (isLastCharUpper && isLastLastCharUpper && /[a-zA-Z]/.test(c) && c.toLowerCase() === c) {
      input = input.slice(0, i - 1) + '-' + input.slice(i - 1);
      isLastLastCharUpper = isLastCharUpper;
      isLastCharUpper = false;
      isLastCharLower = true;
    } else {
      isLastCharLower = c.toLowerCase() === c;
      isLastLastCharUpper = isLastCharUpper;
      isLastCharUpper = c.toUpperCase() === c;
    }
  }

  return input;
};

export default (input, options) => {
  options = Object.assign({
    pascalCase: false
  }, options);

  const postProcess = x => options.pascalCase ? x.charAt(0).toUpperCase() + x.slice(1) : x;

  if (Array.isArray(input)) {
    input = input.map(x => x.trim())
      .filter(x => x.length)
      .join('-');
  } else {
    input = input.trim();
  }

  if (input.length === 0) {
    return '';
  }

  if (input.length === 1) {
    return options.pascalCase ? input.toUpperCase() : input.toLowerCase();
  }

  if (/^[a-z\d]+$/.test(input)) {
    return postProcess(input);
  }

  const hasUpperCase = input !== input.toLowerCase();

  if (hasUpperCase) {
    input = preserveCamelCase(input);
  }

  input = input
    .replace(/^[_.\- ]+/, '')
    .toLowerCase()
    .replace(/[_.\- ]+(\w|$)/g, (m, p1) => p1.toUpperCase());

  return postProcess(input);
};
